查看更多>>摘要：The hexaploid sweetpotato(Ipomoea batatas)is one of the most important root crops worldwide.However,its genetic origin remains controversial,and its domestication history remains unknown.In this study,we used a range of genetic evidence and a newly developed haplotype-based phylogenetic analysis to identify two probable progenitors of sweetpotato.The diploid progenitor was likely closely related to Ipomoea ae-quatoriensis and contributed the B1 subgenome,IbT-DNA2,and the lineage 1 type of chloroplast genome to sweetpotato.The tetraploid progenitor of sweetpotato was most likely I.batatas 4x,which donated the B2 subgenome,IbT-DNA1,and the lineage 2 type of chloroplast genome.Sweetpotato most likely originated from reciprocal crosses between the diploid and tetrapioid progenitors,followed by a subsequent whole-genome duplication.In addition,we detected biased gene exchanges between the subgenomes;the rate of B1 to B2 subgenome conversions was nearly three times higher than that of B2 to B1 subgenome conver-sions.Our analyses revealed that genes involved in storage root formation,maintenance of genome stabil-ity,biotic resistance,sugar transport,and potassium uptake were selected during the speciation and domestication of sweetpotato.This study sheds light on the evolution of sweetpotato and paves the way for improvement of this crop.
查看更多>>摘要：Jasmonic acid(JA)is a crucial phytohormone that regulates plant immunity.The endogenous JA level is determined by the rates of its biosynthesis and catabolism in plants.The activation of JA biosynthesis has been well documented;however,how plants repress JA catabolism upon pathogen infection remains elusive.In this study,we identified and characterized Botrytis cinerea-induced F-box protein 1(BFP1)in Arabidopsis.The expression of BFP1 was induced by B.cinerea in a JA signaling-dependent manner,and BFP1 protein was critical for plant defense against B.cinerea and plant response to JA.In addition,BFP1 overexpression increased plant defenses against broad-spectrum pathogens without fitness costs.Further experiments demonstrated that BFP1 interacts with and mediates the ubiquitination and degrada-tion of jasmonic acid oxidases(JAOs,also known as jasmonate-induced oxygenases,JOXs),the enzymes that hydroxylate JA to 12OH-JA.Consistent with this,BFP1 affects the accumulation of JA and 12OH-JA during B.cinerea infection.Moreover,mutation of JAO2 complemented the phenotypes of the bfp1 mutant.Collectively,our results unveil a new mechanism used by plants to activate immune responses upon path-ogen infection:suppressing JA catabolism.
查看更多>>摘要：Defensin-like proteins are conserved in multicellular organisms and contribute to innate immune re-sponses against fungal pathogens.In rice,defensins play a novel role in regulating cadmium(Cd)efflux from the cytosol.However,whether the antifungal activity of defensins correlates with Cd-efflux function remains unknown.In this study,we isolated an endophytic Fusarium,designed Fo10,by a comparative mi-crobiome analysis of rice plants grown in a paddy contaminated with Cd.Fo10 is tolerant to high levels of Cd,but is sensitive to the defensin-like protein OsCAL1,which mediates Cd efflux to the apoplast.We found that Fo10 symbiosis in rice is regulated by OsCAL1 dynamics,and Fo10 coordinates multiple plant pro-cesses,including Cd uptake,vacuolar sequestration,efflux to the environment,and formation of Fe pla-ques in the rhizosphere.These processes are dependent on the salicylic acid signaling pathway to keep Cd levels low in the cytosol of rice cells and to decrease Cd levels in rice grains without any yield penalty.Fo10 also plays a role in Cd tolerance in the poaceous crop maize and wheat,but has no observed effects in the eudicot plants Arabidopsis and tomato.Taken together,these findings provide insights into the mech-anistic basis underlying how a fungal endophyte and host plant interact to control Cd accumulation in host plants by adapting defense responses to promote the establishment of a symbiosis that permits adaptation to high-Cd environments.
查看更多>>摘要：Xanthomonas oryzae pv.oryzae(Xoo)causes bacterial blight(BB),a globally devastating disease of rice(Oryza sativa)that is responsible for significant crop loss.Sugars and sugar metabolites are important for pathogen infection,providing energy and regulating events associated with defense responses;howev-er,the mechanisms by which they regulate such events in BB are unclear.As an inevitable sugar metabolite,methylglyoxal(MG)is involved in plant growth and responses to various abiotic stresses,but the underlying mechanisms remain enigmatic.Whether and how MG functions in plant biotic stress responses is almost completely unknown.Here,we report that the Xoo strain PXO99 induces OsWRKY62.1 to repress transcrip-tion of OsGLY Ⅱ genes by directly binding to their promoters,resulting in overaccumulation of MG.MG negatively regulates rice resistance against PXO99:osglyll2 mutants with higher MG levels are more sus-ceptible to the pathogen,whereas OsGLYⅡ2-overexpressing plants with lower MG content show greater resistance than the wild type.Overexpression of OsGLYⅡ2 to prevent excessive MG accumulation confers broad-spectrum resistance against the biotrophic bacterial pathogens Xoo and Xanthomonas oryzae pv.oryzicola and the necrotrophic fungal pathogen Rhizoctonia solani,which causes rice sheath blight.Further evidence shows that MG reduces rice resistance against PXO99 through CONSTITUTIVE DISEASE RESISTANCE 1(OsCDR1).MG modifies the Arg97 residue of OsCDR1 to inhibit its aspartic protease activ-ity,which is essential for OsCDR1-enhanced immunity.Taken together,these findings illustrate how Xoo promotes infection by hijacking a sugar metabolite in the host plant.
查看更多>>摘要：Lipid phosphorylation by diacylglycerol kinase(DGK)that produces phosphatidic acid(PA)plays important roles in various biological processes,including stress responses,but the underlying mechanisms remain elusive.Here,we show that DGK5 and its lipid product PA suppress ABA biosynthesis by interacting with ABA-DEFICIENT 2(ABA2),a key ABA biosynthesis enzyme,to negatively modulate plant response to abiotic stress tested in Arabidopsis thaliana.Loss of DGK5 function rendered plants less damaged,whereas overexpression(OE)of DGK5 enhanced plant damage to water and salt stress.The dgk5 mutant plants exhibited decreased total cellular and nuclear levels of PA with increased levels of diacylglycerol,whereas DGK5-OE plants displayed the opposite effect.Interestingly,we found that both DGK5 and PA bind to the ABA-synthesizing enzyme ABA2 and suppress its enzymatic activity.Consistently,the dgk5 mutant plants exhibited increased levels of ABA,while DGK5-OE plants showed reduced ABA levels.In addition,we showed that both DGK5 and ABA2 are detected in and outside the nuclei,and loss of DGK5 function decreased the nuclear association of ABA2.We found that both DGK5 activity and PA promote nuclear association of ABA2.Taken together,these results indicate that both DGK5 and PA interact with ABA2 to inhibit its enzymatic activity and promote its nuclear sequestration,thereby sup-pressing ABA production in response to abiotic stress.Our study reveals a sophisticated mechanism by which DGK5 and PA regulate plant stress responses.
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