Analyses of a mutant I39 with impaired regulation of Cah1 in Chlamydomonas reinhardtii

Abstract

When Chlamydomonas cells are exposed to CO₂-limiting stress conditions, they sense the change of CO₂ levels and induce a set of genes including Cah1, which encodes a periplasmic carbonic anhydrase. Cah1 is not expressed under high- CO₂ conditions (5% [v/v] CO₂), whereas the transcription is activated within 1 hour after transfer to low- CO₂ conditions (0.04% [v/v] CO₂) in light. The CO₂ -dependent expression of Cah1 is controlled by its 5'-upstream regions (ref.1). A regulatory mutant with Cah1, I39 were isolated by DNA tagging mutagenesis.
In I39, Cah1 mRNA was accumulated under 5% [v/v] CO₂ but was not under 15% [v/v] CO₂. I39 has decreased sensitivity against the environmental CO₂. The inserted tags were present on a single chromosome and the mutated gene was tagged.
ref.1) Kucho et.al. Plant Physiol. (1999) 121: 1329-1337.