As a major subunit of the exocyst complex,members of the EXO70 family have mainly been shown to play roles in cell polarity and morphogenesis in Arabidopsis,but their roles in plant endosymbiosis,such as with arbuscul...As a major subunit of the exocyst complex,members of the EXO70 family have mainly been shown to play roles in cell polarity and morphogenesis in Arabidopsis,but their roles in plant endosymbiosis,such as with arbuscular mycorrhizal fungi(AMF),have rarely been reported.Here,using knockout and overexpression lines,we show that OsEXO70L2,which encodes a divergent EXO70 protein in rice,controls the number of primary roots and is essential for large lateral root formation.Furthermore,the OsEXO70L2 mutant sr1 displayed rare internal AMF hyphaeand no arbuscules.We also found that AMF sporulation can occur in roots despite low colonization and that AMF colonization and sporulation are modulated by photoperiod and co-culture with clover.Finally,genes related to auxin homeostasis were found to be affected in the OsEXO70L2 knockout or overexpression lines,suggesting that auxin is at least partly responsible for the phenotypes.This study provides new perspectives on the role of the exocyst complex during root development and AM in rice.展开更多
Receptor-like kinases(RLKs)are plasma membrane(PM)proteins that monitor the extracellular environment and regulate various processes such as biotic interactions.Lysin motif(LysM)RLKs are a specific class of RLKs invol...Receptor-like kinases(RLKs)are plasma membrane(PM)proteins that monitor the extracellular environment and regulate various processes such as biotic interactions.Lysin motif(LysM)RLKs are a specific class of RLKs involved in the recognition of chitin-derived molecules produced by microorganisms(Buendia et al.,2018).Notably,the LysM-RLK heterocomplex LjNFR1/LjNFR5 recognizes lipochitooligosaccharides(LCOs,also called Nod factors)leading to root nodule symbiosis(RNS)in Lotus japonicus,whereas the heterocomplexes AtLYK5/AtCERK1 and OsCEBIP/OsCERK1 recognize chitooligosaccharides(COs)leading to defense responses in Arabidopsis thaliana and rice,respectively(Buendia et al.,2018).These receptors function as gatekeepers.Extracellular ligand binding activates the intracellular kinase activity of LjNFR1,AtCERK1,and OsCERK1,which mediate phosphorylation-dependent signaling cascades.Regulatory mechanisms are essential to tightly control RLK homeostasis and signaling,allowing cells to respond efficiently while preventing constitutive activation.The PM-resident pool of RLKs must be maintained for rapid response,while RLK endocytosis and ultimately degradation in lytic vacuoles is critical for both signaling and downregulation of the responses.In addition to its role in proteasome-dependent degradation,ubiquitination,a post-translational protein modification,has emerged as a key regulator of PM proteins by inducing their internalization and degradation in lytic vacuoles(Romero-Barrios and Vert,2018).展开更多
Besides the well-understood qualitative disease resistance,plants possess a more complex quantitative form of resistance:quantitative disease resistance(QDR).QDR is commonly defined as a partial but more durable form ...Besides the well-understood qualitative disease resistance,plants possess a more complex quantitative form of resistance:quantitative disease resistance(QDR).QDR is commonly defined as a partial but more durable form of resistance and,therefore,might display a valuable target for resistance breeding.The characterization of QDR phenotypes,especially of wild crop relatives,displays a bottleneck in deciphering QDR's genomic and regulatory background.Moreover,the relationship between QDR parameters,such as infection frequency,lag-phase duration,and lesion growth rate,remains elusive.High hurdles for applying modern phenotyping technology,such as the low availability of phenotyping facilities or complex data analysis,further dampen progress in understanding QDR.Here,we applied a low-cost(<1.000 €)phenotyping system to measure lesion growth dynamics of wild tomato species(e.g.,Solanum pennellii or Solanum pimpinellifolium).We provide insight into QDR diversity of wild populations and derive specific QDR mechanisms and their cross-talk.We show how temporally continuous observations are required to dissect end-point severity into functional resistance mechanisms.The results of our study show how QDR can be maintained by facilitating different defense mechanisms during host-parasite interaction and that the capacity of the QDR toolbox highly depends on the host's genetic context.We anticipate that the present findings display a valuable resource for more targeted functional characterization of the processes involved in QDR.Moreover,we show how modest phenotyping technology can be leveraged to help answer highly relevant biological questions.展开更多
Calcium-dependent protein kinases （CDPKs） comprise a family of plant serine/threonine protein kinases in which the calcium sensing domain and the kinase effector domain are combined within one molecule. So far, a bi...Calcium-dependent protein kinases （CDPKs） comprise a family of plant serine/threonine protein kinases in which the calcium sensing domain and the kinase effector domain are combined within one molecule. So far, a biological function in abiotic stress signaling has only been reported for few CDPK isoforms, whereas the underlying biochemical mechanism for these CDPKs is still mainly unknown. Here, we show that CPK21 from Arabidopsis thaliana is biochemically activated in vivo in response to hyperosmotic stress. Loss-of-function seedlings of cpk21 are more tolerant to hyperosmotic stress and mutant plants show increased stress responses with respect to marker gene expression and metabolite accumulation. In transgenic Arabidopsis complementation lines in the cpk21 mutant background, in which either CPK21 wildtype, or a full-length enzyme variant carrying an amino-acid substitution were stably expressed, stress responsitivity was restored by CPK21 but not with the kinase inactive variant. The biochemical characterization of in planta synthesized and purified CPK21 protein revealed that within the calcium-binding domain, N-terminal EF1- and EF2-motifs compared to C-terminal EF3- and EF4-motifs differ in their contribution to calcium-regulated kinase activity, suggesting a crucial role for the N-terminal EF-hand pair. Our data provide evidence for CPK21 contributing in abiotic stress signaling and suggest that the N-terminal EF-hand pair is a calcium-sensing determinant controlling specificity of CPK21 function.展开更多
Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid （ABA） but how this hormone controls seed germination is...Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid （ABA） but how this hormone controls seed germination is still poorly known. Phenotypic and microscopic observations of the embryo axis of Medicago truncatula during germination in mitotic inhibition condition triggered by 10 μM oryzalin showed that cell division was not required to allow radicle emergence. A suppressive subtractive hybridization showed that more than 10% of up-regulated genes in the embryo axis encoded proteins related to cell-wall biosynthesis. The expression of α-expansins, pectin-esterase, xylogucan-endotransglycosidase, cellulose synthase, and extensins was monitored in the embryo axis of seeds germinated on water, constant and transitory ABA. These genes were overexpressed before completion of germination in the control and strongly inhibited by ABA. The expression was re-established in the ABA transitory-treatment after the seeds were transferred back on water and proceeded to germination. This proves these genes as contributors to the completion of germination and strengthen the idea that cell-wall loosening and remodeling in relation to cell expansion in the embryo axis is a determinant feature in germination. Our results also showed that ABA controls germination through the control of radicle emergence, namely by inhibiting cell-wall loosening and expansion.展开更多
Recognition of a pathogen by the plant immune system often triggers a form of regulated cell death traditionally known as the hypersensitive response(HR).This type of cell death occurs precisely at the site of pathoge...Recognition of a pathogen by the plant immune system often triggers a form of regulated cell death traditionally known as the hypersensitive response(HR).This type of cell death occurs precisely at the site of pathogen recognition,and it is restricted to a few cells.Extensive research has shed light on how plant immune receptors are mechanistically activated.However,two central key questions remain largely unresolved:how does cell death zonation take place,and what are the mechanisms that underpin this phenomenon?Consequently,bona fide transcriptional indicators of HR are lacking,which prevents deeper insight into its mechanisms before cell death becomes macroscopic and precludes early or live observation.In this study,to identify the transcriptional indicators of HR we used the paradigmatic Arabidopsis thaliana–Pseudomonas syringae pathosystem and performed a spatiotemporally resolved gene expression analysis that compared infected cells that will undergo HR upon pathogen recognition with bystander cells that will stay alive and activate immunity.Our data revealed unique and time-dependent differences in the repertoire of differentially expressed genes,expression profiles,and biological processes derived from tissue undergoing HR and that of its surroundings.Furthermore,we generated a pipeline based on concatenated pairwise comparisons between time,zone,and treatment that enabled us to define 13 robust transcriptional HR markers.Among these genes,the promoter of an uncharacterized AAA-ATPase was used to obtain a fluorescent reporter transgenic line that displays a strong spatiotemporally resolved signal specifically in cells that will later undergo pathogen-triggered cell death.This valuable set of genes can be used to define cells that are destined to die upon infection with HR-triggering bacteria,opening new avenues for specific and/or high-throughput techniques to study HR processes at a single-cell level.展开更多
Modern agriculture needs to develop transition pathways toward agroecological,resilient and sustainable farming systems.One key pathway for such agroecological intensification is the diversification of cropping system...Modern agriculture needs to develop transition pathways toward agroecological,resilient and sustainable farming systems.One key pathway for such agroecological intensification is the diversification of cropping systems using intercropping and notably cereal-grain legume mixtures.Such mixtures or intercrops have the potential to increase and stabilize yields and improve cereal grain protein concentration in comparison to sole crops.Species mixtures are complex and the 4C approach is both a pedagogical and scientific way to represent the combination of four joint effects of Competition,Complementarity,Cooperation,and Compensation as processes or effects occurring simultaneously and dynamically between species over the whole cropping cycle.Competition is when plants have fairly similar requirements for abiotic resources in space and time,the result of all processes that occur when one species has a greater ability to use limiting resources(e.g.,nutrients,water,space,light)than others.Complementarity is when plants grown together have different requirements for abiotic resources in space,time or form.Cooperation is when the modification of the environment by one species is beneficial to the other(s).Compensation is when the failure of one species is compensated by the other(s)because they differ in their sensitivity to abiotic stress.The 4C approach allows to assess the performance of arable intercropping versus classical sole cropping through understanding the use of abiotic resources.展开更多
Quantitative disease resistance(QDR)remains the most prevalent form of plant resistance in crop fields and wild habitats.Genome-wide association studies(GWAS)have proved to be successful in deciphering the quantitativ...Quantitative disease resistance(QDR)remains the most prevalent form of plant resistance in crop fields and wild habitats.Genome-wide association studies(GWAS)have proved to be successful in deciphering the quantitative genetic basis of complex traits such as QDR.To unravel the genetics of QDR to the devastating worldwide bacterial pathogen Ralstonia solanacearum,we performed a GWAS by challenging a highly polymorphic local mapping population of Arabidopsis thaliana with four R.solanacearum type III effector(T3E)mutants,identified as key pathogenicity determinants after a first screen on an A.thaliana core collection of 25 accessions.Although most quantitative trait loci(QTLs)were highly specific to the identity of the T3E mutant(ripAC,ripAG,ripAQ,and ripU),we finely mapped a common QTL located on a cluster of nucleotide-binding domain and leucine-rich repeat(NLR)genes that exhibited structural variation.We functionally validated one of these NLRs as a susceptibility factor in response to R.solanacearum,named it Bacterial Wilt Susceptibility 1(BWS1),and cloned two alleles that conferred contrasting levels of QDR.Further characterization indicated that expression of BWS1 leads to suppression of immunity triggered by different R.solanacearum effectors.In addition,we showed a direct interaction between BWS1 and RipAC T3E,and BWS1 and SUPPRESSOR OF G2 ALLELE OF skp1(SGT1b),the latter interaction being suppressed by RipAC.Together,our results highlight a putative role for BWS1 as a quantitative susceptibility factor directly targeted by the T3E RipAC,mediating negative regulation of the SGT1-dependent immune response.展开更多
基金supported by the National Natural Science Foundation of China(32171970)the Chongqing Talent Program,China(cstc2022ycjh-bgzxm0073)+1 种基金the Natural Science Foundation of Chongqing,China(cstc2021jcyjcxtt X0004)the Rice Innovative Research Team of Chongqing Modern Agricultural Industrial Technology System,China(CQMAITS202301)。
文摘As a major subunit of the exocyst complex,members of the EXO70 family have mainly been shown to play roles in cell polarity and morphogenesis in Arabidopsis,but their roles in plant endosymbiosis,such as with arbuscular mycorrhizal fungi(AMF),have rarely been reported.Here,using knockout and overexpression lines,we show that OsEXO70L2,which encodes a divergent EXO70 protein in rice,controls the number of primary roots and is essential for large lateral root formation.Furthermore,the OsEXO70L2 mutant sr1 displayed rare internal AMF hyphaeand no arbuscules.We also found that AMF sporulation can occur in roots despite low colonization and that AMF colonization and sporulation are modulated by photoperiod and co-culture with clover.Finally,genes related to auxin homeostasis were found to be affected in the OsEXO70L2 knockout or overexpression lines,suggesting that auxin is at least partly responsible for the phenotypes.This study provides new perspectives on the role of the exocyst complex during root development and AM in rice.
文摘Receptor-like kinases(RLKs)are plasma membrane(PM)proteins that monitor the extracellular environment and regulate various processes such as biotic interactions.Lysin motif(LysM)RLKs are a specific class of RLKs involved in the recognition of chitin-derived molecules produced by microorganisms(Buendia et al.,2018).Notably,the LysM-RLK heterocomplex LjNFR1/LjNFR5 recognizes lipochitooligosaccharides(LCOs,also called Nod factors)leading to root nodule symbiosis(RNS)in Lotus japonicus,whereas the heterocomplexes AtLYK5/AtCERK1 and OsCEBIP/OsCERK1 recognize chitooligosaccharides(COs)leading to defense responses in Arabidopsis thaliana and rice,respectively(Buendia et al.,2018).These receptors function as gatekeepers.Extracellular ligand binding activates the intracellular kinase activity of LjNFR1,AtCERK1,and OsCERK1,which mediate phosphorylation-dependent signaling cascades.Regulatory mechanisms are essential to tightly control RLK homeostasis and signaling,allowing cells to respond efficiently while preventing constitutive activation.The PM-resident pool of RLKs must be maintained for rapid response,while RLK endocytosis and ultimately degradation in lytic vacuoles is critical for both signaling and downregulation of the responses.In addition to its role in proteasome-dependent degradation,ubiquitination,a post-translational protein modification,has emerged as a key regulator of PM proteins by inducing their internalization and degradation in lytic vacuoles(Romero-Barrios and Vert,2018).
基金partly funded by the DFG(STA1547/6 and SFB924)and the ANR(ANR-21-CE20-30)for the collab-orative project ResiDEvo.Exchange visits were supported by the DAAD and the Partenariat Hubert Curien programme of Campus France.
文摘Besides the well-understood qualitative disease resistance,plants possess a more complex quantitative form of resistance:quantitative disease resistance(QDR).QDR is commonly defined as a partial but more durable form of resistance and,therefore,might display a valuable target for resistance breeding.The characterization of QDR phenotypes,especially of wild crop relatives,displays a bottleneck in deciphering QDR's genomic and regulatory background.Moreover,the relationship between QDR parameters,such as infection frequency,lag-phase duration,and lesion growth rate,remains elusive.High hurdles for applying modern phenotyping technology,such as the low availability of phenotyping facilities or complex data analysis,further dampen progress in understanding QDR.Here,we applied a low-cost(<1.000 €)phenotyping system to measure lesion growth dynamics of wild tomato species(e.g.,Solanum pennellii or Solanum pimpinellifolium).We provide insight into QDR diversity of wild populations and derive specific QDR mechanisms and their cross-talk.We show how temporally continuous observations are required to dissect end-point severity into functional resistance mechanisms.The results of our study show how QDR can be maintained by facilitating different defense mechanisms during host-parasite interaction and that the capacity of the QDR toolbox highly depends on the host's genetic context.We anticipate that the present findings display a valuable resource for more targeted functional characterization of the processes involved in QDR.Moreover,we show how modest phenotyping technology can be leveraged to help answer highly relevant biological questions.
文摘Calcium-dependent protein kinases （CDPKs） comprise a family of plant serine/threonine protein kinases in which the calcium sensing domain and the kinase effector domain are combined within one molecule. So far, a biological function in abiotic stress signaling has only been reported for few CDPK isoforms, whereas the underlying biochemical mechanism for these CDPKs is still mainly unknown. Here, we show that CPK21 from Arabidopsis thaliana is biochemically activated in vivo in response to hyperosmotic stress. Loss-of-function seedlings of cpk21 are more tolerant to hyperosmotic stress and mutant plants show increased stress responses with respect to marker gene expression and metabolite accumulation. In transgenic Arabidopsis complementation lines in the cpk21 mutant background, in which either CPK21 wildtype, or a full-length enzyme variant carrying an amino-acid substitution were stably expressed, stress responsitivity was restored by CPK21 but not with the kinase inactive variant. The biochemical characterization of in planta synthesized and purified CPK21 protein revealed that within the calcium-binding domain, N-terminal EF1- and EF2-motifs compared to C-terminal EF3- and EF4-motifs differ in their contribution to calcium-regulated kinase activity, suggesting a crucial role for the N-terminal EF-hand pair. Our data provide evidence for CPK21 contributing in abiotic stress signaling and suggest that the N-terminal EF-hand pair is a calcium-sensing determinant controlling specificity of CPK21 function.
文摘Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid （ABA） but how this hormone controls seed germination is still poorly known. Phenotypic and microscopic observations of the embryo axis of Medicago truncatula during germination in mitotic inhibition condition triggered by 10 μM oryzalin showed that cell division was not required to allow radicle emergence. A suppressive subtractive hybridization showed that more than 10% of up-regulated genes in the embryo axis encoded proteins related to cell-wall biosynthesis. The expression of α-expansins, pectin-esterase, xylogucan-endotransglycosidase, cellulose synthase, and extensins was monitored in the embryo axis of seeds germinated on water, constant and transitory ABA. These genes were overexpressed before completion of germination in the control and strongly inhibited by ABA. The expression was re-established in the ABA transitory-treatment after the seeds were transferred back on water and proceeded to germination. This proves these genes as contributors to the completion of germination and strengthen the idea that cell-wall loosening and remodeling in relation to cell expansion in the embryo axis is a determinant feature in germination. Our results also showed that ABA controls germination through the control of radicle emergence, namely by inhibiting cell-wall loosening and expansion.
文摘Recognition of a pathogen by the plant immune system often triggers a form of regulated cell death traditionally known as the hypersensitive response(HR).This type of cell death occurs precisely at the site of pathogen recognition,and it is restricted to a few cells.Extensive research has shed light on how plant immune receptors are mechanistically activated.However,two central key questions remain largely unresolved:how does cell death zonation take place,and what are the mechanisms that underpin this phenomenon?Consequently,bona fide transcriptional indicators of HR are lacking,which prevents deeper insight into its mechanisms before cell death becomes macroscopic and precludes early or live observation.In this study,to identify the transcriptional indicators of HR we used the paradigmatic Arabidopsis thaliana–Pseudomonas syringae pathosystem and performed a spatiotemporally resolved gene expression analysis that compared infected cells that will undergo HR upon pathogen recognition with bystander cells that will stay alive and activate immunity.Our data revealed unique and time-dependent differences in the repertoire of differentially expressed genes,expression profiles,and biological processes derived from tissue undergoing HR and that of its surroundings.Furthermore,we generated a pipeline based on concatenated pairwise comparisons between time,zone,and treatment that enabled us to define 13 robust transcriptional HR markers.Among these genes,the promoter of an uncharacterized AAA-ATPase was used to obtain a fluorescent reporter transgenic line that displays a strong spatiotemporally resolved signal specifically in cells that will later undergo pathogen-triggered cell death.This valuable set of genes can be used to define cells that are destined to die upon infection with HR-triggering bacteria,opening new avenues for specific and/or high-throughput techniques to study HR processes at a single-cell level.
基金The authors acknowledge the support received from the European Union through the H2020 ReMIX project(Redesigning European cropping systems based on species mixturesGrant agreement ID:727217).
文摘Modern agriculture needs to develop transition pathways toward agroecological,resilient and sustainable farming systems.One key pathway for such agroecological intensification is the diversification of cropping systems using intercropping and notably cereal-grain legume mixtures.Such mixtures or intercrops have the potential to increase and stabilize yields and improve cereal grain protein concentration in comparison to sole crops.Species mixtures are complex and the 4C approach is both a pedagogical and scientific way to represent the combination of four joint effects of Competition,Complementarity,Cooperation,and Compensation as processes or effects occurring simultaneously and dynamically between species over the whole cropping cycle.Competition is when plants have fairly similar requirements for abiotic resources in space and time,the result of all processes that occur when one species has a greater ability to use limiting resources(e.g.,nutrients,water,space,light)than others.Complementarity is when plants grown together have different requirements for abiotic resources in space,time or form.Cooperation is when the modification of the environment by one species is beneficial to the other(s).Compensation is when the failure of one species is compensated by the other(s)because they differ in their sensitivity to abiotic stress.The 4C approach allows to assess the performance of arable intercropping versus classical sole cropping through understanding the use of abiotic resources.
基金supported by the Laboratoire d’Excellence(LABEX)TULIP(ANR-10-LABX-41)funded by a grant from the Lebanese University+4 种基金INRAE,Campus France,and the INRAE Plant Health and Environment division(SPE)for their support and fundinga PhD grant co-financed by the Occitanie Regional Council and the INRAE Plant Health and Environment division(SPE)funded by a grant from the French Ministry of National Education and Researchsupported by France Genomique National infrastructurefunded as part of the Investissement d’avenir program managed by Agence Nationale de la Recherche(contract ANR-10-INBS-09).
文摘Quantitative disease resistance(QDR)remains the most prevalent form of plant resistance in crop fields and wild habitats.Genome-wide association studies(GWAS)have proved to be successful in deciphering the quantitative genetic basis of complex traits such as QDR.To unravel the genetics of QDR to the devastating worldwide bacterial pathogen Ralstonia solanacearum,we performed a GWAS by challenging a highly polymorphic local mapping population of Arabidopsis thaliana with four R.solanacearum type III effector(T3E)mutants,identified as key pathogenicity determinants after a first screen on an A.thaliana core collection of 25 accessions.Although most quantitative trait loci(QTLs)were highly specific to the identity of the T3E mutant(ripAC,ripAG,ripAQ,and ripU),we finely mapped a common QTL located on a cluster of nucleotide-binding domain and leucine-rich repeat(NLR)genes that exhibited structural variation.We functionally validated one of these NLRs as a susceptibility factor in response to R.solanacearum,named it Bacterial Wilt Susceptibility 1(BWS1),and cloned two alleles that conferred contrasting levels of QDR.Further characterization indicated that expression of BWS1 leads to suppression of immunity triggered by different R.solanacearum effectors.In addition,we showed a direct interaction between BWS1 and RipAC T3E,and BWS1 and SUPPRESSOR OF G2 ALLELE OF skp1(SGT1b),the latter interaction being suppressed by RipAC.Together,our results highlight a putative role for BWS1 as a quantitative susceptibility factor directly targeted by the T3E RipAC,mediating negative regulation of the SGT1-dependent immune response.
