OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) OA All Versions of this Article: 143/3/1372    most recent pp.106.090811v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (7) Citing Articles via Google Scholar Google Scholar Articles by Padham, A. K. Articles by Thompson, J. E. Search for Related Content PubMed PubMed Citation Articles by Padham, A. K. Articles by Thompson, J. E. Pubmed/NCBI databases Gene GEO Profiles HomoloGene UniGene Compound via MeSH Substance via MeSH Agricola Articles by Padham, A. K. Articles by Thompson, J. E.

SYSTEMS BIOLOGY, MOLECULAR BIOLOGY, AND GENE REGULATION

Characterization of a Plastid Triacylglycerol Lipase from Arabidopsis^1,[OA]

Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (A.K.P., M.T.H., T.-W.W., L.M.M., M.L., C.A.T., J.E.T.); and Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5 (L.G.L.R., M.D.S.)

Full-length cDNA corresponding to Arabidopsis (Arabidopsis thaliana) gene At2g31690, which has been annotated in GenBank as a putative triacylglycerol (TAG) lipase, was obtained by reverse transcription-polymerase chain reaction using RNA from senescing rosette leaves of Arabidopsis as a template. The cognate protein was found to contain the lipase active site sequence, and corresponding recombinant protein proved capable of deesterifying TAG. In vitro chloroplast import assays indicated that the lipase is targeted to chloroplasts. This was confirmed by confocal microscopy of rosette leaf tissue treated with fluorescein isocyanate-labeled, lipase-specific antibody, which revealed that lipase protein colocalizes with plastoglobular neutral lipids. Western-blot analysis indicated that the lipase is expressed in roots, inflorescence stems, flowers, siliques, and leaves and that it is strongly up-regulated in senescing rosette leaf tissue. Transgenic plants with suppressed lipase protein levels were obtained by expressing At2g31690 cDNA in antisense orientation under the regulation of a constitutive promoter. Transgenic plants bolted and flowered at the same time as wild-type plants, but were severely stunted and exhibited delayed rosette senescence. Moreover, the stunted growth phenotype correlated with irregular chloroplast morphology. The chloroplasts of transgenic plants were structurally deformed, had reduced abundance of thylakoids that were abnormally stacked, and contained more plastoglobular neutral lipids than chloroplasts of wild-type plants. These observations collectively indicate that this TAG lipase plays a role in maintaining the structural integrity of chloroplasts, possibly by mobilizing the fatty acids of plastoglobular TAG.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: John E. Thompson (jet{at}sciborg.uwaterloo.ca).

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.106.090811

^* Corresponding author; e-mail jet{at}sciborg.uwaterloo.ca; fax 519–746–2543.

Received October 3, 2006; accepted January 3, 2007; published January 26, 2007.