The AbcCl1 transporter of Colletotrichum lindemuthianum acts as a virulence factor involved in fungal detoxification during common bean (Phaseolus vulgaris) infection

Abstract

Anthracnose, caused by Colletotrichum lindemuthianum, is a disease affecting the common bean plant, Phaseolus vulgaris. To establish infection, the phytopathogen must survive the toxic compounds (phytoanticipins and phytoalexins) that are produced by the plant as a defense mechanism. To study the detoxification and efflux mechanisms in C. lindemuthianum, the abcCl1 gene, which encodes an ABC transporter, was analyzed. The abcCl1 gene (4558 pb) was predicted to encode a 1450-amino acid protein. Structural analysis of 11 genome sequences from Colletotrichum spp. showed that the number of ABC transporters varied from 34 to 64. AbcCl1 was classified in the ABC-G family of transporters, and it appears to be orthologs to ABC1 from Magnaporthe grisea and FcABC1 from Fusarium culmorum, which are involved in pleiotropic drug resistance. A abcT3 (ΔabcCl1) strain showed reduction on aggressivity when inoculated on bean leaves that presented diminishing anthracnose symptoms, which suggests the important role of AbcCl1 as a virulence factor and in fungal resistance to host compounds. The expression of abcCl1 increased in response to different toxic compounds, such as eugenol, hygromycin, and pisatin phytoalexin. Together, these results suggest that AbcCl1 is involved in fungal resistance to the toxic compounds produced by plants or antagonistic microorganisms.

Keywords: Defense mechanism; Phytoalexin; Phytopathogen; Plant; Transporter.