Completing the acylation landscape in plants: GDSL enzymes join the BAHD and SCPL acyltransferase families

Specialized metabolites are essential for plant adaptation to the environment. Their biosynthesis requires multiple chemical modifications of core structures, among which acylation is one of the most frequent. In plants, two families of acyltransferases are typically described. The BAHD superfamily, a family with many characterized members, uses mostly CoA esters as acyl donor, while the serine carboxypeptidase-like (SCPL) family uses mainly 1-O-β-D-glucose esters. Although these enzyme families catalyze most acyltransfer reactions in plants, enzymes from the Gly-Asp-Ser-Leu (GDSL) esterase/lipase family have recently been identified as acyltransferases in the biosynthesis of several specialized metabolites. These enzymes use various energy-rich donors, including CoA esters, chlorogenic acid, glycerol esters, and triacylglycerides, to acetylate a wide range of molecules. Interestingly, acyltransferases exhibit distinct subcellular localization: BAHD, SCPL, and GDSL are usually localized in the cytoplasm, vacuole, and apoplast, respectively. Together, these enzymes form a complex network of acyltransferases that modify specialized metabolites throughout plant cells. In this review, we aim to summarize the current knowledge on plant acyltransferases and their applications, particularly aiming to add GDSL transferases to BAHD and SCPL, which are usually considered for these types of reactions.