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The induction of the CO 2 concentrating mechanism in a starch‐less mutant of Chlamydomonas reinhardtii
Author(s) -
Villarejo Arsenio,
Martinez Flor,
Pino Plumed Maria,
Ramazanov Ziyadin
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb06687.x
Subject(s) - chlamydomonas reinhardtii , pyrenoid , starch , mutant , chlamydomonas , photosynthesis , biochemistry , biophysics , chloroplast , chemistry , chlorophyceae , biology , microbiology and biotechnology , chlorophyta , botany , algae , gene
In Chlamydomonas reinhardtii the formation of a starch sheath surrounding the pyrenoid is observed when cells grown under high CO 2 (5% CO 2 in air) are transferred to low CO 2 (0.03%) conditions. Formation of the starch sheath occurs coincidentally with induction of the CO 2 concentrating mechanism and with de novo synthesis of 5 polypeptides with molecular masses of 21, 36, 37, 42–44 kDa. We studied the effect of CO 2 concentrations on photosynthesis, ultrastructure and protein synthesis in Chlamydomonas reinhardtii cw‐15 (wild phenotype for photosynthesis) and in the starch‐less mutant BAFJ ‐6, with the aim to clarify the role of the pyrenoid starch sheath in the operation of the CO 2 concentrating mechanism and whether these low CO 2 ‐inducible polypeptides are involved in the formation of starch sheath. When wild type and starch‐less mutant cells were transferred from high to low CO 2 , the CO 2 requirement for half‐maximal rates of photosynthesis decreased from 40 μM to 2 μM CO 2 . 35 SO 4 2‐ labeling analyses showed that the starch‐less mutant induced the 5 low CO 2 ‐inducible polypeptides. These observations suggest that the starch‐less mutant was able to induce a fully active CO 2 concentrating mechanism. Since the starch‐less mutant did not form a pyrenoid starch sheath, we suggest that the starch sheath is not involved in the operation of the CO 2 concentrating mechanism and that none of these 5 low CO 2 ‐inducible proteins is involved in the formation of the starch sheath in Chlamydomonas .