Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa Hachioji, Tokyo 192-0397, Japan.
J Exp Bot. 2010 Jun;61(11):3101-5. doi: 10.1093/jxb/erq131. Epub 2010 May 12.
In angiosperms, a zygote generally divides into a two-celled proembryo consisting of an apical and a basal cell that possess different cell fates. This first division of the zygote is a putative step in the formation of the apical-basal axis of the proembryo. The gamete fusion activates the egg, and the gamete fusion site on the zygote has been reported to provide a possible cue for subsequent zygotic development and/or embryonic patterning in animals and plants. In this study, the gamete fusion site on the rice zygote was labelled by in vitro fertilization of a rice egg cell with a fluorescence-stained sperm cell. The positional relationship between the gamete fusion site and the division plane formed by zygotic cleavage was monitored using a fixed culture of the fusion site-labelled zygote until the two-celled proembryo stage. The results indicate that gamete fusion sites exist on two-celled proembryos with no relation to the position of the first division plane, and that the gamete fusion site on the rice zygote does not function as a determinant for positioning the zygote division plane.
在被子植物中，受精卵通常会分裂成一个由顶端细胞和基端细胞组成的二细胞原胚，这两种细胞具有不同的细胞命运。这种受精卵的第一次分裂被认为是原胚顶-基轴形成的一个假定步骤。配子融合激活卵子，而在动物和植物中，已报道配子融合在受精卵上的位点可能为随后的合子发育和/或胚胎模式提供一个可能的线索。在这项研究中，通过用荧光染色的精子细胞体外受精水稻卵细胞，标记水稻受精卵上的配子融合位点。通过固定融合位点标记的受精卵培养，监测配子融合位点与合子分裂形成的分裂面之间的位置关系，直到二细胞原胚阶段。结果表明，配子融合位点存在于与第一次分裂面位置无关的二细胞原胚上，并且水稻受精卵上的配子融合位点不作为定位合子分裂面的决定因素。
