Genes associated with the induction of the carbon-concentrating mechanism in Chlamydomonas reinhardtii: Functional roles of CCM1 and LCIB in photosynthetic acclimation to CO2-limiting stress

H. Fukuzawa, T. Yamano, Y. Yamahara, T. Tsujikawa, H. Nakano, and T. Kohinata

Grad. School of Biostudies, Kyoto University, Kyoto 606-8502, Japan

Acclimation to varying CO2 concentrations and light intensities is associated with the monitoring of environmental changes by controlling genetic and physiological responses through CO2- and light-signal transduction. While CO2 and light signals are indispensable for photosynthesis, and these environmental factors have been proposed as strongly associated with each other, studies linking these components are largely limited to work on higher plants. In this study, we examined the physiological characteristics of a green alga, Chlamydomonas reinhardtii, exposed to various light intensities or CO2 concentrations. Acclimation to CO2-limiting conditions Chlamydomonas cells induce a carbon-concentrating mechanism (CCM) to allow the uptake of inorganic carbon (Ci) and increase the affinity for Ci. We revealed that the induction of the CCM is not solely dependent on absolute environmental Ci concentrations but is also affected by light intensity. Using a cDNA array containing 10,368 ESTs, we obtained global expression profiles related to the physiological responses. The induction of several CCM-associated genes was strongly affected by high-light as well as CO2 concentrations (1). We have characterized the master regulatory factor CCM1 (2) and one of the essential components of CCM, LCIB, based on biochemical studies. 1) Yamano T. et al. Plant Physiol. in press. 2)Kohinata T. et al. Plant Cell Physiol.49: 273-283 (2008)

e-mail address of presenting author: fukuzawa@lif.kyoto-u.ac.jp