Cloning And Characterization Of A G-Protein γ Subunit Gene In The Chestnut Blight Fungus, Cryphonectria Parasitica

Heterotrimeric G-protein (Gα,Gβand Cγ) mediated signal transduction is one ofthe most important signaling pathways in Eukaryocytes. In Cryphonectriaparasitica,3 Gαsubunits (CPG-1,CPG-2 and CPG-3) and 1 Gβ(CPGB-1) hadbeen found. In this work, we reported the first Gγsubunit gene cpgg-1 that wascomposed of three exons and two introns, which locate at the ORF and5'-untranslated region, respectively. The predicted CPGG-1 protein consists of93 amino acids showing 89% and 88% identities with filamentous fungiNeurospora crassa and Magnaporthe grisea, respectively. Deletion of cpgg-1 inC. parasitica resulted in a phenotype very similar to the cpgb-1 mutant, withlowered asexual sporulation level, reduced virulence, pigmentation, and hyphalbranching, but with enhanced growth on PDA medium, demonstrating thatCPGG-1 was involved in many signaling pathways that range from growth tovirulence. The△cpgg-1 was more sensitive to hypertonic and heat stressescompared with the wild type strain EP155 and parental strain△cpku80. Compared with Gβknockout strain△cpgb-1,△cpgg-1 was more tolerate tothe stress conditions, suggesting that Gβand Gγmay play different roles inCryphonectria parasitica besides functioning by forming Gβ/Gγdimer.