Risso-Pascotto C, Pagliarini M S, Borges do Valle C, Jank L
Department of Cell Biology and Genetics, State University of Maringá, 87020-900, PR, Brazil.
Plant Cell Rep. 2004 Jul;22(12):945-50. doi: 10.1007/s00299-004-0784-0. Epub 2004 Mar 24.
This paper reports the occurrence of chromosome elimination during microsporogenesis in an interspecific hybrid between a sexual diploid accession (SEX) of Brachiaria ruziziensis (2n=2x=18) and an apomictic tetraploid accession (APO) of B. brizantha (2 n=4 x=36). Meiosis was very abnormal in the triploid hybrid (2n=3x=27); we observed a distinct asynchrony from metaphase I to the end of meiosis. The APO and the SEX genomes did not show the same meiotic rhythm. When the former, with nine bivalents, was in metaphase I, the nine SEX univalents were not yet aligned; when the latter reached the plate, the APO genome was already in anaphase. In subsequent stages, the APO genome had reached the poles while the SEX was undergoing sister-chromatid segregation. As the SEX genome always remained temporally behind, it gave rise to one extra-nucleus in each pole. In the second division, the behavior was the same but anaphase II did not occur for the SEX genome, and only one extra-nucleus was observed in each cell in telophase II. Chromosome elimination for the SEX genome ranged from partial to total. The importance of these findings with respect to Brachiaria breeding programmes is discussed.
本文报道了在鲁氏臂形草（2n = 2x = 18）的有性二倍体材料（SEX）与巴西臂形草（2n = 4x = 36）的无融合生殖四倍体材料（APO）的种间杂交中，小孢子发生过程中染色体消除的情况。三倍体杂种（2n = 3x = 27）的减数分裂非常异常；我们观察到从减数第一次分裂中期到减数分裂结束存在明显的不同步。APO和SEX基因组没有表现出相同的减数分裂节奏。当具有9个二价体的前者处于减数第一次分裂中期时，9个SEX单价体尚未排列整齐；当后者到达赤道板时，APO基因组已经处于后期。在随后的阶段，APO基因组已经到达两极，而SEX基因组正在进行姐妹染色单体分离。由于SEX基因组在时间上总是滞后，它在每个极产生了一个额外的核。在第二次分裂中，行为相同，但SEX基因组没有发生减数第二次分裂后期，在减数第二次分裂末期每个细胞中只观察到一个额外的核。SEX基因组的染色体消除范围从部分到完全。讨论了这些发现对臂形草育种计划的重要性。
