Transcription factors Som1 and Vta3 of Verticillium dahliae control sequential infection steps of plant host root adhesion, penetration, colonisation and fungal development

The nuclear transcription factors Som1 and Vta3 of the vascular plant pathogen Verticillium dahliae can rescue adhesion in a flo8-deficient Saccharomyces cerevisiae strain by inducing expression of the adhesion encoding yeast genes FLO1 and FLO11. Som1 and Vta3 activate distinct transcriptional networks in V. dahliae which are required for two sequential infection steps of root penetration and colonisation of the plant host. The molecular function of Som1 is conserved between the plant pathogen V. dahliae and the opportunistic human pathogen Aspergillus fumigatus. Som1 controls the expression of genes for adhesion and oxidative stress response supporting fungal adhesion to roots as well as root penetration. Som1 controls septa positioning and the size of vacuoles, and subsequently hyphal development including aerial hyphae formation and normal hyphal branching. Som1 is required earlier than Vta3 in the colonisation of plant root surfaces and tomato plant infection. Som1 and Vta3 antagonise oxidative stress responses. Both factors regulate a genetic network for conidiation, microsclerotia formation and pathogenicity of V. dahliae.