Comparative genomics of three Colletotrichum scovillei strains and genetic analysis revealed genes involved in fungal growth and virulence on chili pepper

Abstract

Colletotrichum scovillei is a virulent pathogen and the dominant species causing anthracnose of chili pepper in many Asian countries. Three strains of this pathogen, Coll-524, Coll-153 and Coll-365, show varied virulence on chili pepper fruit. Among the three strains, Coll-365 showed significant defects in growth and virulence. To decipher the genetic variations among these strains and identify genes contributing to growth and virulence, in this study, comparative genomic analysis and gene transformation to verify gene function were applied. The genomes of the three strains were sequenced and Coll-524 had 1.3% and 1.5% more genes than Coll-153 and Coll-365, respectively. Compared to Coll-524 and Coll-153, Coll-365 had numerous gene losses including 33 effector genes that are distributed in different scaffolds and a cluster of 14 genes in a 34-kb genomic fragment. Through gene transformation, three genes in the 34-kb fragment were identified to have functions in growth and/or virulence of C. scovillei. Gene 15019 encoding a protein related to phospholipase A2-activating protein enhanced the growth of Coll-365. A combination of 15019 with one transcription factor gene 15022 and one C6 zinc finger domain-containing protein gene 15029 was found to enhance the pathogenicity of Coll-365. Introduction of gene 15215, which encodes a LysM domain-containing protein, into Coll-365 caused a reduction in the germination rate of Coll-365. In conclusion, the higher virulent strain Coll-524 had more genes and encoded more pathogenicity related proteins and transposable elements than the other two strains, which may contribute to the high virulence of Coll-524. In addition, the absence of the 34-kb fragment plays a critical role in the defects of growth and virulence of strain Coll-365.