PrLPAAT4, a Putative Lysophosphatidic Acid Acyltransferase from Paeonia rockii, Plays an Important Role in Seed Fatty Acid Biosynthesis

Lysophosphatidic acid acyltransferases (LPAATs) are essential for the acylation of lysophosphatidic acid (LPA) and the synthesis of phosphatidic acid (PA), a key intermediate in the synthesis of membrane phospholipids and storage lipids. Here, a putative lysophosphatidic acid acyltransferase gene, designated PrLPAAT4, was isolated from seed unsaturated fatty acid (UFA)-rich P. rockii. The complete PrLPAAT4 cDNA contained a 1116-bp open reading frame (ORF), encoding a 42.9 kDa protein with 371 amino acid residues. Bioinformatic analysis indicates that PrLPAAT4 is a plasma membrane protein belonging to acyl-CoA:1-acylglycerol-sn-3-phosphate acyltranferases (AGPAT) family. PrLPAAT4 shared high sequence similarity with its homologs from Citrus clementina, Populus trichocarpa, Manihot esculenta, and Ricinus communis. In Arabidopsis, overexpression of PrLPAAT4 resulted in a significant increase in the content of oleic acid (OA) and total fatty acids (FAs) in seeds. AtDGAT1, AtGPAT9, and AtOleosin, involved in TAG assembly, were upregulated in PrLPAAT4-overexpressing lines. These results indicated that PrLPAAT4 functions may be as a positive regulator in seed FA biosynthesis.