Ferulic acid, an abundant maize phenolic, regulates ABC and MFS transporter gene expression in the maize pathogen Cochliobolus heterostrophus

Abstract

Plant pathogens encounter pre-existing and induced defense compounds when they invade the host. Pathogen ATP-binding cassette (ABC) and major facilitator superfamily (MFS) transporters can provide protection during infection through efflux removal of plant defense compounds from the cell. In the current work, we identified a total of 973 transporter genes, including 232 MFS and 39 ABC transporters, in the genome of the southern corn leaf blight pathogen Cochliobolus heterostrophus. We compared these genes with a recently published transcriptomic data set from C. heterostrophus exposed to the phenolic maize defense compound ferulic acid (FA) and identified four transporter gene families that were significantly (P\u2009<\u20090.05) enriched among genes upregulated by FA, including MFS and ABC transporters, the mitochondrial carrier family and the fatty acid transporter family. Phylogenetic analyses further classified most FA-upregulated ABC transporters into subgroups G (pleiotropic drug resistance transporters), B (multi-drug resistance transporters) and C (multi-drug resistance-associated transporters). Out of the 74 MFS transporter genes induced by FA, 29 were classified as members of the 2.A.1.2 Drug:H\u2009+\u2009Antiporter-1 (DHA1) family. The results support the idea that efflux of plant defense compounds by drug resistance membrane transporters contributes to pathogen virulence. The provided MFS and ABC transporter classification should be readily extendable to other Dothideomycete pathogen genomes.