Wu S S, Platt K A, Ratnayake C, Wang T W, Ting J T, Huang A H
Department of Botany and Plant Sciences, University of California, Riverside, CA 92521-0124, USA.
Proc Natl Acad Sci U S A. 1997 Nov 11;94(23):12711-6. doi: 10.1073/pnas.94.23.12711.
The monolayer tapetum cells of the maturing flowers of Brassica napus contain abundant subcellular globuli-filled plastids and special lipid particles, both enriched with lipids that are supposed to be discharged and deposited onto the surface of adjacent maturing pollen. We separated the two organelles by flotation density gradient centrifugation and identified them by electron microscopy. The globuli-filled plastids had a morphology similar to those described in other plant species and tissues. They had an equilibrium density of 1.02 g/cm(3) and contained neutral esters and unique polypeptides. The lipid particles contained patches of osmiophilic materials situated among densely packed vesicles and did not have an enclosing membrane. They exhibited osmotic properties, presumably exerted by the individual vesicles. They had an equilibrium density of 1.05 g/cm(3) and possessed triacylglycerols and unique polypeptides. Several of these polypeptides were identified, by their N-terminal sequences or antibody cross-reactivity, as oleosins, proteins known to be associated with seed storage oil bodies. The morphological and biochemical characteristics of the lipid particles indicate that they are novel organelles in eukaryotes that have not been previously isolated and studied. After lysis of the tapetum cells at a late stage of floral development, only the major plastid neutral ester was recovered, whereas the other abundant lipids and proteins of the two tapetum organelles were present in fragmented forms or absent on the pollen surface.
甘蓝型油菜成熟花的单层绒毡层细胞含有丰富的充满亚细胞小球的质体和特殊的脂质颗粒，两者都富含脂质，这些脂质被认为会被释放并沉积到相邻成熟花粉的表面。我们通过浮选密度梯度离心法分离了这两种细胞器，并通过电子显微镜对它们进行了鉴定。充满小球的质体形态与其他植物物种和组织中描述的相似。它们的平衡密度为1.02 g/cm³，含有中性酯和独特的多肽。脂质颗粒含有位于密集排列的囊泡之间的嗜锇物质斑块，且没有封闭膜。它们表现出渗透特性，可能是由单个囊泡发挥作用。它们的平衡密度为1.05 g/cm³，含有三酰甘油和独特的多肽。通过其N端序列或抗体交叉反应性鉴定出其中几种多肽为油质蛋白，这是一种已知与种子储存油体相关的蛋白质。脂质颗粒的形态和生化特征表明它们是真核生物中的新型细胞器，此前尚未被分离和研究。在花发育后期绒毡层细胞裂解后，仅回收了主要的质体中性酯，而两种绒毡层细胞器的其他丰富脂质和蛋白质则以碎片形式存在或不存在于花粉表面。
