Leguminous plants can establish symbiotic associations with diazotropic rhizobia to form nitrogen- fixating nodules, which are classified as determinate or indeterminate based on the persistence of nodule meristem. Th...Leguminous plants can establish symbiotic associations with diazotropic rhizobia to form nitrogen- fixating nodules, which are classified as determinate or indeterminate based on the persistence of nodule meristem. The formation of nitrogen-fixing nodules requires coordinating rhizobial infection and root nodule organogenesis. The formation of an infection thread and the extent of nodule formation are largely under plant control, but vary with environmental conditions and the physiological state of the host plants. Many achievements in these two areas have been made in recent decades. Phytohormone signaling pathways have gradually emerged as important regulators of root nodule symbio- sis. Cytokinin, strigolactones （SLs） and local accumulation of auxin can promote nodule development. Ethylene, jasmonic acid （JA）, abscisic acid （ABA） and gibberellic acid （GA） all negatively regulate infection thread formation and nodule development. However, salicylic acid （SA） and brassinosteroids （BRs） have different effects on the formation of these two nodule types. Some peptide hormones are also involved in nodulation. This review summarizes recent findings on the roles of these plant hormones in legume-rhizobial symbiosis, and we propose that DELLA proteins may function as a node to integrate plant hormones to regulate nodulation.展开更多
An important question in biology is how organisms can associate with different microbes that pose no threat (commensals), pose a severe threat (pathogens) and those that are beneficial (symbionts). The root nodule sym...An important question in biology is how organisms can associate with different microbes that pose no threat (commensals), pose a severe threat (pathogens) and those that are beneficial (symbionts). The root nodule symbiosis serves as important model system to address such questions in the context of plant-microbe interactions. It is now generally accepted that rhizobia have the abilities to actively suppress host immune responses during the infection process, analogous to the way in which plant pathogens can evade immune recognition. However, much remains to be elucidated with regard to the mechanisms by which the host recognizes the rhizobia as pathogens and how, subsequently, these pathways are suppressed to allow establishment of the nitrogen fixing symbiosis. In this study, we found that SymRK (Symbiosis Receptor-like Kinase) is required for rhizobial suppression of plant innate immunity in Lotus japonicus. SymRK associates with LjBAK1 (BRASSINOSTEROID INSENSITIVE 1-Associated receptor Kinase 1), a well characterized, positive regulator of plant innate immunity, and directly inhibits LjBAK1 kinase activity. Rhizobial inoculation enhances the association between SymRK and LjBAK1 in planta. LjBAK1 is required to regulate plant innate immunity and plays a negative role in mediating rhizobial infection in L. japonicus. The data indicate that the protein complex of SymRK-LjBAK1 serves as an intersection point between rhizobial symbiotic signaling pathways and innate immunity pathways, which provides an evidence that rhizobia might actively suppress the host's ability to mount a defense response in the legume-rhizobium symbiosis.展开更多
基金supported by National Key R&D Program of China (2016YFA0500502) to J.Y.National Natural Science Foundation of China (31500233 to N.Y., 31522007 to E.W.)
文摘Leguminous plants can establish symbiotic associations with diazotropic rhizobia to form nitrogen- fixating nodules, which are classified as determinate or indeterminate based on the persistence of nodule meristem. The formation of nitrogen-fixing nodules requires coordinating rhizobial infection and root nodule organogenesis. The formation of an infection thread and the extent of nodule formation are largely under plant control, but vary with environmental conditions and the physiological state of the host plants. Many achievements in these two areas have been made in recent decades. Phytohormone signaling pathways have gradually emerged as important regulators of root nodule symbio- sis. Cytokinin, strigolactones （SLs） and local accumulation of auxin can promote nodule development. Ethylene, jasmonic acid （JA）, abscisic acid （ABA） and gibberellic acid （GA） all negatively regulate infection thread formation and nodule development. However, salicylic acid （SA） and brassinosteroids （BRs） have different effects on the formation of these two nodule types. Some peptide hormones are also involved in nodulation. This review summarizes recent findings on the roles of these plant hormones in legume-rhizobial symbiosis, and we propose that DELLA proteins may function as a node to integrate plant hormones to regulate nodulation.
基金This work was supported by the National Key R&D Program of China(2019YFA0904700)the National Natural Science Foundation of China(31870217,32070273,and 32090063)+2 种基金the HZAU Scientific&Technological Self-Innovation Foundation(2662019PY026)the Natural Science Foundation of Hubei Province(2020CFA008 and 2020CFB289)Work performed in the Stacey laboratory was funded by a grant from the US National Science Foundation Plant Genome Program(1734145).
文摘An important question in biology is how organisms can associate with different microbes that pose no threat (commensals), pose a severe threat (pathogens) and those that are beneficial (symbionts). The root nodule symbiosis serves as important model system to address such questions in the context of plant-microbe interactions. It is now generally accepted that rhizobia have the abilities to actively suppress host immune responses during the infection process, analogous to the way in which plant pathogens can evade immune recognition. However, much remains to be elucidated with regard to the mechanisms by which the host recognizes the rhizobia as pathogens and how, subsequently, these pathways are suppressed to allow establishment of the nitrogen fixing symbiosis. In this study, we found that SymRK (Symbiosis Receptor-like Kinase) is required for rhizobial suppression of plant innate immunity in Lotus japonicus. SymRK associates with LjBAK1 (BRASSINOSTEROID INSENSITIVE 1-Associated receptor Kinase 1), a well characterized, positive regulator of plant innate immunity, and directly inhibits LjBAK1 kinase activity. Rhizobial inoculation enhances the association between SymRK and LjBAK1 in planta. LjBAK1 is required to regulate plant innate immunity and plays a negative role in mediating rhizobial infection in L. japonicus. The data indicate that the protein complex of SymRK-LjBAK1 serves as an intersection point between rhizobial symbiotic signaling pathways and innate immunity pathways, which provides an evidence that rhizobia might actively suppress the host's ability to mount a defense response in the legume-rhizobium symbiosis.
