Chlamydomonas reinhardtii cDNAs upregulated in low-CO2 conditions: Expression and analyses

Aravind Somanchi, Louisiana State University
Eric R. Handley, Louisiana State University
James V. Moroney, Louisiana State University

Abstract

Unicellular algae acquire the ability to raise their internal CO2 concentrations under low-CO2 conditions because of the presence of a CO2 concentrating mechanism (CCM). In Chlamydomonas reinhardtii, this mechanism is induced when cells grown in high-CO2 conditions are switched to low-CO2 conditions. To elucidate the genes and proteins involved in this mechanism, we constructed a cDNA library from low CO2 adapted cells and differentially screened the library for cDNAs upregulated under low-CO2 conditions. Earlier studies identified-six classes of clones specific to low CO2 adapting cells. To identify other genes and proteins playing a role in this mechanism, we have systematically characterized the cDNA clones that appear to be upregulated by low-CO2 adaptation but do not cross-hybridize with the six previously identified classes. We identified seven new classes of clones that are distinctly upregulated in low-CO2 conditions. These clones were checked by Northern analyses, sequencing, and homology studies. One class of clone represents a novel gene, lci 3. We report on the seven classes of clones and the characterization of lci 3.