Changes in Photorespiratory Enzyme Activity in Response to Limiting CO₂ in Chlamydomonas reinhardtii

Abstract

The activity of two photorespiratory enzymes, phosphoglycolate phosphatase (PGPase) and glycolate dehydrogenase (glycolate DH), changes when C02-enriched wild-type (WT) Chlamydomonas reinhardtii cells are transferred to air levels of CO2. Adaptation to air levels of C02 by Chiamydomonas involves induction of a C02-concentrating mechanism (CCM) which increases the internal inorganic carbon concentration and suppresses oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase. PGPase in cell extracts shows a transient increase in activity that reaches a maximum 3 to 5 hours after transfer and then declines to the original level within 48 hours.The decline in PGPase activity begins at about the time that physiological evidence indicates the CCM is approaching maximal activity. Glycolate DH activity in 24 hour air-adapted WT cells is double that seen in C02-enriched cells. Unlike WT, the high-C02-requiring mutant, cia-5, does not respond to limiting CO2 conditions: it does not induce any known aspects of the CCM and it does not show changes in PGPase or glycolate DH activities. Other known mutants of the CCM show patterns of PGPase and glycolate DH activity after transfer to limiting CO2 which are different from WT and cia-5 but which are consistent with changes in activity being initiated by the same factor that induces the CCM, although secondary regulation must also be involved.

A Metabolomic Approach to Study Major Metabolite Changes during Acclimation to Limiting CO2 in Chlamydomonas reinhardtii

“…3C). Ser is an essential amino acid and a metabolite in the photorespiratory pathway, which is known to be up-regulated upon induction of the CCM (Marek and Spalding, 1991;Tural and Moroney, 2005). Malate is a central metabolite in many different metabolic pathways (e.g.…”

“…Many genes coding for enzymes of the photorespiratory pathway are up-regulated (Marek and Spalding, 1991;Miura et al, 2002Miura et al, , 2004 within 20 min and show a transient expression pattern (Tural and Moroney, 2005;Yamano et al, 2008). A decline in starch content is also detectable within 30 min after transfer to low CO 2 (Kuchitsu et al, 1988).…”

Insertional Mutants of Chlamydomonas reinhardtii That Require Elevated CO2 for Survival

“…Isolation and characterization of the C. reinhardtii mutants, ca-1 and pmp-1, demonstrated the requirement for active transport and accumulation of C i (Badger et al, 1980;Spalding et al, 1983b) and for a thylakoid lumen CA (Spalding et al, 1983a;Funke et al, 1997;Karlsson et al, 1998) for function of the CCM. Another C. reinhardtii HCR mutant, cia-5, exhibits no apparent low-CO 2 acclimation responses, such as induction of CCM, up-regulation of low CO 2 -inducible polypeptides, up-regulation of photorespiratory enzymes, or down-regulation of Rubisco biosynthesis (Moroney et al, 1989;Marek and Spalding, 1991;Spalding et al, 1991;Burow et al, 1996). This mutant is thought to be defective in the signal transduction pathway for acclimation to limiting CO 2 .…”

Phenotypic Complementation of High CO2-Requiring Mutants of the Cyanobacterium Synechococcus sp. Strain PCC 7942 by Inosine 5′-Monophosphate

“…Modification of several sites within the genomic region of rbc in Synechococcus PCC 7942, including rbcS, resulted in high C02-requiring mutants (9,13,20). It was, therefore, suggested that this region contains a cluster of genes, the products of which are involved in various functions of the Ci-concentrating mechanism and, hence, in the ability of cyanobacteria to grow in the presence of low CO2.…”

“…Most of these mutants exhibit an apparent photosynthetic affinity approximately 2 orders of magnitude lower than that of high C02-grown wild type (5, 7, 9, 10, 12, 15-17, 19, 22, 25). High C02-requiring mutants in which the photosynthetic characteristics are similar to those observed in wild-type cells grown under high C02 were isolated from Chlamydomonas reinhardtii (13) and Synechococcus sp. PCC 7942 (10).…”