Effect of Light Intensity under Different Photoperiods on Expression Level of Carbonic Anhydrase Genes of the α- and ß-Families in Arabidopsis thaliana Leaves.

Changes in expression levels of genes encoding carbonic anhydrases α-CA1, α-CA2, α-CA4, ß-CA1, ß-CA2, ß-CA3, ß-CA4, ß-CA5, and ß-CA6 in Arabidopsis thaliana leaves after light increase from 80 to 400 µmol PAR quanta·m-2·s-1 were investigated under short day (8 h) and long day (16 h) photoperiods. The expression of two forms of the gene, At3g01500.2 and At3g01500.3, encoding the most abundant carbonic anhydrase of leaves, ß-CA1, situated in chloroplast stroma, was found. The content of At3g01500.3 transcripts was higher by approximately an order of magnitude compared to the content of At3g01500.2 transcripts. When plants were adapted to high light intensity under short day photoperiod, the expression level of both forms increased, whereas under long day photoperiod, the content of At3g01500.3 transcripts increased, and the content of transcripts of At3g01500.2 decreased. The expression levels of the At3g01500.3 gene and of genes encoding chloroplast carbonic anhydrases α-CA1, α-CA4, α-CA2 and cytoplasmic carbonic anhydrase ß-CA2 increased significantly in response to increase in light intensity under short day, and these of the first three genes increased under long day as well. The expression level of the gene encoding α-CA2 under long day photoperiod as well as of genes of chloroplast ß-CA5 and ß-CA4 from plasma membranes and mitochondrial ß-CA6 under both photoperiods depended insignificantly on light intensity. Hypotheses about the roles in higher plant metabolism of the studied carbonic anhydrases are discussed considering the effects of light intensity on expression levels of the correspondent genes.

Carbonic anhydrases in photosynthetic cells of higher plants.

This review presents information about carbonic anhydrases, enzymes catalyzing the reversible hydration of carbon dioxide in aqueous solutions. The families of carbonic anhydrases are described, and data concerning the presence of their representatives in organisms of different classes, and especially in the higher plants, are considered. Proven and hypothetical functions of carbonic anhydrases in living organisms are listed. Particular attention is given to those functions of the enzyme that are relevant to photosynthetic reactions. These functions in algae are briefly described. Data about probable functions of carbonic anhydrases in plasma membrane, mitochondria, and chloroplast stroma of higher plants are discussed. Update concerning carbonic anhydrases in chloroplast thylakoids of higher plants, i.e. their quantity and possible participation in photosynthetic reactions, is given in detail.

The size of the light-harvesting antenna of higher plant photosystem II is regulated by illumination intensity through transcription of antenna protein genes.

In arabidopsis plants, with an increase in illumination intensity during growth the extent of reduction of the plastoquinone pool in the photosynthetic electron transport chain increased, whereas the effective quantum yield of photosynthesis decreased. After 5 days of growth under high illumination intensity, these parameters in high light returned to values observed in "shade-adapted" plants in low light. During the same period, the size of the antenna decreased, correlating with a decrease in the amounts of proteins of peripheral pigment-protein complexes. It was found that the decrease in the amounts of these proteins occurred due to suppression of transcription of their genes.