Nicotiana tabacum(2n=4x=48),an economically important non-food crop and a model plant for genetic studies,faces challenges in efficient genotyping of novel germplasm.To address this,we developed the Ta-LD-SC,a 20K SNP...Nicotiana tabacum(2n=4x=48),an economically important non-food crop and a model plant for genetic studies,faces challenges in efficient genotyping of novel germplasm.To address this,we developed the Ta-LD-SC,a 20K SNP Affymetrix Axiom array,based on resequencing data from 150 tobacco accessions.A total of 20,213 unique SNPs were carefully selected,achieving coverage of over 90%of the tobacco genome(Nitab4.5 and NtaSR1)with a uniform probe distribution,limiting density to no more than 5 SNPs per 200 kb.The array underwent extensive validation using 866 tobacco accessions(NP panel)and 288 F2 individuals from a cross between K326 and Oxford 26(GP panel).Performance metrics demonstrated its robustness,with high SNP call rates(93.6%-99.8%),a low technical error rate(<1%),and a superior PolyHighResolution SNP rate(79.79%)compared to other crop SNP arrays.Population structure analysis of the NP panel revealed two major introductions of foreign germplasm that have significantly influenced the genetic diversity of Chinese tobacco resources.Using the array,a genome-wide association study(GWAS)identified 62 genes linked to eight agronomic traits,and a high-density genetic map encompassing 4553 SNPs across 6606.08 cM was constructed.The Ta-LD-SC array provides a valuable tool for rapid,high-quality genotyping offering supporting marker annotations that may benefit genetic research and breeding of tobacco.展开更多
Human-derived tumor models are essential for preclinical development of new anti-cancer drug entities.Generating animal models bearing tumors of human origin,such as patient-derived or cell line-derived xenograft tumo...Human-derived tumor models are essential for preclinical development of new anti-cancer drug entities.Generating animal models bearing tumors of human origin,such as patient-derived or cell line-derived xenograft tumors,is dependent on immuno-deficient strains.Tumor-bearing immunodeficient mice are susceptible to develop-ing unwanted disorders primarily irrelevant to the tumor nature;and if get involved with such disorders,reliability of the study results will be undermined,inevitably con-founding the research in general.Therefore,a rigorous health surveillance and clinical monitoring system,along with the establishment of a strictly controlled barrier facility to maintain a pathogen-free state,are mandatory.Even if all pathogen control and biosafety measures are followed,there are various noninfectious disorders capable of causing tissue and multiorgan damage in immunodeficient animals.Therefore,the re-searchers should be aware of sentinel signs to carefully monitor and impartially report them.This review discusses clinical signs of common unwanted disorders in experi-mental immunodeficient mice,and how to examine and report them.展开更多
Tobacco(Nicotiana tabacum,2n=48)is a key non-food economic crop,yet its stress response and gene regulatory mechanisms remain poorly understood.By analyzing 603 transcriptome datasets,this study identified 1405 tissue...Tobacco(Nicotiana tabacum,2n=48)is a key non-food economic crop,yet its stress response and gene regulatory mechanisms remain poorly understood.By analyzing 603 transcriptome datasets,this study identified 1405 tissue-specific genes,revealing tissue-specific synthesis of terpenoids and other ecologically important secondary metabolites in sepals and other tissues.Comparative stress-response analysis highlighted distinct gene expression patterns in leaves and roots under biotic and abiotic stresses.Additionally,28,396 expression quantitative trait loci(eQTLs)were mapped in leaves,offering valuable genetic regulatory markers.These findings provide crucial insights into tobacco’s gene expression characteristics and their functional implications,serving as a foundation for future research.展开更多
MYB-type transcription factors contain the conserved MYB DNA-binding domain of approximately 50 amino acids and are involved in the regulation of many aspects of plant growth, development, metabolism and stress respon...MYB-type transcription factors contain the conserved MYB DNA-binding domain of approximately 50 amino acids and are involved in the regulation of many aspects of plant growth, development, metabolism and stress responses. From soybean plants, we identified 156 GmMYB genes using our previously obtained 206 MYB unigenes, and 48 were found to have full-length open-reading frames. Expressions of all these identified genes were examined, and we found that expressions of 43 genes were changed upon treatment with ABA, salt, drought and/or cold stress. Three GmMYB genes, GmMYB76, GmMYB92 and GmMYB177, were chosen for further analysis. Using the yeast assay system, GmMYB76 and GmMYB92 were found to have transactivation activity and can form homodimers. GmMYB177 did not appear to have transactivation activity but can form heterodimers with GmMYB76. Yeast onehybrid assay revealed that all the three GmMYBs could bind to cis-elements TAT AAC GGT TTT TT and CCG GAA AAA AGG AT, but with different affinity, and GmMYB92 could also bind to TCT CAC CTA CC. The transgenic Arabidopsis plants overexpressing GmMYB 76 or GmMYB177 showed better performance than the GmMYB92-transgenic plants in salt and freezing tolerance. However, these transgenic plants exhibited reduced sensitivity to ABA treatment at germination stage in comparison with the wild-type plants. The three GmMYB genes differentially affected a subset of stress-responsive genes in addition to their regulation of a common subset of stress-responsive genes. These resuits indicate that the three GmMYB genes may play differential roles in stress tolerance, possibly through regulation of stress-responsive genes.展开更多
Plasma membrane intrinsic proteins （PIPs） are a subfamily ofaquaporins that enable fast and controlled translocation of water across the membrane. In this study, we systematically identified and cloned ten PIP genes...Plasma membrane intrinsic proteins （PIPs） are a subfamily ofaquaporins that enable fast and controlled translocation of water across the membrane. In this study, we systematically identified and cloned ten PIP genes from rice. Based on the similarity of the amino acid sequences they encoded, these rice PIP genes were classified into two groups and designated as OsPIP1-1 to OsPIP1-3 and OsPIP2-1 to OsPIP2-7 following the nomenclature of PIP genes in maize. Quantitative RT-PCR analysis identified three root-specific and one leaf-specific OsPIP genes. Furthermore, the expression profile of each OsPIP gene in response to salt, drought and ABA treatment was examined in detail. Analysis on transgenic plants over-expressing of either OsPIP1 （OsPIP1-1） or OsPIP2 （OsPIP2-2） in wild-type Arabidopsis, showed enhanced tolerance to salt （100 mM of NaCl） and drought （200 mM ofmannitol）, but not to salt treatment of higher concentration （150 mM of NaCl）. Taken together, these data suggest a distinct role of each OsPIP gene in response to different stresses, and should add a new layer to the understanding of the physiological function of rice PIP genes.展开更多
1-Deoxy-D-xylulose-5-phosphate reductoisomerase （DXR） is an important enzyme involved in the 2-C-methyi-D- erythritol-4-phosphate （MEP） pathway which provides the basic five-carbon units for isoprenoid biosynthesi...1-Deoxy-D-xylulose-5-phosphate reductoisomerase （DXR） is an important enzyme involved in the 2-C-methyi-D- erythritol-4-phosphate （MEP） pathway which provides the basic five-carbon units for isoprenoid biosynthesis. To investigate the role of the MEP pathway in plant development and metabolism, we carried out detailed analyses on a dxr mutant （GK_215C01） and two DXR transgenic co-suppression fines, OX-DXR-L2 and OX-DXR-L7. We found that the dxr mutant was albino and dwarf. It never bolted, had significantly reduced number of trichomes and most of the stomata could not close normally in the leaves. The two co-suppression lines produced more yellow inflorescences and albino sepals with no trichomes. The transcription levels of genes involved in tricbome initiation were found to be strongly affected, including GLABRA1, TRANSPARENT TESTA GLABROUS 1, TRIPTYCHON and SPINDLY, expression of which is regulated by gibberellic acids （GAs）. Exogenous application of GA3 could partially rescue the dwarf phenotype and the trichome initiation of dxr, whereas exogenous application of abscisic acid （ABA） could rescue the stomata closure defect, suggesting that lower levels of both GA and ABA contribute to the phenotype in the dxr mutants. We further found that genes involved in the biosynthetic pathways of GA and ABA were coordinately regulated. These results indicate that disruption of the plastidial MEP pathway leads to biosynthetic deficiency of photosynthetic pigments, GAs and ABA, and thus the developmental abnormalities, and that the flux from the cytoplasmic mevalonate pathway is not sufficient to rescue the deficiency caused by the blockage of the plastidial MEP pathway. These results reveal a critical role for the MEP biosynthetic pathway in controlling the biosynthesis of isoprenoids.展开更多
Cytokinin is a critical growth regulator for various aspects of plant growth and development. In Arabidopsis, cytokinin signaling is mediated by a two-component system-based phosphorelay that transmits a signal from t...Cytokinin is a critical growth regulator for various aspects of plant growth and development. In Arabidopsis, cytokinin signaling is mediated by a two-component system-based phosphorelay that transmits a signal from the receptors, through histidine phosphotransfer proteins, to the downstream response regulators （ARRs）. Of these ARRs, type-A ARR genes, whose transcription can be rapidly induced by cytokinin, act as negative regulators of eytokinin signaling. However, because of functional redundancy, the function of type-A ARR genes in plant growth and development is not well understood by analyzing loss-of-function mutants. In this study, we performed a comparative functional study on all ten type-A ARR genes by analyzing transgenic plants overexpressing these ARR genes fused to a MYC epitope tag. Overexpression of ARR genes results in a variety of cytokinin-associated phenotypes. Notably, overexpression of different ARR transgenes causes diverse phenotypes, even between phylogenetically closely-related gene pairs, such as within the ARR3-ARR4 and ARR5-ARR6 pairs. We found that the accumulation of a subset of ARR proteins （ARR3, ARR5, ARR7, ARR16 and ARR17; possibly ARR8 and ARR15） is increased by MG132, a specific proteasomal inhibitor, indicating that stability of these proteins is regulated by proteasomal degradation. Moreover, similar to that of previously characterized ARR5, ARR6 and ARR7, stability of ARR16 and ARR17, possibly including ARR8 and ARR15, is regulated by cytokinin. These results suggest that type-A ARR proteins are regulated by a combinatorial mechanism involving both the cytokinin and proteasome pathways, thereby executing distinctive functions in plant growth and development.展开更多
Metabolism of S-nitrosoglutathione （GSNO）, a major biologically active nitric oxide （NO） species, is catalyzed by the evolutionally conserved GSNO reductase （GSNOR）. Previous studies showed that the Arabidopsis ...Metabolism of S-nitrosoglutathione （GSNO）, a major biologically active nitric oxide （NO） species, is catalyzed by the evolutionally conserved GSNO reductase （GSNOR）. Previous studies showed that the Arabidopsis GSNOR1/ HOT5 gene regulates salicylic acid signaling and thermotolerance by modulating the intracellular S-nitrosothiol level. Here, we report the characterization of the Arabidopsisparaquat resistant2-1 （par2-1） mutant that shows an anti-cell death phenotype. The production of superoxide in par2-1 is comparable to that of wild-type plants when treated by paraquat （1,1＇-dimethyl-4,4＇-bipyridinium dichloride）, suggesting that PAR2 acts downstream of superoxide to regulate cell death. PAR2, identified by positional cloning, is shown to be identical to GSNOR1/HOT5. The par2-1 mutant carries a missense mutation in a highly conserved glycine, which renders the mutant protein unstable. Compared to wild type, par2-1 mutant has a higher NO level, as revealed by staining with 4,5-diaminofluorescein diacetate. Consistent with this result, wild-type plants treated with an NO donor display resistance to paraquat. Interestingly, the GSNOR1/HOT5/PAR2 protein level, other than its steady-state mRNA level, is induced by paraquat, but is reduced by NO donors. Taken together, these results suggest that GSNOR1/HOT5/PAR2 plays an important role in regulating cell death in plant cells through modulating intracellular NO level.展开更多
Carotenoids play an important role in many physiological processes in plants and the phytoene desaturase gene （PDS3） encodes one of the important enzymes in the carotenoid biosynthesis pathway. Here we report the id...Carotenoids play an important role in many physiological processes in plants and the phytoene desaturase gene （PDS3） encodes one of the important enzymes in the carotenoid biosynthesis pathway. Here we report the identification and analysis of a T-DNA insertion mutant of PDS3 gene. Functional complementation confirmed that both the albino and dwarfphenotypes ofthepds3 mutant resulted from functional disruption of the PDS3 gene. Chloroplast development was arrested at the proplastid stage in thepds3 mutant. Further analysis showed that high level ofphytoene was accumulated in the pds3 mutant. Addition of exogenous GA3 could partially rescue the dwarf phenotype, suggesting that the dwarf phenotype ofthepds3 mutant might be due to GA deficiency. Microarray and RT-PCR analysis showed that disrupting PDS3 gene resulted in gene expression changes involved in at least 20 metabolic pathways, including the inhibition of many genes in carotenoid, chlorophyll, and GA biosynthesis pathways. Our data suggest that the accumulated phytoene in the pds3 mutant might play an important role in certain negative feedbacks to affect gene expression of diverse cellular pathways.展开更多
MYB proteins play important roles in eukaryotic organisms. In plants, the R1R2R3-type MYB proteins function in cell cycle control. However, whether the R2R3-type MYB protein is also involved in the cell division proce...MYB proteins play important roles in eukaryotic organisms. In plants, the R1R2R3-type MYB proteins function in cell cycle control. However, whether the R2R3-type MYB protein is also involved in the cell division process remains unknown. Here, we report that an R2R3-type transcription factor gene, AtMYB59, is involved in the regulation of cell cycle progression and root growth. The AtMYB59 protein is localized in the nuclei of onion epidermal cells and has transactivation activity. Expression of AtMYB59 in yeast cells suppresses cell proliferation, and the transfor- mants have more nuclei and higher anenpioid DNA content with longer cells. Mutation in the conserved domain of AtMYB59 abolishes its effects on yeast cell growth. In synchronized Arabidopsis cell suspensions, the AtMYB59 gene is specifically expressed in the S phase during cell cycle progression. Expression and promoter-GUS analysis reveals that the AtMYB59 gene is abundantly expressed in roots. Transgenic plants overexpressing AtMYB59 have shorter roots compared with wild-type plants （Arabidopsis accession Col-0）, and around half of the mitotic cells in root tips are at metaphase. Conversely, the null mutant myb59-1 has longer roots and fewer mitotic cells at metaphase than Col, suggesting that AtMYB59 may inhibit root growth by extending the metaphase of mitotic cells. AtMYB59 regulates many downstream genes, including the CYCB1;1 gene, probably through binding to MYB-responsive elements. These results support a role forAtMYB59 in cell cycle regulation and plant root growth.展开更多
Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and ch...Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 （spcl-1） and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative ζ-carotene desaturase （ZDS） in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC 1/ZDS were substantially reduced in spc1-1, suggesting that SPC 1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1. 1, Lhcbl. 4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development.展开更多
Lipoxygenase （LOX, EC1.13.11.12） is a key enzyme during the degradation of lipids in animals and even plants, and also the first key enzyme responsible for the biosynthesis of jasmonate. To purify and characterize t...Lipoxygenase （LOX, EC1.13.11.12） is a key enzyme during the degradation of lipids in animals and even plants, and also the first key enzyme responsible for the biosynthesis of jasmonate. To purify and characterize the OsLOX1 gene from rice seeds, the entire coding region of the OsLOX1 gene was inserted into an expression vector pET30a（＋） and transformed into Escherichia coil BL21 （DE3）. Expression of the fusion protein was successfully induced by isopropyl-β-D- thiogalactopyranoside （IPTG） and the purified recombinant protein was obtained by His.Bind Kits. Further assay showed that the purified recombinant protein exhibited the LOX activity. The optimum pH was 4.8 （acetate buffer） and the optimum temperature was 30℃ for the above enzyme. Thus, the recombinant might confer an available usage for the synthesis of jasmonate in vitro, and also provides a possibility for elucidating the inter-relationship between the primary structure of the plant seed lipoxygenase protein and its physiological functions.展开更多
Complex I （the NADH：ubiquinone oxidoreductase） of the mitochondrial respiratory chain is a complicated, multi-subunit, membrane- bound assembly and contains more than 40 different proteins in higher plants. In this...Complex I （the NADH：ubiquinone oxidoreductase） of the mitochondrial respiratory chain is a complicated, multi-subunit, membrane- bound assembly and contains more than 40 different proteins in higher plants. In this paper, we characterize the Arabidopsis homologue （designated as AtCIB22） of the B22 subunit of eukaryotic mitochondriai Complex I. AtCIB22 is a single-copy gene and is highly con- served throughout eukaryotes. AtCIB22 protein is located in mitochondria and the AtC1B22 gene is widely expressed in different tissues. Mutant Arabidopsis plants with a disrupted AtC1B22 gene display pleiotropic phenotypes including shorter roots, smaller plants and de- layed flowering. Stress analysis indicates that the AtC1B22 mutants＇ seed germination and early seedling growth are severely inhibited by sucrose deprivation stress but more tolerant to ethanol stress. Molecular analysis reveals that in moderate knockdown AtCIB22 mutants, genes including cell redox proteins and stress related proteins are significantly up-regulated, and that in severe knockdown AtCIB22 mu- tants, the alternative respiratory pathways including NDA1, NDB2, AOXla and AtPUMP1 are remarkably elevated. These data demon- strate that AtCIB22 is essential for plant development and mitochondrial electron transport chains in Arabidopsis. Our findings also en- hance our understanding about the physiological role of Complex I in plants.展开更多
Lipoxygenase 3 (LOX3) is a major component of the LOX isozymes in mature rice seeds. To investigate the role of LOX3 gene under stresses, a plant expression vector containing antisense cDNA of LOX3 was constructed. Ri...Lipoxygenase 3 (LOX3) is a major component of the LOX isozymes in mature rice seeds. To investigate the role of LOX3 gene under stresses, a plant expression vector containing antisense cDNA of LOX3 was constructed. Rice varieties Wuyunjing 7 and Kasalath were transformed by the Agrobacterium-mediated method and transgenic rice plants were generated. PCR and Southern blot results showed that the antisense LOX3 gene was integrated into the rice genome. Analyses of embryo LOX3 deletion and semi-quantitative RT-PCR confirmed the antisense suppression of LOX3 gene in transgenic plants. The T2 antisense plants of LOX3 were sensitive to drought stress, rice blast and bacterial blight compared with non-transgenic plants. These results suggest that the LOX3 gene might function in response to stresses.展开更多
基金supported by the Guizhou Provincial Basic Research Program(Natural Science)[(2024)648]the Program of China National Tobacco Corporation(110202101032(JY-09),110202201003(JY-03))the Program of Guizhou Branch of China National Tobacco Corporation(2023XM02,2021XM05,2022XM05,2024XM01).
文摘Nicotiana tabacum(2n=4x=48),an economically important non-food crop and a model plant for genetic studies,faces challenges in efficient genotyping of novel germplasm.To address this,we developed the Ta-LD-SC,a 20K SNP Affymetrix Axiom array,based on resequencing data from 150 tobacco accessions.A total of 20,213 unique SNPs were carefully selected,achieving coverage of over 90%of the tobacco genome(Nitab4.5 and NtaSR1)with a uniform probe distribution,limiting density to no more than 5 SNPs per 200 kb.The array underwent extensive validation using 866 tobacco accessions(NP panel)and 288 F2 individuals from a cross between K326 and Oxford 26(GP panel).Performance metrics demonstrated its robustness,with high SNP call rates(93.6%-99.8%),a low technical error rate(<1%),and a superior PolyHighResolution SNP rate(79.79%)compared to other crop SNP arrays.Population structure analysis of the NP panel revealed two major introductions of foreign germplasm that have significantly influenced the genetic diversity of Chinese tobacco resources.Using the array,a genome-wide association study(GWAS)identified 62 genes linked to eight agronomic traits,and a high-density genetic map encompassing 4553 SNPs across 6606.08 cM was constructed.The Ta-LD-SC array provides a valuable tool for rapid,high-quality genotyping offering supporting marker annotations that may benefit genetic research and breeding of tobacco.
文摘Human-derived tumor models are essential for preclinical development of new anti-cancer drug entities.Generating animal models bearing tumors of human origin,such as patient-derived or cell line-derived xenograft tumors,is dependent on immuno-deficient strains.Tumor-bearing immunodeficient mice are susceptible to develop-ing unwanted disorders primarily irrelevant to the tumor nature;and if get involved with such disorders,reliability of the study results will be undermined,inevitably con-founding the research in general.Therefore,a rigorous health surveillance and clinical monitoring system,along with the establishment of a strictly controlled barrier facility to maintain a pathogen-free state,are mandatory.Even if all pathogen control and biosafety measures are followed,there are various noninfectious disorders capable of causing tissue and multiorgan damage in immunodeficient animals.Therefore,the re-searchers should be aware of sentinel signs to carefully monitor and impartially report them.This review discusses clinical signs of common unwanted disorders in experi-mental immunodeficient mice,and how to examine and report them.
基金supported by the Guizhou Provincial Basic Research Program(Natural Science)[(2024)648]the Program of China National Tobacco Corporation(110202101032(JY-09),110202201003(JY-03))+2 种基金the Program of Guizhou Branch of China National Tobacco Corporation(2023XM02,2022XM05 and 2024XM01)the Qiankehe Platform Project(ZSYS[2025]028)the Program of China National Tobacco Corporation(110202102034).
文摘Tobacco(Nicotiana tabacum,2n=48)is a key non-food economic crop,yet its stress response and gene regulatory mechanisms remain poorly understood.By analyzing 603 transcriptome datasets,this study identified 1405 tissue-specific genes,revealing tissue-specific synthesis of terpenoids and other ecologically important secondary metabolites in sepals and other tissues.Comparative stress-response analysis highlighted distinct gene expression patterns in leaves and roots under biotic and abiotic stresses.Additionally,28,396 expression quantitative trait loci(eQTLs)were mapped in leaves,offering valuable genetic regulatory markers.These findings provide crucial insights into tobacco’s gene expression characteristics and their functional implications,serving as a foundation for future research.
基金Acknowledgments This work was supported by the National Natural Science Foundation of China （30490254, 30671316）, the National Basic Research Program of China （2006CB100102）, and the Hi-Tech Research and Development Program of China （2006AA10Z113, 2006AA10A111）.
文摘MYB-type transcription factors contain the conserved MYB DNA-binding domain of approximately 50 amino acids and are involved in the regulation of many aspects of plant growth, development, metabolism and stress responses. From soybean plants, we identified 156 GmMYB genes using our previously obtained 206 MYB unigenes, and 48 were found to have full-length open-reading frames. Expressions of all these identified genes were examined, and we found that expressions of 43 genes were changed upon treatment with ABA, salt, drought and/or cold stress. Three GmMYB genes, GmMYB76, GmMYB92 and GmMYB177, were chosen for further analysis. Using the yeast assay system, GmMYB76 and GmMYB92 were found to have transactivation activity and can form homodimers. GmMYB177 did not appear to have transactivation activity but can form heterodimers with GmMYB76. Yeast onehybrid assay revealed that all the three GmMYBs could bind to cis-elements TAT AAC GGT TTT TT and CCG GAA AAA AGG AT, but with different affinity, and GmMYB92 could also bind to TCT CAC CTA CC. The transgenic Arabidopsis plants overexpressing GmMYB 76 or GmMYB177 showed better performance than the GmMYB92-transgenic plants in salt and freezing tolerance. However, these transgenic plants exhibited reduced sensitivity to ABA treatment at germination stage in comparison with the wild-type plants. The three GmMYB genes differentially affected a subset of stress-responsive genes in addition to their regulation of a common subset of stress-responsive genes. These resuits indicate that the three GmMYB genes may play differential roles in stress tolerance, possibly through regulation of stress-responsive genes.
文摘Plasma membrane intrinsic proteins （PIPs） are a subfamily ofaquaporins that enable fast and controlled translocation of water across the membrane. In this study, we systematically identified and cloned ten PIP genes from rice. Based on the similarity of the amino acid sequences they encoded, these rice PIP genes were classified into two groups and designated as OsPIP1-1 to OsPIP1-3 and OsPIP2-1 to OsPIP2-7 following the nomenclature of PIP genes in maize. Quantitative RT-PCR analysis identified three root-specific and one leaf-specific OsPIP genes. Furthermore, the expression profile of each OsPIP gene in response to salt, drought and ABA treatment was examined in detail. Analysis on transgenic plants over-expressing of either OsPIP1 （OsPIP1-1） or OsPIP2 （OsPIP2-2） in wild-type Arabidopsis, showed enhanced tolerance to salt （100 mM of NaCl） and drought （200 mM ofmannitol）, but not to salt treatment of higher concentration （150 mM of NaCl）. Taken together, these data suggest a distinct role of each OsPIP gene in response to different stresses, and should add a new layer to the understanding of the physiological function of rice PIP genes.
基金Acknowledgments This work was supported by the National Natural Science Foundation of China （NSFC Grant 90717003 to L-J Qu）.
文摘1-Deoxy-D-xylulose-5-phosphate reductoisomerase （DXR） is an important enzyme involved in the 2-C-methyi-D- erythritol-4-phosphate （MEP） pathway which provides the basic five-carbon units for isoprenoid biosynthesis. To investigate the role of the MEP pathway in plant development and metabolism, we carried out detailed analyses on a dxr mutant （GK_215C01） and two DXR transgenic co-suppression fines, OX-DXR-L2 and OX-DXR-L7. We found that the dxr mutant was albino and dwarf. It never bolted, had significantly reduced number of trichomes and most of the stomata could not close normally in the leaves. The two co-suppression lines produced more yellow inflorescences and albino sepals with no trichomes. The transcription levels of genes involved in tricbome initiation were found to be strongly affected, including GLABRA1, TRANSPARENT TESTA GLABROUS 1, TRIPTYCHON and SPINDLY, expression of which is regulated by gibberellic acids （GAs）. Exogenous application of GA3 could partially rescue the dwarf phenotype and the trichome initiation of dxr, whereas exogenous application of abscisic acid （ABA） could rescue the stomata closure defect, suggesting that lower levels of both GA and ABA contribute to the phenotype in the dxr mutants. We further found that genes involved in the biosynthetic pathways of GA and ABA were coordinately regulated. These results indicate that disruption of the plastidial MEP pathway leads to biosynthetic deficiency of photosynthetic pigments, GAs and ABA, and thus the developmental abnormalities, and that the flux from the cytoplasmic mevalonate pathway is not sufficient to rescue the deficiency caused by the blockage of the plastidial MEP pathway. These results reveal a critical role for the MEP biosynthetic pathway in controlling the biosynthesis of isoprenoids.
文摘Cytokinin is a critical growth regulator for various aspects of plant growth and development. In Arabidopsis, cytokinin signaling is mediated by a two-component system-based phosphorelay that transmits a signal from the receptors, through histidine phosphotransfer proteins, to the downstream response regulators （ARRs）. Of these ARRs, type-A ARR genes, whose transcription can be rapidly induced by cytokinin, act as negative regulators of eytokinin signaling. However, because of functional redundancy, the function of type-A ARR genes in plant growth and development is not well understood by analyzing loss-of-function mutants. In this study, we performed a comparative functional study on all ten type-A ARR genes by analyzing transgenic plants overexpressing these ARR genes fused to a MYC epitope tag. Overexpression of ARR genes results in a variety of cytokinin-associated phenotypes. Notably, overexpression of different ARR transgenes causes diverse phenotypes, even between phylogenetically closely-related gene pairs, such as within the ARR3-ARR4 and ARR5-ARR6 pairs. We found that the accumulation of a subset of ARR proteins （ARR3, ARR5, ARR7, ARR16 and ARR17; possibly ARR8 and ARR15） is increased by MG132, a specific proteasomal inhibitor, indicating that stability of these proteins is regulated by proteasomal degradation. Moreover, similar to that of previously characterized ARR5, ARR6 and ARR7, stability of ARR16 and ARR17, possibly including ARR8 and ARR15, is regulated by cytokinin. These results suggest that type-A ARR proteins are regulated by a combinatorial mechanism involving both the cytokinin and proteasome pathways, thereby executing distinctive functions in plant growth and development.
基金We thank Dr Gary Loake （University of Edinburgh, UK） for providing gsnor1-3 seeds. We are grateful to Drs Chuanyou Li, Shuhua Yang and Yiqin Wang for critically reading the manuscript. This study was supported by grants from the National Natural Science Foundation of China （30330360）, the Ministry of Science and Technology of China （2006AA 10A 112） and the Chinese Academy of Sciences （KSCX2-YW-N-015）.
文摘Metabolism of S-nitrosoglutathione （GSNO）, a major biologically active nitric oxide （NO） species, is catalyzed by the evolutionally conserved GSNO reductase （GSNOR）. Previous studies showed that the Arabidopsis GSNOR1/ HOT5 gene regulates salicylic acid signaling and thermotolerance by modulating the intracellular S-nitrosothiol level. Here, we report the characterization of the Arabidopsisparaquat resistant2-1 （par2-1） mutant that shows an anti-cell death phenotype. The production of superoxide in par2-1 is comparable to that of wild-type plants when treated by paraquat （1,1＇-dimethyl-4,4＇-bipyridinium dichloride）, suggesting that PAR2 acts downstream of superoxide to regulate cell death. PAR2, identified by positional cloning, is shown to be identical to GSNOR1/HOT5. The par2-1 mutant carries a missense mutation in a highly conserved glycine, which renders the mutant protein unstable. Compared to wild type, par2-1 mutant has a higher NO level, as revealed by staining with 4,5-diaminofluorescein diacetate. Consistent with this result, wild-type plants treated with an NO donor display resistance to paraquat. Interestingly, the GSNOR1/HOT5/PAR2 protein level, other than its steady-state mRNA level, is induced by paraquat, but is reduced by NO donors. Taken together, these results suggest that GSNOR1/HOT5/PAR2 plays an important role in regulating cell death in plant cells through modulating intracellular NO level.
基金the National Natural Science Foundation of China （Grant No. 30470172）.
文摘Carotenoids play an important role in many physiological processes in plants and the phytoene desaturase gene （PDS3） encodes one of the important enzymes in the carotenoid biosynthesis pathway. Here we report the identification and analysis of a T-DNA insertion mutant of PDS3 gene. Functional complementation confirmed that both the albino and dwarfphenotypes ofthepds3 mutant resulted from functional disruption of the PDS3 gene. Chloroplast development was arrested at the proplastid stage in thepds3 mutant. Further analysis showed that high level ofphytoene was accumulated in the pds3 mutant. Addition of exogenous GA3 could partially rescue the dwarf phenotype, suggesting that the dwarf phenotype ofthepds3 mutant might be due to GA deficiency. Microarray and RT-PCR analysis showed that disrupting PDS3 gene resulted in gene expression changes involved in at least 20 metabolic pathways, including the inhibition of many genes in carotenoid, chlorophyll, and GA biosynthesis pathways. Our data suggest that the accumulated phytoene in the pds3 mutant might play an important role in certain negative feedbacks to affect gene expression of diverse cellular pathways.
文摘MYB proteins play important roles in eukaryotic organisms. In plants, the R1R2R3-type MYB proteins function in cell cycle control. However, whether the R2R3-type MYB protein is also involved in the cell division process remains unknown. Here, we report that an R2R3-type transcription factor gene, AtMYB59, is involved in the regulation of cell cycle progression and root growth. The AtMYB59 protein is localized in the nuclei of onion epidermal cells and has transactivation activity. Expression of AtMYB59 in yeast cells suppresses cell proliferation, and the transfor- mants have more nuclei and higher anenpioid DNA content with longer cells. Mutation in the conserved domain of AtMYB59 abolishes its effects on yeast cell growth. In synchronized Arabidopsis cell suspensions, the AtMYB59 gene is specifically expressed in the S phase during cell cycle progression. Expression and promoter-GUS analysis reveals that the AtMYB59 gene is abundantly expressed in roots. Transgenic plants overexpressing AtMYB59 have shorter roots compared with wild-type plants （Arabidopsis accession Col-0）, and around half of the mitotic cells in root tips are at metaphase. Conversely, the null mutant myb59-1 has longer roots and fewer mitotic cells at metaphase than Col, suggesting that AtMYB59 may inhibit root growth by extending the metaphase of mitotic cells. AtMYB59 regulates many downstream genes, including the CYCB1;1 gene, probably through binding to MYB-responsive elements. These results support a role forAtMYB59 in cell cycle regulation and plant root growth.
基金grants from National Natural Science Foundation of China （Grant Nos. 30330360, 30125025 , 30221002） Chinese Academy of Sciences （Grant No. KSCX2- YW-N-015）
文摘Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 （spcl-1） and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative ζ-carotene desaturase （ZDS） in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC 1/ZDS were substantially reduced in spc1-1, suggesting that SPC 1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1. 1, Lhcbl. 4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development.
基金grants from the National Basic Research Program of China (Grant No. 2004CB2117204)the National High-tech Research and Development Program of China (Grant No. 2006AA100101)+1 种基金the National Program of Science Technology and Tackle Key Problem of Chinathe Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) of China
文摘Lipoxygenase （LOX, EC1.13.11.12） is a key enzyme during the degradation of lipids in animals and even plants, and also the first key enzyme responsible for the biosynthesis of jasmonate. To purify and characterize the OsLOX1 gene from rice seeds, the entire coding region of the OsLOX1 gene was inserted into an expression vector pET30a（＋） and transformed into Escherichia coil BL21 （DE3）. Expression of the fusion protein was successfully induced by isopropyl-β-D- thiogalactopyranoside （IPTG） and the purified recombinant protein was obtained by His.Bind Kits. Further assay showed that the purified recombinant protein exhibited the LOX activity. The optimum pH was 4.8 （acetate buffer） and the optimum temperature was 30℃ for the above enzyme. Thus, the recombinant might confer an available usage for the synthesis of jasmonate in vitro, and also provides a possibility for elucidating the inter-relationship between the primary structure of the plant seed lipoxygenase protein and its physiological functions.
基金supported by the National Basic Research Program of China (No. 2009CB941503)
文摘Complex I （the NADH：ubiquinone oxidoreductase） of the mitochondrial respiratory chain is a complicated, multi-subunit, membrane- bound assembly and contains more than 40 different proteins in higher plants. In this paper, we characterize the Arabidopsis homologue （designated as AtCIB22） of the B22 subunit of eukaryotic mitochondriai Complex I. AtCIB22 is a single-copy gene and is highly con- served throughout eukaryotes. AtCIB22 protein is located in mitochondria and the AtC1B22 gene is widely expressed in different tissues. Mutant Arabidopsis plants with a disrupted AtC1B22 gene display pleiotropic phenotypes including shorter roots, smaller plants and de- layed flowering. Stress analysis indicates that the AtC1B22 mutants＇ seed germination and early seedling growth are severely inhibited by sucrose deprivation stress but more tolerant to ethanol stress. Molecular analysis reveals that in moderate knockdown AtCIB22 mutants, genes including cell redox proteins and stress related proteins are significantly up-regulated, and that in severe knockdown AtCIB22 mu- tants, the alternative respiratory pathways including NDA1, NDB2, AOXla and AtPUMP1 are remarkably elevated. These data demon- strate that AtCIB22 is essential for plant development and mitochondrial electron transport chains in Arabidopsis. Our findings also en- hance our understanding about the physiological role of Complex I in plants.
基金supported by the grants from the National Basic Research Program of China (Grant No. 2004CB117204 and No. 2006CB100200).
文摘Lipoxygenase 3 (LOX3) is a major component of the LOX isozymes in mature rice seeds. To investigate the role of LOX3 gene under stresses, a plant expression vector containing antisense cDNA of LOX3 was constructed. Rice varieties Wuyunjing 7 and Kasalath were transformed by the Agrobacterium-mediated method and transgenic rice plants were generated. PCR and Southern blot results showed that the antisense LOX3 gene was integrated into the rice genome. Analyses of embryo LOX3 deletion and semi-quantitative RT-PCR confirmed the antisense suppression of LOX3 gene in transgenic plants. The T2 antisense plants of LOX3 were sensitive to drought stress, rice blast and bacterial blight compared with non-transgenic plants. These results suggest that the LOX3 gene might function in response to stresses.
