The revegetation of mined areas poses a great challenge to the iron ore mining industry.The initial recovery process in degraded areas might rely on the use of Fe-resistant grasses.Tropical grasses, such as Paspalum d...The revegetation of mined areas poses a great challenge to the iron ore mining industry.The initial recovery process in degraded areas might rely on the use of Fe-resistant grasses.Tropical grasses, such as Paspalum densum and Echinochloa crus-galli, show different resistance strategies to iron toxicity; however, these mechanisms are poorly understood.The Fe-resistance mechanisms and direct iron toxicity as a function of root apex removal were investigated. To achieve this purpose, both grass species were grown for up to 480 hr in a nutrient solution containing 0.019 or 7 mmol/L Fe-EDTA after the root apices had been removed or maintained. Cultivation in the presence of excess iron-induced leaf bronzing and the formation of iron plaque on the root surfaces of both grass species, but was more significant on those plants whose root apex had been removed. Iron accumulation was higher in the roots, but reached phytotoxic levels in the aerial parts as well. It did not hinder the biosynthesis of chloroplastidic pigments. No significant changes in gas exchange and chlorophyll a fluorescence occurred in either grass when their roots were kept intact; the contrary was true for plants with excised root apices. In both studied grasses, the root apoplastic barriers had an important function in the restriction of iron translocation from the root to the aerial plant parts, especially in E. crus-galli. Root apex removal negatively influenced the iron toxicity resistance mechanisms(tolerance in P. densum and avoidance in E. crus-galli).展开更多
During the attack of a pathogen, a variety of defense-associated proteins are released by the host plant in the apoplast to impede the perceived attack. This study utilized the mass spectrometry(LC-MS/MS) and label-fr...During the attack of a pathogen, a variety of defense-associated proteins are released by the host plant in the apoplast to impede the perceived attack. This study utilized the mass spectrometry(LC-MS/MS) and label-free quantification method to analyze the apoplastic fluid(APF) from maize stalk and identified the proteins responsive to the Fusarium verticillioides infection. We have identified 742 proteins, and among these, 119 proteins were differentially accumulated(DAPs), i.e., 35 up-regulated, 18 down-regulated, and 66 proteins were only induced by the pathogen infection. The differentially accumulated proteins were analyzed for their Gene Ontology(GO) and Kyoto Encyclopedia of Gene and Genomes(KEGG) pathway enrichment. The highly enriched Biological Process(BP) term was the L-serine biosynthesis process, whereas the most enriched Molecular Function(MF) term was the cysteine-type endopeptidase inhibitor activity. It was also found that the pathways related to the biosynthesis of amino acid, biosynthesis of secondary metabolites, protein processing in the endoplasmic reticulum, and carbohydrate metabolic pathways were significantly enriched. Moreover, 61 out of 119 differentially accumulated proteins were predicted as secretory proteins. The secretory pathways analysis showed that a greater number of proteins were secreted through the conventional secretion system compared to the unconventional secretion system. The identified secreted proteins were related to a variety of pathways in defense responses including cell redox homeostasis, cell wall modification, signal transduction, carbohydrate metabolism, binding proteins(metal ion binding, RNA binding and heme-binding), maintenance and stabilization of other proteins, indicating a complex response from the plant to the fungal infection. Our data suggested that a number of host proteins belonging to various pathways have been modulated in the apoplastic region.展开更多
Translucency is a recurring problem for pineapple industry. Translucent fruit contained more sucrose, glucose and fructose in apoplast than those in apoplast of normal fruit. There were more liquid in intercellular sp...Translucency is a recurring problem for pineapple industry. Translucent fruit contained more sucrose, glucose and fructose in apoplast than those in apoplast of normal fruit. There were more liquid in intercellular space of translucent fruit than that of normal flesh. The contents of alcohol and ethylene in translucent fruit were higher than those in normal fruit. Translucent fruit contained less calcium than normal fruit. Electrolyte leakage of translucent flesh was more than that of normal flesh. There were 205 proteins of which the expressions in translucent flesh were higher than those in normal flesh. Calcium-ions-binding protein EF-hand domain-containing protein, ethylene-synthesizing enzyme 1-aminpcyclopropane-1-carboxylate oxidase, ROS-producing protein universal stress protein A-like protein were the top three proteins of which the expressions in translucent flesh were higher than those in normal fruit. When much sugar was transferred into fruit pulp and accumulated in intercellular space, water will be absorbed from cells around and translucence formed. The accumulation of sugar and liquid in apoplast were due to that cell wall and membrane were degraded, which was from being attacked by ROS. There might be more and larger pores in cell wall and membranes of translucent flesh. These data played foundations for researching methods for controlling pineapple translucency.展开更多
Cadmium (Cd) is a toxic metal with high mobility from soil and known translocation into plants (Song et al., 2015).Because the main source of human exposure to Cd is from food consumption, there has been increased res...Cadmium (Cd) is a toxic metal with high mobility from soil and known translocation into plants (Song et al., 2015).Because the main source of human exposure to Cd is from food consumption, there has been increased research examining Cd uptake in agricultural plants (Li et al., 2014;Rizwan et al., 2016;Song et al., 2015).展开更多
Cotton(Gossypium spp.),a major global fiber crop,serves as an ideal model for research on plant cell development.According to the acid growth theory,plasma membrane(PM)H+-ATPase(HA)regulates cell wall acidification,th...Cotton(Gossypium spp.),a major global fiber crop,serves as an ideal model for research on plant cell development.According to the acid growth theory,plasma membrane(PM)H+-ATPase(HA)regulates cell wall acidification,thereby promoting cell elongation and providing a mechanistic framework for understanding this process.However,its application to cotton fiber cells has remained limited.In this study,the acid growth theory was utilized to investigate the elongation of cotton fibers.Comparative genomics revealed an expansion in the number of gene family members associated with acid growth,including PM HA and transmembrane kinase(TMK)genes,in tetraploid cotton.Transcriptomic analysis highlighted the co-expression of these genes during fiber elongation.Functional validation using chemical modulators and CRISPR-Cas9-mediated knockout mutants demonstrated that PM HA activity is essential for apoplastic acidification and fiber elongation.Specifically,GhHA4A and GhTMK3A were identified as potential regulators of proton extrusion;their loss-of-function mutants exhibited elevated apoplastic pH and reduced fiber length.Furthermore,the results indicated that an optimal apoplastic pH is required for fiber elongation,whereas insufficient or excessive acidification inhibits growth.Spatiotemporal modulation of PM HA activity in transgenic cotton plants enhanced fiber length without affecting other fiber-and seed-related traits,demonstrating the potential of the acid growth theory for fiber improvement.These findings not only extend the acid growth theory beyond conventional model systems but also provide an innovative strategy for increasing fiber length in cotton breeding.展开更多
The pH plays a key role in the growth and colonization of plant pathogens as well as the onset and progression of the symptoms they cause within the host.Plants may quickly alter their apoplastic pH(pH_(apo))to protec...The pH plays a key role in the growth and colonization of plant pathogens as well as the onset and progression of the symptoms they cause within the host.Plants may quickly alter their apoplastic pH(pH_(apo))to protect themselves against infection.However,pathogens can also alter the pH of their ambient environment to promote their own growth.Citrus canker is a serious plant disease caused by Xanthomonas citri subsp.citri(Xcc).This Gram-negative aerobic rod is usually cultured in LuriaeBertani(LB)medium at pH 7.However,little is known about the changes in pH both in this medium as Xcc grows and in the leaf apoplast in response to Xcc infection and colonization.Moreover,the differences in leaf apoplast pH between Xcc-resistant and Xcc-susceptible citrus genotypes are also unknown.Here,Xcc grew well in liquid LB medium at initial pH 6e8 and the pathogen altered the medium pH to 6.8±0.4.Xcc growth declined at pH 5 and was zero at pH 3,4,9,and 10.In susceptible sweet orange infected with Xcc inoculum,canker symptoms were inhibited at pH 3,4,and 10 but did not differ in the range of pH 5e9.As expected,canker symptoms were absent at all inoculum pH in the resistant Citron C-05.For both genotypes,Xcc only grew well in the leaves exposed to pH 5e8 inoculums.At four days post-inoculation(4 dpi),the foliar pH_(apo) of resistant Citron C-05 had rapidly declined from 5.6 to 4.4.At 2 dpi,the pH_(apo) of susceptible sweet orange had rapidly increased from 5.6 to 6.7,Xcc grew quickly,and canker symptoms appeared.Plasma membrane(PM)Ht-ATPase activation with fusicoccin(FC)acidified the apoplast and upregulated the pathogenesis-related genes(PRs)in the sweet orange leaves.Hence,Xcc colonization and canker development were inhibited.The results of this study revealed that apoplastic acidification is implicated in the resistance of Citron C-05 to Xcc infection and provided insight into the association between pH_(apo) regulation and resistance to bacterial pathogen invasion in plants.展开更多
The apoplast is one of the first cellular compartments outside the plasma membrane encountered by phytopathogenic microbes in the early stages of plant tissue invasion.Plants have developed sophisticated surveillance ...The apoplast is one of the first cellular compartments outside the plasma membrane encountered by phytopathogenic microbes in the early stages of plant tissue invasion.Plants have developed sophisticated surveillance mechanisms to sense danger events at the cell surface and promptly activate immunity.However,a fine tuning of the activation of immune pathways is necessary to mount a robust and effective defense response.Several endogenous proteins and enzymes are synthesized as inactive precursors,and their post-translational processing has emerged as a critical mechanism for triggering alarms in the apoplast.In this review,we focus on the precursors of phytocytokines,cell wall remodeling enzymes,and proteases.The physiological events that convert inactive precursors into immunomodulatory active peptides or enzymes are described.This review also explores the functional synergies among phytocytokines,cell wall damage-associated molecular patterns,and remodeling,highlighting their roles in boosting extracellular immunity and reinforcing defenses against pests.展开更多
The apoplast is an interconnected compartment with a thin water-film that alkalinizes under stress. This systemic pH increase may be a secondary effect without functional implications, arising from ion movements or pr...The apoplast is an interconnected compartment with a thin water-film that alkalinizes under stress. This systemic pH increase may be a secondary effect without functional implications, arising from ion movements or proton-pump regulations. On the other hand, there are increasing indications that it is part of a mechanism to withstand stress. Regardless of this controversy, alkalinization of the apoplast has received little attention. The apoplastic pH （PHapo） increases not only during plant-pathogen interactions but also in response to salinity or drought. Not much is known about the mechanisms that cause the leaf apoplast to alkalinize, nor whether, and if so, how functional impact is conveyed. Controversial explanations have been given, and the unusual complexity of pHapo regulation is considered as the primary reason behind this lack of knowledge. A gathering of scattered information revealed that changes in PHapo convey functionality by regulating stomatal aperture via the effects exerted on abscisic acid. Moreover, apoplastic alkalinization may regulate growth under stress, whereas this needs to be verified. In this review, a comprehensive survey about several physiological mechanisms that alkalize the apoplast under stress is given, and the suitability of apoplastic alkalinization as transducing element for the transmission of sensory information is discussed.展开更多
Apoplastic ascorbate oxidases(AOs)play a critical role in reactive oxygen species(RoS)-mediated innate host immunity by regulating the apoplast redox state.To date,little is known about how apoplastic effectors of the...Apoplastic ascorbate oxidases(AOs)play a critical role in reactive oxygen species(RoS)-mediated innate host immunity by regulating the apoplast redox state.To date,little is known about how apoplastic effectors of the riceblast fungus Magnaportheoryzaemodulate the apoplast redox state of rice to subvert plant immunity.In this study,we demonstrated that M.oryzae MoAo1 is an Ao that plays a role in virulence by modulating the apoplast redox status of rice cells.We showed that MoAo1 inhibits the activity of rice OsAO3and OsAO4,which also regulate the apoplast redox status and plant immunity.In addition,we found that MoAo1,OsAO3,andOsAO4 allexhibit polymorphic variations whosevaried interactions orchestrate pathogen virulence and rice immunity.Taken together,our results reveal a critical role for extracellular redox enzymes during rice blast infection and shed light on the importance of the apoplast redox state anditsregulation inplant-pathogeninteractions.展开更多
Phytophthora capsici is one of the most harmful pathogens in agriculture, which threatens the safe production of multiple crops and causes serious economic losses worldwide. Here, we identified a P. capsici expansin-l...Phytophthora capsici is one of the most harmful pathogens in agriculture, which threatens the safe production of multiple crops and causes serious economic losses worldwide. Here, we identified a P. capsici expansin-like protein, Pc EXLX1, by liquid chromatography-tandem mass spectrometry from Nicotiana benthamiana apoplastic fluid infected with P. capsici. Clustered regularly interspaced short palindromic repeats/crispr associated protein9(CRISPR/Cas9)-mediated Pc EXLX1 knockout mutants exhibited significantly enhanced virulence,while the overexpression of Pc EXLX1 impaired the virulence. Prokaryotically expressed Pc EXLX1 activated multiple plant immune responses, which were BRI1-associated kinase 1(BAK1)-and suppressor of BIR1-1(SOBIR1)-dependent. Furthermore, overexpression of Pc EXLX1 homologs in N. benthamiana could also increase plant resistance to P. capsici. A G-type lectin receptor-like kinase from N. benthamiana, expansin-regulating kinase 1(ERK1), was shown to regulate the perception of Pc EXLX1 and positively mediate the plant resistance to P. capsici. These results reveal that the expansin-like protein, Pc EXLX1, is a novel apoplastic effector with plant immunity-inducing activity of oomycetes, perception of which is regulated by the receptor-like kinase, ERK1.展开更多
The effects of ammonium (NH4+-N) and nitrate (NO3- - N) were examined on Fe fractions and FeCN (ferricyanide) reductase activity in intact root tips (0-3 cm) of young maize (Zea mays L. cv. Lenz) in solution culture b...The effects of ammonium (NH4+-N) and nitrate (NO3- - N) were examined on Fe fractions and FeCN (ferricyanide) reductase activity in intact root tips (0-3 cm) of young maize (Zea mays L. cv. Lenz) in solution culture by using short-term experiment under controlled Fe deficiency conditions (containing high HCO3- concentration in pre-culture solution). The results showed that Fe(Ⅱ) concentrations in root tip apoplast of maize were only 20-40 nmol/g FW which accounted for 7%-13% of total Fe. Most of Fe in root tips existed as Fe(Ⅲ) compounds. Imposition of the roots to NH4+ - N or NO3- - N for 60 min led to an increase of Fe(Ⅱ) in root tip apoplast. NH4+ - N led to an increased concentration of Fe(Ⅱ) and exchangeable Fe (Fe(Ⅱ) and Fe (Ⅲ)) in root tips, while NO3- - N increased FeCN reductase activity. The relationship between pH and Fe fractions, FeCN reductase activity was also discussed.展开更多
Plants associate with diverse microbes that exert beneficial,neutral,or pathogenic effects inside the host.During the initial stages of invasion,the plant apoplast constitutes a hospitable environment for invading mic...Plants associate with diverse microbes that exert beneficial,neutral,or pathogenic effects inside the host.During the initial stages of invasion,the plant apoplast constitutes a hospitable environment for invading microbes,providing both water and nutrients.In response to microbial infection,a number of secreted proteins from host cells accumulate in the apoplastic space,which is related to microbial association or colonization processes.However,the molecular mechanisms underlying plant modulation of the apoplast environment and how plant-secreted proteases are involved in pathogen resistance are still poorly understood.Recently,several studies have reported the roles of apoplastic proteases in plant resistance against bacteria,fungi,and oomycetes.On the other hand,microbe-secreted proteins directly and/or indirectly inhibit host-derived apoplastic proteases to promote infection.These findings illustrate the importance of apoplastic proteases in plant–microbe interactions.Therefore,understanding the protease-mediated apoplastic battle between hosts and pathogens is of fundamental importance for understanding plant–pathogen interactions.Here,we provide an overviewof plant–microbe interactions in the apoplastic space.We define the apoplast,summarize the physical and chemical properties of these structures,and discuss the roles of plant apoplastic proteases and pathogen protease inhibitors in host–microbe interactions.Challenges and future perspectives for research into protease-mediated apoplastic interactions are discussed,which may facilitate the engineering of resistant crops.展开更多
Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage although the developmental mechanism is not clear yet. In the present study, the anatomical an...Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage although the developmental mechanism is not clear yet. In the present study, the anatomical and chemical characteristics as well as some ecophysiological features in the brittleness culm mutation of rice （Oryza sativa L.） were investigated. Compared with the wild type （WT）, the brittleness culm mutant （bcm） exhibited higher culm vascular bundle distance and lower culm wall thickness, leaf interveinal distance and leaf thickness. Ratio of bundle sheath cell/whole bundle and areas of whole vascular bundles and bundle sheath of leaves were reduced while ratios of xylem and phloem to whole bundles were elevated in bcm. The Fourier transform infrared （FTIR） microspectroscopy analysis and further histochemical and physiological measurements revealed that the different contents and depositions of cell wall components such as pectins, lignin, suberin and cellulose all participated in the mutation of brittleness. However, the mutant presented no significant changes in leaf photosynthetic dynamics and apoplastic transport ability. These results strongly indicate that the alterations in anatomical and chemical characteristics, rather than changes in major ecophysiological features such as photosynthesis and apoplastic transport were involved in the brittleness mutation of rice.展开更多
基金supported by Vale S.A. (No. ACA 5500023606/ 5900022781)the National Council for Scientific and Technological Development - CNPq (No. 311532/2017-9)the Minas Gerais Research Foundation - FAPEMIG
文摘The revegetation of mined areas poses a great challenge to the iron ore mining industry.The initial recovery process in degraded areas might rely on the use of Fe-resistant grasses.Tropical grasses, such as Paspalum densum and Echinochloa crus-galli, show different resistance strategies to iron toxicity; however, these mechanisms are poorly understood.The Fe-resistance mechanisms and direct iron toxicity as a function of root apex removal were investigated. To achieve this purpose, both grass species were grown for up to 480 hr in a nutrient solution containing 0.019 or 7 mmol/L Fe-EDTA after the root apices had been removed or maintained. Cultivation in the presence of excess iron-induced leaf bronzing and the formation of iron plaque on the root surfaces of both grass species, but was more significant on those plants whose root apex had been removed. Iron accumulation was higher in the roots, but reached phytotoxic levels in the aerial parts as well. It did not hinder the biosynthesis of chloroplastidic pigments. No significant changes in gas exchange and chlorophyll a fluorescence occurred in either grass when their roots were kept intact; the contrary was true for plants with excised root apices. In both studied grasses, the root apoplastic barriers had an important function in the restriction of iron translocation from the root to the aerial plant parts, especially in E. crus-galli. Root apex removal negatively influenced the iron toxicity resistance mechanisms(tolerance in P. densum and avoidance in E. crus-galli).
基金partially supported by the National Key Research and Development Program of China(2017YFC1600903 and 2016YFD040015)the National Natural Science Foundation of China(32072377)+2 种基金the Beijing Natural Science Foundation,China(6192023)the Agricultural Science and Technology Innovation Program of China(CAAS-ASTIP-2020-IFST-03)the scholarship grant from the China Scholarship Council(CSC)(2017GXZ022555)。
文摘During the attack of a pathogen, a variety of defense-associated proteins are released by the host plant in the apoplast to impede the perceived attack. This study utilized the mass spectrometry(LC-MS/MS) and label-free quantification method to analyze the apoplastic fluid(APF) from maize stalk and identified the proteins responsive to the Fusarium verticillioides infection. We have identified 742 proteins, and among these, 119 proteins were differentially accumulated(DAPs), i.e., 35 up-regulated, 18 down-regulated, and 66 proteins were only induced by the pathogen infection. The differentially accumulated proteins were analyzed for their Gene Ontology(GO) and Kyoto Encyclopedia of Gene and Genomes(KEGG) pathway enrichment. The highly enriched Biological Process(BP) term was the L-serine biosynthesis process, whereas the most enriched Molecular Function(MF) term was the cysteine-type endopeptidase inhibitor activity. It was also found that the pathways related to the biosynthesis of amino acid, biosynthesis of secondary metabolites, protein processing in the endoplasmic reticulum, and carbohydrate metabolic pathways were significantly enriched. Moreover, 61 out of 119 differentially accumulated proteins were predicted as secretory proteins. The secretory pathways analysis showed that a greater number of proteins were secreted through the conventional secretion system compared to the unconventional secretion system. The identified secreted proteins were related to a variety of pathways in defense responses including cell redox homeostasis, cell wall modification, signal transduction, carbohydrate metabolism, binding proteins(metal ion binding, RNA binding and heme-binding), maintenance and stabilization of other proteins, indicating a complex response from the plant to the fungal infection. Our data suggested that a number of host proteins belonging to various pathways have been modulated in the apoplastic region.
文摘Translucency is a recurring problem for pineapple industry. Translucent fruit contained more sucrose, glucose and fructose in apoplast than those in apoplast of normal fruit. There were more liquid in intercellular space of translucent fruit than that of normal flesh. The contents of alcohol and ethylene in translucent fruit were higher than those in normal fruit. Translucent fruit contained less calcium than normal fruit. Electrolyte leakage of translucent flesh was more than that of normal flesh. There were 205 proteins of which the expressions in translucent flesh were higher than those in normal flesh. Calcium-ions-binding protein EF-hand domain-containing protein, ethylene-synthesizing enzyme 1-aminpcyclopropane-1-carboxylate oxidase, ROS-producing protein universal stress protein A-like protein were the top three proteins of which the expressions in translucent flesh were higher than those in normal fruit. When much sugar was transferred into fruit pulp and accumulated in intercellular space, water will be absorbed from cells around and translucence formed. The accumulation of sugar and liquid in apoplast were due to that cell wall and membrane were degraded, which was from being attacked by ROS. There might be more and larger pores in cell wall and membranes of translucent flesh. These data played foundations for researching methods for controlling pineapple translucency.
文摘Cadmium (Cd) is a toxic metal with high mobility from soil and known translocation into plants (Song et al., 2015).Because the main source of human exposure to Cd is from food consumption, there has been increased research examining Cd uptake in agricultural plants (Li et al., 2014;Rizwan et al., 2016;Song et al., 2015).
基金supported by the National Key R&D Program of China(2024YFD1200305)the Henan Province Graduate Joint Training Base Project(YJS2024JD26)the Henan Kaifeng Cotton Science and Tech-nology Backyard.
文摘Cotton(Gossypium spp.),a major global fiber crop,serves as an ideal model for research on plant cell development.According to the acid growth theory,plasma membrane(PM)H+-ATPase(HA)regulates cell wall acidification,thereby promoting cell elongation and providing a mechanistic framework for understanding this process.However,its application to cotton fiber cells has remained limited.In this study,the acid growth theory was utilized to investigate the elongation of cotton fibers.Comparative genomics revealed an expansion in the number of gene family members associated with acid growth,including PM HA and transmembrane kinase(TMK)genes,in tetraploid cotton.Transcriptomic analysis highlighted the co-expression of these genes during fiber elongation.Functional validation using chemical modulators and CRISPR-Cas9-mediated knockout mutants demonstrated that PM HA activity is essential for apoplastic acidification and fiber elongation.Specifically,GhHA4A and GhTMK3A were identified as potential regulators of proton extrusion;their loss-of-function mutants exhibited elevated apoplastic pH and reduced fiber length.Furthermore,the results indicated that an optimal apoplastic pH is required for fiber elongation,whereas insufficient or excessive acidification inhibits growth.Spatiotemporal modulation of PM HA activity in transgenic cotton plants enhanced fiber length without affecting other fiber-and seed-related traits,demonstrating the potential of the acid growth theory for fiber improvement.These findings not only extend the acid growth theory beyond conventional model systems but also provide an innovative strategy for increasing fiber length in cotton breeding.
基金supported by grants from the Provincial Special Project of the Research and Demonstration of High-Efficiency Breeding Technology for Citrus,China(Grant No.2024sfq02)Postgraduate Scientific Research Innovation Project of Hunan Province,China(Grant No.CX20210671).
文摘The pH plays a key role in the growth and colonization of plant pathogens as well as the onset and progression of the symptoms they cause within the host.Plants may quickly alter their apoplastic pH(pH_(apo))to protect themselves against infection.However,pathogens can also alter the pH of their ambient environment to promote their own growth.Citrus canker is a serious plant disease caused by Xanthomonas citri subsp.citri(Xcc).This Gram-negative aerobic rod is usually cultured in LuriaeBertani(LB)medium at pH 7.However,little is known about the changes in pH both in this medium as Xcc grows and in the leaf apoplast in response to Xcc infection and colonization.Moreover,the differences in leaf apoplast pH between Xcc-resistant and Xcc-susceptible citrus genotypes are also unknown.Here,Xcc grew well in liquid LB medium at initial pH 6e8 and the pathogen altered the medium pH to 6.8±0.4.Xcc growth declined at pH 5 and was zero at pH 3,4,9,and 10.In susceptible sweet orange infected with Xcc inoculum,canker symptoms were inhibited at pH 3,4,and 10 but did not differ in the range of pH 5e9.As expected,canker symptoms were absent at all inoculum pH in the resistant Citron C-05.For both genotypes,Xcc only grew well in the leaves exposed to pH 5e8 inoculums.At four days post-inoculation(4 dpi),the foliar pH_(apo) of resistant Citron C-05 had rapidly declined from 5.6 to 4.4.At 2 dpi,the pH_(apo) of susceptible sweet orange had rapidly increased from 5.6 to 6.7,Xcc grew quickly,and canker symptoms appeared.Plasma membrane(PM)Ht-ATPase activation with fusicoccin(FC)acidified the apoplast and upregulated the pathogenesis-related genes(PRs)in the sweet orange leaves.Hence,Xcc colonization and canker development were inhibited.The results of this study revealed that apoplastic acidification is implicated in the resistance of Citron C-05 to Xcc infection and provided insight into the association between pH_(apo) regulation and resistance to bacterial pathogen invasion in plants.
基金supported by Sapienza University of Rome,grants RM120172 B78CFDF2,RM11916B7A142CF1,RM122181424F1F42,and RG12117 A898EABE0by the European Union“NextGenerationEU”program“Project ECS 0000024 Rome Technopole”-CUP B83C22002820006,PNRR Missione 4 Componente 2 Investimento 1.5by the Italian Ministry for Education,University and Research(MUR)with the project REACH-XY:CUP B93C22001920001.
文摘The apoplast is one of the first cellular compartments outside the plasma membrane encountered by phytopathogenic microbes in the early stages of plant tissue invasion.Plants have developed sophisticated surveillance mechanisms to sense danger events at the cell surface and promptly activate immunity.However,a fine tuning of the activation of immune pathways is necessary to mount a robust and effective defense response.Several endogenous proteins and enzymes are synthesized as inactive precursors,and their post-translational processing has emerged as a critical mechanism for triggering alarms in the apoplast.In this review,we focus on the precursors of phytocytokines,cell wall remodeling enzymes,and proteases.The physiological events that convert inactive precursors into immunomodulatory active peptides or enzymes are described.This review also explores the functional synergies among phytocytokines,cell wall damage-associated molecular patterns,and remodeling,highlighting their roles in boosting extracellular immunity and reinforcing defenses against pests.
文摘The apoplast is an interconnected compartment with a thin water-film that alkalinizes under stress. This systemic pH increase may be a secondary effect without functional implications, arising from ion movements or proton-pump regulations. On the other hand, there are increasing indications that it is part of a mechanism to withstand stress. Regardless of this controversy, alkalinization of the apoplast has received little attention. The apoplastic pH （PHapo） increases not only during plant-pathogen interactions but also in response to salinity or drought. Not much is known about the mechanisms that cause the leaf apoplast to alkalinize, nor whether, and if so, how functional impact is conveyed. Controversial explanations have been given, and the unusual complexity of pHapo regulation is considered as the primary reason behind this lack of knowledge. A gathering of scattered information revealed that changes in PHapo convey functionality by regulating stomatal aperture via the effects exerted on abscisic acid. Moreover, apoplastic alkalinization may regulate growth under stress, whereas this needs to be verified. In this review, a comprehensive survey about several physiological mechanisms that alkalize the apoplast under stress is given, and the suitability of apoplastic alkalinization as transducing element for the transmission of sensory information is discussed.
基金This research was supported by the China National Funds for Innovative Research Groups(31721004)the key program of the Natural Science Foundation of China(NSFC)(32030091)+3 种基金the NSFC Youth Program(31901832)Youth Program for Natural Science Foundation of Jiangsu Province(BK2019054)the program of NSFC-DFG(31861133017)the NSFC program(32172377)。
文摘Apoplastic ascorbate oxidases(AOs)play a critical role in reactive oxygen species(RoS)-mediated innate host immunity by regulating the apoplast redox state.To date,little is known about how apoplastic effectors of the riceblast fungus Magnaportheoryzaemodulate the apoplast redox state of rice to subvert plant immunity.In this study,we demonstrated that M.oryzae MoAo1 is an Ao that plays a role in virulence by modulating the apoplast redox status of rice cells.We showed that MoAo1 inhibits the activity of rice OsAO3and OsAO4,which also regulate the apoplast redox status and plant immunity.In addition,we found that MoAo1,OsAO3,andOsAO4 allexhibit polymorphic variations whosevaried interactions orchestrate pathogen virulence and rice immunity.Taken together,our results reveal a critical role for extracellular redox enzymes during rice blast infection and shed light on the importance of the apoplast redox state anditsregulation inplant-pathogeninteractions.
基金supported by the Fundamental Research Funds for the Central Universities(KYLH201703)the National Natural Science Foundation of China(32072507)。
文摘Phytophthora capsici is one of the most harmful pathogens in agriculture, which threatens the safe production of multiple crops and causes serious economic losses worldwide. Here, we identified a P. capsici expansin-like protein, Pc EXLX1, by liquid chromatography-tandem mass spectrometry from Nicotiana benthamiana apoplastic fluid infected with P. capsici. Clustered regularly interspaced short palindromic repeats/crispr associated protein9(CRISPR/Cas9)-mediated Pc EXLX1 knockout mutants exhibited significantly enhanced virulence,while the overexpression of Pc EXLX1 impaired the virulence. Prokaryotically expressed Pc EXLX1 activated multiple plant immune responses, which were BRI1-associated kinase 1(BAK1)-and suppressor of BIR1-1(SOBIR1)-dependent. Furthermore, overexpression of Pc EXLX1 homologs in N. benthamiana could also increase plant resistance to P. capsici. A G-type lectin receptor-like kinase from N. benthamiana, expansin-regulating kinase 1(ERK1), was shown to regulate the perception of Pc EXLX1 and positively mediate the plant resistance to P. capsici. These results reveal that the expansin-like protein, Pc EXLX1, is a novel apoplastic effector with plant immunity-inducing activity of oomycetes, perception of which is regulated by the receptor-like kinase, ERK1.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 30000103 and 39870480)the National Key Basic Research Special Funds (Grant No. G1999011707)by the Deutsche Forschungsgemeinschaft (DFG) for a personal grant on th
文摘The effects of ammonium (NH4+-N) and nitrate (NO3- - N) were examined on Fe fractions and FeCN (ferricyanide) reductase activity in intact root tips (0-3 cm) of young maize (Zea mays L. cv. Lenz) in solution culture by using short-term experiment under controlled Fe deficiency conditions (containing high HCO3- concentration in pre-culture solution). The results showed that Fe(Ⅱ) concentrations in root tip apoplast of maize were only 20-40 nmol/g FW which accounted for 7%-13% of total Fe. Most of Fe in root tips existed as Fe(Ⅲ) compounds. Imposition of the roots to NH4+ - N or NO3- - N for 60 min led to an increase of Fe(Ⅱ) in root tip apoplast. NH4+ - N led to an increased concentration of Fe(Ⅱ) and exchangeable Fe (Fe(Ⅱ) and Fe (Ⅲ)) in root tips, while NO3- - N increased FeCN reductase activity. The relationship between pH and Fe fractions, FeCN reductase activity was also discussed.
文摘Plants associate with diverse microbes that exert beneficial,neutral,or pathogenic effects inside the host.During the initial stages of invasion,the plant apoplast constitutes a hospitable environment for invading microbes,providing both water and nutrients.In response to microbial infection,a number of secreted proteins from host cells accumulate in the apoplastic space,which is related to microbial association or colonization processes.However,the molecular mechanisms underlying plant modulation of the apoplast environment and how plant-secreted proteases are involved in pathogen resistance are still poorly understood.Recently,several studies have reported the roles of apoplastic proteases in plant resistance against bacteria,fungi,and oomycetes.On the other hand,microbe-secreted proteins directly and/or indirectly inhibit host-derived apoplastic proteases to promote infection.These findings illustrate the importance of apoplastic proteases in plant–microbe interactions.Therefore,understanding the protease-mediated apoplastic battle between hosts and pathogens is of fundamental importance for understanding plant–pathogen interactions.Here,we provide an overviewof plant–microbe interactions in the apoplastic space.We define the apoplast,summarize the physical and chemical properties of these structures,and discuss the roles of plant apoplastic proteases and pathogen protease inhibitors in host–microbe interactions.Challenges and future perspectives for research into protease-mediated apoplastic interactions are discussed,which may facilitate the engineering of resistant crops.
基金Supported by the National Natural Science Foundation of China (30470274)the Zhejiang Provincial Natural Science Foundation (Y306087)
文摘Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage although the developmental mechanism is not clear yet. In the present study, the anatomical and chemical characteristics as well as some ecophysiological features in the brittleness culm mutation of rice （Oryza sativa L.） were investigated. Compared with the wild type （WT）, the brittleness culm mutant （bcm） exhibited higher culm vascular bundle distance and lower culm wall thickness, leaf interveinal distance and leaf thickness. Ratio of bundle sheath cell/whole bundle and areas of whole vascular bundles and bundle sheath of leaves were reduced while ratios of xylem and phloem to whole bundles were elevated in bcm. The Fourier transform infrared （FTIR） microspectroscopy analysis and further histochemical and physiological measurements revealed that the different contents and depositions of cell wall components such as pectins, lignin, suberin and cellulose all participated in the mutation of brittleness. However, the mutant presented no significant changes in leaf photosynthetic dynamics and apoplastic transport ability. These results strongly indicate that the alterations in anatomical and chemical characteristics, rather than changes in major ecophysiological features such as photosynthesis and apoplastic transport were involved in the brittleness mutation of rice.
