Nucleotide Sequence of a Complementary DNA Encoding Plasma Membrane H-ATPase from Rice (Oryza sativa L.).

The plant plasma membrane H+-ATPase (EC 3.6.1.3) had been shown to be essential for generating the membrane potential and concomitant electrochemical gradient, the means for translocating various solutes such as cations, anions, amino acids, and sugars across the plasma membrane by secondary transport systems (6, 7, 9, 10). Two cDNAs, OSA1 and OSA2, which encode H+-ATPase from rice cali (Oryza sativa L. cv Nipponbare), were isolated from a cDNA library constituted from rice cali in suspension culture (5). Two primers [GTICCIGT(T,C)TTITCI(GA/CT)ICA and ACIGGIGA(T,C)GGIGTIAA(T,C)GA] synthesized from consensus amino acid sequences (Fig. 1, breakline) of eukaryotic vanadate-sensitive ATPase as a probe for screening were amplified by the PCR2 (Table I). Here, we present the nucleotide sequence offull-length rice cDNA and the deduced amino acid sequence of OSA1 (Fig. 1). The protein predicted from the nucleotide sequence was found to encode 956 amino acids, have a molecular mass of 105,078 D, and possess both conserved regions of eukaryotic vanadate-sensitive ATPases and at least eight transmembrane domains (underlines). Nucleotide sequence homologies of OSA 1 compared with those of tomato (Lycopersicon esculentum) (2), tobacco (Nicotiana plumbaginifolia) (1), Arabidopsis thaliana (4), Neurospora crassa (3), and Saccharomyces cerevisiae (8) were 75.8, 74.9, 70.9, 51.2, and 51.0%, respectively. A homology comparison of amino acid sequence with these higher plants indicated that OSA1 had a novel sequence in the region from 731 to 756 at the position of the amino acid (Fig. 1, double line). This region is located between transmembrane domains 6 and 7 and faces the cytoplasm. It could not be found in any data base by a homology search, and it possibly functions as a regulator of enzymes. It is our understanding that this represents the first gene for a monocotyledon plasma membrane H+-ATPase to be cloned and sequenced.