Unfolded Protein Response and Scaffold Independent Pheromone MAP Kinase Signaling Control Growth, Development, and Plant Pathogenesis.

Differentiation, growth, and virulence of the vascular plant pathogen depend on a network of interconnected cellular signaling cascades. The transcription factor Hac1 of the endoplasmic reticulum-associated unfolded protein response (UPR) is required for initial root colonization, fungal growth, and vascular propagation by conidiation. Hac1 is essential for the formation of microsclerotia as long-time survival resting structures in the field. Single endoplasmic reticulum-associated enzymes for linoleic acid production as precursors for oxylipin signal molecules support fungal growth but not pathogenicity. Microsclerotia development, growth, and virulence further require the pheromone response mitogen-activated protein kinase (MAPK) pathway, but without the Ham5 scaffold function. The MAPK phosphatase Rok1 limits resting structure development of , but promotes growth, conidiation, and virulence. The interplay between UPR and MAPK signaling cascades includes several potential targets for fungal growth control for supporting disease management of the vascular pathogen .