Aminoalcoholphosphotransferase (AAPT) catalyzes the synthesis of phosphatidylcholine and phosphatidylethanolamine from diacylglycerol plus a CDP-aminoalcohol such as CDP-choline or CDP-ethanolamine. Previously we reported the cloning of a cDNA encoding this enzyme from Chinese cabbage roots, and suggested the presence of possible isoforms [Min et al. (1997) J. Plant Biol. 40: 234]. We now report the cDNA cloning and expression analysis of a second AAPT from Chinese cabbage. This AAPT cDNA, AAPT2, contains an open reading frame of 1,170 bp coding for a protein of 389 amino acids. It shares 95% identity and 96% similarity with Chinese cabbage AAPT1 at the deduced amino acid level. The results from reverse transcriptase-PCR indicate that expression of AAPT2 is regulated temporally and up-regulated by low temperature.