Comparative proteomics of osmotic signal transduction mutants inBotrytis cinereaexplain loss of pathogenicity phenotypes and highlight interaction with cAMP and Ca²⁺signalling pathways

Abstract

Signal transduction (ST) is essential for rapid adaptive responses to changing environmental conditions through rapid post-translational modifications of signalling proteins and downstream effectors that regulate the activity of target proteins and/or the expression of downstream genes.• We have performed a 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.• Multiplex shotgun proteomics detected 628 differential proteins between mutants and wild-type, 280 common to both mutants, indicating independent and shared regulatory functions for both kinases. Gene ontology analysis 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. Intracellular accumulation of secreted proteins in the ∆bos1 histidine-kinase mutant suggests a potential secretion defect. The proteome data also highlight a new link between Sak1 MAPK, cAMP and Ca 2+ signalling.• This study reveals the potential of proteomic analyses of signal transduction mutants to decipher their biological functions. key-words: gene ontology, infection related function, protein kinase, reactive oxygen species, secondary metabolism, secreted proteins