Abstract

Phytophthora sojae is a pathogen that causes stem and root rot in soybean (Glycine max [L.] Merr.). We previously demonstrated that GmBTB/POZ, a BTB/POZ domain-containing nuclear protein, enhances resistance to P. sojae in soybean, via a process that depends on salicylic acid (SA). Here, we demonstrate that GmBTB/POZ associates directly with soybean LIKE HETEROCHROMATIN PROTEIN1 (GmLHP1) in vitro and in vivo and promotes its ubiquitination and degradation. Both overexpression and RNA interference analysis of transgenic lines demonstrate that GmLHP1 negatively regulates the response of soybean to P. sojae by reducing SA levels and repressing GmPR1 expression. The WRKY transcription factor gene, GmWRKY40, a SA-induced gene in the SA signaling pathway, is targeted by GmLHP1, which represses its expression via at least two mechanisms (directly binding to its promoter and impairing SA accumulation). Furthermore, the nuclear localization of GmLHP1 is required for the GmLHP1-mediated negative regulation of immunity, SA levels and the suppression of GmWRKY40 expression. Finally, GmBTB/POZ releases GmLHP1-regulated GmWRKY40 suppression and increases resistance to P. sojae in GmLHP1-OE hairy roots. These findings uncover a regulatory mechanism by which GmBTB/POZ-GmLHP1 modulates resistance to P. sojae in soybean, likely by regulating the expression of downstream target gene GmWRKY40.

Highlights

  • Phytophthora sojae is a pathogen that causes stem and root rot in soybean (Glycine max [L.] Merr.)

  • We previously demonstrated that GmBTB/POZ positively regulates the response of soybean to P. sojae infection and GmBTB/POZ interacted with GmLHP1 (LIKE HETEROCHROMATIN PROTEIN1) in a bimolecular fluorescence complementation (BiFC) assay[35]

  • We demonstrated that GmLHP1 is an important component of the GmBTB/POZmediated salicylic acid (SA) and immune signaling pathway, providing evidence that the linkage between GmBTB/POZ and GmLHP1 is involved in the response of soybean to P. sojae attack

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Summary

Introduction

Phytophthora sojae is a pathogen that causes stem and root rot in soybean (Glycine max [L.] Merr.). We demonstrate that GmBTB/POZ associates directly with soybean LIKE HETEROCHROMATIN PROTEIN1 (GmLHP1) in vitro and in vivo and promotes its ubiquitination and degradation Both overexpression and RNA interference analysis of transgenic lines demonstrate that GmLHP1 negatively regulates the response of soybean to P. sojae by reducing SA levels and repressing GmPR1 expression. The waxy cuticle and preformed antimicrobial compounds provide passive protection against pathogens rather than attacking a specific host[1], whereas plants rely on innate immunity to defend themselves against widespread diseases[3,4] These immunity responses arise via a regulatory network coordinating immune response proteins, transcriptional regulators, and other structural components[5,6,7].

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