Molecular characterization and functional analyses of ZtWor1, a transcriptional regulator of the fungal wheat pathogen Zymoseptoria tritici
Résumé
Zymoseptoria tritici causes the major fungal wheat disease
septoria tritici blotch, and is increasingly being used as a model for
transmission and population genetics, as well as host–pathogen
interactions. Here, we study the biological function of ZtWor1, the
orthologue of Wor1 in the fungal human pathogen Candida
albicans, as a representative of a superfamily of regulatory proteins involved in dimorphic switching. In Z. tritici, this gene is
pivotal for pathogenesis, as ZtWor1 mutants were nonpathogenic
and complementation restored the wild-type phenotypes.
In planta expression analyses showed that ZtWor1 is up-regulated
during the initiation of colonization and fructification, and regulates candidate effector genes, including one that was discovered
after comparative proteome analysis of the Z. tritici wild-type
strain and the ZtWor1 mutant, which was particularly expressed
in planta. Cell fusion and anastomosis occur frequently in ZtWor1
mutants, reminiscent of mutants of MgGpb1, the β-subunit of the
heterotrimeric G protein. Comparative expression of ZtWor1 in
knock-out strains of MgGpb1 and MgTpk2, the catalytic subunit of
protein kinase A, suggests that ZtWor1 is downstream of the cyclic
adenosine monophosphate (cAMP) pathway that is crucial for
pathogenesis in many fungal plant pathogens.