Participation of Two Carbonic Anhydrases of the Alpha Family in Photosynthetic Reactions in Arabidopsis thaliana.

The expression of genes of two carbonic anhydrases (CA) belonging to the α-family, α-CA2 and α-CA4 (according to the nomenclature in N. Fabre et al. (2007) Plant Cell Environ., 30, 617-629), was studied in arabidopsis (Arabidopsis thaliana, var. Columbia) leaves. The expression of the At2g28210 gene coding α-CA2 decreased under increase in plant illumination, while the expression of the At4g20990 gene coding α-CA4 increased. Under conditions close to optimal for photosynthesis, in plants with gene At2g28210 knockout, the effective quantum yield of photosystem 2 and the light-induced accumulation of hydrogen peroxide in leaves were lower than in wild type plants, while the coefficient of non-photochemical quenching of leaf chlorophyll a fluorescence and the rate of CO2 assimilation in leaves were higher. In plants with At4g20990 gene knockout, the same characteristics changed in opposite ways relative to wild type. Possible mechanisms of the participation of α-CA2 and α-CA4 in photosynthetic reactions are discussed, taking into account that protons can be either consumed or released in the reactions they catalyze.