The sensing, response and subsequent acclimation of plants to suboptimal and adverse conditions is of pivotal importance to productivity and crop yield. Natural fluctuations in environmental growth conditions have the potential to strongly alter growth rate and adversely affect fitness of photosynthetic organisms. However, plants and algae have developed elaborate acclimation mechanisms that fine tune the metabolism of the organism to this altered environment, enabling cells to adjust and optimize growth capacity upon establishing a new homeostasis. My PhD research was focused on identification of novel genes and proteins that are involved in the signal transduction pathway involved in these acclimation mechanisms to fluctuations in carbon-dioxide level in the unicellular green alga Chlamydomonas reinhardtii.
Approximately 50% of the world’s photosynthesis occurs in the aquatic environment by organisms that employ a carbon concentrating mechanism (CCM). Aquatic photosynthetic organisms have evolved different forms of CCMs to aid the enzyme Rubisco in capturing CO2 from the surrounding environment. One aspect of all CCMs is the critical roles played by various extracellular and intracellular carbonic anhydrases (CAs). CAs are of four sub types namely alpha, beta, gamma and epsilon. My PhD research was focused on identification of some novel carbonic anhydrase genes in C. reinhardtii, a green alga with a well studied CO2 concentrating mechanism (CCM). At the time of my PhD study, five carbonic anhydrases were known to exist in C. reinhardtii. I have identified two novel genes encoding beta type CA (CAH6 and CAH8) and two gamma CA like genes (GLP1 and GLP2. Two of these proteins, Cah6 (chloroplastic) and GLP1 (cytoplasmic) and a known thylakoid alpha CA (CAH3) protein were overexpressed as recombinant MBP (maltose binding protein)-fusion proteins to assay enzyme activities. I demonstrated that the recombinant CAH6 and CAH3 fusion proteins are enzymatically active but GLP1 is not. The purified recombinant CAH6 and CAH3 proteins were used to raise antibodies for immunolocalization and biochemical studies. RNA interference, a powerful gene silencing tool, was employed, along with traditional molecular biological methods like Northern and Western blotting, to study the functional role of CAH6 in the CCM and photosynthesis.