Antoine A F, Faure J E, Cordeiro S, Dumas C, Rougier M, Feijó J A
Laboratoire Reproduction et Développement des Plantes, Unité Mixte de Recherche 5667 Centre National de la Recherche Scientifique/Institut National de la Recherche Scientifique/Ecole Normale Supérieure/Université de Lyon I, France.
Proc Natl Acad Sci U S A. 2000 Sep 12;97(19):10643-8. doi: 10.1073/pnas.180243697.
In this paper, we report direct measurement of an influx of extracellular Ca(2+) induced by gamete fusion in flowering plants. This result was obtained during maize in vitro fertilization with the use of an extracellular Ca(2+)-selective vibrating probe. Ca(2+) influx recorded at the surface of isolated egg cells, with or without adhesion of a male sperm cell, was close to zero and stable over time. Gamete fusion, however, triggered a Ca(2+) influx in the vicinity of the sperm entry site with a delay of 1.8 +/- 0.6 sec. The Ca(2+) influx spread subsequently through the whole egg cell plasma membrane as a wavefront, progressing at an estimated rate of 1.13 micrometer.(-1). Once established, Ca(2+) influx intensities were sustained, monotonic and homogeneous over the whole egg cell, with an average peak influx of 14.92 pmol .cm(-2).(-1) and an average duration of 24.4 min. The wavefront spread of channel activation correlates well with the cytological modifications induced by fertilization, such as egg cell contraction, and with the cytosolic Ca(2+) ((c)[Ca(2+)]) elevation previously reported. Calcium influx was inhibited effectively by gadolinium, possibly implicating mechanosensitive channels. Furthermore, artificial influxes created by incubation with Ca(2+) ionophores mimicked some aspects of egg activation. Taken together, these results suggest that, during fertilization in higher plants, gamete membrane fusion starts the first embryonic events by channel opening and Ca(2+) influx. In turn, (c)[Ca(2+)] may work as a trigger and possibly a space and time coordinator of many aspects of egg activation.
在本文中，我们报告了对开花植物中配子融合诱导的细胞外Ca(2+)内流的直接测量。该结果是在玉米体外受精过程中，使用细胞外Ca(2+)选择性振动探针获得的。在分离的卵细胞表面记录到的Ca(2+)内流，无论有无雄配子粘附，均接近零且随时间稳定。然而，配子融合在精子进入位点附近触发了Ca(2+)内流，延迟时间为1.8±0.6秒。随后，Ca(2+)内流以波前形式穿过整个卵细胞的质膜，估计传播速度为1.13微米·秒(-1)。一旦建立，Ca(2+)内流强度在整个卵细胞中持续、单调且均匀，平均峰值内流为14.92皮摩尔·厘米(-2)·秒(-1)，平均持续时间为24.4分钟。通道激活的波前传播与受精诱导的细胞学变化（如卵细胞收缩）以及先前报道的胞质Ca(2+)（(c)[Ca(2+)]）升高密切相关。钆有效地抑制了钙内流，这可能涉及机械敏感通道。此外，与Ca(2+)离子载体孵育产生的人工内流模拟了卵细胞激活的某些方面。综上所述，这些结果表明，在高等植物受精过程中，配子膜融合通过通道开放和Ca(2+)内流启动了最初的胚胎事件。反过来，(c)[Ca(2+)]可能作为触发因素，并且可能是卵细胞激活许多方面的空间和时间协调者。
