AHL13, AHL19 and AHL20 Genes Differentially Regulate Cell Wall-Associated Defense Responses under Fumonisin B1-Induced Stress in Arabidopsis thaliana.

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium species, induces oxidative stress and cell wall-associated defense responses in plants. However, the regulatory factors that determine how different components of cell wall defense are coordinated under toxin-induced stress remain poorly understood. AT-hook motif nuclear-localized (AHL) proteins are chromatin-associated transcriptional regulators, but their roles in FB1-induced cell wall remodeling have not been directly examined. In this study, we investigated the distinct roles of AHL13, AHL19, and AHL20 genes in FB1-induced defense responses in Arabidopsis thaliana. Wild-type Col-0 and ahl13, ahl19, and ahl20 loss-of-function mutants were treated with 10µM FB1 for 4 days, and growth, oxidative stress markers, defense-related enzyme activities, and cell wall associated gene expression were analyzed. The three mutants displayed genotype-specific responses rather than a uniform defense pattern. In ahl13 mutant, weakening of the peroxidase-associated responses was accompanied by activation of biosynthetic and remodeling-related components. In ahl19 mutant, a biosynthesis-oriented wall defense program became more prominent. In ahl20 mutant, oxidative damage remained limited, while selected antioxidant and defense mechanisms were activated. These findings indicate that AHL13, AHL19, and AHL20 genes do not simply enhance or suppress FB1-induced cell wall defense. Instead, they appear to act as regulatory factors that may differentially influence ROS production/detoxification, peroxidase activity, phenylpropanoid input, callose-related responses, cellulose biosynthesis, and wall remodeling pathways.