Effect of light intensity under different photoperiods on expression level of carbonic anhydrase genes of the α- and β-families in Arabidopsis thaliana leaves

Changes in expression levels of genes encoding carbonic anhydrases alpha-CA1, alpha-CA2, alpha-CA4, beta-CA1, beta-CA2, beta CA3, beta-CA4, beta-CA5, and beta-CA6 in Arabidopsis thaliana leaves after light increase from 80 to 400 mu mol PAR quanta center dot m-2 center dot 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, beta-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 alpha-CA1, alpha-CA4, alpha-CA2 and cytoplasmic carbonic anhydrase beta-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 alpha-CA2 under long day photoperiod as well as of genes of chloroplast beta-CA5 and beta-CA4 from plasma membranes and mitochondrial beta-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.