Epigenetics: Role of methyltransferases in the pathogenesis of Alternaria brassicicola

Alternaria brassicicola is the causing agent of black spot disease in Brassicaceae. This pathogenic fungus is able to transmit itself on and by seeds. Then it has developed resistance mechanisms against hydric, osmotic and osmolar stresses.

Epigenetic mechanisms are hereditary modifications of gene activities without mutations in the DNA sequence and show an implication in the virulence and plant defense molecules response of pathogen fungi. In A. brassicicola, 2 methyltransferases (abDIM-2, abDIM-5) have been identified.

In this study, we investigated the implication of epigenetic mechanisms on the virulence and the seed transmission of A. brassicicola.

Phenotyping of abDIMs deleted mutants didn’t show involvement of epigenetic mechanisms in their growth, sporulation, virulence or susceptibility against plant defense molecules. However, abDIM mutants are able to transmit better to seeds due to an increased resistance to hydric and osmotic stresses. Expression study of known A. brassicicola genes involved in these stresses resistance showed different expression pattern between abDIM mutants and the wild-type strain and also according to the exposure time to osmotic stress.