Legumes are highly important food, feed and biofuel crops. With few exceptions, they can enter into an intricate symbiotic relationship with specific soil bacteria called rhizobia. This interaction results in the form...Legumes are highly important food, feed and biofuel crops. With few exceptions, they can enter into an intricate symbiotic relationship with specific soil bacteria called rhizobia. This interaction results in the formation of a new root organ called the nodule in which the rhizobia convert atmospheric nitrogen gas into forms of nitrogen that are useable by the plant. The plant tightly controls the number of nodules it forms, via a complex root-to-shoot-to-root signaling loop called autoregulation of nodulation （AON）. This regulatory process involves peptide hormones, receptor kinases and small metabolites. Using modern genetic and genomic techniques, many of the components required for nodule formation and AON have now been isolated. This review addresses these recent findings, presents detailed models of the nodulation and AON processes, and identifies gaps in our understanding of these process that have yet to be fully explained.展开更多
Reactive oxygen species play a crucial role in various stages of the legume-rhizobia symbiosis,from initial nodulation signaling to nodule senescence.However,how rhizobial redox-related proteins regulate symbiotic nod...Reactive oxygen species play a crucial role in various stages of the legume-rhizobia symbiosis,from initial nodulation signaling to nodule senescence.However,how rhizobial redox-related proteins regulate symbiotic nodulation in legumesremains largely unknown.By combining transcriptomics,proteomics,and biochemical and molecular genetics,we investigated the role of the Sinorhizobium fredii Q8 enzyme 3-mercaptopyruvate sulfurtransferase(3MST).Although 3MST was not the primary enzyme responsible for hydrogen sulfide(HS)production under our conditions,its absence significantly impaired symbiotic nodule development,redox homeostasis,infection capacity,and nitrogen-fixation efficiency in soybean.We identified a host plasma membrane-localized NADPH oxidase,respiratory burst oxidase homolog B(RbohB),as a key regulator of immune activation during nodule development.Notably,3MST was secreted during nodulation and localized in the nucleoid and cytoplasmic membrane,where it interacts with and persulfidates RbohB at Cys791,thereby suppressing the NADPH oxidase activity of RbohB.We observed that 3MST-mediated persulfidation of RbohB maintains symbiotic redox balance and promotes nodule development.Genetic analyses in soybean,including RbohB overexpression,RNA interference,and site-directed mutagenesis at Cys791,further supported this observation,linking the 3MST-RbohB interaction to effective rhizobial colonization and improved plant growth.Taken together,these findings uncover a rhizobia-initiated symbiotic regulatory mechanism by which a rhizobial sulfurtransferase modulates soybean RbohB via persulfidation to limit NADPH oxidase activity and promote nodulation.展开更多
The discovery of the enzyme L,L‐diaminopimelate aminotransferase（LL‐DAP‐AT, EC 2.6.1.83） uncovered a unique step in the L‐lysine biosynthesis pathway in plants. In Arabidopsis thaliana, LL‐DAP‐AT has been show...The discovery of the enzyme L,L‐diaminopimelate aminotransferase（LL‐DAP‐AT, EC 2.6.1.83） uncovered a unique step in the L‐lysine biosynthesis pathway in plants. In Arabidopsis thaliana, LL‐DAP‐AT has been shown to play a key role in plant‐pathogen interactions by regulation of the salicylic acid（SA） signaling pathway. Here, a full‐length cDNA of LL‐DAP‐AT named as LjALD1 from Lotus japonicus（Regel）Larsen was isolated. The deduced amino acid sequence shares 67% identity with the Arabidopsis aminotransferase AGD2‐LIKE DEFENSE RESPONSE PROTEIN1（AtALD1） and is predicted to contain the same key elements： a conserved aminotransferase domain and a pyridoxal‐5＇‐phosphate cofactor binding site.Quantitative real‐time PCR analysis showed that LjALD1 was expressed in all L. japonicus tissues tested, being strongest in nodules. Expression was induced in roots that had been infected with the symbiotic rhizobium Mesorhizobium loti or treated with SA agonist benzo‐（1, 2, 3）‐thiadiazole‐7‐carbothioic Researchacid. LjALD1 Knockdown exhibited a lower SA content, an increased number of infection threads and nodules, and a slight reduction in nodule size. In addition, compared with wild‐type,root growth was increased and shoot growth was suppressed in LjALD1 RNAi plant lines. These results indicate that LjALD1 may play important roles in plant development and nodulation via SA signaling in L. japonicus.展开更多
基金the Australian Research Council for Centre of Excellence funding
文摘Legumes are highly important food, feed and biofuel crops. With few exceptions, they can enter into an intricate symbiotic relationship with specific soil bacteria called rhizobia. This interaction results in the formation of a new root organ called the nodule in which the rhizobia convert atmospheric nitrogen gas into forms of nitrogen that are useable by the plant. The plant tightly controls the number of nodules it forms, via a complex root-to-shoot-to-root signaling loop called autoregulation of nodulation （AON）. This regulatory process involves peptide hormones, receptor kinases and small metabolites. Using modern genetic and genomic techniques, many of the components required for nodule formation and AON have now been isolated. This review addresses these recent findings, presents detailed models of the nodulation and AON processes, and identifies gaps in our understanding of these process that have yet to be fully explained.
基金supported by the Innovative Research Group Project of the National Natural Science Foundation of China(NSFC)(U21A2029)the Biological Breeding-National Science and Technology Major Project(2024ZD04079)the NSFC(42477370).
文摘Reactive oxygen species play a crucial role in various stages of the legume-rhizobia symbiosis,from initial nodulation signaling to nodule senescence.However,how rhizobial redox-related proteins regulate symbiotic nodulation in legumesremains largely unknown.By combining transcriptomics,proteomics,and biochemical and molecular genetics,we investigated the role of the Sinorhizobium fredii Q8 enzyme 3-mercaptopyruvate sulfurtransferase(3MST).Although 3MST was not the primary enzyme responsible for hydrogen sulfide(HS)production under our conditions,its absence significantly impaired symbiotic nodule development,redox homeostasis,infection capacity,and nitrogen-fixation efficiency in soybean.We identified a host plasma membrane-localized NADPH oxidase,respiratory burst oxidase homolog B(RbohB),as a key regulator of immune activation during nodule development.Notably,3MST was secreted during nodulation and localized in the nucleoid and cytoplasmic membrane,where it interacts with and persulfidates RbohB at Cys791,thereby suppressing the NADPH oxidase activity of RbohB.We observed that 3MST-mediated persulfidation of RbohB maintains symbiotic redox balance and promotes nodule development.Genetic analyses in soybean,including RbohB overexpression,RNA interference,and site-directed mutagenesis at Cys791,further supported this observation,linking the 3MST-RbohB interaction to effective rhizobial colonization and improved plant growth.Taken together,these findings uncover a rhizobia-initiated symbiotic regulatory mechanism by which a rhizobial sulfurtransferase modulates soybean RbohB via persulfidation to limit NADPH oxidase activity and promote nodulation.
基金supported by a grant from the National Natural Science Foundation of China (31100217)
文摘The discovery of the enzyme L,L‐diaminopimelate aminotransferase（LL‐DAP‐AT, EC 2.6.1.83） uncovered a unique step in the L‐lysine biosynthesis pathway in plants. In Arabidopsis thaliana, LL‐DAP‐AT has been shown to play a key role in plant‐pathogen interactions by regulation of the salicylic acid（SA） signaling pathway. Here, a full‐length cDNA of LL‐DAP‐AT named as LjALD1 from Lotus japonicus（Regel）Larsen was isolated. The deduced amino acid sequence shares 67% identity with the Arabidopsis aminotransferase AGD2‐LIKE DEFENSE RESPONSE PROTEIN1（AtALD1） and is predicted to contain the same key elements： a conserved aminotransferase domain and a pyridoxal‐5＇‐phosphate cofactor binding site.Quantitative real‐time PCR analysis showed that LjALD1 was expressed in all L. japonicus tissues tested, being strongest in nodules. Expression was induced in roots that had been infected with the symbiotic rhizobium Mesorhizobium loti or treated with SA agonist benzo‐（1, 2, 3）‐thiadiazole‐7‐carbothioic Researchacid. LjALD1 Knockdown exhibited a lower SA content, an increased number of infection threads and nodules, and a slight reduction in nodule size. In addition, compared with wild‐type,root growth was increased and shoot growth was suppressed in LjALD1 RNAi plant lines. These results indicate that LjALD1 may play important roles in plant development and nodulation via SA signaling in L. japonicus.
