Signal transduction (ST) is essential for rapid adaptive responses to changing environmental conditions. It acts through rapid post-translational modifications of signalling
proteins and downstream effectors that regulate the activity and/or subcellular localisation of target
proteins, or the expression of downstream genes. We have performed a quantitative, comparative proteomics study of ST mutants in the phytopathogenic fungus Botrytis cinerea during axenic growth under non-stressed conditions to decipher the roles of two
kinases of the hyper-osmolarity pathway in B. cinerea physiology. We studied the mutants of the
sensor histidine kinase Bos1 and of the MAP
kinase Sak1. Label-free shotgun proteomics detected 2425
proteins, 628 differentially abundant between mutants and wild-type, 270 common to both mutants, indicating independent and shared regulatory functions for both
kinases. Gene ontology analysis showed significant changes in functional categories that may explain in vitro growth and virulence defects of both mutants (secondary metabolism
enzymes, lytic
enzymes,
proteins linked to osmotic, oxidative and cell wall stress). The
proteome data also highlight a new link between Sak1 MAPK, cAMP and Ca2+ signalling. This study reveals the potential of proteomic analyses of signal transduction mutants to decipher their
biological functions. TEXT-VULGARISATION: The fungus Botrytis cinerea is responsible for grey mold disease of hundreds of plant species. During
infection, the fungus has to face important changes of its environment. Adaptation to these changing environmental conditions involves
proteins of such called signal transduction pathways that regulate the production, activity or localisation of cellular components, mainly
proteins. While the components of such signal transduction pathways are well known, their role globally understood, the precise impact on
protein production remains unknown. In this study we have analysed and compared the global
protein content of two Botrytis cinerea signal transduction mutants - both avirulent - to the pathogenic parental strain. The data of 628 differential
proteins between mutants and wild-type, showed significant changes in
proteins related to plant
infection (secondary metabolism
enzymes, lytic
enzymes,
proteins linked to osmotic, oxidative and cell wall stress) that may explain the virulence defects of both mutants. Moreover, we observed intracellular accumulation of secreted
proteins in one of the mutants suggesting a potential secretion defect.