Constitutive and UV-inducible synthesis of photoprotective compounds (carotenoids and mycosporines) by freshwater yeasts

DIEGO LIBKIND; PATRICIA PÉREZ; RUBEN SOMMARUGA; MARÍA DEL CARMEN DIÉGUEZ; MARCELA FERRARO; SILVIA BRIZZIO; HORACIO ZAGARESE; MARÍA VAN BROOCK

Photochemical and Photobiological Sciences

The Royal Society of Chemistry

Lugar: Cambridge; Año: 2004 vol. 3 p. 281 - 286

1474-905X

Twelve yeast strains, 9 ?red? and 3 ?white?, isolated from lakes of Northwestern Patagonia (Argentina) were studied. Three laboratory experiments were performed to assess the effect of PAR and UVR on the production of photoprotective compounds (carotenoids pigments and mycosporine-like aminoacids (MAA)).Carotenoid pigment synthesis was clearly stimulated in six out of nine red yeast strains upon exposure to PAR alone, or PAR in combination with UVR. The latter treatment showed the strongest response and a negative exponential relationship between pigmentation increment after UVR-PAR exposure and basal carotenoid content. This suggests that cells with higher constitutive levels of carotenoids are less responsive to induction by UVR-PAR. Four yeast strains, R. minuta, R. pinicola, Rhodotorula sp. nov. C and C. laurentii were able to produce a UV-absorbing compound when exposed to PAR or UV-PAR. This compound has a peak at 309-310 nm and was identified as mycosporine-glutaminol-glucoside, belonging to a group known as mycosporine-like aminoacids. In these 4 strains, the exposure to PAR or UVR-PAR resulted in elevated concentrations of both carotenoids and MAAs. To our knowledge, this is the first time in which the production of MAAs by yeasts is reported. All strains that developed under UVR-PAR were able to synthesize carotenoids either constitutively or in response to PAR exposure, and a few of them also produced MAAs. Collectively our results suggest that the presence of carotenoids, either alone or in combination with MAAs, are required for sustaining yeasts growth under exposure to UVR-PAR.