Abstract
Fungal development and secondary metabolism is intimately associated via activities of the fungi-specific velvet family proteins including VeA, VosA, VelB and VelC. Among these, VelC has not been characterized in Aspergillus nidulans. In this study, we characterize the role of VelC in asexual and sexual development in A. nidulans. The velC mRNA specifically accumulates during the early phase of sexual development. The deletion of velC leads to increased number of conidia and reduced production of sexual fruiting bodies (cleistothecia). In the velC deletion mutant, mRNA levels of the brlA, abaA, wetA and vosA genes that control sequential activation of asexual sporulation increase. Overexpression of velC causes increased formation of cleistothecia. These results suggest that VelC functions as a positive regulator of sexual development. VelC is one of the five proteins that physically interact with VosA in yeast two-hybrid and GST pull down analyses. The ΔvelC ΔvosA double mutant produced fewer cleistothecia and behaved similar to the ΔvosA mutant, suggesting that VosA is epistatic to VelC in sexual development, and that VelC might mediate control of sex through interacting with VosA at specific life stages for sexual fruiting.
Highlights
The genus Aspergillus is found ubiquitously in our environment and some species are of tremendous importance to humankind as serious human and plant pathogens and as agricultural aids [1]
To correlate phenotypic changes caused by the absence of velC with the molecular events, we examined the mRNA levels of various asexual development-specific genes including brlA, abaA, wetA, and vosA in WT and DvelC strains grown under conditions that induce asexual development (Fig. 2B)
We present the experimental evidence that VelC plays a vital role in controlling asexual and sexual development in A. nidulans
Summary
The genus Aspergillus is found ubiquitously in our environment and some species are of tremendous importance to humankind as serious human and plant pathogens and as agricultural aids [1]. Previous studies proposed that production of some mycotoxins including the most potent natural carcinogens, aflatoxins, is tightly correlated with asexual development (conidiation) [2,3,4]. The velvet family proteins, including VosA, VeA, VelB and VelC, have been identified as key regulators that bridge spore formation and mycotoxin production in Aspergillus [8,9,10]. The VelB-VosA hetero-complex plays a key role in maturation, dormancy and germination of spores [12]. VeA regulates the biosynthesis of secondary metabolites, including aflatoxin in A. flavus [20] and A. parasiticus [21], gliotoxin in A. fumigatus[16], and penicillin in A. oryzae [22]
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