Brassinosteroids （BRs） are an important class of phytohormones which regulates a wide range of physiological processes. Genetic and physiological studies have revealed that BR responses usually depend on an intact a...Brassinosteroids （BRs） are an important class of phytohormones which regulates a wide range of physiological processes. Genetic and physiological studies have revealed that BR responses usually depend on an intact auxin signaling pathway. Here, we demonstrate that high BR concentration or enhanced BR signaling induce the differential growth of etiolated hypocotyls and result in the morphological changes, while auxin-resistant mutants, msg2 （dominant mutant of IAA19） and arf7, are insensitive to the BR effect and can partially suppress the phenotype of bzrl-D （dominant mutant of BZR1 with enhanced BR signaling）. Interestingly, BZR1 protein can directly bind to the promoter regions of both IAA19 and ARFT, indicating that IAA19 and ARF7 mediate the BR-induced differential growth by serving as direct targets of BZR1. Systemic microarray analysis revealed that a number of BR-responsive genes showed reduced BR response in msg2, confirming that BR employs auxin signaling components IAA19 and ARF7 to modulate the specific downstream processes. These results provide informative clues on the crosstalk of BR-auxin signaling and the mechanisms of BR-auxin effects in regulating differential growth.展开更多
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
基金This study was supported by the National Science Foundation of China （Grant Nos： 91117009 and 90717001）.Wethank Dr Kotaro T. Yamamoto （Hokkaido University） for the gifts of msg2-1 seeds, Dr Zhi-Yong Wang （Stanford University） for providing bzrl-D seeds and seeds of pBZRI：：mBZR1-CFP transgenic plants, Prof. Hong-Quan Yang （Shanghai Jiao Tong University） for axr2-1 seeds, and Dr Jian-Ming Li （University of Michigan） for det2-1 seeds. No conflict of interest declared.
文摘Brassinosteroids （BRs） are an important class of phytohormones which regulates a wide range of physiological processes. Genetic and physiological studies have revealed that BR responses usually depend on an intact auxin signaling pathway. Here, we demonstrate that high BR concentration or enhanced BR signaling induce the differential growth of etiolated hypocotyls and result in the morphological changes, while auxin-resistant mutants, msg2 （dominant mutant of IAA19） and arf7, are insensitive to the BR effect and can partially suppress the phenotype of bzrl-D （dominant mutant of BZR1 with enhanced BR signaling）. Interestingly, BZR1 protein can directly bind to the promoter regions of both IAA19 and ARFT, indicating that IAA19 and ARF7 mediate the BR-induced differential growth by serving as direct targets of BZR1. Systemic microarray analysis revealed that a number of BR-responsive genes showed reduced BR response in msg2, confirming that BR employs auxin signaling components IAA19 and ARF7 to modulate the specific downstream processes. These results provide informative clues on the crosstalk of BR-auxin signaling and the mechanisms of BR-auxin effects in regulating differential growth.
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.
