title: Isolation and characterization of novel high-CO2-requiring mutants of Chlamydomonas reinhardtii.
abstract: Aquatic microalgae induce a carbon-concentrating mechanism (CCM) to maintain photosynthetic activity in low-CO2 (LC) conditions. Although the molecular mechanism of the CCM has been investigated using the single-cell green alga Chlamydomonas reinhardtii, and several CCM-related genes have been identified by analyzing high-CO2 (HC)-requiring mutants, many aspects of the CO2-signal transduction pathways remain to be elucidated. In this study, we report the isolation of novel HC-requiring mutants defective in the induction of CCM by DNA tagging. Growth rates of 20,000 transformants grown under HC and LC conditions were compared, and three HC-requiring mutants (H24, H82, and P103) were isolated. The photosynthetic CO2-exchange activities of these mutants were significantly decreased compared with that of wild-type cells, and accumulation of HLA3 and both LCIA and HLA3 were absent in mutants H24 and H82, respectively. Although the insertion of the marker gene and the HC-requiring phenotype were linked in the tetrad progeny of H82, and a calcium-sensing receptor CAS was disrupted by the insertion, exogenous expression of CAS alone could not complement the HC-requiring phenotype.
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Lianyong
authors.initials: L
authors.lastname: Wang
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamano
authors.forename: Masataka
authors.initials: M
authors.lastname: Kajikawa
authors.forename: Masafumi
authors.initials: M
authors.lastname: Hirono
authors.forename: Hideya
authors.initials: H
authors.lastname: Fukuzawa
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology
chemical_list: D002245:Carbon Dioxide