Involvement of a velvet protein ClVelB in the regulation of vegetative differentiation, oxidative stress response, secondary metabolism, and virulence in Curvularia lunata.

The ortholog of Aspergillus nidulans VelB, which is known as ClVelB, was studied to gain a broader insight into the functions of a velvet protein in Curvularia lunata. With the expected common and specific functions of ClVelB, the deletion of clvelB results in similar though not identical phenotypes. The pathogenicity assays revealed that ΔClVelB was impaired in colonizing the host tissue, which corresponds to the finding that ClVelB controls the production of conidia and the methyl 5-(hydroxymethyl) furan-2-carboxylate toxin in C. lunata. However, the deletion of clvelB led to the increase in aerial hyphae and melanin formation. In addition, ΔClVelB showed a decreased sensitivity to iprodione and fludioxonil fungicides and a decreased resistance to cell wall-damaging agents and osmotic stress and tolerance to HO. The ultrastructural analysis indicated that the cell wall of ΔClVelB became thinner, which agrees with the finding that the accumulated level of glycerol in ΔClVelB is lower than the wild-type. Furthermore, the interaction of ClVelB with ClVeA and ClVosA was identified in the present research through the yeast two-hybrid and bimolecular fluorescence complementation assays. Results indicate that ClVelB plays a vital role in the regulation of various cellular processes in C. lunata.