烟粉虱三个隐种雌雄虫转录组的研究与烟粉虱进化机制探讨

发布时间：2018-09-05 13:16

【摘要】：烟粉虱Bemisia tabci在全球广泛分布,是棉花、烟草、蔬菜和园林花卉等作物的主要害虫之一。烟粉虱是一个物种复合体,至少包含35个形态上难以区分但遗传组成有显著差异的隐种。该隐种复合体的MEAM1和MED隐种入侵性很强,分布广泛。而AsiaⅡ3是分布在中国的一种土著烟粉虱,与入侵种相比,为害性较弱。MEAM1可以通过生殖干涉的方式竞争取代本地种AsiaⅡ3,而且能通过寄主植物与双生病毒获得间接互惠,促进种群增长和病毒传播。MED得益于更高的抗药性,在频繁施用杀虫剂的生境中,MED可以竞争取代MEAM 1。MEAM 1和MED能高效地传播一些能引起重大危害的植物病毒病。粉虱是一类单双倍体昆虫,未受精卵发育成雄虫,为单倍体,受精卵发育成雌虫,为二倍体。烟粉虱雌性和雄性在外表和行为上有明显差异。然而在基因水平上,雌雄之间仅有染色体拷贝数上的差异,雌虫有两套、雄虫只有一套,每一套染色体都是相同的。这意味着雌雄间在外观和行为上有差异的性状在很大程度上是同样的基因差异性表达的结果。性别偏好表达基因包括在某一性别特有表达的基因,以及在两性中均表达但在某一性别表达水平显著地高于另一性别的基因。对果蝇、哺乳动物、鸟类等动物的研究表明,性别偏好表达基因趋向于在蛋白质序列上快速进化。与蛋白序列类似,基因表达量也会在自然选择下发生进化,而且基因表达量的进化与蛋白质序列的进化可能有一定的正相关性。RNA-seq高通量测序技术使我们能便捷地得到基因编码区序列和基因表达水平。本论文拟通过对MEAM1、MED和AsiaⅡ3三个隐种同源基因编码区的进化的研究,并结合雌性和雄性成虫整体基因的表达谱进行分析,以求了解烟粉虱性别偏好表达基因以及雌雄基因表达量的进化模式。本研究主要结果如下:(1)通过对MEAM 1、MED和Asia Ⅱ3三个隐种之间的同源基因的编码区进化的比较分析,找到160条在两个以上物种间可能的正向选择基因。这些基因可能与三个隐种之间不同的生物学特性密切相关,也可能与隐种间的分化相关。而这些基因的分布与性别偏好表达情况的相关性不显著。三个隐种中进化较快的基因大多集中在营养消化、代谢、解毒、与寄主互作,以及神经与嗅觉方面。这些可能与MEAM 1和MED的一些入侵特性相关。(2)对雌雄两性差异表达基因和同源基因编码区的综合分析表明,三个隐种的同源基因中雄性偏好表达基因,尤其是偏好表达不高(偏好表达在2到8倍)的基因,总体上进化速度比雌性偏好表达和无偏好表达基因慢。这可能意味着在烟粉虱中雄性偏好表达基因进化得较慢。这种雌雄间基因编码区的进化模式和性染色体的二倍体生物如果蝇、鸟类和哺乳动物不同,与社会性的单双倍体昆虫红火蚁雄蚁和蚁后间基因编码区的进化模式有些类似。这种性别偏好表达基因的进化模式可能与单双倍体昆虫的遗传进化特点有关。(3)通过对MEAM1、MED和AsiaⅡ3三个隐种之间同源基因的表达量的比较分析,发现与性别偏好无关的基因在种内变异较小,种间变异较大,可能更多地受到正向的自然选择。而雄性和雌性偏好表达的基因相比来说,种内和种间变化差异均较大,受到的自然选择较弱。这种基因表达量进化模式与果蝇、哺乳动物等均不同。这种基因表达量的进化模式或许也与单双倍体昆虫的遗传方式有关。与基因沉默和信号转导相关的基因在种间变异大,种内变异不大,在表达量上进化较快,这可能也与不同隐种的形成以及两个入侵烟粉虱隐种的一些入侵特性相关。(4)在烟粉虱雌雄虫的比较转录组学分析和表达谱研究中,得到了大量的RNA-seq数据。利用这些数据和生物信息学工具,开发了一个烟粉虱基因表达分析网站,能进行基因注释和表达量的查询,还能对RNA-seq的实验样本进行基因差异表达方面的数据挖掘。综上所述,本论文首次对非社会性单双倍体昆虫进行性别偏好表达基因的研究,找到了这类生物在进化与性别偏好表达基因之间的联系。通过对烟粉虱两个入侵隐种MEAM1、MED及土著隐种AsiaⅡ3同源基因进化速率上的扫描,找到了一些可能的正选择的基因,为后续研究烟粉虱不同种间的基因差异提供了思路,也为找到与烟粉虱隐种分化密切相关的基因提供了备选。通过对烟粉虱基因表达进化方面的分析,初步找出了非社会性单双倍体昆虫基因表达进化的一些规律。此外,本研究开发了烟粉虱基因表达网站,为后续的烟粉虱研究提供了基因分析的平台。
[Abstract]:Bemisia tabci is one of the main pests of cotton, tobacco, vegetables and garden flowers. Bemisia tabci is a species complex which contains at least 35 cryptospecies which are difficult to distinguish in morphology but have significant genetic differences. The cryptospecies MEAM1 and MED of the cryptospecies complex are highly invasive and widely distributed. MEAM1 can compete for the replacement of native Asia II 3 by reproductive interference, and can gain indirect reciprocity through host plants and geminiviruses, thus promoting population growth and virus transmission. MED benefits from higher resistance to insecticides and is being used frequently. Med can compete to replace MEAM 1.MEAM 1 and MED in the habitats of insecticides and can efficiently transmit some plant viral diseases that can cause serious harm. Whitefly is a kind of haploid and diploid insect. Unfertilized eggs develop into males and become haploid. Females and males of Bemisia tabaci have obvious differences in appearance and behavior. At the genetic level, there are only differences in the number of copies of chromosomes between males and females. There are two sets of chromosomes in females, one set in males, and each set of chromosomes is the same. Gender-specific genes and genes that are expressed in both sexes but are significantly higher in one sex than in the other. Studies in Drosophila, mammals, birds and other animals have shown that sex-preference genes tend to evolve rapidly in protein sequences. Similar to protein sequences, gene expression is also natural. High throughput RNA-seq sequencing technology enables us to easily obtain the sequence of gene coding region and the level of gene expression. In this paper, we intend to study the evolution of three cryptogenic homologous gene coding regions MEAM1, MED and Asia II 3. The main results of this study are as follows: (1) The coding region of homologous genes between MEAM 1, MED and ASIA II 3 was found to be 160 by comparing the evolutionary patterns of sex preference expression genes and the expression levels of male and female genes in Bemisia tabaci. These genes may be closely related to the different biological characteristics of the three cryptospecies or to the differentiation of the cryptospecies. The distribution of these genes is not significantly related to the expression of gender preference. Digestion, metabolism, detoxification, host interaction, and neural and olfactory aspects. These may be related to some invasive characteristics of MEAM 1 and MED. (2) Comprehensive analysis of male and female differentially expressed genes and coding regions of homologous genes showed that the male preferred to express genes, especially those with low preference for expression (preference for expression). In general, genes evolve more slowly than female-preferred and non-preferred genes. This may mean that male-preferred genes evolve more slowly in Bemisia tabaci. The evolutionary pattern of the gene coding region between the male and queen of diploid red fire ant is somewhat similar. The evolutionary pattern of the sex preference expression gene may be related to the genetic evolution characteristics of haploid and diploid insects. (3) By comparing the expression of homologous genes among MEAM1, MED and Asia II 3, it was found that there was no sex preference. Compared with male and female preference genes, intraspecific and interspecific variations are greater and natural selection is weaker. The evolutionary pattern of gene expression is different from that of Drosophila and mammals. Quantitative evolutionary patterns may also be related to the genetic pattern of haploid insects. Genes related to gene silencing and signal transduction exhibit large inter-species variations, small intra-species variations, and rapid evolution in expression, which may also be related to the formation of different cryptospecies and some intrusive characteristics of two invasive Bemisia tabaci cryptospecies. A large number of RNA-seq data have been obtained from comparative transcriptome analysis and expression profiling of insects. Using these data and bioinformatics tools, a website for gene expression analysis of Bemisia tabaci has been developed, which can query the amount of gene annotation and expression, and can also conduct data mining on gene differential expression of experimental RNA-seq samples. In this paper, we first studied the sex preference expression genes of non-social haploid insects and found the relationship between evolution and sex preference expression genes of these organisms. The positive selection of genes provides a new way to study the genetic differences among different species of Bemisia tabaci, and also provides an alternative to find genes closely related to the differentiation of Bemisia tabaci. In this study, we developed the gene expression website of Bemisia tabaci, which provides a platform for gene analysis for the follow-up study of Bemisia tabaci.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S433

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