Cmcrf1, a Putative Zn2Cys6 Fungal Transcription Factor, Is Involved in Conidiation, Carotenoid Production, and Fruiting Body Development in Cordyceps militaris

Abstract

Cordyceps militaris is a high-value medicinal and edible fungus that produces many bioactive compounds, including carotenoid, and thus, improving the carotenoid productivity of C. militaris will increase its commercial value. However, little is known about the genetic regulatory mechanism of carotenoid biosynthesis in C. militaris. To further understanding the regulatory mechanism of carotenoid biosynthesis, we performed a large-scale screen of T-DNA insertional mutant library and identified a defective mutant, denoted T111, whose colonies did not change color from white to yellow upon exposure to light. Mutation analysis confirmed that a single T-DNA insertion occurred in the gene encoding a 695-amino-acid putative fungal-specific transcription factor with a predicted Zn2Cys6 binuclear cluster DNA-binding domain found uniquely in fungi. Targeted deletion of this gene, denoted C. militaris carotenogenesis regulatory factor 1 (Cmcrf1), generated the ΔCmcrf1 mutant that exhibited drastically reduced carotenoid biosynthesis and failed to generate fruiting bodies. In addition, the ΔCmcrf1 mutant showed significantly increased conidiation and increased hypersensitivity to cell-wall-perturbing agents compared with the wild-type strain. However, the Cmcrf1 gene did not have an impact on the mycelia growth of C. militaris. These results show that Cmcrf1 is involved in carotenoid biosynthesis and is required for conidiation and fruiting body formation in C. militaris.

Research Progress in Understanding the Molecular Biology of Cordyceps militaris

“…As early as 2011, Zheng et al [58] constructed a C. militaris mutant library and identified the functions of these genes. He et al [59] obtained a defective mutant using ATMT with a colony phenotype that was white after light exposure; the results showed that the Cmcrf1 gene was involved in fruiting body development and carotenoid biosynthesis. In 2019, Lou Haiwei et al [55] transformed Cmtns into a deleted mutant (∆Cmtns) using ATMT, discovering that Cmtns significantly affects carotenoid biosynthesis; this provides an important basis for the future study and promotion of carotenoid production.…”

Chitinase Is Involved in the Fruiting Body Development of Medicinal Fungus Cordyceps militaris

“…The vegetative growth of a CmSnf1 deletion mutant (Δ CmSnf1 ) was reduced by 42.2% with arabinose as a sole carbon source in C. militaris , and CmSnf1 was necessary for mycelium to penetrate the insect cuticle to form the fruiting body on silkworm pupae, consistent with the down-regulation of chitinase- and protease-encoding genes in Δ CmSnf1 [ 8 ]. The Δ Cmcrf1 and Δ Cmfhp mutant cultured on rice medium did not produce fruiting bodies and did not have an impact on the mycelia growth of C. militaris [ 9 , 10 ]. In addition, light is an essential factor for pigment formation and fruiting body development in C. militaris [ 11 ].…”