Unraveling the Molecular Basis for sunscreen Biosynthesis in Yeasts

DIONISIA SEPÚLVEDA; DIEGO GOMEZ-CASATI; FERNANDO COLABELLA; VÍCTOR CIFUENTES; MARTÍN MOLINÉ; DIEGO LIBKIND

Awaji Island

Congreso; 14° International Congress on Yeasts; 2016

Introduction: Mycosporines (MYC) and mycosporine-like amino acids (MAA) arewater-soluble molecules with bqth direct and indirect photoprotective activity. Previous evidence suggests that MYC and MAA biosynthesis proceeds from a branch-point intermediate of shikimate pathway, but a specific MAA biosynthetic pathway in cyanobacteria was reported, which proceed from an intermediate of pentose phosphate pathway involving four genes, 2-epi-5-epivaliolone synthase (eevs), 0-methyl transferase (omt), ATP-grasp (atpg) and non-ribosomal peptide synthase (nrps). Directed knockout studies demonstrated that the two mentioned pathways converged (through Omt enzyme) to produce MAA in cyanobacteria. In contrast, the genetic basis.of MYC biosynthesis still remains unclear.Results and Discussion: In this work we studied the MYC biosynthesis pathway ineukaryotic organism's. In the genome of the mycosporinogenic yeast Phafjia rhodozyma, a gene cluster similar to the reported in cyanobacteria in was localized. The quantification of mRNA levels of amt and atpg through RT-qPCR after a UV pulse showed an overexpression in both cases, supporting theit participation in photostimulated processes. Moreover, HPLC analysis of ethanolic extracts of both wild-type ai1d several knockout strains of the eevs, om! or atpg genes in P. rhodozyma showed that both wild-type and delta-EEVS are able to produce MGG, the latter was relatively much lower and only occurred when cultured without aromatic amino acids (inhibitors of Shikimate pathway). Strain delta-OMT could not produce MGG by any pathway and in delta-ATP-grasp strain 4-deoxygadusol like compound was detected (intermediate of MYC and MAAbiosynthesis). Therefore, we demonstrated the role of these 3 genes in MGG biosynthesis and the existence, as for cyanobacteria, of two convergent pathways (pentose phosphate and shikimate). In contrast to cyanobacteria, shikimate pathway does not seem to be the predominant one in yeasts.