Plant pathogens are some of the most devastating crop stressors. Protein acetylation has emerged as a major post-translational modification that modulates many different cellular processes, including plant immunity and stress responses. Acetylation and deacetylation alter the state of defense gene promoters, promoting susceptibility or resistance. Cochlibolus carbonum, Northern Leaf Spot, produces an effector molecule called HC-Toxin that functions as a histone deacetylase inhibitor, which is required for pathogen virulence. ZmREL2, ramosa1 enhancer locus, encodes a transcriptional corepressor that is homologous to the TOPLESS (TPL) gene in Arabidopsis. Furthermore, expression of ZmREL2 in Arabidopsis rescues developmental defects in tpl mutants. The TPL family acts as corepressors in many different pathways including auxin (TPL-IAA-ARF) and jasmonate (TPL-JAZ-MYC2) signaling. We identified a site of lysine acetylation on REL2 using global acetylome profiling of corn plants treated with HC-Toxin or infected with C. carbonum. We have found that rel2 mutant corn plants are susceptible to C. carbonum infection, unlike their B73 counterparts, which demonstrates that this gene is directly related to plant immunity. In addition, using Yeast Two Hybrid assays, we have shown that mutations of REL2 that mimic acetylation result in reduced interaction of REL2 with transcription factors containing DLN and RLFGV repression motifs. Finally, we confirmed using luciferase corepression assays that REL2 acts as a corepressor. Furthermore, REL2 acetylation null mutations abolish the repression activity of REL2. Ultimately the goal of this work is to elucidate how hyperacetylation impacts the biological activity of REL2 and its roles in plant pathogen interactions.
Coauthors: Mary Galli – Waksman Institute of Microbiology, Rutgers University;Christian Montes-Serey – Iowa State University;Andrea Gallavotti – Waksman Institute of Microbiology, Rutgers University;Justin Walley – Iowa State University