Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA.
J Genet Genomics. 2010 Jan;37(1):79-84. doi: 10.1016/S1673-8527(09)60027-8.
It has been known for decades that the maize B chromosome undergoes nondisjunction at the second pollen mitosis. Fluorescence in-situ hybridization (FISH) was used to undertake a quantitative study of maize plants with differing numbers of B chromosomes to observe if instability increases by increasing B dosage in root tip tissue. B chromosome nondisjunction was basically absent at low copy number, but increased at higher B numbers. Thus, B nondisjunction rates are dependent on the dosage of B's in the sporophyte. Differences in nondisjunction were also documented between odd and even doses of the B. In plants that have inherited odd numbered doses of the B chromosome, B loss is nearly twice as likely as B gain in a somatic division. When comparing plants with even doses of B's to plants with odd doses of B's, plants with even numbers had a significantly higher chance to increase in number. Therefore, the B's non-disjunctive capacity, previously thought to be primarily restricted to the gametophyte, is present in sporophytic cells.
几十年来，人们已经知道玉米 B 染色体在第二次花粉有丝分裂时发生不分离。荧光原位杂交（FISH）被用来对具有不同数量 B 染色体的玉米植株进行定量研究，以观察在根尖组织中增加 B 剂量是否会导致不稳定性增加。B 染色体不分离在低拷贝数时基本不存在，但在较高的 B 数时增加。因此，B 染色体不分离率取决于孢子体中 B 的剂量。在具有奇数剂量 B 染色体的植物中，B 染色体不分离率在体细胞分裂中几乎是 B 染色体获得的两倍。在比较具有奇数剂量 B 染色体的植物和具有偶数剂量 B 染色体的植物时，具有偶数数量的 B 染色体的植物增加的机会明显更高。因此，以前认为主要局限于配子体的 B 染色体非分离能力，存在于孢子体细胞中。
