Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
Curr Biol. 2011 Mar 22;21(6):497-502. doi: 10.1016/j.cub.2011.02.013.
Flowering plants have evolved a unique reproductive process called double fertilization, whereby two dimorphic female gametes are fertilized by two immotile sperm cells conveyed by the pollen tube. The two sperm cells are arranged in tandem with a leading pollen tube nucleus to form the male germ unit and are placed under the same genetic controls. Genes controlling double fertilization have been identified, but whether each sperm cell is able to fertilize either female gamete is still unclear. The dynamics of individual sperm cells after their release in the female tissue remain largely unknown. In this study, we photolabeled individual isomorphic sperm cells before their release and analyzed their fate during double fertilization in Arabidopsis thaliana. We found that sperm delivery was composed of three steps. Sperm cells were projected together to the boundary between the two female gametes. After a long period of immobility, each sperm cell fused with either female gamete in no particular order, and no preference was observed for either female gamete. Our results suggest that the two sperm cells at the front and back of the male germ unit are functionally equivalent and suggest unexpected cell-cell communications required for sperm cells to coordinate double fertilization of the two female gametes.
开花植物进化出一种独特的生殖过程，称为双受精，即两个二态雌性配子被花粉管携带的两个不活动的精子细胞受精。这两个精子细胞与一个领先的花粉管核串联排列，形成雄性生殖单位，并受到相同的遗传控制。已经鉴定出控制双受精的基因，但每个精子细胞是否能够受精任一雌性配子仍不清楚。精子细胞在雌性组织中释放后的个体动态在很大程度上仍然未知。在这项研究中，我们在释放前对单个同形精子细胞进行了光标记，并分析了它们在拟南芥中的双受精过程中的命运。我们发现，精子输送由三个步骤组成。精子细胞一起被投射到两个雌性配子之间的边界。经过长时间的不活动后，每个精子细胞以任意顺序与任一雌性配子融合，并且没有观察到对任一雌性配子的偏好。我们的结果表明，雄性生殖单位前后的两个精子细胞在功能上是等效的，并表明精子细胞协调两个雌性配子的双受精需要意想不到的细胞间通讯。
