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Sarikaya Bayram Ö; Dettmann A; Karahoda B; Moloney NM; Ormsby T; McGowan J; Cea-Sánchez S; Miralles-Durán A; Brancini GTP; Luque EM; Fitzpatrick DA; Cánovas D; Corrochano LM; Doyle S; Selker EU; Seiler S; Bayram Ö
Control of development, secondary metabolism and light-dependent carotenoid biosynthesis by the velvet complex of Neurospora crassa
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Neurospora crassa is an established reference organism to investigate carotene biosynthesis and light regulation. However, there is little evidence of its capacity to produce secondary metabolites. Here, we report the role of the fungal-specific regulatory velvet complexes in development and secondary metabolism (SM) in N. crassa. Three velvet proteins VE-1, VE-2, VOS-1 and a putative methyltransferase LAE-1 show light-independent nucleocytoplasmic localization. Two distinct velvet complexes, a heterotrimeric VE-1/VE-2/LAE-1 and a heterodimeric VE-2/VOS-1 are found in vivo. The heterotrimer-complex, which positively regulates sexual development and represses asexual sporulation, suppresses siderophore coprogen production under iron starvation conditions. The VE-1/VE-2 heterodimer controls carotene production. VE-1 regulates the expression of more than 15% of the whole genome, comprising mainly regulatory and developmental features. We also studied inter-genera functions of the velvet complex through complementation of A. nidulans veA, velB, laeA, vosA mutants with their N. crassa orthologues ve-1, ve-2, lae-1 and vos-1, respectively. Expression of VE-1 and VE-2 in A. nidulans successfully substitutes the developmental and SM functions of VeA and VelB by forming two functional chimeric velvet complexes in vivo, VelB/VE-1/LaeA and VE-2/VeA/LaeA, respectively. Reciprocally, expression of veA restores the phenotypes of the N. crassa ve-1 mutant. All N. crassa velvet proteins heterologously expressed in A. nidulans are localized to the nuclear fraction independent of light. These data highlight the conservation of the complex formation in N. crassa and A. nidulans. However, they also underline the inter-genera similarities and differences of velvet roles according to different life styles, niches and ontogenetic processes.
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