Kaska D D, Piscopo I C, Gibor A
Exp Cell Res. 1985 Oct;160(2):371-9. doi: 10.1016/0014-4827(85)90183-1.
Gametes of the unicellular green alga Chlamydomonas reinhardii recognize and adhere to cells of the opposite mating type by flagellar contact. Adhesion between these specialized organelles signals a rapid series of mating events which result in gamete fusion. The sequence of morphological changes (flagellar tip activation, cell wall loss, and mating structure elongation), which occur as a consequence of the sexual signalling, have been characterized. The signalling mechanisms have, however, not been defined. Calcium is known to be involved during fertilization of animal species. Increased intracellular free calcium, which can be achieved either by calcium influx or by mobilization of ions from intracellular stores, has been observed during activation of both eggs and sperm. A recent report by Bloodgood & Levin that gametes of C. reinhardii preloaded with 45Ca showed a transient increase in Ca efflux following mating, suggests that intracellular Ca redistribution may also accompany mating in this algal species. We have used X-ray microanalysis to analyze the subcellular distribution of bound calcium during mating in Chlamydomonas reinhardii. X-ray maps reveal that calcium is sequestered in discrete granules within the gamete cell body prior to mating and that during activation and cell fusion, calcium is diffuse throughout the cell. This suggests the possibility that calcium serves as a second messenger in this species.
单细胞绿藻莱茵衣藻的配子通过鞭毛接触识别并黏附到相反交配型的细胞上。这些特殊细胞器之间的黏附标志着一系列快速的交配事件，最终导致配子融合。因性信号传导而发生的形态变化序列（鞭毛尖端激活、细胞壁丢失和交配结构伸长）已得到描述。然而，信号传导机制尚未明确。已知钙在动物物种受精过程中起作用。在卵子和精子激活过程中都观察到细胞内游离钙增加，这可以通过钙内流或从细胞内储存库中动员离子来实现。Bloodgood和Levin最近的一份报告指出，预先加载了45Ca的莱茵衣藻配子在交配后显示出Ca外流的短暂增加，这表明在这种藻类物种中，交配过程可能也伴随着细胞内钙的重新分布。我们使用X射线微分析来分析莱茵衣藻交配过程中结合钙的亚细胞分布。X射线图谱显示，交配前钙被隔离在配子细胞体内的离散颗粒中，而在激活和细胞融合过程中，钙在整个细胞中扩散。这表明钙在该物种中可能作为第二信使。
