Abstract
About this talk
The CO2 Concentration Mechanism (CCM) in Chlamydomonas is an adaptation to changing CO2 availability and constraints imposed due to the less efficient CO2-fixing enzyme, RuBisCo. It depends upon rapid scavenging of CO2 and active uptake and transport of both HCO2 and CO2 to the site of RuBisCo. The induction of CCM takes place under low or very low CO2 conditions and accumulates 100-fold more CO2 than environmental CO2, representing the most efficient CO2 pumping system discovered so far. The present work is planned with an idea that exposure of cells to gamma irradiation may develop high CO2-requiring mutants. This kind of use of radiation induced mutagenesis for developing plant cells with high biomass assumes lot of importance owing to the association of regulatory and safety issues with GM cells.
The studied objectives were to screen the effect of gamma irradiation on C. Reinhardtii and to analyze the physiological and biochemical alterations induced by gamma irradiation across various CO2 concentrations and light conditions. The cells were exposed to the gamma irradiation (G-5000) at Baba Atomic Research Centre, Mumbai. The results revealed that both colony and cell numbers decreased with increasing gamma radiation. Cells exposed to gamma radiation exhibited more chlorophyll and carotenoid content, notably at 200 Gy. Interestingly, irradiated cells exhibited twofold increased biomass under high CO2 and high light conditions. The mutants displayed aberrant starch sheath, thylakoid membrane organizations, PS activities, and multiple pyrenoids with high CO2 needs. The gamma radiation-based random mutagenesis and screening led to the identification four putative high carbon requiring mutants.
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