Tobacco zygotic embryogenesis in vitro:: the original cell wall of the zygote is essential for maintenance of cell polarity, the apical-basal axis and typical suspensor formation
Tobacco zygotic embryogenesis in vitro:: the original cell wall of the zygote is essential for maintenance of cell polarity, the apical-basal axis and typical suspensor formation
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DOI：
10.1111/j.1365-313x.2006.02970.x
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发表时间：
2007-02-01
期刊：
影响因子：
7.2
通讯作者：
Yang, Hong-Yuan
中科院分区：
文献类型：
--
作者：
He, Yu-Chi;He, Yu-Qing;Yang, Hong-Yuan
我们在烟草中开发了可靠的体外合子胚胎发生系统。双子叶植物的单个受精卵能够在共培养系统的帮助下通过直接胚胎发生发育成可育植物，其中受精胚珠用作饲养层。结果证实，烟草受精卵可以按照 Solanad 型的基本胚胎发生模式在体外分裂。受精卵细胞壁和定向扩张是维持顶底极性和决定受精卵发育命运的两个关键点。只有那些分离出来的原始细胞壁几乎完整的受精卵才能在体外继续进行有限的定向扩增，也只有这些定向扩增的受精卵才能分裂成典型的顶端细胞和基底细胞，最终发育成典型的有胚柄的胚胎。相反，被剥夺细胞壁的分离的受精卵原生质体可以扩大，但不能定向伸长，就像体内受精卵在细胞分裂前所做的那样，即使细胞壁在体外培养过程中再生。受精卵原生质体还可以进行不对称分裂，形成一个较小和一个较大的子细胞，这些子细胞可以发育成胚胎愈伤组织或没有胚柄的球状胚胎。即使是松散地悬挂在原生质体周围的细胞壁也似乎发挥了功能，并且与第一次合子分裂的方向和顶底轴密切相关，进一步表明原始合子细胞壁在维持顶底极性和细胞分裂方向以及体外早期胚胎发育过程中随后的细胞分化中的重要作用。
We have developed a reliable in vitro zygotic embryogenesis system in tobacco. A single zygote of a dicotyledonous plant was able to develop into a fertile plant via direct embryogenesis with the aid of a co-culture system in which fertilized ovules were employed as feeders. The results confirmed that a tobacco zygote could divide in vitro following the basic embryogenic pattern of the Solanad type. The zygote cell wall and directional expansion are two critical points in maintaining apical-basal polarity and determining the developmental fate of the zygote. Only those isolated zygotes with an almost intact original cell wall could continue limited directional expansion in vitro, and only these directionally expanded zygotes could divide into typical apical and basal cells and finally develop into a typical embryo with a suspensor. In contrast, isolated zygote protoplasts deprived of cell walls could enlarge but could not directionally elongate, as in vivo zygotes do before cell division, even when the cell wall was regenerated during in vitro culture. The zygote protoplasts could also undergo asymmetrical division to form one smaller and one larger daughter cell, which could develop into an embryonic callus or a globular embryo without a suspensor. Even cell walls that hung loosely around the protoplasts appeared to function, and were closely correlated with the orientation of the first zygotic division and the apical-basal axis, further indicating the essential role of the original zygotic cell wall in maintaining apical-basal polarity and cell-division orientation, as well as subsequent cell differentiation during early embryo development in vitro.