Key Laboratory of Herbage and Endemic Crop Biology, Ministry of Education, Inner Mongolia University, Hohhot, 010020, Inner Mongolia, China.
College of Life Science, Inner Mongolia University, Hohhot, 010020, Inner Mongolia, China.
Theor Appl Genet. 2024 Oct 4;137(10):245. doi: 10.1007/s00122-024-04734-6.
The major irregular chromosome pairing and mis-segregation were detected during meiosis through unambiguous chromosome identification and found that allotriploid Brassica can undergo meiosis successfully and produce mostly viable aneuploid gametes. Triploids have played a crucial role in the evolution of species by forming polyploids and facilitating interploidy gene transfer. It is widely accepted that triploids cannot undergo meiosis normally and predominantly produce nonfunctional aneuploid gametes, which restricts their role in species evolution. In this study, we demonstrated that natural and synthetic allotriploid Brassica (AAC), produced by crossing natural and synthetic Brassica napus (AACC) with Brassica rapa (AA), exhibits basically normal chromosome pairing and segregation during meiosis. Homologous A chromosomes paired faithfully and generally segregated equally. Monosomic C chromosomes were largely retained as univalents and randomly entered daughter cells. The primary irregular meiotic behaviors included associations of homoeologs and 45S rDNA loci at diakinesis, as well as homoeologous chromosome replacement and premature sister chromatid separation at anaphase I. Preexisting homoeologous arrangements altered meiotic behaviors in both chromosome irregular pairing and mis-segregation by increasing the formation of A-genomic univalents and A-C bivalents, as well as premature sister chromatid separation and homologous chromosome nondisjunction. Meiotic behaviors depended significantly on the genetic background and heterozygous homoeologous rearrangement. AAC triploids mainly generated aneuploid gametes, most of which were viable. These results demonstrate that allotriploid Brassica containing an intact karyotype can proceed through meiosis successfully, broadening our current understanding of the inheritance and role in species evolution of allotriploid.
在减数分裂过程中，通过明确的染色体鉴定检测到主要的染色体不规则配对和错误分离，发现异源三倍体芸薹属可以成功进行减数分裂，并产生大多数可育的非整倍体配子。三倍体通过形成多倍体和促进种间基因转移，在物种进化中发挥了关键作用。人们普遍认为，三倍体不能正常进行减数分裂，主要产生无功能的非整倍体配子，这限制了它们在物种进化中的作用。在这项研究中，我们证明了通过将自然和合成甘蓝型油菜（AACC）与白菜（AA）杂交产生的自然和合成异源三倍体芸薹属（AAC），在减数分裂过程中表现出基本正常的染色体配对和分离。同源 A 染色体配对准确，通常均等分离。单 C 染色体大部分作为单价体保留，随机进入子细胞。主要的不规则减数分裂行为包括同源对和 45S rDNA 位点在减数分裂前期的联会，以及同源染色体的替换和后期 I 的姐妹染色单体过早分离。同源排列的预先存在改变了染色体不规则配对和错误分离的减数分裂行为，增加了 A 基因组单价体和 A-C 二价体的形成，以及姐妹染色单体过早分离和同源染色体不分离。减数分裂行为显著依赖于遗传背景和杂合同源重排。AAC 三倍体主要产生非整倍体配子，其中大多数是可育的。这些结果表明，含有完整染色体组的异源三倍体芸薹属可以成功进行减数分裂，拓宽了我们对异源三倍体遗传和在物种进化中作用的认识。
