Isolation And Characterization Of A Novel Mutant S12 That Cannot Repress The Expression Of Cah1 Under CO₂-rich Condition From Chlamydomonas reinhardtii

Abstract

Acclimation to CO₂-limiting stress is associated with the monitoring of the environment changes by controlling genetic and physiological responses through signal transduction pathways. A unicellular green alga, Chlamydomonas reinhardtii, acclimates to CO₂-limitng stress by inducing a set of genes for a carbon-concentrating mechanism. This set includes Cah1 encoding a periplasmic carbonic anhydrase. Using ProCah1:Ars screening system, a novel regulatory mutant, which could not repress the Cah1 under CO₂-rich conditions, was isolated and named as S12. S12 exhibited high rate of CO₂-uptake under high-CO₂ condition, suggesting that the S12 induces the CCM even under high-CO₂ conditions. The possible roles of the corresponding gene of S12 in CO₂-signal transduction pathways and relationships to previously known regulatory factors will be discussed based on cDNA array data.