AUTHOR=Behera Jyoti , Rahman Md Mahbubur , Shockey Jay , Kilaru Aruna 

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

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1056582

DOI=10.3389/fpls.2022.1056582

ISSN=1664-462X

ABSTRACT=<p>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 (<italic>Persea americana</italic>) 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 (<italic>DGAT1</italic>) and <italic>PDAT1</italic>, although type-2 DGAT (<italic>DGAT2</italic>) 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 <italic>PaDGAT1, PaDGAT2</italic>, and <italic>PaPDAT1</italic> in bakers’ yeast and leaves of <italic>Nicotiana benthamiana</italic>. <italic>PaDGAT1</italic> complemented the TAG biosynthesis deficiency in the quadruple mutant yeast strain H1246, and substantially elevated total cellular lipid content. <italic>In vitro</italic> enzyme assays showed that <italic>Pa</italic>DGAT1 prefers oleic acid compared to palmitic acid (16:0). Both <italic>PaDGAT1</italic> and <italic>PaPDAT1</italic> increased the lipid content and elevated oleic acid levels when expressed independently or together, transiently in <italic>N. benthamiana</italic> leaves. These results indicate that <italic>Pa</italic>DGAT1 and <italic>Pa</italic>PDAT1 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 <italic>Pa</italic>DGAT1 and <italic>Pa</italic>PDAT1.</p>