The Farnesyltransferase β-Subunit Ram1 Regulates Mating, Pathogenicity and Cell Wall Integrity.

The basidiomycetous fungus causes a serious sugarcane smut disease in major sugarcane growing areas. Sexual mating is essential for infection to the host; however, its underlying molecular mechanism has not been fully studied. In this study, we identified a conserved farnesyltransferase (FTase) β subunit Ram1 in . The Δ mutant displayed significantly reduced mating/filamentation, thus of weak pathogenicity to the host cane. The Δ mutant sporidia showed more tolerant toward cell wall stressor Congo red compared to that of the wild-type. Transcriptional profiling showed that Congo red treatment resulted in notable up-regulation of the core genes involving in cell wall integrity pathway in Δ sporidia compared with that of WT, indicating that Ram1 may be involved in cell wall integrity regulation. In yeast the heterodimeric FTase is responsible for post-translational modification of Ras (small G protein) and a-factor (pheromone). We also identified and characterized two conserved Ras proteins, Ras1 and Ras2, respectively, and a pheromone precursor Mfa1. The Δ, Δ and Δ mutants all displayed reduced mating/filamentation similar as the Δ mutant. However, both Δ and Δ mutants were hypersensitive to Congo red while the Δ mutant was the same as wild-type. Overall our study displayed that plays an essential role in mating/filamentation, pathogenicity, and cell wall stability.