Cloning and molecular characterization of a class A lysophosphatidate acyltransferase gene (EpLPAT2) from Echium (Boraginaceae)

摘要

Lysophosphatidate acyltransferase (LPAT) catalyzes the incorporation of acyl groups into the sn-2 position of lysophosphatidate (LPA) rendering phosphatidic acid (PA), a key intermediary in the synthesis of phospholipids (PLs) and triacylglycerols (TAGs). It is considered as a highly selective activity and a strong determinant of fatty acid (FA) composition of membranes and reserve glycerolipids in diverse plants. In this work, we have cloned a gene encoding the microsomal class A LPAT (LPAT2) from Echium pitardii (Boraginaceae), a species that accumulates high levels of long chain polyunsaturated FAs (LCPUFAs) in the seed oil. The Echium gene (EpLPAT2) is ubiquitously expressed in diverse organs of the plant, although the transcript level is increased in those tissues with a higher -linolenic acid (18:3n3) content. Functionality of EpLPAT2 was proven by complementation of a LPAT defective mutant of Escherichia coli (plsC), and by a biochemical assay of the expressed enzyme in membrane extracts. Acyl-CoA specificity recorded for EpLPAT2, using oleoyl-LPA (18:1-LPA) as acyl-acceptor, shows a clear preference for unsaturated acyl substrates, with 18:3n3-CoA being used at similarly high rates as 18:1-CoA. Overexpression of EpLPAT2 in yeast increased FA content, and modified the FA profile of membrane lipids in agreement to the in vitro specificity. Practical applications: One can envisage that overexpression of EpLPAT2 in transgenic plants, either alone or in combination with other genes could increase seed oil content. Moreover, the observed specificity of EpLPAT2 might be a useful characteristic in tailoring of a plant engineered for LCPUFA-enriched oil.