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
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 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.
