Characterization and expression analysis of genes encoding α and β carbonic anhydrases in Arabidopsis

Abstract

Carbonic anhydrases (CAs) are Zn-containing metalloenzymes that catalyse the reversible hydration of CO2. We investigated the a CA and b CA families in Arabidopsis, which contain eight aCA (AtaCA1-8) and six b CA genes (AtbCA1-6). Analyses of expressed sequence tags (ESTs) from The Arabidopsis Information Resource (TAIR) database indicate that all the b CA encoding sequences, but only three of the Ata CA, are expressed. Using semiquantitative PCR experiments, functional CA genes were more strongly expressed in green tissue, but strong expression was also found in roots for b CA3, b CA6 and a CA2. Two a CA genes were shown to respond to the CO2 environment, while the others were unresponsive. Using the green fluorescent reporter protein gene fused with cDNA sequences coding for b CAs, we provided evidence that b CAs were targeted to specific subcellular compartments: b CA1 and b CA5 were targeted to the chloroplast, b CA2 and b CA3 to the cytosol, b CA4 to the plasma membrane and b CA6 to the mitochondria. The targeting and the pattern of gene expression suggest that CA isoforms play specific roles in subcellular compartments, tissues and organs. The data indicate that other CA isoforms than the well-characterized b CA1 may contribute to the CO2 transfer in the cell to the catalytic site of ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco).

The Cytoplasmic Carbonic Anhydrases βCA2 and βCA4 Are Required for Optimal Plant Growth at Low CO2

“…The six bCA isoforms are found in a number of subcellular locations. bCA1 and bCA5 have been localized to the chloroplast (Fabre et al, 2007;Hu et al, 2015), while bCA2 and bCA3 are found in the cytosol (Fabre et al, 2007). The two other bCAs, bCA4 and bCA6, have been reported to be localized to the plasma membrane (Fabre et al, 2007;Hu et al, 2010Hu et al, , 2015 and the mitochondria (Fabre et al, 2007;Jiang et al, 2014), respectively.…”

“…CAs are highly expressed and can account for up to 1% of the soluble protein in a leaf (Tobin, 1970), with the bCAs being the most highly expressed CA genes in leaves (Fett and Coleman, 1994;Schmid et al, 2005;Fabre et al, 2007;Winter et al, 2007;Hu et al, 2010). The six bCA isoforms are found in a number of subcellular locations.…”

“…The six bCA isoforms are found in a number of subcellular locations. bCA1 and bCA5 have been localized to the chloroplast (Fabre et al, 2007;Hu et al, 2015), while bCA2 and bCA3 are found in the [OPEN] Articles can be viewed without a subscription. www.plantphysiol.org/cgi…”

Carbonic anhydrases in fungi

“…Similar to S. macrospora, A. thaliana encodes multiple CA isoenzymes that are localized to the cytoplasm, plasma membrane and mitochondria, as well as to chloroplasts (Fabre et al, 2007;Parisi et al, 2004). The major CA of A. thaliana was shown to be the chloroplast-localized AtbCA1 (Ferreira et al, 2008).…”

“…In mammals, plants and algae, different isoforms of CAs are targeted to different tissues and organelles (Fabre et al, 2007;Supuran, 2008;Ynalvez et al, 2008), so it is likely that fungal CAs are also unequally distributed within the fungal cell. The first evidence for an intracellular CA comes from yeast, where CA activity was measured only inside the living cell, indicating that Saccharomyces cerevisiae does not encode a secreted CA isoform (Amoroso et al, 2005).…”