Changes in lipid and carotenoid metabolism in Chlamydomonas reinhardtii during induction of CO 2 -concentrating mechanism: Cellular response to low CO 2 stress

• Published in: Algal research (Amsterdam) 2020, Vol.52
• Main Authors: Abreu, Ilka N., Aksmann, Anna, Bajhaiya, Amit K., Benlloch, Reyes, Giordano, Mario, Pokora, Wojciech, Selstam, Eva, Moritz, Thomas
• Format: Article
• Language: English
• Subjects: Betaine lipids; Carotenogenesis; CCM; Chlamydomonas; Lipid droplets
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2020.102099

Photosynthetic organisms strictly depend on CO 2 availability and the CO 2 :O 2 ratio, as both CO 2 /O 2 compete for catalytic site of Rubisco. Green alga Chlamydomonas reinhardtii , can overcome CO 2 shortage by inducing CO 2 -concentrating mechanism (CCM). Cells transferred to low-CO 2 are subjected to light-driven oxidative stress due to decrease in the electron sink. Response to environmental perturbations is mediated to some extent by changes in the lipid and carotenoid metabolism. We thus hypothesize that when cells are challenged with changes in CO 2 availability, changes in the lipidome and carotenoids profile occur. These changes expected to be transient, when CCM is activated, CO 2 limitation will be substantially ameliorated. In our experiments, cells were transferred from high (5%) to low (air equilibrium) CO 2 . qPCR analysis of genes related to CCM and lipid metabolism was carried out. Lipidome was analyzed both in whole cells and in isolated lipid droplets. We characterized the changes in polar lipids, fatty acids and ketocarotenoids. In general, polar lipids significantly and transiently increased in lipid droplets during CCM. Similar pattern was observed for xanthophylls, ketocarotenoids and their esters. The data supports our hypothesis about the roles of lipids and carotenoids in tackling the oxidative stress associated with acclimation to sub-saturating CO 2 .