The response of carotenoids and chlorophylls during virus infection of Emiliania huxleyi (Prymnesiophyceae)

We report the response of carotenoids and chlorophylls during 120 h time series virus infection experiments of the marine coccolithophorid Emiliania huxleyi (Lohm.) Hay et Mohler culture. The response of individual carotenoids to infection varied: Diatoxanthin (Dtx) increased rapidly relative to chlorophyll-a, whereas diadinoxanthin (Ddx) and β-carotene showed a rapid decrease and fucoxanthin and 19′hexanoyloxyfucoxanthin a slight increase. The response of the individual carotenoids reflects their role in epoxy/de-epoxidation cycling, antioxidant protection, biosynthetic conversion and vulnerability to photooxidative destruction. We observed for the first time the operation of the diadinoxanthin cycle occurring in response to viral infection in E. huxleyi with the de-epoxidation ratio (Dtx / (Dtx + Ddx)) increasing exponentially with time (R² = 0.92) and decreasing exponentially with F_V / F_M (R² = 0.97). Our findings contribute to our understanding of the conversion and fate of key biochemical cell constituents in algae and are important in understanding the physiological stress response to virus infection.