A soybean NAC homolog contributes to resistance to Phytophthora sojae mediated by dirigent proteins

Abstract

Phytophthora sojae infection severely impairs soybean production. We previously identified a dirigent protein, GmDRR1 (Glycine max Disease Resistant Response 1), that increases soybean resistance to P. sojae. However, the molecular basis of GmDRR1 function remained largely uncharacterized. In the present study, analysis of GmDRR1-RNAi, GmDRR1-overexpressing, and CRISPR/Cas9-derived Gmdrr1 mutant lines revealed that GmDRR1 expression significantly restricted P. sojae growth. Combining co-immunoprecipitation with liquid chromatography–tandem mass spectrometry revealed a GmDRR1-interacting protein, GmDRR2, which is homologous to GmDRR1. An E-coniferyl alcohol coupling assay indicated that GmDRR1 promotes the synthesis of (+)-pinoresinol, which helps to protect plants from P. sojae. The GmNAC1 (Glyma.05G025500) transcription factor bound to the GmDRR1 promoter both in vitro and in vivo to upregulate GmDRR1 expression. Soybean resistance to P. sojae was increased by overexpression of GmNAC1. Our findings suggest a novel signaling pathway involving a NAC transcription factor that mediates soybean resistance to P. sojae. Specifically, GmNAC1 directly induces GmDRR1 expression to increase resistance of soybean plants to P. sojae.