Xuemei Zhang
Yuanyuan Zong
Di Gong
Feng Zhang
Lirong Yu
Yang Bi
Edward Sionov
Dov Prusky

RacA is a signaling molecule of the small GTPase family that regulates fungal morphology and cellular function and activates NADPH oxidase (Nox) transmit signaling molecules. In this study, we performed subcellular localization analysis of RacA in P. expansum and by fusion expression of RacA with GFP, we found that RacA was mostly localized in the cytoplasm and organelle membranes. We also examined the effects of RacA gene on spore and mycelium growth, secondary metabolism and virulence of P. expansum with a knockout mutant strain. The results showed that the ΔPeRacA strain had a rough spore morphology with declined expression of key spore developmental regulators, increased mycelial branching, and slow colonization on fruit tissues. In the ΔPeRacA strain, the accumulation of patulin was markedly reduced and the expression of key genes involved in patulin biosynthesis was significantly reduced. The virulence of ΔPeRacA was greatly impaired in pear fruit and the gene expression of pathogenicity-related extracellular enzymes was also significantly decreased. In addition, we also found that the gene expression of ROS regulatory factors (NoxA and NoxR) was reduced significantly with RacA deletion. These results indicated that RacA might function in P. expansum conidia growth, patulin synthesis and virulence by regulating the expression of ROS related factors.