Poster: Photosynthesis

Abs # 363: Physiological and molecular characterization of slc 230, an insertional mutant in Chlamydomonas reinhardtii unable acclimate to photo-oxidative stress

Presenter:	Adams, James E, jeadams@lsu.edu
Authors	Adams, James E (A)   Mason, Catherine B (A)   Godfrey, Ashley C (A)   Colombo, Sergio L (A)   Moroney, James V (A)
Affiliations:	(A): Department of Biological Sciences, Louisiana State University

Photosynthetic microorganisms must acclimate to changing conditions that may lead to photo-oxidative stress, such as low CO₂ environments or high light. Chlamydomonas reinhardtii, a unicellular, green alga with a Carbon Concentrating Mechanism (CCM) effectively accumulates inorganic carbon (C_i) above external concentrations. C. reinhardtii also acclimates to photo-oxidative stress through such mechanisms as antennae re-arrangement, photochemical quenching and scavenging of oxygen radicals formed when the electron transport chain is over-reduced. The mutant, slc 230, generated by insertional mutagenesis with a Ble^R cassette, was initially selected as a mutant unable to grow well under low CO₂ conditions. However, upon further examination of the phenotype it was determined that slc 230 has a defect in its ability to acclimate to photo-oxidative stress. Sequence analysis of the DNA flanking the Ble^R insert obtained by iPCR indicated that a gene with significant homology to the haloacid dehalogenase-like hydrolase family was interrupted in slc 230. Proteins in this family include phosphatases and epoxide hydrolases. In addition, the protein interrupted in slc 230 is predicted to be localized to the chloroplast and to have a membrane spanning helix. Data will be presented comparing analyses of pigment levels, lipid peroxide levels, growth rates, and oxygen evolution rates of slc 230 and wild-type. Supported by NSF grant IBN-0212093 to JVM and a HHMI award to ACG.