Family-wide expression characterization of Arabidopsis beta-carbonic anhydrase genes using qRT-PCR and Promoter::GUS fusions

Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes found throughout the phylogenetic tree. The β-class carbonic anhydrases (β-CAs) are the predominating class of CAs in plants. Growing evidence underscores the importance of β-CAs in plant immunity and environmental adaptation in addition to their roles in photosynthesis. However, many fundamental problems in Arabidopsis βCAs expression remain unsolved. Here we examined the transcript abundance of AtβCAs in different tissues of Arabidopsis thaliana, and the accumulation of mRNA in response to CO2 and darkness. Histochemical analysis was performed to study the promoter activity of AtβCAs during post-germination seedling growth and in mature plants. All six members of the AtβCA subfamily showed a response to changed CO2 level and darkness, but each member showed a specific dynamic pattern. Although expression of each AtβCA was unique, in general most AtβCAs were synchronously expressed in green leaves since 5 days after germination until flowering. AtβCA1 and AtβCA2 were most highly expressed in leaves but AtβCA2 displayed weaker expression in roots. The level of AtβCA3 transcripts was highest in flowers, while AtβCA5 was most widely expressed and might be involved in more processes than other members. AtβCA6 was unique for increased expression in darkness and no expression in either the anther or pistil. The present study provides useful information for further functional investigation.