Identification of GmGPATs and their effect on glycerolipid biosynthesis through seed-specific expression in soybean

Abstract

Genetic improvement of soybean oil content depends on in-depth study of the glycerolipid biosynthesis pathway. The first acylation reaction catalysed by glycerol-3-phosphate acyltransferase (GPAT) is the rate-limiting step of triacylglycerol biosynthesis. However, the genes encoding GPATs in soybean remain unknown. We used a novel yeast genetic complementation system and seed-specific heterologous expression to identify GmGPAT activity and molecular function in glycerolipid biosynthesis. Sixteen GmGPAT genes were cloned by reverse transcription-PCR for screening in yeast genetic complementation. The results showed that GmGPAT9-2 could restore the conditional lethal double knockout mutant strain ZAFU1, and GmGPAT1-1 exhibited low acyltransferase activity in serial dilution assays. In addition, the spatiotemporal expression pattern of GmGPAT9-2 exhibited tissue specificity in leaves, flowers and seeds at different developmental stages. Furthermore, both the proportion of arachidic acid and erucic acid were significantly elevated in Arabidopsis thaliana transgenic lines containing the seed-specific GmGPAT9-2 compared wild type, but the oil content was not affected. Together, our results provide reference data for future engineering of triacylglycerol biosynthesis and fatty acid composition improvement through GPATs in soybean.