Identification of Clt-1-Regulated Proteins Associated with the Production of Non-Host-Specific Toxin and Pathogenicity in Cochliobolus lunatus

The Curvularia leaf spot is caused by Curvularia lunata (telemorph: Cochliobolus lunatus), which produces a non-host-specific toxin known as methyl 5-(hydroxymethyl) furan-2-carboxylate (M5HF2C). The Clt-1 gene, which is from a pathogen closely associated with M5HF2C production and pathogenicity, was successfully cloned. However, the proteins related to toxin production or pathogenicity were not identified. In this study, a proteomic approach based on two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) techniques was used to identify the specific proteins associated with Clt-1 expression in C.lunatus wild-type CX-3 and Clt-1 deletion mutant Clt-1. Five upregulated and two downregulated proteins were identified in Clt-1. Succinate dehydrogenase flavoprotein subunit (Sdh1p) functions as a coenzyme of dehydrogenase in the anabolism of toxin. Eukaryotic elongation factor 3 (EF-3) facilitates the synthesis of important proteins required for the production of toxins in C.lunatus. Melanin synthesis-related protein scytalone dehydratase (SCD) and stress tolerance-related proteins (HSP30 and HSP70) contribute to the pathogenicity of C.lunatus. Real-time quantitative PCR (RT-qPCR) analysis showed that the Scd gene exhibited similar expression pattern at the transcriptional level, corresponding to the protein detected by 2-DE. Bioinformatics analysis showed that Scd encodes a scytalone dehydratase subunit of 188 amino acids, which is clustered into one branch with dothideomycete SCD homologs in a phylogenetic tree. Further study on the exact role of the Scd gene is underway.