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Variation Patterns of rRNA Genes in Pinus (Pinaceae) and Their Evolutionary Implications for Genome Structure, Gene Evolution, and Speciation Inferences

Author: LiuZhanLin
Tutor: HongDeYuan;WangXiaoRu;ZhangDaMing
School: Institute of Botany
Course: Botany
Keywords: Pinus rDNA Hybrid origin Molecular Evolution Genome relations Fluorescence in situ hybridization FISH Genomic in situ hybridization GISH
CLC: Q943
Type: PhD thesis
Year: 2002
Downloads: 397
Quote: 4
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Abstract


Angiosperms rRNA gene has been studied in depth. Diploid angiosperms typically have 1-4 pairs of 18S-5.8S-26S rDNA loci and 1-2 on the 5S rDNA loci. As a special multi-gene family members, rDNA will be affected by homogenization force (homogenizing forces) role, through gene conversion, unequal exchange mechanism, the formation genes concerted evolution (concerted evolution). Over the years, we have always thought that animals and plants high levels of rDNA concerted evolution, various copies of the sequence is almost exactly the same, it can be applied directly sequencing PCR method for molecular systematic studies. However, due to research data in gymnosperms lack, so we gymnosperms rDNA variation patterns are poorly understood. Pinus plants as gymnosperms largest groups, it is what characteristics rDNA variation and evolution, and angiosperms are the same, the evolution of this important group of studies is not yet resolved. Content of this study from three aspects: (1) rDNA chromosomal localization Currently, Pinus of 18S-5.8S-26S rDNA chromosomal localization study included only five species, three of which involve both the 5S rDNA positioning . These findings indicate that the presence of different kinds of dissimilar number of rDNA loci, even different individuals rDNA loci have changed. Whose common denominator is, 18S-5.8S-26S rDNA loci average more than angiosperms, 5S rDNA in addition to Pinus radiata, but in other species where the similarity with angiosperms. This phenomenon is loose or gymnosperms are a common feature, also, or exceptions it? Limited research limits the gymnosperms rDNA understanding. One of the aims of this study is to study the Pinus spp rDNA in spatial distribution of Pinus spp hope to understand the relationship between gymnosperms and angiosperms rDNA in comparative genomic level differences. (2) 5S rDNA molecular evolution of 5S rDNA sequence level evolutionary studies in Pinus still blank. 5S rDNA in chromosome number does not show differences in gymnosperms and angiosperms, gymnosperms mean Pinus even the 5S rDNA is also the same as angiosperms - concerted evolution completely, sequences are highly consistent? Cloning and sequencing method using the loose genus 5S rDNA research is undoubtedly a pioneering work, you can explore the gymnosperms 5S rDNA evolutionary mechanisms and inter-relationships. (3) hybrid genome hybridization of species origin and evolution of the current biological research hotspot, through hybrid genome research, you can learn hybrid genome composition, organization and evolutionary history, explore the hybridization events into a kind of process, impact and significance . This study involves the alpine pine, Yunnan pine and pine. Reason for using these three plants because allozyme, cpDNA and mtDNA evidence pine and mountain pine Pinus yunnanensis natural hybrids. But the evidence does not adequately reflect the recombinant hybrid nuclear genome composition and characteristics and laws of evolution. We use rDNA-FISH, 5S rDNA and genomic in situ hybridization analysis of three kinds of pine relationship between genome for revealing the evolutionary mechanisms and mountain pine history provides a new basis. This study obtained the following results: a. rDNA fluorescence in situ hybridization (FISH) through the pine and whitebark pine subgenus the two single vascular plants and pine, Yunnan pine, mountain pine, pine and Pinus latteri other five pairs of vascular Asian genus 18S rDNA and 5S rDNA fluorescence in situ hybridization, the results showed that: (1) gymnosperms 18S rDNA loci significantly more than the diploid number of angiosperms. The main number of sites, there are seven pairs of pine, mountain pine 5 pairs, eight pairs of Yunnan pine, pine 10 pairs, Pinus latteri six pairs, tree three pairs, pine 10 pairs, with an average in seven pairs; addition, some pine there are still weak sites. Both sites are part of the strength present in the centromeric regions of chromosomes, except Akamatsu (Pinu dens gamma raX In other Pinaceae and did not find this phenomenon. Whether it is the result of gene transfer or this locus is 18s riZNTA The original location of origin has yet to be confirmed. (2) SS fi3: NA locus relative variation is considerable and angiosperms addition to a drought on pine SS d3NA sites, pine only one pair of loci, other pine SS riZNA number of sites are two pairs, and in double-vascular Cambodia Asia there is a genus belonging to the weak sites. (3) two kinds fi3NA existence of different chain model. pair vascular Asian genus, SS and 18s rDNA same chain in the same chromosome arm or two arms in the same chromosome arm, 18s fi3NA at arm's distal end. single vascular Asian genus of the SS and 185 d7NA or chain on the same arm of the same chromosome, or are in different chromosomes. former case, SS n3NA located distal arm whereby subgenus can explain two rDNA structure in large genomic level differentiation. (4) the relationship between pine species and alpine pine karyotype characteristics due to the SS and the 18s n3NA different linkage can be single and double vascular bundle subgenus subgenus apart. different species of the subgenus hybridization sites can be based on the number, location, signal strength karyotype constituted Figure distinguish and constitute some system relationship hybrid origin of alpine pine genomes, showing Pinus yunnanensis two parents and the different characteristics of each chromosome inheritance and restructuring, and produce unique characteristics with its * One chromosome deletions 18s rDNA loci, chromosomal rearrangements may be traces of two. SS if7: NA sequence variation and molecular evolution using molecular cloning and DNA sequencing analysis of the pine, Yunnan pine, pine, tree, and different genetic background of alpine pine populations SS iLNA gene sequence variation and gene evolution law, the following main results: (1) SS rDNA structural features. pair vascular length Subgenus 658 Diao 28 hp, Bungeana compared with 49952 hp. length difference is reflected in the intergenic region, and the gene region ultraconservative, \

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