GSE123783
The Neurospora crassa VE-1/VE-2/LAE-1 velvet complex controls development, secondary metabolism and light-dependent carotenoid biosynthesis
Neurospora crassa is a reference organism to study carotene biosynthesis and light regulation for decades. However, there is no evidence of its capacity to produce secondary metabolites, a characteristic of many filamentous fungi. In this work, we report the role of the fungal specific velvet regulator complex in development and secondary metabolism in N. crassa. Four velvet genes were found in the genome. Deletion of ve-1 or ve-2 affects asexual and sexual development, secondary metabolism and light-dependent carotene biosynthesis. Deletion of vos-1 did not show significant differences in comparison to wild type. Deletion of lae-1 resulted in reduced protoperithecia formation and affected secondary metabolism. VE-1, VE-2, LAE-1 and VOS-1 showed nucleo-cytoplasmic localization, which was independent of light input. Two distinct velvet complexes were found in vivo: a heterotrimeric VE-1/VE-2/LAE-1 and a heterodimeric VE-2/VOS-1 complex, respectively. The heterotrimer-complex positively regulated sexual development and repressed asexual spore formation. Moreover, it repressed siderophore coprogen production under iron starvation conditions. The VE-1/VE-2 heterodimer controlled the production of carotene pigments. VE-1 regulated the expression of more than 15% of the whole genome, which corresponded mainly to regulatory, developmental and redox proteins. We also studied intergenera functions of the velvet complex through complementation of A. nidulans veA, velB, laeA, vosA mutants with their Neurospora crassa orthologues ve-1, ve-2, lae-1 and vos-1, respectively. Expression of VE-1 and VE-2 in A. nidulans successfully substituted the developmental and secondary metabolite functions of VeA and VelB by forming two functional chimeric velvet complexes in vivo, VelB/VE-1/LaeA and VE-2/VeA/LaeA, respectively. The N. crassa lae-1 and vos-1 genes did not complement respective A. nidulans mutants and failed to form corresponding complexes. Reciprocally, expression of veA restored the phenotypes of the N. crassa ve-1 mutant. All N. crassa velvet proteins heterologously expressed in A. nidulans were predominantly localized to nuclear fraction independent of light signal. These data highlight the conservation of the complex formation potential in N. crassa and A. nidulans. However, they also underline the similarities and differences of the velvet roles across genera according to the different life styles, niches and ontogenetic processes. Overall design: Neurospora crassa wild-type or ve-1 duplicate cultures were incubated under standard and iron-free conditions for 48 hours and analyzed with polyA RNAseq.