DOES ASTAXANTHIN PROTECT HAEMATOCOCCUS AGAINST LIGHT DAMAGE

The photoprotective function of the ketocarotenoid astaxanthin in Haem atococcus was questioned. When exposed to high irradiance and/or nutri tional stress, green Haematococcus cells turned red due to accumulatio n of an immense quantity of the red pigment astaxanthin. Our results d emonstrate that: 1) The addition of diphenylamine, an inhibitor of ast axanthin biosynthesis, causes cell death under high light intensity; 2 ) Red cells are susceptible to high light stress to the same extent or even higher then green ones upon exposure to a very high light intens ity (4000 mu mol photon m(-2) s(-1)); 3) Addition of O-1(2) generators (methylene blue rose bengal) under noninductive conditions (low light of 100 mu mol photon m(-2) s(-1))induced astaxanthin accumulation. Th is can be reversed by an exogenous O-1(2) quencher (histidine); 4) His tidine can prevent the accumulation of astaxanthin induced by phosphat e starvation. We suggest that: 1) Astaxanthin is the result of the pho toprotection process rather than the protective agent; 2) O-1(2) is in volved indirectly in astaxanthin accumulation process.