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

Jessica Starke,Rebekka Harting,Kai Heimel,Isabel Maurus,Rica Bremenkamp,Miriam Leonard,James W. Kronstad,Gerhard H. Braus

doi:10.3390/jof7040305

Abstract

Differentiation, growth, and virulence of the vascular plant pathogen Verticillium dahliae 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 V. dahliae, 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 V. dahliae.

Highlights

Verticillium dahliae is a soil-borne asexual ascomycete causing vascular wilt disease in a broad range of plants including high value crops [1,2]
Similar signaling component mutant phenotypes observed in this study suggest an interplay between the unfolded protein response (UPR) and pheromone response mitogen-activated protein kinase (MAPK) signaling, which both affect fungal growth, resting structure development, and virulence in the vascular pathogen V. dahliae
A Hac1-like UPR transcription factor was predicted in V. dahliae by BLASTp search

Summary

Introduction

Verticillium dahliae is a soil-borne asexual ascomycete causing vascular wilt disease in a broad range of plants including high value crops [1,2]. Unfavorable conditions induce the formation of highly resistant, black melanized microsclerotia as characteristic dormant structures which persist in the soil and can overwinter for at least 14 years [1,3,4]. The fungus germinates upon recognition of an appropriate host and enters the plant preferably via natural root wounds, root tips, or lateral root hairs [5,6,7,8]. Hyphae grow from cortical cells towards the central cylinder and some of them successfully reach the xylem. Asexual spores spread via the transpiration stream [9]. Colonization of tissues neighboring the xylem correlates with induction of disease symptoms [10]

Methods

Results

Conclusion