PEREZ Alejandra patricia
congresos y reuniones científicas
Synthesis and accumulation of photoprotective compounds in heterotrophic aquatic organisms: the role of UV radiation.
PATRICIA PÉREZ; DIEGO LIBKIND; RUBÉN SOMMARUGA; MARÍA C. DIÉGUEZ; MARCELA FERRARO; HORACIO E. ZAGARESE; MARÍA R. VANBROCK
La Plata, Argentina
Otro; VIII Encuentro Latinoamericano de Fotoquímica y Fotobiología; 2004
Within aquatic organisms the production of carotenoids and mycosporine like aminoacids (MAAs) has been attributed to bacteria and algae. These compounds are produced through the shikimic acid pathway (present in bacteria, algae and fungi) and act as quenchers and screens having an important role in photoprotection. Most heterotrophs lack the ability to synthesize carotenoids and MAAs and thus, present dietary uptake storing the compounds in their tissues. Fungi are important constituents of aquatic communities and several species of this group are known to produced carotenoids. However, up to now, there is no evidence that they would synthesize mycosporine like aminoacids. In this work we analyze the effect of UV radiation in the production of carotenoids and mycosporine like aminoacids in aquatic wild yeasts. Besides, we study the dietary uptake of these compounds in a common freshwater planktonic copepod under different radiation scenarios. Laboratory experiments were performed to analyze the synthesis of carotenoids and MAAs in several aquatic wild yeast strains isolated from Patagonian lakes under different light treatments (Dark, PAR and PAR+UVR). Besides, the dietary uptake of mycosporine like aminoacids produced by wild yeasts was studied by long-term cultures of the copepod Boeckella antiqua under PAR and PAR+UVR treatments. Carotenoids yields in the yeasts strains tested in our experiments were highly stimulated by PAR+UVR compared to PAR alone and Dark treatments. Besides, several strains produced also a UV absorbing compound (309 nm) exclusively in the PAR and PAR+UVR treatments. This compound was determined as mycosporine glutaminol glucoside (myc-glu-glu) by means of HPLC and mass spectrometry analyses. A similar pattern was found when culturing the copepod B. antiqua fed with the yeast Rhodotorula minuta (MAAs+, induced production of myc-glu-glu by PAR+UVR). Uptake of the yeasts MAA by this copepod was found exclusively in the PAR-UVR treatment. Overall, our results show that production and accumulation of photoprotective compounds are stimulated under UVR stress and are likely to favor sustained growth under enhanced UV radiation.