Ford Caroline S, Wilkinson Mike J
School of Agriculture Food and Wine, The University of Adelaide, Waite Campus, PMB 1, Glen Osmond, Adelaide, SA 5064, Australia.
Sex Plant Reprod. 2012 Sep;25(3):169-83. doi: 10.1007/s00497-012-0188-1. Epub 2012 May 27.
Cocoa (Theobroma cacao) has an idiosyncratic form of late-acting self-incompatibility that operates through the non-fusion of incompatible gametes. Here, we used high-resolution confocal microscopy to define fine level changes to the embryo sac of the strongly self-incompatible cocoa genotype SCA 24 in the absence of pollination, and following compatible and incompatible pollination. All sperm nuclei had fused with the female nuclei by 48 h following compatible pollinations. However, following incompatible pollinations, we observed divergence in the behaviour of sperm nuclei following release into the embryo sac. Incomplete sperm nucleus migration occurred in approximately half of the embryo sacs, where the sperm nuclei had so far failed to reach the female gamete nuclei. Sperm nuclei reached but did not fuse with the female gamete nuclei in the residual cases. We argue that the cellular mechanisms governing sperm nucleus migration to the egg nucleus and those controlling subsequent nuclear fusion are likely to differ and should be considered independently. Accordingly, we recommend that future efforts to characterise the genetic basis of LSI in cocoa should take care to differentiate between these two events, both of which contribute to failed karyogamy. Implications of these results for continuing efforts to gain better understanding of the genetic control of LSI in cocoa are discussed.
可可（Theobroma cacao）具有一种特殊形式的晚期作用自交不亲和性，其通过不亲和配子的不融合来发挥作用。在此，我们使用高分辨率共聚焦显微镜来确定在未授粉时以及在进行亲和与不亲和授粉后，高度自交不亲和的可可基因型SCA 24胚囊的精细水平变化。在亲和授粉后48小时，所有精核都已与雌核融合。然而，在不亲和授粉后，我们观察到精核释放到胚囊后的行为存在差异。大约一半的胚囊中发生了不完全的精核迁移，在这些胚囊中精核尚未到达雌配子核。在其余情况下，精核到达了雌配子核但未与之融合。我们认为，控制精核向卵核迁移的细胞机制以及控制随后核融合的机制可能不同，应独立考虑。因此，我们建议未来在表征可可中晚期自交不亲和性的遗传基础时，应注意区分这两个事件，这两个事件都会导致核融合失败。讨论了这些结果对继续努力更好地理解可可中晚期自交不亲和性的遗传控制的意义。
