The Role of the Cia5 Gene in the Carbon Concentrating Mechanism in Chlamydomonas Reinhardtii

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

The carbon concentrating mechanism (CCM) plays a major role in the earth's photosynthetic productivity and its capacity to cycle carbon. The CCM is essential for photosynthesis at atmospheric levels of CO2 in Chlamydomonas and most other eukaryotic and prokaryotic algae. Knowledge gained regarding the CCM in C. reinhardtii through this three-year project, coupled with information from other laboratories, should allow a more complete understanding of how algal cells are able to survive and flourish in their CO2-limited, aqueous environment. The primary goal of this research project is to elucidate components and mechanisms of regulation of the CCM in Chlamydomonas reinhardtii. The focus of the project is the complete characterization of the Cia5 gene and its role as a master regulator of the cell's response to changes in environmental CO2 and HCO3 concentrations. Based on the weight of present evidence, it appears the Cia5 gene encodes a transcription factor that is part of one or more signal transduction cascades that allow, or reverse, formation of a functional CCM. Experiments to fully characterize the Cia5 gene are outlined along with studies of the CIA5 protein, its subcellular location, post-translational modification(s), DNA binding specificities and other features required for its function in controlling assembly of the CCM. A model is proposed in which the CIA5 protein could act either as an inducer or repressor of transcription of genes whose expression is dramatically increased during a shift of cells from high to low CO2 levels. Experiments are outlined that will resolve the uncertainty of whether CIA5 acts as an inducer or repressor of gene expression. In the long term, an increased understanding of the CCM has the potential for practical application in agriculture. For example, certain crop plants have been demonstrated to produce higher yields under elevated levels of CO2. If appropriate portions of the CCM can be transferred to those crops, their resultant ability to increase internal CO2 concentrations could lead to substantially improved crop yields.