The Cryptochrome CryA Regulates Lipid Droplet Accumulation, Conidiation, and Trap Formation via Responses to Light in <i>Arthrobotrys oligospora</i>

Abstract

Light is a key environmental factor affecting conidiation in filamentous fungi. The cryptochrome/photolyase CryA, a blue-light receptor, is involved in fungal development. In the present study, a homologous CryA (AoCryA) was identified from the widely occurring nematode-trapping (NT) fungus Arthrobotrys oligospora, and its roles in the mycelial growth and development of A. oligospora were characterized using gene knockout, phenotypic comparison, staining technique, and metabolome analysis. The inactivation of AocryA caused a substantial decrease in spore yields in dark conditions but did not affect spore yields in the wild-type (WT) and ∆AocryA mutant strains in light conditions. Corresponding to the decrease in spore production, the transcription of sporulation-related genes was also significantly downregulated in dark conditions. Contrarily, the ∆AocryA mutants showed a substantial increase in trap formation in dark conditions, while the trap production and nematode-trapping abilities of the WT and mutant strains significantly decreased in light conditions. In addition, lipid droplet accumulation increased in the ∆AocryA mutant in dark conditions, and the mutants showed an increased tolerance to sorbitol, while light contributed to the synthesis of carotenoids. Finally, AoCryA was found to affect secondary metabolic processes. These results reveal, for the first time, the function of a homologous cryptochrome in NT fungi.

Keywords

• nematode-trapping fungi
• light regulation
• mycelial development
• secondary metabolism
• pathogenicity