Regulation of the JUB1 stress-related transcription factor in Arabidopsis thaliana in response to biotrophic fungus Oidium neolycopersici

Abstract

Biotic stresses influence fitness of the plants and may decrease their productivity. Especially biotrophic fungi govern complex regulation of host metabolism to fulfill their nutritional needs, while the plant tries to avoid this fungal activity. The defense system of the plant may involve transcription of stress-dependent genes, activation of signaling pathways or production of antimicrobial compounds. The responsible signal molecule in biotrophic pathogen-host interaction was found to be mostly the salicylic acid (SA). We studied here, whether the salicylic acid (SA) is required for the induction of a stress-related transcription factor JUB1 by the biotrophic fungus of tomato Oidium neolycopersici or not. To prove the regulation of JUB1, we isolated the upstream region of the gene and transcriptionally fused to gus reporter gene. This promoter::reporter fusion was then transferred into wild type and two salicylic acid insensitive mutants of Arabidopsis thaliana (nim1-1 and nahG). The transgenic plants were infected by powdery mildew (PM) O. neolycopersici. We found an obvious increase of reporter gene expression in all three lines mostly at the area, where the pathogen was contacted to the plants. Based on the result, the stress-dependent JUB1 transcription factor is probably not influenced by the SA mutations of nim1-1 and nahG. However, the induction appeared along with hydrogen-peroxide development, which suggests that this gene regulation in response to powdery mildew is probably regulated via H₂O₂ and not by SA signaling.