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

Abstract

SummaryTranscription 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.

Two CCAAT‐box‐binding transcription factors redundantly regulate early steps of the legume‐rhizobia endosymbiosis

“…NF‐induced expression of NSP2 depends on DMI3 (Kalo et al ., ) but beyond this genetic evidence, the molecular mechanism, involving CYCLOPS/IPD3 or not, remains however unknown. In addition to being a target of CYCLOPS, NIN also seems to be a target of NSP1 in M. truncatula (Hirsch et al ., ), and of IPN2, a MYB TF that interacts with NSP2 in L. japonicus (Kang et al ., ). However, it remains to be determined whether this is the case during earlier NF‐signaling steps.…”

The small secreted effector protein MiSSP7.6 of Laccaria bicolor is required for the establishment of ectomycorrhizal symbiosis

“…tumefaciens infiltration was conducted as described in Kang et al . (). Fluorescence of the lower epidermis of leaf discs was assayed 3–5 days after infiltration using Zeiss LSM780 CLSM.…”

“…All expression constructs were transferred into A. tumefaciens strain GV3101 by electroporation. Transient expression of proteins in N. benthamiana leaves by A. tumefaciens infiltration was conducted as described in Kang et al (2014). Fluorescence of the lower epidermis of leaf discs was assayed 3-5 days after infiltration using Zeiss LSM780 CLSM.…”

Introduction to a Virtual Special Issue on cell biology at the plant–microbe interface

“…IPN2 has strong transactivation activity and localizes to nuclei of L. japonicus root cells. RNAi‐mediated IPN2 gene silencing compromised rhizobial infection and nodule formation, suggesting that NSP2 and IPN2 may form a transcription factor complex to promote the expression of a set of genes that are essential for nodule development ( Kang et al ., ).…”