Interaction between crgA and wc-1b in carotenoid synthesis in Blakeslea trispora.

β-Carotene is an important pigment widely used in the food industry, and its large-scale production can be achieved using Blakeslea trispora. In B. trispora, CrgA is a key negative regulator of β-carotene synthesis, while Wc-1b is a photoreceptor whose role in carotenoid synthesis remains unknown. Although the light-induced synthesis of carotenoids may be related to both, the relationship between them is unclear. To clarify the roles of crgA and wc-1b in regulating β-carotene synthesis in B. trispora and their potential interaction, the effects of btcrgA and btwc-1b on β-carotene production and the relationship between them were investigated at both the transcriptional and protein levels. The relative transcription levels of btcrgA, btwc-1b, and carotenoid structural genes (carRA and carB) were highly correlated under short-term light irradiation, suggesting that btcrgA and btwc-1b may interact in regulating β-carotene synthesis. In darkness, btcrgA affected β-carotene synthesis by negatively regulating the transcription levels of carRA and carB, and light attenuated this transcriptional regulation. However, btcrgA did not regulate btwc-1b at the transcriptional level. Conversely, btwc-1b positively regulated the transcription of carRA and carB and β-carotene synthesis in darkness, but this regulation was completely abolished by light. Likewise, btwc-1b did not regulate btcrgA at the transcriptional level. At the protein level, BtCrgA and BtWC-1b were shown to interact with each other both in vitro and in vivo, indicating that BtCrgA may regulate carotenoid synthesis through BtWC-1b.