SGER: The Response of Marine Phytoplankton to Climate Change: Characterization of Rubisco Activase

University Of Washington, Seattle WA

Investigators

Abstract

Inorganic carbon plays a crucial role in regulating marine productivity and species composition in phytoplankton communities. Therefore understanding the mechanisms underlying inorganic carbon fixation by different phytoplankton assemblages is critical if we are to understand the response of phytoplankt on photosynthesis to global climate change, and to develop realistic models of biogeochernical carbon flux in the ocean. Rubisco is a keystone enzyme that drives Calvin cycle function. However, it is now well documented that terrestrial plant Rubisco is catalytically non?functional without the co?operative interplay of Rubisco activase. To date, no information exists in the literature concerning the function of Rubisco activase for gLny chromophytic alga. In fact, except for Heterosigma akashiwo and two Cylindrotheca species, no data exists on Rubisco catalytic function for any other representative of this assemblage that is so critical in global carbon processing. The Goals of this project are to: a) Isolate and characterize Rubisco activase using Heterosigma as model chromophytic algal species; and, in particular, to b) Extend Rubisco activase studies to include diatoms since they rank as primary contributors in C02 management. The study is feasible because: a) The cloned, putative Heterosigma activase gene has now been over?expressed in E. coli; b) Extensive analysis of Heterosigma Rubisco has been accomplished; c) Patterns of Rubisco mRNA production in response to light cues have been documented; d) Heterosigma and diatom Rubisco antibodies have been shown to cross react; e) Flow cytometric measurements of antibody?tagged Rubisco have been made. While the effort in understanding the regulation of Rubisco by Rubisco activase in phytoplankton may be risky, this study will establish a primary database for chromophytic algae wherein the biochemistry of inorganic carbon processing via Rubisco/Rubisco activase interaction is deciphered. The long?term benefit this study is highly significant when considered in terms of predicting photosynthetic performance in response to climate change.