A MYB coiled‐coil transcription factor interacts with NSP2 and is involved in nodulation in Lotus japonicus

• DOI: 10.1111/nph.12593
• Publication Date: 2013-11-11T15:01:00Z
• Authors: Heng Kang; Xiaojie Chu; Chao Wang; Aifang Xiao; Hui Zhu; Songli Yuan; Zhenzhen Yang; Danxia Ke; Shaobo Xiao; Zonglie Hong; Zhongming Zhang
• Keywords: Cell Nucleus; Transcriptional Activation; 0301 basic medicine; 0303 health sciences; Time Factors; DNA, Plant; Molecular Sequence Data; Plant Root Nodulation; Protein Structure, Tertiary; 03 medical and health sciences; Phenotype; Gene Expression Regulation, Plant; Lotus; RNA Interference; Amino Acid Sequence; Root Nodules, Plant; Glucuronidase; Plant Proteins; Protein Binding; Rhizobium; Subcellular Fractions; Transcription Factors

Summary

Transcription factor complex formation is a central step in regulating gene expression. In this report, a novel MYB coiled‐coil transcription factor referred to as IPN2, for Interacting Protein of NSP2, is described. The interaction between IPN2 and NSP2 was examined by protein pull‐down assays and bimolecular fluorescence complementation (BiFC). Subcellular localization of proteins, gene expression and gene function were assessed in transgenic hairy roots expressing tagged recombinant proteins, promoter‐reporter and RNA interference (RNAi) constructs, respectively. The GRAS domain of NSP2 and the coiled‐coil domain of IPN2 were found to be responsible for the interaction between the two proteins. IPN2 had strong transcription activation activity, bound directly to the NIN gene promoter, and was localized to the nuclei of Lotus japonicus root cells. The expression of IPN2 was elevated during nodule development, coinciding with increased NSP2 gene expression during nodule organogenesis. RNAi‐mediated knockdown expression of IPN2 did not affect arbuscular mycorrhizal development, but had deleterious effects on rhizobial infection and nodule formation in L. japonicus. These results demonstrate an important role of IPN2 in nodule organogenesis and place a new MYB transcription factor in the Nod signaling pathway.