Felismino Mariana Ferrari, Pagliarini Maria Suely, do Valle Cacilda Borges
Department of Cell Biology and Genetics, State University of Maringá, Maringá, Paraná, Brazil.
Cell Biol Int. 2008 Nov;32(11):1459-63. doi: 10.1016/j.cellbi.2008.07.001. Epub 2008 Jul 15.
Several mutations are known to alter the normal progression of meiosis and can be correlated with defects in microtubule distribution. The dv mutation affects the spindle organization and chromosomes do not converge into focused poles. Two Brachiaria hybrids presented the phenotypic expressions of dv mutation but exhibited many more details in the second division. Bivalents were distantly positioned and spread over a large metaphase plate and failed to converge into focused poles. Depending on the distance of chromosomes at the poles, telophase I nuclei were elongated or the chromosomes were grouped into various micronuclei of different sizes in each cell. The first cytokinesis occurred. However, when there were micronuclei, a second cytokinesis immediately took place dividing the prophase II meiocytes into three or four cells. In each meiocyte, meiosis progressed to the second division. Slightly elongated nuclei or micronuclei were recorded in telophase II. After a third cytokinesis, hexads or octads were formed. Pollen grains of different sizes were generated. One of these hybrids presented a higher frequency of abnormal cells than when previously analyzed. The fate of these hybrids as genitors or as candidates for cultivars in the Brachiaria breeding program is discussed.
已知有几种突变会改变减数分裂的正常进程，并且可能与微管分布缺陷相关。dv突变影响纺锤体组织，染色体无法汇聚到聚焦的两极。两种臂形草杂种表现出dv突变的表型表达，但在第二次分裂中展现出更多细节。二价体位置较远，分布在较大的中期板上，无法汇聚到聚焦的两极。根据染色体在两极的距离，末期I细胞核拉长，或者染色体在每个细胞中被分成大小各异的多个微核。第一次胞质分裂发生。然而，当存在微核时，第二次胞质分裂立即发生，将前期II减数分裂细胞分成三个或四个细胞。在每个减数分裂细胞中，减数分裂进入第二次分裂。末期II记录到略拉长的细胞核或微核。经过第三次胞质分裂后，形成了六分体或八分体。产生了不同大小的花粉粒。其中一种杂种出现异常细胞的频率比之前分析时更高。本文讨论了这些杂种作为臂形草育种计划中的亲本或品种候选者的命运。
