Abstracts now available online - Euro Fed Lipid

Identification and functional analysis of a new triacylglycerol-lipasefamily
in Arabidopsis thaliana
Martina Körner, Maike Rudolph, Xuan Wang, Karin Athenstaedt 1 , Günther Daum 1 and
Ivo Feussner
Georg-August-University Göttingen, Albrecht-von-Haller-Institute for Plant Sciences,
Department of Plant Biochemistry, Jusutus-von-Liebig-Weg 11, D-37077 Göttingen,
Germany
1
Technical University Graz, Institute for Biochemistry, Petersgasse 12/2, A-8010 Graz,
Austria.
Many organisms accumulate carbon skeletons in the form of triacylglycerol (TAG) that is
stored in lipid bodies. In plants lipid bodies are found in many tissues and are
particularly abundant in seeds, where upon germination the TAG is broken down to fuel
post-germinative growth. The initial step is catalysed by a lipase, which hydrolyses TAG
at the lipid body surface. Little is known about the molecular identity of these TAGhydrolysing
lipases (TGLs) in plants. In order to identify this enzyme, a reverse genomic
analysis was performed on the Arabidopsis genome. A protein of about 45-kDa was
identified (AtTGL1), which shares homology with lipases from the GDSL-acylhydrolase
family and is preferentially expressed in seedlings. In Arabidopsis it belongs to small
gene family with 9 members (AtTGL1-9). AtTGL1 was expressed heterologously in E.
coli and was characterized in detail after expression in insect cells. It was shown to
hydrolyze triolein at a neutral to acid pH, but is neither active on phospholipids (PC, PI)
nor on sterol esters and has no acyltransferase activity. In addition it complements a
TGL mutant from yeast (tgl3). Transient expression studies in soybean embryos of
AtTGL1-YFP were used to show that the protein is associated with the surface of lipid
bodies. Moreover homozygous knock out lines of AtTGL1 failed to germinate in the
absence of sucrose, and it is likely that AtTGL1 play an important role in regulating
lipolysis during post-germinative growth.