【作者】 李杨；

【导师】 沈星星；

【作者基本信息】 浙江大学 ， 农业昆虫与害虫防治， 2023， 博士

【摘要】 昆虫是动物界数量最多、种类最丰富的类群,已知的昆虫种类数超过100万,占所有动物种类的50%以上。水平基因转移(Horizontal gene transfer,HGT)是指存在生殖隔离的物种直接基因交流的现象,被认为是塑造原核生物和真核生物基因组的重要演化动力。近年来,关于昆虫水平基因转移的研究已有许多报道。例如,蚜虫从真菌中获取类胡萝卜素合成酶,来改变体色;烟粉虱从植物中获取丙二酰转移酶,来减少植物酚类物质的毒性;一些鳞翅目昆虫从病毒中获取寄生蜂寄生因子,以抵抗寄生蜂的寄生。这些HGT基因提高了昆虫对环境的适应性,并帮助物种在演化过程中脱颖而出。然而,先前的研究往往聚焦于特定物种或个别类群。本研究通过基因组学和系统发育生物学,结合生物信息学和分子生物学等方法,利用昆虫基因组数据,系统地筛选和分析了昆虫纲广泛存在的水平基因转移。探究水平基因转移如何重塑昆虫基因组,以及外源基因如何适应昆虫基因组等问题。主要研究内容如下:1、昆虫纲广泛存在的水平基因转移。结合218种昆虫高质量基因组及HGT高通量筛选算法,对近300万个基因样本进行了大数据分析和筛查,共鉴定到1,410个HGT基因,通过741个不同的HGT事件从非后生动物类群获得。HGT基因广泛地存在于整个昆虫纲中,包括多种蝶类、蛾类、甲虫、飞虱、蜜蜂等。平均而言,鳞翅目(如小菜蛾、黑脉金斑蝶等)获得16个HGT基因/物种,半翅目(如稻飞虱等)获得13个HGT基因/物种,鞘翅目(如赤拟谷盗等)获得6个HGT基因/物种,膜翅目(如中华蜜蜂,寄生蜂等)获得3个HGT基因/物种。从HGT来源来说,79%的HGT基因来源于细菌,13.8%来源于真菌,2.6%来源于病毒,3%来源于植物,1.6%的来源未知。2、昆虫HGT基因内含子的来源及HGT基因适应性进化。为了解析HGT基因在昆虫体内的命运,本研究基于昆虫HGT基因和供体中对应基因的比较基因组学研究,发现HGT基因转移到昆虫基因组后,伴随着演化过程积累变异,许多HGT基因中会插入昆虫的重复序列。这些序列往往带有调控作用,并促使HGT基因高水平表达。更重要的是,在演化的时间尺度上,越早获得HGT基因,它的基因结构与昆虫自身的基因结构越相似。结果说明,HGT基因伴随着昆虫适应性演化,其基因功能和结构也随之变化,从而免于被昆虫清除,达到在昆虫基因组上“存活”的目的。3、在蛾类和蝶类中普遍存在的外源基因增强雄蛾向雌蛾的求偶行为。进一步分析发现,蝶类和蛾类均从李斯特菌(Listeria)获得HGT基因LOC105383139。以十字花科的重要农业害虫小菜蛾作为研究对象,利用基因编辑技术敲除HGT基因LOC105383139,相比较野生型小菜蛾,突变体小菜蛾的后代数减少了约70%,但其生长发育、运动和生殖器官等均未受到影响。通过行为学实验,发现突变体雄蛾对雌蛾的求偶欲望显著降低。结果表明,蝶类和蛾类获得的HGT基因LOC105383139有助于增强雄蛾对雌蛾求偶行为。综上所述,本文阐明了HGT基因在218种昆虫的分布情况、适应性以及昆虫求偶基因的生物学功能,强调了水平基因转移对昆虫演化和适应性的重要性。本研究对于HGT在昆虫多样性和适应性进化以及其对农业危害生物防治具有重要的指导意义。更多还原

【Abstract】 Insects are the most abundant and diverse lineage in the animal kingdom and comprise over one million known species that account for over 50% of all described living animals on Earth.Horizontal gene transfer(HGT)refers to the exchange of genetic material between species with reproductive isolation and is considered a driving force shaping prokaryotic and eukaryotic genomes.In recent years,there have been many reports on HGT in insects.For example,carotenoid biosynthesis genes transferred from fungi to aphids contribute to aphid body coloration,genes that neutralize phenolic glucosides acquired by whiteflies from plants contribute to whitefly detoxification capabilities,andapara-sitoid killing factor gene transferred from a virus to lepidopterans contributes to lepidopteran defense.These HGT-acquired genes help insects adapt to new environment and stand out in the evolution.However,previous studies have shown the occurrence of HGT in insects,but their taxon sampling strategies focused on eithera few insects of interest or on a specific order of insects.We systematically carried out a comprehensive investigation of HGTs using large-scale insect genomics,along with bioinformatics and molecular biology methods.In addition,this study examined how HGTs shaped insect genomes and how they innovated biological functions in insects.1.Numerous horizontal gene transfers into insects.Using a robust and conservative phylogeny-based approach to examine the protein sequence of each of the nearly 3 million genes in the high-quality genomes of 218 insects,we systematically identified 1,410 HGT genes in 192 insect genomes that were likely acquired via 741 distinct events from non-metazoan source.These insect species include various butterflies,moths,beetles,planthoppers,and bees.On average,Lepidoptera(eg,diamondback moth and small white butterfly)acquired 16 HGT genes/species,Hemiptera(eg,brown planthopper)acquired 13 HGT genes/species,Coleoptera(eg,the red flour beetle)acquired 6 HGT genes/species,and Hymenoptera(eg,bees and parasitoid wasps)acquired 3 HGT genes/species.From the source of HGT’s donor,79% of HGT genes stem from bacteria,13.8% from fungi,2.6% from viruses,3% from plants,and 1.6% from unknown donors.2.Origin of introns in HGT-acquired genes and adaptation of HGT in insects.To determine the fate of transferred genes in insects,we characterized the gene structures of 1,410HGT-acquired genes in the putative donor and recipient genomes as well as of all native insect genes.We found that repeat-rich intron gains from native insect genomes,which enabled these foreign genes to increase their lengths toward the average length of native genes,were likely involved in adaptation of HGTs in insect genomes.Collectively,HGT-acquired genes containing introns exhibited substantially higher expression levels than genes lacking introns,suggesting that intron gains were likely involved in HGT adaptation,thereby avoiding being removed in the long-term evolution and surviving in insect genomes.3.The last common ancestor of moths and butterflies horizontally acquired a foreign gene that enhances male courtship behavior.We found that the prevalent HGT-acquired gene LOC105383139 was transferred into the last common ancestor of moths and butterflies from a donor in the bacterial genus Listeria.We used the CRISPR-Cas9 system to knock out the gene LOC105383139 in the diamondback moth Plutella xylostella,a serious agricultural pest of crucifer vegetables.We initially found that knockout(MT-139)moths have a much lower number of offspring but have no significant differences in five develop-mental phenotypes,including body size,feeding,movement,testis size,and sperm activity.Through further observations,we found that MT-139 moths had apparently lower mating rates than WT moths.In words,HGT-acquired gene LOC105383139 enhances male courtship behavior in moths and butterflies.In summary,this study elucidated the distribution,adaption and functional identification of male courtship-associated gene in 218 insects,and highlighted the importance of HGT in insect evolution and adaptation.It contributed to our understanding of HGTs in insect diversity and adaptation and its impact on agriculture.更多还原