Regulation of the low-CO2-inducible polypeptides in Chlamydomonas reinhardtii

Abstract

Abstract. Polypeptides of 21, 36 and 37 kDa are induced in the unicellular green alga Chlamydomonas reinhardtii Dang. when cells are transferred from high (2%) to low (0.03%) CO2 concentrations. The synthesis of these polypeptides is correlated with the induction of the CO2-concentrating mechanism. In this work we studied the effect of the growth conditions on the synthesis of these polypeptides with the aim of clarifying whether the induction of all three of these low-CO2-inducible polypeptides requires the same environmental factor. Our results showed that induction of the 21-and 36-kDa polypeptides under low-CO2 conditions occurred only in the light, while the 37-kDa periplasmic carbonic anhydrase (EC 4.2.1.1) was induced in light, darkness, and in both synchronous and asynchronous cultures. In addition, induction of these polypeptides appeared to be determined more by the O2/CO2 ratio than by the CO2 concentrations. None of these polypeptides could be induced in either of two different mutants of C. reinhardtii, one lacking ribulose-l,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) and the other with inactive enzyme, Our results indicate that the 21-and 36-kDa polypeptides are regulated by a mechanism different from that controlling the 37-kDa polypeptide.

CO2 CONCENTRATING MECHANISMS IN PHOTOSYNTHETIC MICROORGANISMS

“…In contrast, synthesis of a third low-CO 2 -induced polypeptide, 36 kDa, was not affected by the inhibitor (153) and was inducible in the dark (151). Induction by low CO 2 of Mca1 and Mca2, encoding a mitochondrial CA, occurred in the dark but only when light-dark alternations had produced a diurnal rhythm.…”

Acclimation of Chlamydomonas to changing carbon availability

“…Acclimation often has been studied using expression of Cah1 as a reporter by monitoring CA activity, protein (pCA1) abundance, or mRNA abundance. Reports that induction (or de-repression) of periplasmic CA by limiting-CO 2 concentrations required light, was blocked by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) in the light, and did not occur in non-photosynthetic mutants, argue for a photosynthetic activity requirement (Spalding and Ogren 1982;Spencer et al 1983;Dionisio et al 1989a, b;Dionisio-Sese et al 1990;Villarejo et al 1996b). Induction of pCA1 was High CO 2 Low CO 2 Very low CO 2 Fig.…”

Regulation of the expressions of HCO3- uptake and intracellular carbonic anhydrase in response to CO2 concentration in the marine diatom Phaeodactylum sp.

“…There have also been a number of reports that suggest the occurrence of metabolic signals in response to altering concentrations of carbon source. Photorespiratory metabo-lites have been suggested as one of the light-dependent inducers for CCM in cyanobacteria and Chlamydomonas reinhardtii (Marcus et al 1983;Villarejo et al 1996). These studies strongly suggest that algal response to changing pCO 2 occurs at multiple levels, both in inductive and repressive manners.…”