Acyl-CoA-dependent and acyl-CoA-independent avocado acyltransferases positively influence oleic acid content in nonseed triacylglycerols

Abstract

In higher plants, acyl-CoA:diacylglycerol acyltransferase (DGAT) and phospholipid:diacylglycerol acyltransferase (PDAT) catalyze the terminal step of triacylglycerol (TAG) synthesis in acyl-CoA-dependent and -independent pathways, respectively. Avocado (Persea americana) mesocarp, a nonseed tissue, accumulates significant amounts of TAG (~70% by dry weight) that is rich in heart-healthy oleic acid (18:1). The oil accumulation stages of avocado mesocarp development coincide with high expression levels for type-1 DGAT (DGAT1) and PDAT1, although type-2 DGAT (DGAT2) expression remains low. The strong preference for oleic acid demonstrated by the avocado mesocarp TAG biosynthetic machinery represents lucrative biotechnological opportunities, yet functional characterization of these three acyltransferases has not been explored to date. We expressed avocado PaDGAT1, PaDGAT2, and PaPDAT1 in bakers’ yeast and leaves of Nicotiana benthamiana. PaDGAT1 complemented the TAG biosynthesis deficiency in the quadruple mutant yeast strain H1246, and substantially elevated total cellular lipid content. In vitro enzyme assays showed that PaDGAT1 prefers oleic acid compared to palmitic acid (16:0). Both PaDGAT1 and PaPDAT1 increased the lipid content and elevated oleic acid levels when expressed independently or together, transiently in N. benthamiana leaves. These results indicate that PaDGAT1 and PaPDAT1 prefer oleate-containing substrates, and their coordinated expression likely contributes to sustained TAG synthesis that is enriched in oleic acid. This study establishes a knowledge base for future metabolic engineering studies focused on exploitation of the biochemical properties of PaDGAT1 and PaPDAT1.

PDAT1 genome editing reduces hydroxy fatty acid production in transgenic Arabidopsis

“…2C ). PDAT has a catalytic S-D-H triad (S254, D573, H626), which is one of the typical features of lecithin:cholesterol acyltransferase (LCAT) ( 26 - 28 ). Comparing the mutated AtPDAT1 amino acid of the P327-atpdat1 lines with wild-type AtPDAT1, P327-atpdat1 3 lines have a premature stop codon at the 647 amino acid, and P327-atpdat1 5 lines have a mutation in H626 of the S-D-H traid and a premature stop codon at the 628 amino acid ( Fig.…”

Effect of phosphorus and sodium acetate on lipid accumulation from Ankistrodesmus sp. IFRPD 1061 in an open pond

“…Muthuraj et al [ 32 ] discovered that under phosphorus restricting conditions, the carbohydrate content of the alga decreased up to 2.5 times with an increase in neutral lipid content. Acetyl-CoA carboxylase (ACCase) enzyme catalyses the conversion of acetyl-CoA to malonyl-CoA, which is followed by the creation of fatty acids [ 33 , 34 ]. During phosphate limitation, most of the intracellular carbon reserve generated by carbohydrate catabolism is diverted to the Krebs cycle to boost fatty acid synthesis; phosphate constraint increases the expression of ACCasa [ 2 ].…”