The defence response of Arabidopsis thaliana roots against the fungal pathogen Fusarium oxysporum

Abstract

Fusarium oxysporum is a root-infecting fungal pathogen that causes wilt disease on a broad range of plant species, including Arabidopsis thaliana. Investigation of the defence response against this pathogen has primarily been conducted using leaf tissue and little is known about the root defence response. In this study, we analysed the expression of root genes after infection with F. oxysporum by microarray analysis. In contrast to the leaf response, the root tissue did not show a strong induction of defence associated gene expression and instead showed a greater proportion of repressed genes. Screening insertion mutants from differentially expressed genes in the microarray uncovered a role for the transcription factor ETHYLENE RESPONSE FACTOR72 (ERF72) in providing susceptibility to F. oxysporum. Due to the role of ERF72 in suppressing programmed cell death and detoxifying reactive oxygen species, we examined other mutants known to possess higher and lower ROS production in response to pathogen challenge. We found that the pub22/pub23/pub24 U-box type E3 ubiquitin ligase triple mutant which possesses an enhanced oxidative burst as well as the peroxidase33 mutant which possesses a reduced oxidative burst to have increased resistance and increased susceptibility, respectively, to F. oxysporum infection. We therefore identify a role for the oxidative burst in F. oxysporum resistance and identify new genes involved in the root response to F. oxysporum.3