Isolation of a new gene, LciR1, which regulates CO₂-responsive genes to acclimate to low-CO₂ stress conditions in Chlamydomonas reinhardtii

Abstract

When Chlamydomonas cells are exposed to CO₂-limiting stress conditions, they induce a set of genes for a carbon-concentrating mechanism (CCM) under the CO₂-limiting conditions. To elucidate molecular mechanisms of CO₂-signal transduction pathways, we have isolated regulatory mutants of the low-CO₂ inducible gene Cah1, which encodes a periplasmic carbonic anhydrase. Using arylsulfatase reporter gene driven by the Cah1-promoter, a regulatory mutant of Cah1 was isolated and named as C44. C44 showed a moderate high-CO₂ requiring phenotype and partially defective in the CCM-induction. The C44-mutation was caused by a single-tag insertion. The corresponding gene, LciR1 encodes a protein containing a single Myb-like DNA binding domain in its N-terminus region. Expression of the LciR1 was also induced by lowering CO₂, and regulated by Ccm1 gene which controls carbon concentrating mechanism in Chlamydomonas.