Control of Development, Secondary Metabolism and Light-Dependent Carotenoid Biosynthesis by the Velvet Complex of Neurospora crassa

Abstract

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 >15% of the whole genome, comprising mainly regulatory and developmental features. We also studied intergenera functions of the velvet complex through complementation of Aspergillus nidulans veA, velB, laeA, vosA mutants with their N. crassa orthologs 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 intergenera similarities and differences of velvet roles according to different life styles, niches and ontogenetic processes.

The velvet protein Vel1 controls initial plant root colonization and conidia formation for xylem distribution in Verticillium wilt

“…crassa and V . dahliae [ 17 , 22 , 28 ], whereas other interactions might vary between different fungi or different cultivation conditions. Vel2 is part of two heterodimers, which suggests that the control of the ratio between the distribution of Vel2 to either Vel2-Vel1 or Vel2-Vos1 might be an important conserved fungal control mechanism for development, pathogenesis and secondary metabolite formation.…”

“…V. dahliae Vel1-Vel2, Vel2-Vos1 and Vel3-Vos1 heterodimers could be verified, but interactions to putative methyltransferases are yet missing and it is unclear whether they exist during specific growth conditions. Especially, the formation of the two heterodimers Vel2-Vel1 and Vel2-Vos1 is a common feature, which is conserved between A. nidulans, N. crassa and V. dahliae [17,22,28], whereas other interactions might vary between different fungi or different cultivation conditions. Vel2 is part of two heterodimers, which suggests that the control of the ratio between the distribution of Vel2 to either Vel2-Vel1 or Vel2-Vos1 might be an important conserved fungal control mechanism for development, pathogenesis and secondary metabolite formation.…”

“…In contrast, Neurospora crassa VE-1 functions light-independently. VE-1 promotes hyphal growth, protoperithecia formation and secondary metabolism, but reduces asexual conidiation [ 21 , 22 ]. Light-dependent processes such as macroconidia and sclerotia formation as well as melanin biosynthesis are regulated by VEL1 of the plant pathogen Botrytis cinerea .…”

Polyamines Upregulate Cephalosporin C Production and Expression of β-Lactam Biosynthetic Genes in High-Yielding Acremonium chrysogenum Strain

“…There are a number of models for the functioning of the velvet complex [34,37]. One of the most important roles of this complex is associated with the global regulation of the secondary metabolism of fungi [38][39][40].…”

Tailoring in fungi for next generation cellulase production with special reference to CRISPR/CAS system

“…(HapB/C/E), T. reesei (Hap2/3/5), and N. crassa (Hap2/3/5). They allow moderate expression of cellulase and xylanase genes in T. reesei ( cbh2 and xyn2 ) [ 109 ] Lae1 and VELVET complex In T. reesei (LaeA orthologue in A. nidulans ), it act as a methyltransferase induces cellulase expression and forming the VELVET complex, which in turn regulates the transcription of major cellulase genes [ 110 ] PacC/Pac1 In A. nidulans and T. reesei , it respond to pH variance in the external environment, stimulate or prevent cellulase production. At neutral pH, the abolition of the pac1 gene increases Xyr1 activity [ 5 , 55 ] PoxMBF1 In Penicillium oxalicum , it binds directly to the promoter regions of principal cellulase and xylanase genes to induce cellulase production [ 111 ] PoxFlbC In Penicillium oxalicum (FlbC orthologue in Aspergillus ), it upregulates most of the cellulase genes [ 112 ] PoxAtf1 In filamentous fungi, it controls the expression of cellulase and xylanase genes during the solid-state fermentation [ 113 ] Blr1, Blr2, and Env1 Photoreceptor proteins (Blr1, Blr2, and Env1) in both light and dark regulate the cellulase gene from T. reesei .…”