CHLAMYDOMONAS-REINHARDTII CDNAS UP-REGULATED IN LOW-CO2 CONDITIONS - EXPRESSION AND ANALYSES

Unicellular algae acquire the ability to raise their internal CO2 conc entrations under low-CO2 conditions because of the presence of a CO2 c oncentrating mechanism (CCM). In Chlamydomonas reinhardtii, this mecha nism is induced when cells grown in high-CO2 conditions are switched t o low-CO2 conditions. To elucidate the genes and proteins involved in this mechanism, we constructed a cDNA library from low CO, adapted cel ls 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 protei ns playing a role in this mechanism, we have systematically characteri zed the cDNA clones that appear to be upregulated by low-CO2 adaptatio n but do not cross-hybridize with the six previously identified classe s. We identified seven new classes of clones that are distinctly upreg ulated in low-CO2 conditions. These clones were checked by Northern an alyses, sequencing, and homology studies. One class of clone represent s a novel gene, lci 3. We report on the seven classes of clones and th e characterization of lci 3.