Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA.
Biol Cell. 2010 Apr 9;102(7):421-34. doi: 10.1042/BC20100011.
Poly P (inorganic polyphosphate) is a polymer formed by P(i) residues linked by high-energy phosphoanhydride bonds. The presence of poly P in bacteria, fungi, algae and protists has been widely recognized, but the distribution of poly P in more complex eukaryotes has been poorly studied. Poly P accumulates, together with calcium, in acidic vesicles or acidocalcisomes in a number of organisms and possesses a diverse array of functions, including roles in stress response, blood clotting, inflammation, calcification, cell proliferation and apoptosis.
We report here that a considerable amount of phosphorus in the yolk of chicken eggs is in the form of poly P. DAPI (4',6-diamidino-2-phenylindole) staining showed that poly P is localized mainly in electron-dense vesicles located inside larger vacuoles (compound organelles) that are randomly distributed in the yolk. These internal vesicles were shown to contain calcium, potassium, sodium, magnesium, phosphorus, chlorine, iron and zinc, as detected by X-ray microanalysis and elemental mapping. These vesicles stain with the acidophilic dye Acridine Orange. The presence of poly P in organellar fractions of the egg yolk was evident in agarose gels stained with Toluidine Blue and DAPI. Of the total phosphate (Pi) of yolk organelles, 16% is present in the form of poly P. Total poly P content was not altered during the first 4 days of embryogenesis, but poly P chain length decreased after 1 day of development.
The results of the present study identify a novel organelle in chicken egg yolk comprising acidic vesicles with a morphology, physiology and composition similar to those of acidocalcisomes, within larger acidic vacuoles. The elemental composition of these acidocalcisomes is proportionally similar to the elemental composition of the yolk, suggesting that most of these elements are located in these organelles, which might be an important storage compartment in eggs.
聚磷（无机多聚磷酸盐）是由通过高能磷酸酐键连接的 P(i) 残基形成的聚合物。多聚磷在细菌、真菌、藻类和原生动物中的存在已被广泛认可，但在更复杂的真核生物中多聚磷的分布研究甚少。多聚磷与钙一起在许多生物体的酸性囊泡或酸性钙粒体内积累，并具有多种功能，包括在应激反应、血液凝结、炎症、钙化、细胞增殖和细胞凋亡中发挥作用。
我们在此报告，鸡卵黄中的相当一部分磷以多聚磷的形式存在。DAPI（4',6-二脒基-2-苯基吲哚）染色显示，多聚磷主要定位于位于较大空泡（复合细胞器）内的电子致密囊泡中，这些空泡随机分布在卵黄中。通过 X 射线微分析和元素图谱显示，这些内部囊泡含有钙、钾、钠、镁、磷、氯、铁和锌。这些囊泡用嗜酸性染料吖啶橙染色。卵黄细胞器部分的多聚磷的存在在琼脂糖凝胶中用甲苯胺蓝和 DAPI 染色是明显的。卵黄细胞器的总磷酸盐（Pi）中，有 16%以多聚磷的形式存在。在胚胎发生的前 4 天，多聚磷链长没有改变，但在发育 1 天后，多聚磷链长减少。
本研究的结果在鸡卵黄中鉴定了一种新的细胞器，该细胞器由具有与酸性钙粒体内相似形态、生理学和组成的酸性囊泡组成，位于较大的酸性空泡内。这些酸性钙粒体内的元素组成与卵黄的元素组成比例相似，这表明这些元素中的大部分位于这些细胞器中，这可能是卵黄中的一个重要储存部位。
