Camellia oleifera is the native economic edible oil tree in China and anthracnose occurs commonly in its producing areas. We previously found that ubiquitin-like CfAtg8-related autophagy is essential for the pathogenicity of Colletotrichum fructicola, the major pathogen of anthracnose on C. oleifera. The aim of this study is to further elucidate the roles of autophagy in the pathogenesis of C. fructicola. Based on BLAST_P analysis and reverse genetics, we identified the central hub of another ubiquitin-like system, CfAtg5, and characterized its functions in C. fructicola. As suspected, we found that CfAtg5 is required for autophagy, both in MM-N and H₂O₂ induction conditions. Targeted gene deletion of CfATG5 revealed that CfAtg5 is involved in growth and conidiation. We further found that the ∆Cfatg5 mutant is defective in appressorium formation and in responses to cell wall integrity and oxidative stresses. The combined effects, together with the abolished autophagy, result in the pathogenicity defects of the ∆Cfatg5 mutant. Our study further illustrates the importance of normal autophagy in the physiology and pathogenicity of C. fructicola, and offers a potential target in the development of new anthracnose control strategies.

Camellia oleifera is a woody, edible-oil plant native to China. Anthracnose is the major disease of Ca. oleifera, and Colletotrichum fructicola is the main epidemic pathogen. Our previous research indicated that CfHac1 (homologous to ATF/CREB1) and CfGcn5 (general control nonderepressible 5, Gcn5) are integral to key cellular processes that govern fungal development and pathogenesis. Further transcriptomic analyses of the CfHac1 and CfGcn5 mutants, particularly under conditions of endoplasmic reticulum (ER) stress, hold the potential to unveil additional genes implicated in this critical cellular response. We identified all OST/PMT (oligosaccharyltransferase/Protein O-Mannosyltransferases) genes in C. fructicola and analyzed their expression levels. To elucidate novel glycosylation-related genes that may be important for the virulence of C. fructicola, we took an unbiased transcriptomic approach comparing wild-type and the ∆Cfhac1 mutant. Notably, all OST/PMT genes were induced by dithiothreitol and down-regulated in the ΔCfhac1 mutant, yet only the CfPMT4 (Protein O-Mannosyltransferases 4) gene (A04626) was unaffected in the ΔCfgcn5. The results of targeted gene deletion experiments indicate that CfPMT4 plays a crucial role in both vegetative growth and conidiation. Additionally, our investigation revealed that the ΔCfpmt4 exhibits deficiencies in appressorium formation, as well as in its response to cell wall integrity and endoplasmic reticulum stresses. Furthermore, the mutant displayed impaired glycogen metabolism, which may contribute to reduced penetration ability. Overall, CfPmt4, an O-mannosyltransferase, controls the growth, development, and pathogenicity of Colletotrichum fructicola. Understanding the function of the CfPMT4 homolog could provide a potential molecular target for controlling Ca. oleifera anthracnose.