The Flavoproteins CryD and VvdA Cooperate with the White Collar Protein WcoA in the Control of Photocarotenogenesis in Fusarium fujikuroi

Abstract

Light stimulates carotenoid biosynthesis in the ascomycete fungus Fusarium fujikuroi through transcriptional activation of the structural genes of the pathway carRA, carB, and cart, but the molecular basis of this photoresponse is unknown. The F. fujikuroi genome contains genes for different predicted photoreceptors, including the WC protein WcoA, the DASH cryptochrome CryD and the Vivid-like flavoprotein VvdA. We formerly found that null mutants of wcoA, cryD or vvdA exhibit carotenoid photoinduction under continuous illumination. Here we show that the wild type exhibits a biphasic response in light induction kinetics experiments, with a rapid increase in carotenoid content in the first hours, a transient arrest and a subsequent slower increase. The mutants of the three photoreceptors show different kinetic responses: the wcoA mutants are defective in the rapid response, the cryD mutants are affected in the slower response, while the fast and slow responses were respectively enhanced and attenuated in the vvdA mutants. Transcriptional analyses of the car genes revealed a strong reduction of dark and light-induced transcript levels in the wcoA mutants, while minor or no reductions were found in the cryD mutants. Formerly, we found no change on carRA and carB photoinduction in vvdA mutants. Taken together, our data suggest a cooperative participation of WcoA and CryD in early and late stages of photoinduction of carotenoid biosynthesis in F. fujikuroi, and a possible modulation of WcoA activity by VvdA. An unexpected transcriptional induction by red light of vvdA, cryD and carRA genes suggest the participation of an additional red light-absorbing photoreceptor.

Seeing the world differently: variability in the photosensory mechanisms of two model fungi

“…Although the ΔvvdA mutant accumulates less pigment during the second phase, the rate and peak of the first phase is actually higher than wild type. This suggests that VvdA may inhibit WcoA activity early in the light response, in partial agreement with its function in N. crassa (Castrillo and Avalos, 2015). A direct interaction between the two proteins has yet to be experimentally determined.…”

“…Furthermore, deletion of the cryptochrome ortholog, cryD , in F. fujikuroi leads to reduced light-induction of carotenoid genes. While this in some ways reflects the signaling role of CryA seen in A. nidulans , it is the first report of a cryptochrome regulating carotenoid biosynthesis (Castrillo and Avalos, 2015). …”

“…gibberellins) has made it an organism of interest in the agricultural and brewing industries (Tudzynski, 2005). Similar to N. crassa , F. fujikuroi accumulates large amounts of carotenoids in response to white and blue light; unlike N. crassa , however, this induction persists upon deletion of the white collar-1 ortholog, wcoA (Estrada and Avalos, 2008; Castrillo and Avalos, 2015). Interestingly, the ΔwcoA mutant displays reduced carotenoids in the dark, but increased levels of additional pigments (e.g.…”

“…Although red light does not lead to an overt increase in carotenoids in F. fujikuroi , it was shown to induce the expression of carotenoid biosynthetic genes to approximately 10% of the induction levels seen with blue or white light (Castrillo and Avalos, 2015). The role of the phytochrome ortholog is yet to be investigated, but the red light-induction was dependent upon the presence of wcoA .…”

Biochemical Characterization of the DASH‐Type Cryptochrome CryD From Fusarium fujikuroi

“…Previous studies showed that the DASH‐type cryptochrome CryD plays a light‐dependent regulatory role in secondary metabolism and development in Fusarium fujikuroi and is involved in the photoinduction of carotenoid biosynthesis in this fungus . Here, we have heterologously expressed this protein and studied its spectroscopic and biochemical properties after purification.…”