Photosynthesis and photoprotection characteristics related to ROS production in three Chattonella (Raphidophyceae) species

The toxic potential of Chattonella is associated with a high production of reactive oxygen species (ROS). Chattonella species can tolerate high irradiance levels but seems not to be efficient in the induction of nonphotochemical chl a fluorescence (NPQ) under light stress conditions. Therefore, we postulated that high ROS production of this microalgal group is related to the lack of effective photoprotection mechanisms. We compared the NPQ induction, xanthophyll cycle interconversion (XC), and the production of the ion superoxide (O₂⁻) in Chattonella marina var. antiqua, Chattonella sp., and C. marina acclimated to 43 (LL) and 300 µmol photons · m² · s⁻¹ (HL). We also evaluated the photosynthetic characteristics of the three strains. Photosynthesis saturated at relative high irradiances (above 500 µmol photons · m² · s⁻¹) in LL and HL Chattonella strains. For the first time, we documented the conversion of diadinoxanthin into diatoxanthin in microalgae that have violaxanthin as the major XC carotenoid. The slow NPQ induction indicated that qE (fast component of NPQ) was not present, and this process was related to the interconversion of XC pigments. However, the quenching efficiency (QE) of deepoxidated xanthophylls was low in the three Chattonella strains. The strain with the lowest QE produced the highest amount of a O₂⁻. Therefore, ROS production in Chattonella seems to be related to a low expression of XC-related thermal PSII dissipation.