Carotenoids as protective response against oxidative damage in Dunaliella bardawil

In the present work the relation between carotenoids production and cell response mechanisms to oxidative damage was studied. High light intensity and nitrogen starvation, both conditions, which may increase the oxidative damage in microalgae, significantly increased total carotenoids content in Dunaliella bardawil, the effect of N-starvation being more noticeable when acting synergetically with light on carotenoid production. S-starvation stimulated carotenoids production as much as N-starvation. The use of norflurazon, inhibitor of phytoene desaturase that blocks formation of epsilon-carotene from phytoene, caused a decrease of carotenoid content down to 5% that of the control cells incubated without the inhibitor. The decrease in the oxygen consumption rate of D. bardawil cells exposed to norflurazon suggests a connection between carotenoids desaturation and chloroplastic oxygen species dissipation processes reported in the literature for other algae. It is an indication of the carotenoids involvement in chloroplastic response mechanisms to oxidative damage.