【作者】 马永婷；

【导师】 包颖；

【作者基本信息】 曲阜师范大学 ， 植物学， 2008， 硕士

【摘要】 具有CCDD染色体组的异源四倍体美洲野生稻,包括Oryza alta Swallen、O.grandiglumis(Doell)Prod.和O.latifolia Desv.3个物种,属于O.officinalis复合体,在稻属(Oryza)中是一个比较特殊的类群。长期以来,以其局限的地理分布、错综复杂的分类学地位、不清晰的物种起源以及其异源多倍体的性质,一直吸引着众多学者的关注。总结以往的研究发现主要存在以下几个问题:(1)不同的学者对美洲野生稻这3个物种之间的系统发育关系各持己见;(2)美洲野生稻的起源问题长期以来一直困扰稻属系统分类学家。(3)CCDD物种倍增基因的分子进化问题引人深思。这些野生稻将来自不同染色体组亲本的基因整合到一个共同的核中,导致了整个基因组的倍增,那么这些来自不同染色体组上的倍增基因会采取何种进化方式,发生怎样的遗传改变?以上这些问题都有待于通过大量的实验研究来不断地寻求答案。针对上述问题,我们对美洲野生稻这3个物种的部分个体展开研究,以核低拷贝基因Adh1、GPA1为目的基因,采取序列分析的方法,希望能从DNA水平对这些问题有所揭示,其研究结果如下:(1)通过总结以往稻属异源四倍体中染色体组C和D以及稻属现存的所有二倍体染色体组A、B、C、E、F的乙醇脱氢酶基因(Adh1)片段的序列差异,并以G染色体组序列作为外类群,采用PAUP运算软件中的简约性和距离方法重新计算了各个染色体组之间的系统发育关系,进一步证明了3个CCDD四倍体是一次杂交事件的产物;四倍体中的C染色体组和亚洲的二倍体O.officinalis、O.rhizomatis物种中的C染色体组表现出更近的系统发育关系;而D染色体组和澳洲的O.australiensis物种中的E染色体组表现出较近的亲缘关系,二者可能有共同的祖先;同时进一步阐明了3个美洲野生稻中O.alta和O.grandigulmis的系统发育关系较近。(2)通过对来自不同分布区的含CD染色体组物种以及二倍体物种样品O.officinalis(CC)和O.australiensis(EE)的低拷贝核基因GPA1(G蛋白a亚基基因)的克隆测序,探讨了低拷贝基因在多倍体中的进化模式,从基因序列上揭示CD物种成种后,来自不同染色体组上的倍增基因会出现的可能进化动态。发现在CD物种的核基因组内两种染色体组类型的拷贝同时存在;较其他植物,其核苷酸多样性θw和π值呈现出较低的水平;同时,在3个物种内,C染色体组拷贝的多态性均高于D染色体组拷贝,特别是在O.grandiglumis和O.latifolia这两个种内这种优势更加明显;HK检验没有发现有最小重组事件的发生;除O.alta种内C染色体组的Fu和Li的D检验出现有意义的P值,其他统计检验在3个物种中均没有检测到偏离中性进化的结果。利用GPA1的单倍型构建的单染色体组基因谱系树发现,O.alta和O.grandiglumis两个物种共享较多的单倍型,进一步印证了这两个物种之间的系统发育关系比它们和O.latifolia要近。更多还原

【Abstract】 Three allopolyploids with the CCDD genome,distributing in Latin America,include O.alta Swallen,O.grandiglumis(Doell)Prod.,and O.latifolia Desv.The three species belong to O. officinalis complex,and they have a very complicated status in the genus Oryza,due to their overlapping in the distribution,the intricacies of delimitation and phylogenetic relationships, ambiguous of their origins as well as the characteristics of allopolyploidy,which have attracted many scientists to work on these problems for a long time.The main questions are summarized as follows:(1)Delimitation and phylogenetic relationships of the three species has long been a controversial matter,different viewpoint was mentioned by different academicians;(2)There has been a long history of interest in the possible origins of the three American allopolyploids with C and D genomes,on which different hypotheses were proposed;(3)The evolutionary dynamics of duplicated gene derived by polyploidization has long attracted the interest of geneticist.An allopolyploid speciation event entails the merger of two,differentiated genomes in to a common nucleus in only one of the two parent alcytoplasms,which result in genome-wide gene duplication.What are the primary possibilities for the evolutionary fates of duplicated genes from different genomes? What have been taken place to the duplicated genes on genetics in Oryza allotetraploids?The key of these questions need further studying to look for by a series of experiments.In this work,these unsolved questions,as mentioned above,were explored using the sequences of alcohol dehydrogenase(Adh1)gene and G-protein(GPA1)gene:(1)The phylogeny and the possible origins of the three allopolyploidys were discussed by comparing the sequences of the alcohol dehydrogenase(Adh1)gene from genome C and D in Oryza allotetraploids and the sequences from A,B,C,E and F genomes in extant Oryza diploids. The sequence from G genome was treated as the out-group.Phylogenetic analyses were performed using the parsimony and neighbor-join methods in PAUP soft.The result indicated three allotetraploids with CD genome might originate from a single hybridization event;C genome within the tetraploids showed a closer phylogenetic relationship to the C genome of O. officinalis,O.rhizomatis diploids from the Asia;genome D showed a closer affinity to the genome E of O.australiensis from Australia than the other genomes in diploids,which suggested that D and E genome might have a common ancestor.(2)The sequences of GPA1 from C,D genome in allopolyploids,and their close diploid relatives,O.australiensis with E genomes,O.officinalis with C genomes,were analyzed to investigate the patterns of evolution on duplicated genes in Oryza allotetraploids.The result showed the allopolyploid species contained two homoeologous sequences representing descendants of those contributed by the C and D genome donors at the time of polyploid formation;the three wild species appeared to hold very low levels of nucleotide variation compared to other plant species.Average nucleotide variation in GPA1 genes of C genome was higher than that in D genome,especially,in species of O.grandiglumis and O.latifolia,the phenomenon was more prominent.Based on the algorithm of Hudson and Kaplan,the minimum numbers of historical recombination events were not found in these species.Several statistical tests were used to test the hypothesis that GPA1 sequences have been evolving in accordance with expectations under neutral theory.The significant departure from neutrality was only found in O.alta by Fu and Li’D test.The null hypothesis of the isolation model was not rejected in grandiglumis and O.latifolia.The haplotype networks of the 3 species showed O.alta and O. grandiglumis shared more mutual haploidyes.The result further suggested a closer phylogenetic relationship between the two taxa.更多还原