Changes in lipid and carotenoid metabolism in Chlamydomonas reinhardtii during induction of CO2-concentrating mechanism: Cellular response to low CO2 stress

• Published in: Algal research (Amsterdam) 2020-12, Vol.52, p.102099, Article 102099
• 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; Low-CO2 stress; Microbiology; Mikrobiologi
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2020.102099

Photosynthetic organisms strictly depend on CO2 availability and the CO2:O2 ratio, as both CO2/O2 compete for catalytic site of Rubisco. Green alga Chlamydomonas reinhardtii, can overcome CO2 shortage by inducing CO2-concentrating mechanism (CCM). Cells transferred to low-CO2 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 CO2 availability, changes in the lipidome and carotenoids profile occur. These changes expected to be transient, when CCM is activated, CO2 limitation will be substantially ameliorated. In our experiments, cells were transferred from high (5%) to low (air equilibrium) CO2. 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 CO2. •Chlamydomonas transferred to low-CO2 is subjected to stress due to low electron sink.•When CO2 availability changes, cells lipidome and carotenoids profile also change.•Lipidome was analyzed both in whole cells and in isolated lipid droplets fraction.•Polar lipids and carotenoids transiently increased in lipid droplets under low-CO2.•Lipids and carotenoids play role in facing oxidative stress during low CO2 acclimation.