Transcriptional regulation of NIN expression by IPN2 is required for root nodule symbiosis in Lotus japonicus

作者：Xiao, Aifang; Yu, Haixiang; Fan, Yuqian; Kang, Heng; Ren, Yaping; Huang, Xiaoqin; Gao, Xiumei; Wang, Chao; Zhang, Zhongming; Zhu, Hui^*; Cao, Yangrong^*

来源：NEW PHYTOLOGIST, 2020, 227(2): 513-528.

DOI：10.1111/nph.16553

• DNA binding
• gene expression regulation
• Lotus japonicus
• root nodule symbiosis
• transcription activation

Expression of Nodule Inception (NIN) is essential for initiation of legume-rhizobial symbiosis. An existing model regarding the regulation of NIN expression involves two GRAS transcription factors - NSP1 (Nodulation Signaling Pathway 1) and NSP2. NSP2 forms a complex with NSP1 to directly bind to NIN promoter. However, rhizobial treatment-induced NIN expression could still be detected in the nsp1 mutant plants, suggesting that other proteins must be involved in the regulation of NIN expression. @@@ A combination of molecular, biochemical and genetic analyses was used to investigate the molecular basis of IPN2 in regulating root development and NIN expression in Lotus japonicus. @@@ In this study, we identified that IPN2 is a close homolog of Arabidopsis APL (ALTERED PHLOEM DEVELOPMENT) with essential function in root development. However, Lotus IPN2 has a different expression pattern compared with the Arabidopsis APL gene. IPN2 binds to the IPN2-responsive cis element (IPN2-RE) of NIN promoter and activates NIN expression. IPN2, NSP1 and NSP2 form a protein complex to directly target NIN promoter and activate NIN expression in the legume-rhizobial symbiosis. @@@ Our data refine the regulatory model of NIN expression that NSP2 works together with NSP1 and IPN2 to activate the NIN gene allowing nodulation in L. japonicus.

• 单位
  华中农业大学; 农业微生物学国家重点实验室