Rusche M L, Mogensen H L, Shi L, Keim P, Rougier M, Chaboud A, Dumas C
Department of Biological Sciences, Northern Arizona University, Flagstaff 86011, USA.
Genetics. 1997 Dec;147(4):1915-21. doi: 10.1093/genetics/147.4.1915.
The B chromosomes of maize typically undergo nondisjunction during the second microspore division (generative cell division). When the microspore nucleus contains only one B chromosome, two kinds of sperm result, one with two B chromosomes and one with no B chromosomes. The sperm with the B chromosomes preferentially fertilizes the egg cell. Previous studies of these phenomena have been limited to genetic analysis and chromosome spreads. In this study we show that a B chromosome-specific probe can be used with fluorescence in situ hybridization (FISH) analysis to detect the presence, location, and frequency of B chromosomes in intact interphase nuclei within mature pollen of maize. Using genetic line TB-10L18, our results indicate that nondisjunction of the B centromere occurs at an average frequency of 56.6%, based on four plants and 1306 pollen grains analyzed. This is consistent with the results of genetic studies using the same B-A translocation. In addition, our results suggest that B chromosome nondisjunction can occur during the first microspore division. Spatial distribution of the B chromosome-specific probe appears to be largely confined to one tip of the sperm nucleus, and a DNA fragment found outside the pollen nuclei often hybridizes to the B chromosome-specific probe.
玉米的B染色体通常在第二次小孢子分裂（生殖细胞分裂）期间发生不分离。当小孢子核仅含有一条B染色体时，会产生两种精子，一种含有两条B染色体，另一种不含B染色体。含有B染色体的精子优先使卵细胞受精。此前对这些现象的研究仅限于遗传分析和染色体铺展。在本研究中，我们表明，一种B染色体特异性探针可用于荧光原位杂交（FISH）分析，以检测玉米成熟花粉中完整间期核内B染色体的存在、位置和频率。利用遗传系TB-10L18，基于对四株植物和1306个花粉粒的分析，我们的结果表明，B着丝粒的不分离平均发生率为56.6%。这与使用相同B-A易位的遗传研究结果一致。此外，我们的结果表明，B染色体不分离可能发生在第一次小孢子分裂期间。B染色体特异性探针的空间分布似乎主要局限于精核的一端，并且在花粉核外发现的一个DNA片段常常与B染色体特异性探针杂交。
