Cloning and Expression Analysis of Lysophosphatidic Acid Acyltransferase (LPAT) Encoding Gene in Peanut

Lysophosphatidic acid acyltransferase (LPAT) is one of the key enzymes in biosynthesis pathway of triacylglycerol (TAG) in plant. A full-length cDNA library of peanut (Arachis hypogaea L.) was constructed from seed by means of a large number of sequences of expressed sequence tag (EST) and gene functional annotation. A lysophosphatidic acid acyltransferase gene, designated AhLPAT, and its genomic DNA sequence was isolated from peanut. The sequence of AhLPAT cDNA was 1753 bp, and its genomic sequence was 5331 bp. Bioinformatic analysis showed that AhLPAT was composed of 11 exons and 10 introns with typical GT-AG sequence at the splice site. A peptide of 387 amino acid residues was deduced from AhLPAT, with molecular weight of 43.2 kD and isoelectric point (pI) of 9.42. Conserved domain prediction indicated that AhLPAT comprised a typical conserved acyltransferase domain and a conserved lysophospholipid acyltransferase domain. The deduced amino acid had a high sequence similarity with the LPAT proteins from other species. Similarities for amino acid sequence of LPAT protein between peanut and Tropaeolum majus, Brassica napus, Crambe hispanica subsp. abyssinica, Ricinus communis, and Arabidopsis thaliana were 90%, 89%, 89%, 88%, and 87%, respectively. The phylogenetic tree suggested that AhLPAT and AtLPAT2 derived from A. thaliana were grouped into the same class, and both of them were endoplasmic reticulum type LPATs. The result of quantitative RT-PCR assay indicated that AhLPAT was ubiquitously expressed in root, stem, leaf, flower, gynophore, and seed of peanut with the highest level in gynophore and seed. The peak expression was in the period of 50–60 d after flowering. Correlation between AhLPAT expression and oil accumulation was significant (r = 0.63, P < 0.05). These results suggest that AhLPAT plays an important role in peanut TAG biosynthesis.