Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, University of Goettingen, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany.
New Phytol. 2018 Feb;217(3):1062-1076. doi: 10.1111/nph.14902. Epub 2017 Nov 27.
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.
类似于种子，花粉管中含有储存三酰基甘油（TAG）的脂滴，但 TAG 的命运以及参与其分解的酶尚不清楚。因此，研究了来自烟草和拟南芥的两种潜在的 TAG 脂肪酶，即 NtOBL1（油体脂肪酶 1）和 AtOBL1，特别是它们对花粉管生长的重要性。我们表达了 NtOBL1 和 AtOBL1 作为荧光融合蛋白，通过共焦显微镜研究它们的定位。此外，我们在拟南芥叶片中过表达了 AtOBL1，以酶学特性对其进行了表征。obl1 突变体在体内花粉管生长和种子萌发方面进行了研究。NtOBL1 和 AtOBL1 均定位于脂滴。AtOBL1 在花粉管和幼苗中含量丰富，在 pH 为 5.5 的最适条件下，它可作为 TAG、二酰基甘油和 1-单酰基甘油的脂肪酶发挥作用。obl1 突变体的花粉管生长受阻，而在最佳条件下幼苗的建立不受影响，尽管 AtOBL1 在种子中占主要脂肪酶活性。TAG 可能是花粉管中膜脂合成和参与酰基流动的 OBL 家族蛋白的直接前体。
