ISOLATION AND SEQUENCE-ANALYSIS OF A CDNA-ENCODING THE C-SUBUNIT OF AVACUOLAR-TYPE H-ATPASE FROM THE CAM PLANT KALANCHOE-DAIGREMONTIANA()

We report the sequence of a cDNA clone encoding the c ('16 kDa') subun it of a vacuolar-type H+-ATPase (V-ATPase) from Kalanchoe daigremontia na, a plant in which the cell vacuole plays a pivotal role in crassula cean acid metabolism. The clone, pKVA211, was isolated from a K. daigr emontiana leaf cDNA library constructed in lambda ZAP II using a homol ogous 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 tog ether with a complete 495 bp coding region for a polypeptide with a pr edicted molecular mass of 16 659 Da. The deduced amino acid sequence w as 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 genom ic Southern analysis indicated that the V-ATPase c subunit in K. daigr emontiana is encoded by a small multi-gene family. Steady-state levels of the KVA211 mRNA were much higher in leaves than in roots or flower s, and expression of this transcript in leaves was shown to be strongl y light-dependent.