芸薹属种间杂种的染色体组稳定性研究

Polypliodization has played an important role in evolution of plants and many crops are allopolyploids, So the genetic mechanism of genome changes in evolution of allopolyploids was always focused. In recent years, the hypothesis was proposed that expression of rRNA genes of the genome contributes its stability, but it was not supported widely.The triploid and hexaploid hybrids between Brassica fruticulosa and Brassica cultivated tetraploids have been obtained via interspecific crossing and genome doubling treated by colchicine. Chromosome elimination will be induced by intergenus crossing to obtain euploids.Chromosome elimination will be observed through daul-colour genomic in situ hybridization(GISH); The difference of rRNA genes expression between genomes will be investigated through reverse transcription PCR(RT-PCR) and single strand confirmation polymorphism(SSCP); Shape of nucleolus will be observed by silver staining.The correlation between rRNA genes expression and genome stability will be discovered in hybrids and the mechanism of chromosome elimintion will be discovered too.The study will contribute to the research and application of synthetic allopolyploids.

多倍化在植物自然进化历程中发挥了巨大作用，许多重要的栽培植物都是异源多倍体。异源多倍体形成过程中基因组变化规律及其遗传机制一直是人们关注的焦点。近年来，有人提出核糖体RNA（rRNA）基因的表达有助于多倍体杂种染色体组稳定的假说，但此种说法未得到广泛证实。我们已经使芸薹属四倍体栽培种与野生种Brassica fruticulosa进行杂交获得了三倍体杂种，并经基因组加倍获得了六倍体。在此基础上，采用属间杂交方法诱导六倍体染色体消除获得非整倍体。通过基因组原位杂交（GISH）观察杂种各基因组染色体消除规律；采用反转录PCR（RT-PCR）和单链构象多态性（SSCP）方法分析各基因组间核糖体RNA基因的表达差异；通过银染核仁观察核仁形成规律。旨在揭示杂种rRNA表达与基因组的染色体稳定之间的关系，探索多倍体杂种染色体消除的遗传机制，为人工合成异源多倍体的研究与应用提供理论依据。

多倍化在植物进化史上发挥了巨大作用，染色体消除是多倍化进程中的一种特殊遗传现象。近年来，研究者提出rRNA基因的表达与染色体消除有关，但此种说法未得到广泛证实。本项研究进行了油菜近缘种间的杂交，经基因组加倍获得了种间三倍体和六倍体杂种，并以诸葛菜为父本对部分六倍体授粉诱导染色消除获得了非整倍体材料。研究了芸薹属种间杂交的亲和性，杂种后代的形态学特征和细胞遗传学特征。并通过基因组原位杂交研究了芸苔属基因组间的亲缘关系，观察了影响花粉育性的花粉母细胞减数分裂染色体行为。观察了杂种后代细胞内各基因组染色体消除的频率，原位杂交结果显示染色体组间稳定性关系为B＞A（F）＞C。通过分析各基因组rRNA基因的表达差异，确定A、B、C和F基因组的rRNA基因表达显隐性关系。分析结果表明四个基因组的rRNA表达显性关系与染色体组稳定性关系一致。此结果揭示在杂种体内核仁显性对维持杂种相应基因组稳定起一定作用。还对杂种后代进行了蚜虫抗性鉴定，获得了抗蚜虫的油菜育种新材料。研究结果不但为核仁显性有助于基因表达的说法提供了有力证据，还为油菜远缘杂交育种提供了理论基础。