Abstract
Plastid-localized glycerol-3-phosphate acyltransferase (ATS1) catalyzes the first-step reaction in glycerolipid assembly through transferring an acyl moiety to glycerol-3-phosphate (G3P) to generate lysophosphatidic acid (LPA), an intermediate in lipid metabolism. The effect of ATS1 overexpression on glycerolipid metabolism and growth remained to be elucidated in plants, particularly oil crop plants. Here, we found that overexpression of BnATS1 from Brassica napus enhanced plant growth and prokaryotic glycerolipid biosynthesis. BnATS1 is localized in chloroplasts and an in vitro assay showed that BnATS1 had acylation activity toward glycerol 3-phosphate to produce LPA. Lipid profiling showed that overexpression of BnATS1 led to increases in multiple glycerolipids including phosphatidylglycerol (PG), monogalactosyldiacylglycerol (MGDG), phosphatidylcholine (PC), and phosphatidylinositol (PI), with increased polyunsaturated fatty acids. Moreover, increased MGDG was attributed to the elevation of 34:6- and 34:5-MGDG, which were derived from the prokaryotic pathway. These results suggest that BnATS1 promotes accumulation of polyunsaturated fatty acids in cellular membranes, thus enhances plant growth under low-temperature conditions in Brassica napus.
Highlights
Glycerolipids including phospholipids and galactolipids are essential components of cellular membranes and signal molecules involved in diverse biological processes [1]
Our observation showed that Brassica napus ATS1 (BnATS1) is localized in chloroplasts, implicating its involvement in lipid assembly in the prokaryotic pathway
Fatty acids are synthesized de novo in chloroplasts [2], and this plastid-localized BnATS1 may facilitate the access of acyl groups for glycerolipid assembly
Summary
Glycerolipids including phospholipids and galactolipids are essential components of cellular membranes and signal molecules involved in diverse biological processes [1]. Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first-step reaction in glycerolipid assembly through transferring an acyl moiety to glycerol-3-phosphate (G3P), producing lysophosphatidic acid (LPA), which is further acylated at the sn-2 position of the G3P backbone by lysophosphatidic acid acyltransferase (LPAAT) to generate phosphatidic acid (PA) [2,3,4]. PA is activated by cytidinediphosphate diacylglycerol synthase (CDS) to produce cytidinediphosphate diacylglycerol (CDP-DAG), which is a precursor for phosphatidylglycerol (PG) and phosphatidylinositol (PI) [5,6,7]. PA is dephosphorylated by PA phosphohydrolase (PAH) or lipid phosphate phosphatase (LPP) to produce diacylglycerol (DAG) [8,9], which subsequently reacts with cytidinediphosphate-choline (CDP-choline) and CDP-ethanolamine to produce phosphatidylcholine (PC) and phosphatidylethanolamine (PE), respectively [1,10,11]. DAG is a substrate for galacotolipids such as monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) [12], and storage lipid triacylglycerol (TAG) as well [13]
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