Aminoalcoholphosphotransferase catalyzes the synthesis of phosphatidylcholine and phosphatidylethanolamine from diacylglycerol plus CDP-choline or CDP-ethanolamine as the phosphobase donor. We screened a cDNA library to isolate a clone for use in studying the structure and expression pattern of this enzyme from Pimpinella brachycarpa. The P. brachycarpa aminoalcoholphosphotransferase cDNA contains an open reading frame of 1,170 bp coding for a protein of 389 amino acids. The deduced amino acid sequence shares over 90% similarity with other aminoalcoholphosphotransferase sequences. Hydropathy profile analysis suggests that the secondary structure of P. brachycarpa aminoalcoholphosphotransferase is very similar to that of soybean and Chinese cabbage enzymes, having an overall hydrophobicity and the same number of predicted transmembrane helices. The catalytic domain contains the CDP-alcohol phosphotransferase motif with two aspartate residues. Reverse transcriptase-PCR analysis indicates that the expression of R brachycarpa AAPT is regulated by temperature.