LITHIUM TREATMENT OF NICOTIANA-TABACUM MICROSPORES BLOCKS POLAR NUCLEAR MIGRATION, DISRUPTS THE PARTITIONING OF MEMBRANE-ASSOCIATED CA2+, AND INDUCES SYMMETRICAL MITOSIS
LITHIUM TREATMENT OF NICOTIANA-TABACUM MICROSPORES BLOCKS POLAR NUCLEAR MIGRATION, DISRUPTS THE PARTITIONING OF MEMBRANE-ASSOCIATED CA2+, AND INDUCES SYMMETRICAL MITOSIS
复制标题
DOI：
10.1007/bf00242260
复制
发表时间：
1995-05-01
影响因子：
--
通讯作者：
TUPY, J
中科院分区：
文献类型：
--
作者：
ZONIA, LE;TUPY, J
我们已经发现，烟草小孢子的正常发育途径被阻断或切换时，小孢子暴露于锂，这些影响是可逆的Ca 2+和肌醇。正常发育的特征是：小孢子由球形变为卵圆形，再变为椭圆形，细胞核有两次移位，先从中心位置向细胞周边移动，再从周边向生殖极移动，细胞分裂前，细胞膜上的Ca ~（2+）定位于生殖极，细胞分裂后，细胞核内的Ca ~（2+）浓度逐渐升高，细胞核内Ca ~（2+）浓度逐渐降低。最后，不对称的有丝分裂产生具有分化良好的生殖核和营养核的双细胞花粉粒。锂处理阻止了膜相关的Ca 2+在生殖极的本地化，而是均匀分布在两极。锂处理还阻止了小孢子核在生殖极的不对称定位，并导致对称有丝分裂频率增加约4倍。当钙离子和肌醇与锂一起沿着加入时，其作用显著降低，与对照组相比，对称有丝分裂的频率仅略有增加。处理的时机很重要;在第一次核移位之前分离的小孢子进一步发育的频率较低，而在有丝分裂开始之前立即分离的小孢子对锂的敏感性要低得多，结果是对称有丝分裂的频率仅略有增加。在第一次核置换后分离的小孢子中，暴露于锂1天足以将发育途径从不对称有丝分裂转变为对称有丝分裂，同时仍然允许有限的进一步发育。然而，我们还没有优化胚胎发生的培养条件，在1周培养后观察到的最远发育是四细胞或五细胞的原胚样结构
We have found that the normal developmental pathway of Nicotiana tabacum microspores is blocked or switched when microspores are exposed to lithium, and these effects are reversible with Ca2+ and myo-inositol. Normal development was defined by the following characteristics: changes in microspore shape from spherical to oval and then ellipsoid; two nuclear displacements, first from a central location to the cell periphery, and then from the periphery to the generative pole; a localization of membrane-associated Ca2+ at the generative pole preceding nuclear division; and, finally, an asymmetrical mitosis that results in a two-celled pollen grain with well-differentiated generative and vegetative nuclei. Lithium treatment blocked the localization of membrane-associated Ca2+ at the generative pole, and instead it was evenly distributed at both poles. Lithium treatment also blocked the asymmetrical positioning of the microspore nucleus at the generative pole and resulted in an approximately four-fold increase in the frequency of symmetrical mitosis. When Ca2+ and myoinositol were added along with lithium, the effects were substantially decreased, and there was only a small increase in the frequency of symmetrical mitosis compared with controls. The timing of treatment was important; microspores isolated before the first nuclear displacement had a low frequency of further develop ment, while microspores isolated immediately preceding the onset of mitosis were much less sensitive to lithium, and the result was only a small increase in the frequency of symmetrical mitosis. In microspores isolated after the first nuclear displacement, a 1-day exposure to lithium was sufficient to switch the developmental pathway from an asymmetrical to a symmetrical mitosis while still allowing limited further development. However, we have not optimized culturing conditions for embryogenesis and the furthest development observed after a 1-week culture was to four- or five-celled proembryo-like structures