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Characterization of the enzymatic activity and physiological function of the lipid droplet‐associated triacylglycerol lipase At OBL 1
Author(s) -
Müller Anna Ophelia,
Ischebeck Till
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14902
Subject(s) - pollen tube , lipase , nicotiana benthamiana , pollen , biochemistry , lipid droplet , monoacylglycerol lipase , biology , mutant , germination , diacylglycerol kinase , enzyme , microbiology and biotechnology , chemistry , biophysics , botany , gene , endocannabinoid system , receptor , protein kinase c , pollination
Summary 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, Nt OBL 1 (Oil body lipase 1) and At OBL 1, were investigated, especially with respect to their importance for pollen tube growth. We expressed Nt OBL 1 and At OBL 1 as fluorescent fusion proteins to study their localization by confocal microscopy. Furthermore, we overexpressed At OBL 1 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 Nt OBL 1 and At OBL 1 localized to lipid droplets. At OBL 1 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 At OBL 1 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.