Constitutive and UV-inducible synthesis of photoprotective compounds (carotenoids and MAAs) by freshwater Patagonian yeasts. Photochemical and Photobioological Sciences

DIEGO LIBKIND,; PATRICIA PÉREZ,; RUBEN SOMMARUGA,; DEL CARMEN DIÉGUEZ, MARÍA; MARCELA FERRARO,; SILVIA BRIZZIO,; HORACIO ZAGARESE; ROSA GIRAUDO, MARÍA

Photochemical and Photobiological Sciences

Año: 2004 vol. 3 p. 281 - 286

1474-905X

Twelve yeasts isolated from lakes of Northwestern Patagonia, Argentina, belonging to eight genera (Sporobolomyces, Sporidiobolus, Rhodotorula, Rhodosporidium, Cystofilobasidium, Cryptococcus, Torulaspora, and Candida) were analysed for their ability to produce  photoprotective compounds. For this purpose, three laboratory experiments were performed to study the e?ect of photosynthetically active radiation (PAR) and PAR in combination with UV radiation (PAR   UVR) on the production of carotenoids and mycosporines. The synthesis of carotenoid compounds was clearly stimulated in six out of nine red yeast strains tested upon exposure to PAR or PAR   UVR; however, the latter conditions produced a stronger response than PAR alone. The increase in carotenoids in the red strains under PAR   UVR irradiation showed a negative exponential relationship with their basal carotenoid content, suggesting that cells with higher constitutive levels of carotenoids are less responsive to induction by PAR  UVR. Three red yeasts, Rhodotorula minuta, Rh. pinicola, and Rhodotorula sp., and the colourless Cryptococcus laurentii produced a UV-absorbing compound when exposed to PAR or PAR   UVR. This compound showed an absorption maximum at 309–310 nm and was identified as mycosporine-glutaminol-glucoside (myc–glu–glu). In these strains, exposure to PAR or PAR   UVR resulted in elevated concentrations of both carotenoids and myc–glu–glu. This is the first report on the production of mycosporines by yeasts. All strains that developed under PAR  UVR were able to synthesise carotenoids either constitutively or in response to PAR exposure, and a few of them also produced myc–glu–glu when exposed to PAR. Collectively, our results suggest that the presence of carotenoids, either alone or in combination with mycosporines, are required for sustaining growth under exposure to PAR   UVR in the freshwater yeast strains studied.