Department of Plant Production and Genetics, Faculty of Agriculture, University of Kurdistan, Sanandaj, 66177-15175, Iran.
Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, 06466, Seeland, Germany.
Chromosome Res. 2023 Sep 2;31(3):26. doi: 10.1007/s10577-023-09728-6.
In many species, the transmission of B chromosomes (Bs) does not follow the Mendelian laws of equal segregation and independent assortment. This deviation results in transmission rates of Bs higher than 0.5, a process known as "chromosome drive". Here, we studied the behavior of the 103 Mbp-large B chromosome of Festuca pratensis during all meiotic and mitotic stages of microsporogenesis. Mostly, the B chromosome of F. pratensis segregates during meiosis like standard A chromosomes (As). In some cases, the B passes through meiosis in a non-Mendelian segregation leading to their accumulation already in meiosis. However, a true drive of the B happens during the first pollen mitosis, by which the B preferentially migrates to the generative nucleus. During second pollen mitosis, B divides equally between the two sperms. Despite some differences in the frequency of drive between individuals with different numbers of Bs, at least 82% of drive was observed. Flow cytometry-based quantification of B-containing sperm nuclei agrees with the FISH data.
在许多物种中，B 染色体（Bs）的传递不符合孟德尔均等分离和独立分配的定律。这种偏差导致 Bs 的传递率高于 0.5，这一过程被称为“染色体驱动”。在这里，我们研究了羊茅 103 Mbp 大 B 染色体在小孢子发生的所有减数分裂和有丝分裂阶段的行为。羊茅的 B 染色体在减数分裂中主要像标准 A 染色体（As）一样分离。在某些情况下，B 染色体以非孟德尔的方式通过减数分裂，导致它们在减数分裂中已经积累。然而，真正的 B 染色体驱动发生在第一次花粉有丝分裂期间，通过这一过程，B 染色体优先迁移到生殖核。在第二次花粉有丝分裂中，B 染色体在两个精子之间均等分裂。尽管不同 B 染色体数量的个体之间驱动频率存在一些差异，但至少观察到 82%的驱动。基于流式细胞术的 B 染色体含核精子定量与 FISH 数据一致。
