title: The regulatory properties of Rubisco activase differ among species and affect photosynthetic induction during light transitions.
abstract: Rubisco's catalytic chaperone, Rubisco activase (Rca), uses the energy from ATP hydrolysis to restore catalytic competence to Rubisco. In Arabidopsis (Arabidopsis thaliana), inhibition of Rca activity by ADP is fine tuned by redox regulation of the α-isoform. To elucidate the mechanism for Rca regulation in species containing only the redox-insensitive β-isoform, the response of activity to ADP was characterized for different Rca forms. When assayed in leaf extracts, Rubisco activation was significantly inhibited by physiological ratios of ADP to ATP in species containing both α-Rca and β-Rca (Arabidopsis and camelina [Camelina sativa]) or just the β-Rca (tobacco [Nicotiana tabacum]). However, Rca activity was insensitive to ADP inhibition in an Arabidopsis transformant, rwt43, which expresses only Arabidopsis β-Rca, although not in a transformant of Arabidopsis that expresses a tobacco-like β-Rca. ATP hydrolysis by recombinant Arabidopsis β-Rca was much less sensitive to inhibition by ADP than recombinant tobacco β-Rca. Mutation of 17 amino acids in the tobacco β-Rca to the corresponding Arabidopsis residues reduced ADP sensitivity. In planta, Rubisco deactivated at low irradiance except in the Arabidopsis rwt43 transformant containing an ADP-insensitive Rca. Induction of CO2 assimilation after transition from low to high irradiance was much more rapid in the rwt43 transformant compared with plants containing ADP-sensitive Rca forms. The faster rate of photosynthetic induction and a greater enhancement of growth under a fluctuating light regime by the rwt43 transformant compared with wild-type Arabidopsis suggests that manipulation of Rca regulation might provide a strategy for enhancing photosynthetic performance in certain variable light environments.
authors: United States Department of Agriculture, Agricultural Research Service, Arid-Land Agricultural Research Center, Maricopa, Arizona 85138, USA.
authors: A Elizabete
authors: AE
authors: Carmo-Silva
authors: Michael E
authors: ME
authors: Salvucci
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development / Q000528:radiation effects; D029681:Arabidopsis Proteins; D002245:Carbon Dioxide / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D007527:Isoenzymes / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects*; D010936:Plant Extracts / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013045:Species Specificity; D013997:Time Factors; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D010936:Plant Extracts; D010940:Plant Proteins; C545839:Rca protein, Arabidopsis; D011994:Recombinant Proteins; C054765:rca protein, plant; D002245:Carbon Dioxide; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases