The role of LCIB protein during acclimation to low-CO₂ stress in a green alga, Chlamydomonas reinhardtii

Abstract

Acclimation to low-CO₂ stress is achieved by monitoring of the environmental changes through putative CO₂-signal transduction pathways. Our focus is to understand how the changes in CO₂ levels are sensed by cells, and what are the roles of low-CO₂ responsive genes. Using cDNA array, we identified a gene, named as LciB, encoding a 48-kDa soluble protein, showed rapid induction during the acclimation process to the low-CO₂ stress conditions. LciB complemented the mutant, pmp1, which shows reduced CO₂-transport activity and high-CO₂ requiring phenotype under low-CO₂ conditions. LciB RNAi strains also showed lower growth rate under low-CO₂ conditions. We examined the subcellular localization of LCIB protein by immuno-histochemistry and also found that LCIB form a complex in vivo using a gel filtration assay. Based on the above observations, it is possible that LCIB protein is associated with unidentified cellular components necessary to efficient carbon transport under low-CO₂ conditions.