Attempts to increase photosynthetic output and biomass in Chlamydomonas reinhardtii by over-expressing Calvin cycle enzymes

Wipawee Dejtisakdi1, Julian N. Rosenberg2, George A. Oyler3,4and Stephen M. Miller1

1) Department of Biological Sciences, UMBC, Baltimore, MD 21250 USA 2) Dept. of Chemical & Biomolecular Engineering, JHU, 3400 N Charles St, Baltimore, MD 21218 3) Advanced Technology Laboratory, JHU, 800 Wyman Park Dr, Baltimore, MD 21218 4) Department of Biochemistry, UNL, 1901 Vine Street, Lincoln, NE 68588

Chlamydomonas has great potential as a system for generating biofuels, pharmaceuticals, and other commercially valuable products. Our goal is to improve this potential by increasing photosynthetic output and biomass under both normal and suboptimal growth conditions. Overexpression of two Calvin cycle enzymes, sedoheptulose-1,7-bisphosphatase (SBPase) and fructose-1,6-bisphosphatase (FBPase), improves carbon fixation and growth rate in higher plants, so overexpression of these proteins may yield greater photosynthetic output and biomass in C. reinhardtii. We made separate constructs that place the coding regions of the Chlamydomonas genes for SBPase and FBPase under control of the hybrid Hps70/rbcS promoter and rbcS 3' UTR, in the pRelax vector. After transforming into Chlamydomonas and identifying lines that over-express SBPase and FBPase we will measure photosynthetic rate, growth rate, and accumulation of proteins and non-polar lipids to assess the biotechnological promise of this approach. Progress toward these goals will be reported.

e-mail address of presenting author: wipawee_dej@hotmail.com