Biochemical and Physiological Characterization of Higher Plants with Reduced Photorespiration: Final Report for Period May 25, 1981-May 24, 1985

摘要

To further understanding of mechanisms which may reduce photorespiration in terrestrial higher plants, this project sought to critically evaluate the reported effects of nuclear gene dosage on the kinetic and structural properties of green leaf ribulose bisphosphate carboxylase/oxygenase (Rubisco). The results dispel earlier reports that nuclear gene dosage qualitatively affects the enzymic and physicochemical properties of leaf Rubisco, provides definitive evidence that proteolysis accounts for the large subunit charge microheterogeneity in higher plant Rubisco, indicate that ligand-induced changes in protein conformation are responsible for the formation of the exchange-inert Rubisco-carboxyarabinitol bisphosphate (CABP) complex, and provides the first experimental evidence for negative cooperativity in the CABP-Rubisco tight-binding reaction. A second objective was to elucidate the mechanisms by which photorespiration is reduced in various naturally occurring C sub 3 -C sub 4 intermediate species of Moricandia, Panicum and Flaveria. The findings indicate that a C sub 4 acid-based CO sub 2 -concentrating mechanism such as in C sub 4 - or CAM-photosynthesis is not responsible for reducing photorespiration in the intermediate Moricandia and Panicum species, and provide the first direct experimental evidence to suggest that these C sub 3 -C sub 4 species are capable of an enhanced photosynthetic recycling of photorespiratory CO sub 2 via Rubisco. 13 refs. (ERA citation 12:045231)