Regulation of the carbon-concentrating mechanism in Chlamydomonas reinhardtii
type: CreativeWork
description: Despite accounting for approximately half of global primary productivity, photosynthesis in aquatic environments is often limited by the availability of dissolved carbon dioxide (CO$_{2(aq)}$). To overcome the slow diffusion of CO$_{2(aq)}$ as well as kinetic limitations of the primary photosynthetic carboxylase, Rubisco, carbon concentrating mechanisms (CCMs) have evolved in many aquatic photosynthetic organisms to improve photosynthetic efficiency and growth in CO2- limited environments. In the model eukaryotic green alga Chlamydomonas reinhardtii, the CCM is induced under low CO2 in the light and comprises: active inorganic carbon transport systems, carbonic anhydrases and the localisation of Rubisco to a central chloroplast microcompartment called the pyrenoid. In addition to changes in gene expression, acclimation to low CO2 is accompanied by alterations to metabolism, physiology and even cellular ultrastructure. However, mechanisms governing the regulation and interaction of these molecular components to increase CCM activity remain poorly understood. The overall aim of this study was to investigate regulation of the CCM in wild-type and mutant Chlamydomonas strains at both the whole cell and molecular level. Firstly, investigation of CCM induction in synchronised cultures of wild-type cells identified changes in CCM activity that were uncoupled from accumulation of CCM-related mRNA and protein, contrasting with the coordinated response to low CO2 observed in asynchronous control cultures. Pre-dawn induction of the CCM was coincident with preferential localisation of Rubisco and a thylakoid-lumenal carbonic anhydrase (CAH3) to the pyrenoid, highlighting the possible role of endogenous signals and post-translational modifications in modulating CCM activity. Secondly, in order to probe the relationship between pyrenoid formation and CCM induction and activity, CCM expression was investigated in pyrenoid-negative mutants with substituted Rubisco small subunits (R…
abstract: Despite accounting for approximately half of global primary productivity, photosynthesis in aquatic environments is often limited by the availability of dissolved carbon dioxide (CO$_{2(aq)}$). To overcome the slow diffusion of CO$_{2(aq)}$ as well as kinetic limitations of the primary photosynthetic carboxylase, Rubisco, carbon concentrating mechanisms (CCMs) have evolved in many aquatic photosynthetic organisms to improve photosynthetic efficiency and growth in CO2- limited environments. In the model eukaryotic green alga Chlamydomonas reinhardtii, the CCM is induced under low CO2 in the light and comprises: active inorganic carbon transport systems, carbonic anhydrases and the localisation of Rubisco to a central chloroplast microcompartment called the pyrenoid. In addition to changes in gene expression, acclimation to low CO2 is accompanied by alterations to metabolism, physiology and even cellular ultrastructure. However, mechanisms governing the regulation and interaction of these molecular components to increase CCM activity remain poorly understood. The overall aim of this study was to investigate regulation of the CCM in wild-type and mutant Chlamydomonas strains at both the whole cell and molecular level. Firstly, investigation of CCM induction in synchronised cultures of wild-type cells identified changes in CCM activity that were uncoupled from accumulation of CCM-related mRNA and protein, contrasting with the coordinated response to low CO2 observed in asynchronous control cultures. Pre-dawn induction of the CCM was coincident with preferential localisation of Rubisco and a thylakoid-lumenal carbonic anhydrase (CAH3) to the pyrenoid, highlighting the possible role of endogenous signals and post-translational modifications in modulating CCM activity. Secondly, in order to probe the relationship between pyrenoid formation and CCM induction and activity, CCM expression was investigated in pyrenoid-negative mutants with substituted Rubisco small subunits (R…
author: Mitchell, Madeline
language: en
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/55244f4f-0ac9-45a6-a5ba-e174781973e6/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2015-01-06
date modified: 2026-07-22T22:24:24Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.9248