报春花属植物基因组大小的检测与分析
王怡心
导师周伟
关键词报春花属,基因组大小变异,系统发育信号,环境因子,重复DNA,交配系统 Primula, Genome size variation, Phylogenetic signal, Environmental variables, Repetitive DNA, Mating system
摘要真核生物基因组大小在不同分类群中表现出巨大的差异,对基因组大小变异的解释包括染色体倍性的变化和非编码区DNA数量的差异;除了多倍化导致基因组大小成倍的增加之外,非编码区重复DNA的累积和消除的差异是开花植物基因组大小变异的关键驱动力。针对基因组大小变异的研究,人们在自然选择驱动还是中性过程驱动仍然有着很大的分歧。本研究从属这个分类水平探究基因组大小的变异,使用流式细胞术检测了97个报春花属物种的基因组大小;并使用叶绿体全基因组建立了报春花属的系统发育关系树;结合系统发育比较法分析了基因组大小和生物气候变量之间的相关性;使用浅层测序数据分析了报春花属的重复序列组成;并利用报春花属特有的混合交配系统研究异交向自交的转变对基因组大小变异的影响。本研究主要回答三个科学问题:在报春花属内,基因组大小的变异是否受到分布区环境影响?基因组大小变异与重复序列之间的相关性?在报春花属内,异交向自交的转变是否会导致基因组大小的变异? 主要研究结果如下: (1) 流式细胞术检测到报春花属内基因组大小差异为8倍,基因组大小的变异在属内具有显著性;在报春花属基因组大小中观察到显著的系统发育信号表示基因组大小的进化是比较保守的。系统发育比较分析揭示了基因组大小与年平均温度和降水季节变化等生态气候因子显著相关,表明在报春花属中,基因组大小的变异受到环境条件的限制,自然选择可能在基因组大小变异的过程中发挥着重要作用。 (2) 使用Repeat Explore从浅层测序数据中识别到报春花属物种中33% - 74%的重复序列,发现总重复DNA大约能解释基因组大小60%的变异,且观察到这种差异的48%可能是由LTR/gypsy中的Athila元件和LTR/copia中的SIRE元件驱动的。此外,与大部分关于被子植物的研究一样,报春花基因组大小与LTR反转座子的数量相关。 (3) 使用本研究建立的报春花属系统发育关系树中的16个同型花柱物种和近缘异型花柱组成16个姊妹种对,不同的花柱类型代表了自交种和异交种,对不同交配系统物种的基因组大小差异进行研究。观察发现有11个种对表现出自交种的基因组小于异交种,说明交配系统不同在报春花属内造成了基因组大小的变异的后果。 综上所述,在报春花属内,基因组大小的变异在报春花属中可能受到中性过程和自然选择的共同作用;重复序列分析表明较大的基因组拥有更多的转座子,基因组大小与反转座子的数量密切相关,属内基因组大小的变异受到反转座子内部单个重复元件驱动;异交向自交的转变会带来一系列的表型和遗传效应的后果,导致异交物种预计比自交种拥有更大的基因组,这一趋势在报春花属大部分自交种中发现。; The genome size of eukaryotes shows tremendous variation in different taxa. Explanation for this variation in genome size includes differences in chromosome ploidy and amounts of noncoding DNA. In addition to the doubling of genome size caused by polyploidy, the difference in the accumulation and elimination of repetitive DNA is the key driving force of genome size variation in flowering plants. Research of differences in genome size are still divided over whether they are driven by natural selection or neutral processes. This study explores the variation of genome size at genus level. The genome size of 97 Primula species was determined by flow cytometry. The phylogenetic relationship of Primula was established using chloroplast genome. Phylogenetic comparative methods (PCMs) used to analyze the correlation between genome size and bioclimatic variables. The repetitive DNA composition of Primula was analyzed using genome skimming data. The effects of the transition from predominant selfing from obligate outcrossing on genome size variation were studied using the unique mating system of Primula. This study answers three questions: Are genome size variations influenced by environmental factors in Primula? Is there correlation between genome size variation and repetitive DNA? Does the transition from outcrossing to selfing lead to significant differences in genome size? The main results are as follows: First, genomic size in Primula differed by 8-fold by flow cytometry, and the variation of genomic size was significant within the genus. Significant phylogenetic signals reveal that genome size evolution is conserved. Phylogenetic comparative methods revealed that genome size was significantly correlated with annual mean temperature and precipitation seasonality, suggesting that natural selection may play an important role in the genome size variation in Primula, which is limited by environmental conditions. Second, using genome skimming, repeats in each species were identified in Repeat Explore, ranging from 33% to 74%. Total Repeats explained 60% of the variation in genome size. Most of this difference (48%) was observed may be driven by the Athila element in the Ty3/gypsy LTR-retrotransposons and the SIRE element in the Ty1/Copia LTR-retrotransposons. In addition, as in most flowering plants studies, the genome size of Primula was correlated with the abundance of LTR retrotransposons. Third, 16 sister species pairs were composed of 16 homostyly species and related distyly species in the phylogenetic relationship tree of Primula established in this study. Different styles represented selfing and outcrossing. Genome size variation among species with different mating systems were studied. It was observed that 11 species pairs showed that the genomes of the selfing species were smaller than outcrossing species. Suggesting that the different mating systems caused the variation of genome size in Primula. In conclusion, neutral processes and natural sele
语种中文
2022-05
学位授予单位中国科学院大学
文献类型学位论文
条目标识符http://ir.kib.ac.cn/handle/151853/75125
专题昆明植物所硕博研究生毕业学位论文
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王怡心. 报春花属植物基因组大小的检测与分析[D]. 中国科学院大学,2022.
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