Journal Article

Characterization of the enzymatic activity and physiological function of the lipid droplet-associated triacylglycerol lipase AtOBL1

Till Ischebeck, Anna Ophelia Müller

2018

Overview

Similar to seeds, pollen tubes contain lipid droplets that store triacylglycerol (TAG), but the fate of this TAG as well as the enzymes involved in its breakdown are unknown. Therefore, two potential TAG lipases from tobacco and Arabidopsis, NtOBL1 (Oil body lipase 1) and AtOBL1, were investigated, especially with respect to their importance for pollen tube growth. We expressed NtOBL1 and AtOBL1 as fluorescent fusion proteins to study their localization by confocal microscopy. Furthermore, we overexpressed AtOBL1 in Nicotiana benthamiana leaves to characterize it enzymatically. The obl1 mutant was studied in respect to its pollen tube growth in vivo and its seed germination. Both NtOBL1 and AtOBL1 localized to lipid droplets. AtOBL1 was abundant in pollen tubes and seedlings, and acted as a lipase on TAG, diacylglycerol and 1-monoacylglycerol at a pH optimum of 5.5. The obl1 mutant was hampered in pollen tube growth, whereas seedling establishment was not affected under optimal conditions, even though AtOBL1 accounted for a major lipase activity in seeds. TAG could be a direct precursor for the synthesis of membrane lipids in pollen tubes and proteins of the OBL family involved in the flux of acyl groups.

• Publisher: New Phytologist Trust,Wiley Subscription Services, Inc
• Subject: Arabidopsis / Arabidopsis - enzymology / Arabidopsis - genetics / Arabidopsis - physiology / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / Confocal microscopy / diacylglycerols / Diglycerides / Diglycerides - metabolism / DNA, Bacterial - genetics / Droplets / Enzymatic activity / Enzyme activity / Fatty Acids - metabolism / Fluorescence / Germination / Growth / Hydrogen-Ion Concentration / leaves / Lipase / Lipase - genetics / Lipase - metabolism / lipid bodies / lipid droplet / Lipid Droplets - metabolism / Lipids / Localization / Microscopy / moieties / mutants / Nicotiana - metabolism / Nicotiana benthamiana / Nicotiana tabacum / oil body / Optimization / pH effects / Phospholipids - metabolism / Physiological functions / plant establishment / Plants, Genetically Modified / Pollen / pollen tube / Pollen Tube - growth & development / Pollen Tube - metabolism / Pollen tubes / Proteins / recombinant fusion proteins / seed / Seed germination / Seedlings / Seeds / Seeds - metabolism / Tobacco / triacylglycerol / Triacylglycerol lipase / triacylglycerols / Triglycerides - metabolism / Tubes