The trade-off between yield and environmental effects caused by nitrogen fertilizer application is an important issue in wheat production.A reduction in fertile florets is one of the main reasons for the lower yields ...The trade-off between yield and environmental effects caused by nitrogen fertilizer application is an important issue in wheat production.A reduction in fertile florets is one of the main reasons for the lower yields under low nitrogen application rates.Brassinosteroids(BRs)have been found to play a role in nitrogen-induced rice spikelet degeneration.However,whether BRs play a role in wheat floret development and the mechanisms involved are not clear.Therefore,a nitrogen gradient experiment and exogenous spraying experiment were conducted to investigate the role and mechanism of BRs in wheat floret development under low nitrogen stress.The results showed that as the nitrogen application decreased,the endogenous BRs content of the spikes decreased,photosynthesis weakened,and total carbon,soluble sugar and starch in the spikes decreased,leading to a reduction in the number of fertile florets.Under low nitrogen stress,exogenous spraying of 24-epibrassinolide promoted photosynthesis,and stimulated stem fructan hydrolysis and the utilization and storage of sucrose in spikes,which directed more carbohydrates to the spikes and increased the number of fertile florets.In conclusion,BRs mediate the effects of nitrogen fertilizer on wheat floret development,and under low nitrogen stress,foliar spraying of 24-epibrassinolide promotes the flow of carbohydrates from the stem to the spikes,alleviating wheat floret degeneration.展开更多
Rice is the world's largest food crop,but it often encounters flowering asynchronization problems during hybrid rice seed production.In addition,the slow closure of female florets leads to seed mildew and affects ...Rice is the world's largest food crop,but it often encounters flowering asynchronization problems during hybrid rice seed production.In addition,the slow closure of female florets leads to seed mildew and affects the quality.The hormone abscisic acid(ABA)plays a crucial role in plant responses to abiotic stresses.Previous studies showed that exogenous ABA promotes floret closure,although the molecular mechanisms and effects of endogenous ABA on floret closure remain unknown.In this study,the effect of endogenous ABA on floret closure and the molecular mechanism by which ABA promotes floret closure through sugar transporters were investigated by changing the expression levels of OsNCED3 and OsPYL1 in rice.The results showed that overexpression(OE)-OsNCED3increased the endogenous ABA level of florets.Florets closed 5.91 min earlier and OsNCED3 gene knockout line delayed the closure of florets by 5.08 min compared with the wild type.In addition,OsPYL1 regulated the endogenous ABA content and changed the sensitivity to ABA such that the floret closure times for OE and CRISPR-Cas9(CR)were 9.84 min earlier and 12.78 min later,respectively,resulting in an increase in the split husk rate to 15.4%.The gene expression levels of some sugar transporters(STs)changed.The OsPYL1 and OsSWEET4proteins could interact on the cell membrane.These results indicate that ABA promotes the closure of rice florets and the enhanced sensitivity to ABA promotes this effect even more.The molecular mechanism is mainly related to downstream sugar transporters that respond to the ABA signaling pathway,especially OsSWEET4.展开更多
Reducing nitrogen application rates can mitigate issues such as environmental degradation and resource wastage.However,it can also exacerbate problems such as wheat floret degeneration,leading to reduced yields.Theref...Reducing nitrogen application rates can mitigate issues such as environmental degradation and resource wastage.However,it can also exacerbate problems such as wheat floret degeneration,leading to reduced yields.Therefore,investigating wheat floret degeneration mechanisms under low-nitrogen stress and identifying mitigation measures are conducive to achieving high yields and sustainable development.To investigate the physiological mechanism of how low-nitrogen stress affects wheat floret degradation and whether exogenous brassinosteroids(BRs)can alleviate this stress,experiments were designed with treatments of three nitrogen application rates(N0,no nitrogen application;N1,120 kg ha–1 pure nitrogen;N2,240 kg ha–1 pure nitrogen)and exogenous spraying(N0CK,no nitrogen with water spraying;N0BR,no nitrogen with 24-epibrassinolide(an active brassinosteroid)spraying;N1,120 kg ha–1 pure nitrogen with water spraying).The results indicated that low-nitrogen stress generated a large amount of reactive oxygen species.Although wheat spikes synthesized flavonoids to combat oxidative stress,their energy metabolism(glycolysis and tricarboxylic acid cycle)and ascorbate-glutathione cycle were inhibited,which kept the reactive oxygen levels elevated within the spike,induced cell death and exacerbated floret degeneration.Furthermore,brassinosteroids played a role in regulating wheat floret degeneration under low-nitrogen stress.Exogenous foliar spraying of 24-epibrassinolide promoted energy metabolism and the ascorbate-glutathione cycle within the spike,which enhanced the energy charge and effectively mitigated a portion of the reactive oxygen induced by low-nitrogen stress,thereby alleviating the floret degeneration caused by low-nitrogen stress.In summary,low-nitrogen stress disrupts the redox homeostasis of wheat spikes,leading to floret degeneration,while brassinosteroids alleviate floret degeneration by improving the redox state of wheat spikes.This study provides theoretical support for balancing the contradiction between high yields and sustainable development and will be beneficial for the application of low nitrogen in production.展开更多
With the intensification of climate change,spring low-temperature stress(SLTS)leads to floret degeneration and a decrease in grain number.This study investigated the physiological mechanisms underlying SLTS-induced fl...With the intensification of climate change,spring low-temperature stress(SLTS)leads to floret degeneration and a decrease in grain number.This study investigated the physiological mechanisms underlying SLTS-induced floret degeneration using two wheat varieties with contrasting cold sensitivity.SLTS caused yellowing and shrinkage of floret primordia,increasing floret degeneration and fertile floret abortion,ultimately reducing grains per spike by 12.2%-26.1%.SLTS disrupted nutrient supply,impairing dry matter accumulation in young spikes.At 0-15 d after low-temperature stress(DALTS),SLTS caused a brief increase in the sugar content of young spikes(0-3 DALTS),followed by a rapid decrease(6-15 DALTS),while the total nitrogen content keeps decreasing.SLTS altered key enzyme activities,enhancing sucrose synthase and sucrose phosphate synthase but suppressing nitrate reductase and glutamine synthetase.Transcriptomic analysis revealed that SLTS perturbed starch and sucrose metabolism,carbon and nitrogen metabolism,and amino sugar pathways,altering soluble sugars,sucrose,fructose,and protein levels.SLTS disrupted carbon-nitrogen metabolic homeostasis,thereby reducing the number of fertile florets and ultimately leading to a decrease in grain number per spike.These findings enhance understanding of SLTS impacts on wheat floret development and provide insights for improving low-temperature tolerance and yield stability in wheat.展开更多
The levels of endogenous plant hormones regulate floret development and degeneration, and thus grain set in flower crops. This study was undertaken to characterize the changes of endogenous hormone levels during flor...The levels of endogenous plant hormones regulate floret development and degeneration, and thus grain set in flower crops. This study was undertaken to characterize the changes of endogenous hormone levels during floret development in three wheat ( Triticum aestivum L.) genotypes: “97J1' with the highest grain set and fertile florets per spike, “H8679' with the lowest grain set and fertile florets per spike, and a medium, “YM158'. The results showed that the peak level of ABA appeared between stamen and pistil differentiation and antherlobe formation of floret development, and the timing delayed with the size of spike (earliest in “H8679” and latest in “97J1”). From antherlobe formation to meiosis, the levels of ABA and GA 1+3 decreased sharply in the ears of “97J1”, while in the ears of “H8679” there was only a slight decrease in ABA, and even an increase in GA 1+3 . The ratio of isopentenyladenosine (iPA)/ABA and IAA/ABA in the ears of “97J1” increased sharply from antherlobe formation to meiosis, but changed only slightly in the ears of “H8679”. At antherlobe formation, IAA and GA 1+3 levels were higher in the ears of “97J1”, but lower in the ears of “H8679” than in the leaves. At meiosis, ABA, GA 1+3 and IAA levels in the “97J1” ears were much lower than in the leaves, but similar in “H8679”. These results indicated that the sharp decreases of ABA and GA 1+3 in ears from antherlobe formation to meiosis and the lowest maintenance at meiosis may be favorable for development of fertile florets and enhancement of grain set in wheat.展开更多
Nitrogen(N)fertilization is critical for spike and floret development,which affects the number of fertile florets per spike(NFFs).However,the physiological regulation of the floret development process by N fertilizati...Nitrogen(N)fertilization is critical for spike and floret development,which affects the number of fertile florets per spike(NFFs).However,the physiological regulation of the floret development process by N fertilization is largely unknown.A high temporal-resolution investigation of floret primordia number and morphology,dry matter,and N availability was conducted under three N fertilization levels:0(N0),120(N1)and 240(N2)kg ha^(−1).Interestingly,fertile florets at anthesis stage were determined by those floret primordia with meiotic ability at booting stage:meiotic ability was a threshold that predicted whether a floret primordium became fertile or abortive florets.Because the developmental rate of the 4th floret primordium in the central spikelet was accelerated and then they acquired meiotic ability,the NFFs increased gradually as N application increased,but the increase range decreased under N2.There were no differences in spike N concentration among treatments,but leaf N concentration was increased in the N1 and N2 treatments.Correspondingly,dry matter accumulation and N content of the leaf and spike in the N1 and N2 treatments was increased as compared to N0.Clearly,optimal N fertilization increased leaf N availability and transport of assimilates to spikes,and allowed more floret primordia to acquire meiotic ability and become fertile florets,finally increasing NFFs.There was no difference in leaf N concentration between N1 and N2 treatment,whereas soil N concentration at 0–60 cm soil layers was higher in N2 than in N1 treatment,implying that there was still some N fertilization that remained unused.Therefore,improving the leaf’s ability to further use N fertilizer is vital for greater NFFs.展开更多
Promoting more floret primordia within a spike to acquire fertile potential during the differentiation and pre-dimorphism phases is critical for increasing the number of fertile florets per spike(NFFs).However,it is y...Promoting more floret primordia within a spike to acquire fertile potential during the differentiation and pre-dimorphism phases is critical for increasing the number of fertile florets per spike(NFFs).However,it is yet unknown the physiological mechanism regulating the complex and dynamic process.This study aimed to clarify how intra-spike hormones,pigments,and assimilates coordinate with each other to regulate spike morphology and then floret primordia development.A two-year field experiment was conducted with two winter wheat genotypes:N50(big-spike with greater NFFs)and SM22(mediumspike with fewer NFFs).We monitored high temporal and spatial-resolution changes in the number and morphology of floret primordia within a spike,as well as in intra-spike hormones,pigments,and assimilates.Our results revealed that the big-spike genotype had more NFFs than the medium-spike genotype,not only because they had more spikelets,but also because they had greater NFFs mainly at central spikelets.More floret primordia at central spikelets had sufficient time to develop and acquire fertile potential during the differentiation phase(167-176 d after sowing,DAS)and the pre-dimorphism phase(179 DAS)for the big-spike genotype than the medium-spike genotype.Floret primordia with fertile morphology during the pre-dimorphism phase always developed into fertile florets during the dimorphism phase.Those early-developed floret primordia most proximal and intermediate to the rachis in the big-spike genotype developed faster than the medium-spike genotype.Correspondingly,the spike dry matter and pigments(chlorophyll a,chlorophyll b,carotene,and carotenoids)content during 170-182 DAS,auxin(IAA)and cytokinin(CTK)content on 167 DAS were significantly higher in the big-spike genotype than in the medium-spike genotype,while jasmonic acid(JA)content was significantly lower in the big-spike genotype compared to the medium-spike genotype during 167-182 DAS.Since the significant differences in intra-spike hormone content of the two genotypes appear earlier than those in dry matter and pigments,we propose a possible model that helped the N50 genotype(big-spike)to form more fertile florets,taking the intra-spike hormone content as a signaling molecule induced assimilates and pigments synthesis,which accelerated the development of more floret primordia during the differentiation phase and then acquired fertile potential during the pre-dimorphism phase,finally improved the NFFs.Our high temporal and spatial-resolution analysis provides an accurate time window for precision cultivation and effective physiological breeding to improve the number of fertile florets in wheat.展开更多
A double mutant with streaked leaf and abnormal floret was found and temporarily named streaked leaf and floral organ number mutant （st-fon）. For this mutant, besides white streak appeared on culm, leaves and panicl...A double mutant with streaked leaf and abnormal floret was found and temporarily named streaked leaf and floral organ number mutant （st-fon）. For this mutant, besides white streak appeared on culm, leaves and panicles, the number of floral organs increased and florets cracked. The extreme phenotype was that several small florets grew from one floret or branch rachis in small florets extended and developed into panicles. By using transmission electron microscope to observe the ultrastructure of white histocytes of leaves at the seedling stage, the white tissues which showed abnormal plastids, lamellas and thylakoids could not develop into normal chloroplast, and the development of chloroplast was blocked at the early growth stage of plastid. Scanning electron microscope and paraffin section were also used to observe the development of floral organs, and the results indicated that the development of floral meristem was out of order and unlimited, whereas in the twisty leaves, vascular bundle sheath cells grew excessively, or some bubbly cells increased. Genetic analyses carried out by means of cross and backcross with four normal-leaf-color materials revealed that the mutant is of cytoplasm inheritance.展开更多
Rice(Oryza sativa L.) is one of the most important food crops worldwide and a model monocot plant for gene function analysis, so it is an ideal system for studying flower development. This study reports a mutant, name...Rice(Oryza sativa L.) is one of the most important food crops worldwide and a model monocot plant for gene function analysis, so it is an ideal system for studying flower development. This study reports a mutant, named multi-floret spikelet 3(mfs3), which is related to the spikelet development in rice and derived from the ethylmethane sulfonate(EMS)-treated rice cultivar XIDA 1 B. In mfs3, the main body of palea(bop) was degenerated severely and only glume-like marginal regions of palea(mrp) remained, while other floral organs developed normally, indicating that the palea identity was seriously influenced by the mutation. It was also observed that the number of floral organs was increased in some spikelets, including 2 lemmas, 4 mrp, 4 lodicules, 8–10 stamens, and 2 pistils, which meant that the spikelet determinacy was lost to some degree in mfs3. Furthermore, genetic analysis demonstrated that the mfs3 trait was controlled by a single recessive gene. Using 426 F2 mutants derived from the cross between sterile line 56 S and mfs3, the MULTI-FLORET SPIKELET 3(MFS3) gene was mapped between the molecular markers RM19347 and RM19352 on Chr.6, with a physical distance of 106.3 kb. Sequencing of candidate genes revealed that an 83-bp fragment loss and a base substitution occurred in the LOC_Os06 g04540 gene in the mutant, confirming preliminarily that the LOC_Os06 g04540 gene was the MFS3 candidate gene. Subsequent q PCR analysis showed that the mutation caused the down-regulation of Os MADS1 and FON1 genes, and the up-regulation of Os IDS1 and SNB genes, which are all involved in the regulation of spikelet development. The MFS3 mutation also significantly reduced the transcription of the REP gene, which is involved in palea development. These results indicated that the MFS3 gene might be involved in the spikelet meristem determinacy and palea identity by regulating the expression of these related genes.展开更多
The study was carried out on the effect of nitrogen application in different wheat growth stage on the floret development, the photosynthetic rate, the yield and its components of winter wheat. The result indicated th...The study was carried out on the effect of nitrogen application in different wheat growth stage on the floret development, the photosynthetic rate, the yield and its components of winter wheat. The result indicated that nitrogen application in the pistil-stamen primordium formation stage and the tetrad formation stage of wheat growth prolonged the duration of floret development, promoted the balance growth of floret and reduced the floret decadence number, thus increased the grain number per spike. Nitrogen application in the middle and in the late stages of wheat development increased the photosynthetic ability of the plant leaves in the later stage, and also lengthened the peak of grain filling stage, thus enhanced the grain weight and yield of wheat significantly.展开更多
Diurnal floret opening and closure(DFOC)is essential for rice reproductive development and hybrid breeding,yet transcriptional dynamics and underlying regulatory networks remain poorly characterized.Here,we conducted ...Diurnal floret opening and closure(DFOC)is essential for rice reproductive development and hybrid breeding,yet transcriptional dynamics and underlying regulatory networks remain poorly characterized.Here,we conducted high-temporal-resolution transcriptomic analyses of lodicules to dissect DFOC regulatory networks in two japonica rice cultivars.Analysis of differentially expressed genes(DEGs)uncovered core genes shared by both cultivars,primarily associated with jasmonic acid(JA)signaling and cell wall remodeling.By integrating DNA affinity purification sequencing(DAP-seq),we constructed core regulatory networks mediated by the basic helix-loop-helix transcription factor(TF)OsMYC2,governing DFOC in rice.We identified xyloglucan endotransglycosylase-related gene 1(OsXTR1),which encodes a cell-wall loosening enzyme,as a key gene activated by OsMYC2 during DFOC.Disruption of OsXTR1 resulted in florets failing to close after opening,demonstrating its essential role in linking cell wall dynamics to hormonal regulation.Similarly,we identified a JA biosynthesis gene,allene oxide cyclase(OsAOC),which is implicated in DFOC through an OsMYC2-mediated positive-feedback loop.Additionally,we developed the RiceDFOC database(http://zhoulab.zju.edu.cn/FT/index.html),providing interactive access to spatiotemporal transcriptomes,co-expression networks,and phenomics data.Collectively,our study unveils a hierarchical OsMYC2-centric network that coordinates JA signaling and structural remodeling during DFOC,providing mechanistic insights and resources for optimizing rice breeding.展开更多
Heat waves induced by climate warming have become common in food-producing regions worldwide,frequently coinciding with high temperature(HT)-sensitive stages of many crops and thus threatening global food security.Und...Heat waves induced by climate warming have become common in food-producing regions worldwide,frequently coinciding with high temperature(HT)-sensitive stages of many crops and thus threatening global food security.Understanding the HT sensitivity of reproductive organs is currently of great interest for increasing seed set.The responses of seed set to HT involve multiple processes in both male and female reproductive organs,but we currently lack an integrated and systematic summary of these responses for the world’s three leading food crops(rice,wheat,and maize).In the present work,we define the critical high temperature thresholds for seed set in rice(37.2℃±0.2℃),wheat(27.3℃±0.5℃),and maize(37.9℃±0.4℃)during flowering.We assess the HT sensitivity of these three cereals from the microspore stage to the lag period,including effects of HT on flowering dynamics,floret growth and development,pollination,and fertilization.Our review synthesizes existing knowledge about the effects of HT stress on spikelet opening,anther dehiscence,pollen shedding number,pollen viability,pistil and stigma function,pollen germination on the stigma,and pollen tube elongation.HT-induced spikelet closure and arrest of pollen tube elongation have a catastrophic effect on pollination and fertilization in maize.Rice benefits from pollination under HT stress owing to bottom anther dehiscence and cleistogamy.Cleistogamy and secondary spikelet opening increase the probability of pollination success in wheat under HT stress.However,cereal crops themselves also have protective measures under HT stress.Lower canopy/tissue temperatures compared with air temperatures indicate that cereal crops,especially rice,can partly protect themselves from heat damage.In maize,husk leaves reduce inner ear temperature by about 5℃compared with outer ear temperature,thereby protecting the later phases of pollen tube growth and fertilization processes.These findings have important implications for accurate modeling,optimized crop management,and breeding of new varieties to cope with HT stress in the most important staple crops.展开更多
With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.He Guanghua(何光华)from the Rice Research Institute,Southwest University demonstrates that LATERAL FLORET ...With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.He Guanghua(何光华)from the Rice Research Institute,Southwest University demonstrates that LATERAL FLORET 1induces the'three-florets spikelet'in rice,which was published in PNAS(2017,114(37):9984-9989).展开更多
Chrysanthemum morifolium Ramat.is an important industrial crop with a high medicinal value,whose capitulum consists of ray and disc florets containing numerous bioactive components,such as flavonoids and phenolic acid...Chrysanthemum morifolium Ramat.is an important industrial crop with a high medicinal value,whose capitulum consists of ray and disc florets containing numerous bioactive components,such as flavonoids and phenolic acids.However,the distribution and accumulations of the bioactive metabolites in florets of Chrysanthemum morifolium were unclear.Herein,the ray and disc florets of Chrysanthemum morifolium were separated for comparing the bioactive metabolites.The contents of phenolic compounds and antioxidant activities were significantly different between the two florets.The metabolomic analysis identified 203 and 241 differential metabolites between ray and disc florets at two flowering stages.The derivatives of quercetin,isorhamnetin,tricin,and caffeoylquinic acid were enriched in the disc florets,while apigenin,kaempferol,acacetin,and their glycosides mainly accumulated in the ray florets.Besides,the results of transcriptome and qRT-PCR suggested that the F3H,F3'H,and FLS genes highly expressed in disc florets,while the FNS gene was well expressed in ray florets,which explained the different distribution of phenolic compounds between ray and disc florets.Furthermore,the expression of CmCYC2 genes was found to be significantly related to the distribution of flavones by correlation analysis.It was proved by the luciferase reporter assay that CmCYC2a and CmCYC2d factors could bind and activate the CmFNS promoter to regulate the flavones biosynthesis in ray florets.These results revealed the significant difference of metabolite contents and gene expression profile between ray and disc floret in Chrysanthemum morifolium and demonstrated that the quality of Chrysanthemum morifolium‘Hangju'was closely relevant to its flower morphology.展开更多
基金supported by the Key Research and Development Program of Shaanxi,China(2021NY-083)the National Natural Science Foundation of China(31871567)。
文摘The trade-off between yield and environmental effects caused by nitrogen fertilizer application is an important issue in wheat production.A reduction in fertile florets is one of the main reasons for the lower yields under low nitrogen application rates.Brassinosteroids(BRs)have been found to play a role in nitrogen-induced rice spikelet degeneration.However,whether BRs play a role in wheat floret development and the mechanisms involved are not clear.Therefore,a nitrogen gradient experiment and exogenous spraying experiment were conducted to investigate the role and mechanism of BRs in wheat floret development under low nitrogen stress.The results showed that as the nitrogen application decreased,the endogenous BRs content of the spikes decreased,photosynthesis weakened,and total carbon,soluble sugar and starch in the spikes decreased,leading to a reduction in the number of fertile florets.Under low nitrogen stress,exogenous spraying of 24-epibrassinolide promoted photosynthesis,and stimulated stem fructan hydrolysis and the utilization and storage of sucrose in spikes,which directed more carbohydrates to the spikes and increased the number of fertile florets.In conclusion,BRs mediate the effects of nitrogen fertilizer on wheat floret development,and under low nitrogen stress,foliar spraying of 24-epibrassinolide promotes the flow of carbohydrates from the stem to the spikes,alleviating wheat floret degeneration.
基金supported by the National Natural Science Foundation of China(32260780 and 31360297)the China Postdoctoral Science Foundation(2021M701513)+1 种基金the Jiangxi 2011 Collaborative Innovation Centre of Postharvest Key Technology and Quality Safety of Fruits and Vegetables,China(JXGS-05)the Gan Po 555 Engineering Excel ence Talents Project in Jiangxi Province,China。
文摘Rice is the world's largest food crop,but it often encounters flowering asynchronization problems during hybrid rice seed production.In addition,the slow closure of female florets leads to seed mildew and affects the quality.The hormone abscisic acid(ABA)plays a crucial role in plant responses to abiotic stresses.Previous studies showed that exogenous ABA promotes floret closure,although the molecular mechanisms and effects of endogenous ABA on floret closure remain unknown.In this study,the effect of endogenous ABA on floret closure and the molecular mechanism by which ABA promotes floret closure through sugar transporters were investigated by changing the expression levels of OsNCED3 and OsPYL1 in rice.The results showed that overexpression(OE)-OsNCED3increased the endogenous ABA level of florets.Florets closed 5.91 min earlier and OsNCED3 gene knockout line delayed the closure of florets by 5.08 min compared with the wild type.In addition,OsPYL1 regulated the endogenous ABA content and changed the sensitivity to ABA such that the floret closure times for OE and CRISPR-Cas9(CR)were 9.84 min earlier and 12.78 min later,respectively,resulting in an increase in the split husk rate to 15.4%.The gene expression levels of some sugar transporters(STs)changed.The OsPYL1 and OsSWEET4proteins could interact on the cell membrane.These results indicate that ABA promotes the closure of rice florets and the enhanced sensitivity to ABA promotes this effect even more.The molecular mechanism is mainly related to downstream sugar transporters that respond to the ABA signaling pathway,especially OsSWEET4.
基金supported by the Key Research and Development Program of Shaanxi,China(2021NY-083)the National Natural Science Foundation of China(31871567)。
文摘Reducing nitrogen application rates can mitigate issues such as environmental degradation and resource wastage.However,it can also exacerbate problems such as wheat floret degeneration,leading to reduced yields.Therefore,investigating wheat floret degeneration mechanisms under low-nitrogen stress and identifying mitigation measures are conducive to achieving high yields and sustainable development.To investigate the physiological mechanism of how low-nitrogen stress affects wheat floret degradation and whether exogenous brassinosteroids(BRs)can alleviate this stress,experiments were designed with treatments of three nitrogen application rates(N0,no nitrogen application;N1,120 kg ha–1 pure nitrogen;N2,240 kg ha–1 pure nitrogen)and exogenous spraying(N0CK,no nitrogen with water spraying;N0BR,no nitrogen with 24-epibrassinolide(an active brassinosteroid)spraying;N1,120 kg ha–1 pure nitrogen with water spraying).The results indicated that low-nitrogen stress generated a large amount of reactive oxygen species.Although wheat spikes synthesized flavonoids to combat oxidative stress,their energy metabolism(glycolysis and tricarboxylic acid cycle)and ascorbate-glutathione cycle were inhibited,which kept the reactive oxygen levels elevated within the spike,induced cell death and exacerbated floret degeneration.Furthermore,brassinosteroids played a role in regulating wheat floret degeneration under low-nitrogen stress.Exogenous foliar spraying of 24-epibrassinolide promoted energy metabolism and the ascorbate-glutathione cycle within the spike,which enhanced the energy charge and effectively mitigated a portion of the reactive oxygen induced by low-nitrogen stress,thereby alleviating the floret degeneration caused by low-nitrogen stress.In summary,low-nitrogen stress disrupts the redox homeostasis of wheat spikes,leading to floret degeneration,while brassinosteroids alleviate floret degeneration by improving the redox state of wheat spikes.This study provides theoretical support for balancing the contradiction between high yields and sustainable development and will be beneficial for the application of low nitrogen in production.
基金funded by Scientific Research Projects of Colleges and Universities in Anhui Province,China(2023AH051016)Anhui Province New Era Education Provincial Quality Engineering Project(2023xscx044)+1 种基金Anhui Agricultural University,the First Batch of College Students"Science and Innovation Pilot"Cultivation Program Projectthe National Key Research and Development Program of China(2023YFD1901005)。
文摘With the intensification of climate change,spring low-temperature stress(SLTS)leads to floret degeneration and a decrease in grain number.This study investigated the physiological mechanisms underlying SLTS-induced floret degeneration using two wheat varieties with contrasting cold sensitivity.SLTS caused yellowing and shrinkage of floret primordia,increasing floret degeneration and fertile floret abortion,ultimately reducing grains per spike by 12.2%-26.1%.SLTS disrupted nutrient supply,impairing dry matter accumulation in young spikes.At 0-15 d after low-temperature stress(DALTS),SLTS caused a brief increase in the sugar content of young spikes(0-3 DALTS),followed by a rapid decrease(6-15 DALTS),while the total nitrogen content keeps decreasing.SLTS altered key enzyme activities,enhancing sucrose synthase and sucrose phosphate synthase but suppressing nitrate reductase and glutamine synthetase.Transcriptomic analysis revealed that SLTS perturbed starch and sucrose metabolism,carbon and nitrogen metabolism,and amino sugar pathways,altering soluble sugars,sucrose,fructose,and protein levels.SLTS disrupted carbon-nitrogen metabolic homeostasis,thereby reducing the number of fertile florets and ultimately leading to a decrease in grain number per spike.These findings enhance understanding of SLTS impacts on wheat floret development and provide insights for improving low-temperature tolerance and yield stability in wheat.
文摘The levels of endogenous plant hormones regulate floret development and degeneration, and thus grain set in flower crops. This study was undertaken to characterize the changes of endogenous hormone levels during floret development in three wheat ( Triticum aestivum L.) genotypes: “97J1' with the highest grain set and fertile florets per spike, “H8679' with the lowest grain set and fertile florets per spike, and a medium, “YM158'. The results showed that the peak level of ABA appeared between stamen and pistil differentiation and antherlobe formation of floret development, and the timing delayed with the size of spike (earliest in “H8679” and latest in “97J1”). From antherlobe formation to meiosis, the levels of ABA and GA 1+3 decreased sharply in the ears of “97J1”, while in the ears of “H8679” there was only a slight decrease in ABA, and even an increase in GA 1+3 . The ratio of isopentenyladenosine (iPA)/ABA and IAA/ABA in the ears of “97J1” increased sharply from antherlobe formation to meiosis, but changed only slightly in the ears of “H8679”. At antherlobe formation, IAA and GA 1+3 levels were higher in the ears of “97J1”, but lower in the ears of “H8679” than in the leaves. At meiosis, ABA, GA 1+3 and IAA levels in the “97J1” ears were much lower than in the leaves, but similar in “H8679”. These results indicated that the sharp decreases of ABA and GA 1+3 in ears from antherlobe formation to meiosis and the lowest maintenance at meiosis may be favorable for development of fertile florets and enhancement of grain set in wheat.
基金This study was supported by the National Key Research and Development Program of China(2022YFD1900703,2022YFD2300802)the Earmarked Fund for CARS(CARS-3)+1 种基金the National Natural Science Foundation of China(31871563)China Postdoctoral Science Foundation(2022M723437).
文摘Nitrogen(N)fertilization is critical for spike and floret development,which affects the number of fertile florets per spike(NFFs).However,the physiological regulation of the floret development process by N fertilization is largely unknown.A high temporal-resolution investigation of floret primordia number and morphology,dry matter,and N availability was conducted under three N fertilization levels:0(N0),120(N1)and 240(N2)kg ha^(−1).Interestingly,fertile florets at anthesis stage were determined by those floret primordia with meiotic ability at booting stage:meiotic ability was a threshold that predicted whether a floret primordium became fertile or abortive florets.Because the developmental rate of the 4th floret primordium in the central spikelet was accelerated and then they acquired meiotic ability,the NFFs increased gradually as N application increased,but the increase range decreased under N2.There were no differences in spike N concentration among treatments,but leaf N concentration was increased in the N1 and N2 treatments.Correspondingly,dry matter accumulation and N content of the leaf and spike in the N1 and N2 treatments was increased as compared to N0.Clearly,optimal N fertilization increased leaf N availability and transport of assimilates to spikes,and allowed more floret primordia to acquire meiotic ability and become fertile florets,finally increasing NFFs.There was no difference in leaf N concentration between N1 and N2 treatment,whereas soil N concentration at 0–60 cm soil layers was higher in N2 than in N1 treatment,implying that there was still some N fertilization that remained unused.Therefore,improving the leaf’s ability to further use N fertilizer is vital for greater NFFs.
基金funded by the Scientific and Technological Innovation Team Project of Seed Industry for Saline-alkali Tolerant Crop in Hebei Province(23327501D)the National Key Research and Development Program of China(2022YFD2300802,2022YFD1900703)the China Agriculture Research System(CARS-3).
文摘Promoting more floret primordia within a spike to acquire fertile potential during the differentiation and pre-dimorphism phases is critical for increasing the number of fertile florets per spike(NFFs).However,it is yet unknown the physiological mechanism regulating the complex and dynamic process.This study aimed to clarify how intra-spike hormones,pigments,and assimilates coordinate with each other to regulate spike morphology and then floret primordia development.A two-year field experiment was conducted with two winter wheat genotypes:N50(big-spike with greater NFFs)and SM22(mediumspike with fewer NFFs).We monitored high temporal and spatial-resolution changes in the number and morphology of floret primordia within a spike,as well as in intra-spike hormones,pigments,and assimilates.Our results revealed that the big-spike genotype had more NFFs than the medium-spike genotype,not only because they had more spikelets,but also because they had greater NFFs mainly at central spikelets.More floret primordia at central spikelets had sufficient time to develop and acquire fertile potential during the differentiation phase(167-176 d after sowing,DAS)and the pre-dimorphism phase(179 DAS)for the big-spike genotype than the medium-spike genotype.Floret primordia with fertile morphology during the pre-dimorphism phase always developed into fertile florets during the dimorphism phase.Those early-developed floret primordia most proximal and intermediate to the rachis in the big-spike genotype developed faster than the medium-spike genotype.Correspondingly,the spike dry matter and pigments(chlorophyll a,chlorophyll b,carotene,and carotenoids)content during 170-182 DAS,auxin(IAA)and cytokinin(CTK)content on 167 DAS were significantly higher in the big-spike genotype than in the medium-spike genotype,while jasmonic acid(JA)content was significantly lower in the big-spike genotype compared to the medium-spike genotype during 167-182 DAS.Since the significant differences in intra-spike hormone content of the two genotypes appear earlier than those in dry matter and pigments,we propose a possible model that helped the N50 genotype(big-spike)to form more fertile florets,taking the intra-spike hormone content as a signaling molecule induced assimilates and pigments synthesis,which accelerated the development of more floret primordia during the differentiation phase and then acquired fertile potential during the pre-dimorphism phase,finally improved the NFFs.Our high temporal and spatial-resolution analysis provides an accurate time window for precision cultivation and effective physiological breeding to improve the number of fertile florets in wheat.
基金supported by the Foundation Program,Innovative Team Development Plan of the Ministry of Education,China(Grant No.IRT0453)the Financial Gene Engineering Excellent Article Foundation Program of Sichuan Province,China(Grant No.2011LWJJ-005)
文摘A double mutant with streaked leaf and abnormal floret was found and temporarily named streaked leaf and floral organ number mutant （st-fon）. For this mutant, besides white streak appeared on culm, leaves and panicles, the number of floral organs increased and florets cracked. The extreme phenotype was that several small florets grew from one floret or branch rachis in small florets extended and developed into panicles. By using transmission electron microscope to observe the ultrastructure of white histocytes of leaves at the seedling stage, the white tissues which showed abnormal plastids, lamellas and thylakoids could not develop into normal chloroplast, and the development of chloroplast was blocked at the early growth stage of plastid. Scanning electron microscope and paraffin section were also used to observe the development of floral organs, and the results indicated that the development of floral meristem was out of order and unlimited, whereas in the twisty leaves, vascular bundle sheath cells grew excessively, or some bubbly cells increased. Genetic analyses carried out by means of cross and backcross with four normal-leaf-color materials revealed that the mutant is of cytoplasm inheritance.
基金supported by the National Natural Science Foundation of China (31271304)the National Key Research and Development Program of China (2017YFD0100202)+2 种基金the Natural Science Foundation of Chongqing, China (CSTC2017jcyj BX0062)the Graduate Student Scientific Research Innovation Projects in Chongqing, China (CYS2015066)the Fundamental Research Funds for the Central Universities, China (XDJK2016A013)
文摘Rice(Oryza sativa L.) is one of the most important food crops worldwide and a model monocot plant for gene function analysis, so it is an ideal system for studying flower development. This study reports a mutant, named multi-floret spikelet 3(mfs3), which is related to the spikelet development in rice and derived from the ethylmethane sulfonate(EMS)-treated rice cultivar XIDA 1 B. In mfs3, the main body of palea(bop) was degenerated severely and only glume-like marginal regions of palea(mrp) remained, while other floral organs developed normally, indicating that the palea identity was seriously influenced by the mutation. It was also observed that the number of floral organs was increased in some spikelets, including 2 lemmas, 4 mrp, 4 lodicules, 8–10 stamens, and 2 pistils, which meant that the spikelet determinacy was lost to some degree in mfs3. Furthermore, genetic analysis demonstrated that the mfs3 trait was controlled by a single recessive gene. Using 426 F2 mutants derived from the cross between sterile line 56 S and mfs3, the MULTI-FLORET SPIKELET 3(MFS3) gene was mapped between the molecular markers RM19347 and RM19352 on Chr.6, with a physical distance of 106.3 kb. Sequencing of candidate genes revealed that an 83-bp fragment loss and a base substitution occurred in the LOC_Os06 g04540 gene in the mutant, confirming preliminarily that the LOC_Os06 g04540 gene was the MFS3 candidate gene. Subsequent q PCR analysis showed that the mutation caused the down-regulation of Os MADS1 and FON1 genes, and the up-regulation of Os IDS1 and SNB genes, which are all involved in the regulation of spikelet development. The MFS3 mutation also significantly reduced the transcription of the REP gene, which is involved in palea development. These results indicated that the MFS3 gene might be involved in the spikelet meristem determinacy and palea identity by regulating the expression of these related genes.
文摘The study was carried out on the effect of nitrogen application in different wheat growth stage on the floret development, the photosynthetic rate, the yield and its components of winter wheat. The result indicated that nitrogen application in the pistil-stamen primordium formation stage and the tetrad formation stage of wheat growth prolonged the duration of floret development, promoted the balance growth of floret and reduced the floret decadence number, thus increased the grain number per spike. Nitrogen application in the middle and in the late stages of wheat development increased the photosynthetic ability of the plant leaves in the later stage, and also lengthened the peak of grain filling stage, thus enhanced the grain weight and yield of wheat significantly.
基金supported by the National Key Research and Development Program of China(2023YFF1000500,2022YFF1001600)the Fundamental Research Funds for the Central Universities(226-2024-00102)the Hundred-Talent Program of Zhejiang University,China to M.Z.
文摘Diurnal floret opening and closure(DFOC)is essential for rice reproductive development and hybrid breeding,yet transcriptional dynamics and underlying regulatory networks remain poorly characterized.Here,we conducted high-temporal-resolution transcriptomic analyses of lodicules to dissect DFOC regulatory networks in two japonica rice cultivars.Analysis of differentially expressed genes(DEGs)uncovered core genes shared by both cultivars,primarily associated with jasmonic acid(JA)signaling and cell wall remodeling.By integrating DNA affinity purification sequencing(DAP-seq),we constructed core regulatory networks mediated by the basic helix-loop-helix transcription factor(TF)OsMYC2,governing DFOC in rice.We identified xyloglucan endotransglycosylase-related gene 1(OsXTR1),which encodes a cell-wall loosening enzyme,as a key gene activated by OsMYC2 during DFOC.Disruption of OsXTR1 resulted in florets failing to close after opening,demonstrating its essential role in linking cell wall dynamics to hormonal regulation.Similarly,we identified a JA biosynthesis gene,allene oxide cyclase(OsAOC),which is implicated in DFOC through an OsMYC2-mediated positive-feedback loop.Additionally,we developed the RiceDFOC database(http://zhoulab.zju.edu.cn/FT/index.html),providing interactive access to spatiotemporal transcriptomes,co-expression networks,and phenomics data.Collectively,our study unveils a hierarchical OsMYC2-centric network that coordinates JA signaling and structural remodeling during DFOC,providing mechanistic insights and resources for optimizing rice breeding.
基金supported by the National Science Foundation of China(32272214)the 2115 Talent Development Program of China Agricultural University,and the General Project of Chongqing Natural Science Foundation(cstc2021jcyj-msxmX0747).
文摘Heat waves induced by climate warming have become common in food-producing regions worldwide,frequently coinciding with high temperature(HT)-sensitive stages of many crops and thus threatening global food security.Understanding the HT sensitivity of reproductive organs is currently of great interest for increasing seed set.The responses of seed set to HT involve multiple processes in both male and female reproductive organs,but we currently lack an integrated and systematic summary of these responses for the world’s three leading food crops(rice,wheat,and maize).In the present work,we define the critical high temperature thresholds for seed set in rice(37.2℃±0.2℃),wheat(27.3℃±0.5℃),and maize(37.9℃±0.4℃)during flowering.We assess the HT sensitivity of these three cereals from the microspore stage to the lag period,including effects of HT on flowering dynamics,floret growth and development,pollination,and fertilization.Our review synthesizes existing knowledge about the effects of HT stress on spikelet opening,anther dehiscence,pollen shedding number,pollen viability,pistil and stigma function,pollen germination on the stigma,and pollen tube elongation.HT-induced spikelet closure and arrest of pollen tube elongation have a catastrophic effect on pollination and fertilization in maize.Rice benefits from pollination under HT stress owing to bottom anther dehiscence and cleistogamy.Cleistogamy and secondary spikelet opening increase the probability of pollination success in wheat under HT stress.However,cereal crops themselves also have protective measures under HT stress.Lower canopy/tissue temperatures compared with air temperatures indicate that cereal crops,especially rice,can partly protect themselves from heat damage.In maize,husk leaves reduce inner ear temperature by about 5℃compared with outer ear temperature,thereby protecting the later phases of pollen tube growth and fertilization processes.These findings have important implications for accurate modeling,optimized crop management,and breeding of new varieties to cope with HT stress in the most important staple crops.
文摘With the support by the National Natural Science Foundation of China,a study by the research group led by Prof.He Guanghua(何光华)from the Rice Research Institute,Southwest University demonstrates that LATERAL FLORET 1induces the'three-florets spikelet'in rice,which was published in PNAS(2017,114(37):9984-9989).
基金financially supported by grants from the National Natural Science Foundation of China(Grant No.81503180)the Opening Project of Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine(Grant No.2021E10013)+1 种基金the Opening Project of NMPA Key Laboratory for Quality Research and Evaluation of Traditional Chinese Medicine(Grant No.AHYJ-KFKT-202101)the Earmarked fund for Jiangsu Agricultural Industry Technology System(Grant No.JATS[2022]460)。
文摘Chrysanthemum morifolium Ramat.is an important industrial crop with a high medicinal value,whose capitulum consists of ray and disc florets containing numerous bioactive components,such as flavonoids and phenolic acids.However,the distribution and accumulations of the bioactive metabolites in florets of Chrysanthemum morifolium were unclear.Herein,the ray and disc florets of Chrysanthemum morifolium were separated for comparing the bioactive metabolites.The contents of phenolic compounds and antioxidant activities were significantly different between the two florets.The metabolomic analysis identified 203 and 241 differential metabolites between ray and disc florets at two flowering stages.The derivatives of quercetin,isorhamnetin,tricin,and caffeoylquinic acid were enriched in the disc florets,while apigenin,kaempferol,acacetin,and their glycosides mainly accumulated in the ray florets.Besides,the results of transcriptome and qRT-PCR suggested that the F3H,F3'H,and FLS genes highly expressed in disc florets,while the FNS gene was well expressed in ray florets,which explained the different distribution of phenolic compounds between ray and disc florets.Furthermore,the expression of CmCYC2 genes was found to be significantly related to the distribution of flavones by correlation analysis.It was proved by the luciferase reporter assay that CmCYC2a and CmCYC2d factors could bind and activate the CmFNS promoter to regulate the flavones biosynthesis in ray florets.These results revealed the significant difference of metabolite contents and gene expression profile between ray and disc floret in Chrysanthemum morifolium and demonstrated that the quality of Chrysanthemum morifolium‘Hangju'was closely relevant to its flower morphology.
