Isolation and sequence analysis of a cDNA encoding the c subunit of a vacuolar-type H+-ATPase from the CAM plant Kalanchoe daigremontiana

We report the sequence of a cDNA clone encoding the c ('16 kDa') subunit of a vacuolar-type H+-ATPase (V-ATPase) from Kalanchoe daigremontiana, a plant in which the cell vacuole plays a pivotal role in crassulacean acid metabolism. The clone, pKVA211, was isolated from a K. daigremontiana leaf cDNA library constructed in lambda ZAP II using a homologous PCR-generated cDNA probe for the V-ATPase c subunit. The KVA211 cDNA was 839 nucleotides long and included a 20 bp poly(A)(+) tail together with a complete 495 bp coding region for a polypeptide with a predicted molecular mass of 16 659 Da. The deduced amino acid sequence was highly conserved across the wide range of eukaryotes (vertebrates, invertebrates, fungi, plants and protozoa) in which this gene has now been identified. Sequence comparison of several PCR products and genomic Southern analysis indicated that the V-ATPase c subunit in K. daigremontiana is encoded by a small multi-gene family. Steady-state levels of the KVA211 mRNA were much higher in leaves than in roots or flowers, and expression of this transcript in leaves was shown to be strongly light-dependent.