Identification of proteins associated with the production of methyl 5-(hydroxymethyl) furan-2-carboxylate toxin in Curvularia lunata

Abstract

Curvularia lunata produces a non-host specific toxin known as methyl 5-(hydroxymethyl) furan-2-carboxylate (M5HF2C), a determinant of high virulence to maize. We constructed mutants through Agrobacterium tumefaciens-mediated transformation and found that mutant T806 showed a significant decline in pathogenicity on maize leaves and produced no detectable M5HF2C. Although the tagged gene (Clt-1) has been cloned and demonstrated to be closely association with M5HF2C production and pathogenicity, we expected hypothesized that other proteins might also be related to toxin production. Therefore we used two-dimensional gel electrophoresis to profile T806, and found that there were two up-regulated and six missing proteins in T806 compared to C. lunata wild-type CX-3. These results indicated that these proteins were associated with signal transduction, protein synthesis, secondary metabolism and pathogenicity. Real-time quantitative PCR analysis of five selected genes showed a correlation between low gene expression and detection of the corresponding proteins. Of these, dihydropteroate (DHFA) synthase may be more likely involved in M5HF2C biosynthesis. Bioinformatics analysis showed that DHFA synthase consists of 469 amino acids, which is clustered into one branch with dothideomycete DHFA synthase homolologs in a phylogenetic tree. Further study on the exact role of the DHFA synthase gene is underway.