Researchers from the Genetics area of the University of Salamanca together with several research groups from universities in the US, Australia, Mexico and the University of Seville have characterized the genmadC of the fungus Phycomyces blakesleeanus. This work has just been published in the journal Scientific Reports.
The USAL group (Catalina Sanz, Mahdi Shahriari and Arturo Pérez Eslava), together with the previous groups, had already characterized two genes, madA (Idnurm et al., PNAS 2006) and madB (Sanz et al., PNAS 2009) . Its gene products are photoreceptors and therefore act at the beginning of the path of sensory transduction that goes from the reception of light to the making of response mechanisms. The product of the madC gene was also thought to be part of the beginning of this path, i.e. that it also affected photoreception. However, according to the article published in Scientific Reports, it was observed that madC codes for a RAS-GAP protein belonging to the RAS protein family. These proteins, once activated, stimulate many signal transmission pathways that affect cell proliferation, differentiation, development, etc.
This work demonstrates that the altered phototropism of the madC mutants is not due to defects in the reception of light per se, but to events located downstream in the transmission path of light signals.
Experiments complementing the madC gene in other fungi have shown that this gene also affects the circadian rhythm.
In summary, this work has shown that the product of the madC gene is part of the RAS signaling pathway and that the encoding protein (RAS-GAP) has to do with both phototropism and with the circadian rhythm in fungi. The loss of function of a RAS-GAP homolog in the vinegar fly (Drosophila melanogaster) also produces abnormalities in its circadian rhythm. Similarly, the homologous gene in humans (NF1) is also capable of replacing the mutations in the circadian rhythm detected in the yeast Saccharomyces cerevisiae.
Polaino, S. et al. A Ras GTPase associated protein is involved in the phototropic and circadian photobiology responses in fungi. Sci. Rep. 7, 44790; doi: 10.1038/srep44790 (2017). http://www.nature.com/articles/srep44790#supplementary-information