Ge Xian-Hong, Wang Jing, Li Zai-Yun
National Key Laboratory of Crop Genetic Improvement, National Center of Crop Molecular Breeding Technology, National Center of Oil Crop Improvement (Wuhan), College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, PR China.
Ann Bot. 2009 Jul;104(1):19-31. doi: 10.1093/aob/mcp099. Epub 2009 Apr 29.
In sexual hybrids between cultivated Brassica species and another crucifer, Orychophragmus violaceus (2n = 24), parental genome separation during mitosis and meiosis is under genetic control but this phenomenon varies depending upon the Brassica species. To further investigate the mechanisms involved in parental genome separation, complex hybrids between synthetic Brassica allohexaploids (2n = 54, AABBCC) from three sources and O. violaceus were obtained and characterized.
Genomic in situ hybridization, amplified fragment length polymorphism (AFLP) and single-strand conformation polymorphism (SSCP) were used to explore chromosomal/genomic components and rRNA gene expression of the complex hybrids and their progenies.
Complex hybrids with variable fertility exhibited phenotypes that were different from the female allohexaploids and expressed some traits from O. violaceus. These hybrids were mixoploids (2n = 34-46) and retained partial complements of allohexaploids, including whole chromosomes of the A and B genomes and some of the C genome but no intact O. violaceus chromosomes; AFLP bands specific for O. violaceus, novel for two parents and absent in hexaploids were detected. The complex hybrids produced progenies with chromosomes/genomic complements biased to B. juncea (2n = 36, AABB) and novel B. juncea lines with two genomes of different origins. The expression of rRNA genes from B. nigra was revealed in all allohexaploids and complex hybrids, showing that the hierarchy of nucleolar dominance (B. nigra, BB > B. rapa, AA > B. oleracea, CC) in Brassica allotetraploids was still valid in these plants.
The chromosomes of three genomes in these synthetic Brassica allohexaploids showed different genome-specific stabilities (B > A > C) under induction of alien chromosome elimination in crosses with O. violaceus, which was possibly affected by nucleolar dominance.
在栽培芸苔属物种与另一种十字花科植物诸葛菜（2n = 24）的有性杂种中，有丝分裂和减数分裂过程中亲本基因组的分离受遗传控制，但这种现象因芸苔属物种而异。为了进一步研究亲本基因组分离所涉及的机制，获得并鉴定了来自三个来源的合成芸苔属异源六倍体（2n = 54，AABBCC）与诸葛菜之间的复合杂种。
采用基因组原位杂交、扩增片段长度多态性（AFLP）和单链构象多态性（SSCP）来探究复合杂种及其后代的染色体/基因组组成和rRNA基因表达。
育性各异的复合杂种表现出与雌性异源六倍体不同的表型，并表达了诸葛菜的一些性状。这些杂种是混倍体（2n = 34 - 46），保留了异源六倍体的部分染色体组，包括A和B基因组的整条染色体以及部分C基因组，但没有完整的诸葛菜染色体；检测到诸葛菜特有的、双亲中均未出现且六倍体中不存在的AFLP条带。复合杂种产生的后代染色体/基因组组成偏向芥菜型油菜（2n = 36，AABB），并产生了具有两个不同来源基因组的新型芥菜型油菜品系。在所有异源六倍体和复合杂种中均检测到来自黑芥的rRNA基因表达，表明芸苔属异源四倍体中核仁显性等级（黑芥，BB > 白菜型油菜，AA > 甘蓝型油菜，CC）在这些植物中仍然成立。
在与诸葛菜杂交的异源染色体消除诱导下，这些合成芸苔属异源六倍体的三个基因组的染色体表现出不同的基因组特异性稳定性（B > A > C），这可能受核仁显性影响。
