Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA; Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland.
Curr Biol. 2017 Dec 18;27(24):R1300-R1302. doi: 10.1016/j.cub.2017.10.059.
In flowering plants, two pairs of gametes participate in double fertilization. One of the two sperm delivered by the pollen tube (PT) fuses with the egg cell to form the zygote, whereas the second unites with the central cell to produce the endosperm [1]. Most animal species prevent polyspermy through a transient, fast block established by the depolarization of the egg membrane within milliseconds after encountering the first sperm, followed by a slow block generated through enzymatic changes in the extracellular matrix surrounding the egg [2]. Although in vitro fertilization experiments suggest that the maize zygote starts cell wall deposition within 30 seconds after fusion with a sperm [3], thereby preventing further fertilization events, it is unknown whether plant gametes prevent polyspermy by a fast block. Here, using a genetic approach, the absence of a fast block preventing polyspermy in the maize central cell is demonstrated. A putative polyspermy event involving the egg indicates the existence of tri-parental individuals, which may provide an alternative route to polyploidy, distinct from the one involving unreduced gametes.
在开花植物中，两对配子参与了双受精。花粉管（PT）输送的两个精子中的一个与卵细胞融合形成受精卵，而另一个与中央细胞融合产生胚乳[1]。大多数动物物种通过在遇到第一个精子后的几毫秒内卵膜去极化建立的短暂快速阻断来防止多精入卵，随后通过卵周围细胞外基质的酶变化产生缓慢阻断[2]。尽管体外受精实验表明，玉米受精卵在与精子融合后 30 秒内开始细胞壁沉积，从而防止进一步的受精事件，但尚不清楚植物配子是否通过快速阻断来防止多精入卵。在这里，通过遗传方法，证明了玉米中央细胞中不存在防止多精入卵的快速阻断。一个涉及卵子的多精入卵事件表明存在三亲个体，这可能提供了一种与涉及未减数配子不同的多倍体形成的替代途径。
