SG2-Type R2R3-MYB Transcription Factor MYB15 Controls Defense-Induced Lignification and Basal Immunity in Arabidopsis

Abstract

Lignification of cell wall appositions is a conserved basal defense mechanism in the plant innate immune response. However, the genetic pathway controlling defense-induced lignification remains unknown. Here, we demonstrate the SG2-type R2R3-MYB transcription factor MYB15 as a regulator of defense-induced lignification and basal immunity. Loss of MYB15 reduces the content but not the composition of defense-induced lignin, whereas constitutive expression of increases lignin content independently of immune activation. Comparative transcriptional and metabolomics analyses implicate as necessary for the defense-induced synthesis of guaiacyl lignin and the basal synthesis of the coumarin metabolite scopoletin. MYB15 directly binds to the secondary wall MYB-responsive element consensus sequence, which encompasses the AC elements, to drive lignification. The and lignin biosynthetic mutants show increased susceptibility to the bacterial pathogen , consistent with defense-induced lignin having a major role in basal immunity. A scopoletin biosynthetic mutant also shows increased susceptibility independently of immune activation, consistent with a role in preformed defense. Our results support a role for phenylalanine-derived small molecules in preformed and inducible Arabidopsis defense, a role previously dominated by tryptophan-derived small molecules. Understanding the regulatory network linking lignin biosynthesis to plant growth and defense will help lignin engineering efforts to improve the production of biofuels and aromatic industrial products as well as increase disease resistance in energy and agricultural crops.

Lignin‐based barrier restricts pathogens to the infection site and confers resistance in plants

“…In a recent study, lignification has been implicated in basal immunity, and treatment with the bacterial PAMP flg22 markedly increased lignin accumulation in Arabidopsis seedlings (Chezem et al , ). In this study, we further examined pathogen‐induced lignification by challenging Arabidopsis seedlings (12‐day‐old) and adult plants (6‐week‐old) with virulent P. syringae pv.…”

“…Previous studies have shown that lignification is induced during basal resistance or PTI responses (Robertsen, ; Kawano & Shimamoto, ; Chezem et al , ). In a recent study, the SG2‐type R2R3‐MYB transcription factor MYB15 directly bound to gene promoters required for G‐lignin biosynthesis and activated lignification in response to flg22 (Chezem et al , ).…”

RNA‐Seq identification of candidate defense genes by analyzing Mythimna separata feeding‐damage induced systemic resistance in balsas teosinte

“…The identification of the positive response of MYB15 and MYB 46 to armyworm attack was unique. They were reported as being associated with cell wall biosynthesis and affecting basal immunity in Arabidopsis and Betula platyphylla . MYB115 was documented as a contributor to the proanthocyanidin biosynthesis regulation that provides fungal resistance in poplar .…”

Maize phenylalanine ammonia‐lyases contribute to resistance to Sugarcane mosaic virus infection, most likely through positive regulation of salicylic acid accumulation

“…Lignin quantification was performed as previously described (Chezem et al ., ) with specific modifications. The first SCMV‐infected systemically infected leaves (i.e.…”