Special Interest Group Meeting

Functions of white collar-1 genes in the regulation of Mucor circinelloides photoresponses

Victoriano Garre, Eusebio Navarro, Fátima Silva, Sergio López-García and Santiago Torres-Martínez, Departamento de Genética y Microbiología, Facultad de Biología, Universidad de Murcia, 30100 Murcia, Spain

Light regulates developmental and physiological processes in a wide range of organisms, including fungi. Particularly, Zygomycete fungi have developed complex mechanisms to control the responses to light that await detailed characterization at molecular level. Mucor circinelloides is a good model for this characterization because its genome has been sequenced and there are several molecular tools available for its manipulation. Mucor, like other Zygomycetes, has three white collar-1 genes (mcwc-1a, mcwc-1b and mcwc-1c) that code for proteins with characteristics of photoreceptors.

Analyses of knockout mutants for each gene suggest that each of them controls a specific response to light. Thus, mcwc-1a and mcwc-1c control phototropism and photocarotenogenesis respectively. These analyses also showed that MCWC-1c actives carotene biosynthesis by activating the transcription of carotenogenic genes in response to light. Interestingly, recent molecular analyses of mutant strains in the LOV domain of MCWC-1c suggest that MCWC-1c also controls translation of carotenogenic gene transcripts. In addition to the regulation by mcwc-1c, the product of mcwc‑1b also acts as an activator of photocarotenogenesis, but in this case the activation is independent of light and blocked by a proteolysis-independent ubiquitylation mediated by the product of crgA, a repressor of photocarotenogenesis.