Huang B Q, Fu Y, Zee S Y, Hepler P K
Department of Botany, University of Hong Kong, Hong Kong.
Protoplasma. 1999;209(1-2):105-19. doi: 10.1007/BF01415706.
Actin organization was observed in m-maleimidobenzoic acid N-hydroxysuccinimide ester(MBS)-treated maize embryo sacs by confocal laser scanning microscopy. The results revealed that dynamic changes of actin occur not only in the degenerating synergid, but also in the egg during fertilization. The actin filaments distribute randomly in the chalazal part of the synergid before fertilization; they later become organized into numerous aggregates in the chalazal end after pollination. The accumulation of actin at this region is intensified after the pollen tube discharges its contents. Concurrently, actin patches have also been found in the cytoplasm of the egg cell and later they accumulate in the cortical region. To compare with MBS-treated maize embryo sacs, we have performed phalloidin microinjection to label the actin cytoskeleton in living embryo sacs of Torenia fournieri. The results have extended the previous observations on the three-dimensional organization of the actin arrays in the cells of the female germ unit and confirm the occurrence of the actin coronas in the embryo sac during fertilization. We have found that there is an actin cap occurring near the filiform apparatus after anthesis. In addition, phalloidin microinjection into the Torenia embryo sac has proved the presence of intercellular actin between the cells of the female germ unit and thus confirms the occurrence of the actin coronas in the embryo sac during fertilization. Moreover, actin dynamic changes also take place in the egg and the central cell, accomplished with the interaction between the male and female gametes. The actin filaments initially organize into a distinct actin network in the cortex of the central cell after anthesis; they become fragmented in the micropylar end of the cell after pollination. Similar to maize, actin patches have also been observed in the egg cortex after pollination. This is the first report of actin dynamics in the living embryo sac. The results suggest that the actin cytoskeleton may play an essential role in the reception of the pollen tube, migration of the male gametes, and even gametic fusion.
通过共聚焦激光扫描显微镜观察了用马来酰亚胺苯甲酸N-羟基琥珀酰亚胺酯（MBS）处理的玉米胚囊中的肌动蛋白组织。结果表明，肌动蛋白的动态变化不仅发生在退化的助细胞中，在受精过程中卵细胞中也会发生。受精前，肌动蛋白丝随机分布在助细胞合点端部分；授粉后，它们在合点端组织成许多聚集体。花粉管释放内容物后，该区域肌动蛋白的积累加剧。同时，在卵细胞的细胞质中也发现了肌动蛋白斑，随后它们在皮质区域积累。为了与用MBS处理的玉米胚囊进行比较，我们进行了鬼笔环肽显微注射，以标记蓝猪耳活胚囊中肌动蛋白细胞骨架。结果扩展了先前关于雌性生殖单位细胞中肌动蛋白阵列三维组织的观察结果，并证实了受精过程中胚囊中肌动蛋白冠的存在。我们发现，开花后在丝状器附近出现了一个肌动蛋白帽。此外，将鬼笔环肽显微注射到蓝猪耳胚囊中证明了雌性生殖单位细胞之间存在细胞间肌动蛋白，从而证实了受精过程中胚囊中肌动蛋白冠的存在。此外，肌动蛋白的动态变化也发生在卵细胞和中央细胞中，这与雄雌配子之间的相互作用有关。开花后，肌动蛋白丝最初在中央细胞的皮质中组织成一个明显的肌动蛋白网络；授粉后，它们在细胞的珠孔端断裂。与玉米类似，授粉后在卵细胞皮质中也观察到了肌动蛋白斑。这是关于活胚囊中肌动蛋白动态变化的首次报道。结果表明，肌动蛋白细胞骨架可能在花粉管的接收、雄配子的迁移甚至配子融合中起重要作用。
