The genetic basis of phylosymbiosis and microbe-mediated hybrid lethality

系统共生和微生物介导的混合致死性的遗传基础

• 批准号: 390375589
• 负责人: Dr. Aram Mikaelyan
• 金额: --
• 依托单位: Abteilung Biogeochemie (aufgelöst)
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/390375589?language=en
• 关键词: genetic; basis; phylosymbiosis; microbe; mediated

The intestinal tracts of animals house some of the densest communities of microbial symbionts, and studies over the last decade have elucidated their astounding roles in host biology. In several cases, the fidelity of host-microbiota associations is reflected by host-specific composition of these gut bacterial communities and their metagenomes. Moreover, gut bacterial community relationships can recapitulate the evolutionary relatedness of the host species – a pattern known as “phylosymbiosis”. Notably, disruptions of phylosymbiosis in gut bacterial communities can be linked to severe maladies in hybrid hosts and could be driving host speciation. What are the host genetic factors and mechanisms that regulate phylosymbiosis? How do these genes influence hybrid conditions associated with the gut microbiota? The central hypothesis of this proposal is that phylosymbiosis and microbe-dependent hybrid lethality result from (1) an abnormal migration of gut bacteria into the hemolymph and (2) a misexpression of particular immune genes in hybrids that would otherwise control the resident bacterial population in pure species. The Nasonia wasp model system is ideal to test these hypotheses, because gut microbiota have been observed to contribute to severe larval lethality in interspecific hybrids. Using this model system, I will address the following two aims:I: Track bacterial colonization of the gut and identify the host genes that are hyperexpressed in hybrids in response to gut colonization. Proteus mirabilis is a widespread member of the Nasonia gut microbiota and contributes to hypermelanization and death of gnotobiotic Nasonia hybrids. This aim will use GFP-tagged P. mirabilis to test the hypothesis that, in the pure species, the bacterium exists in the benign, “swimmer” morphotype, but differentiates into the more virulent, “swarmer” morphotype in the hybrid to cause melanization in the hemolymph followed by death. The proliferation rate and sites of P. mirabilis will be studied using fluorescence microscopy. Additionally, RNA-seq analysis and qPCR in germ-free and wasps colonized by microbiota will test the hypothesis that specific candidate immune genes in the hybrid are involved in lethal breakdown in host-microbiota interactions.II: Functionally interrogate candidate genes underlying hybrid lethality and phylosymbiosis. Candidate genes responsible for hybrid lethality and phylosymbiosis will be shortlisted based on expression profiles obtained in Aim 1 from hybrid and non-hybrid larvae. This aim will test the hypothesis that when an important candidate gene for hybrid lethality is repressed by RNAi or CRISPR, hybrid viability will be restored. Moreover, repression of the same genes within species will disrupt a phylosymbiotic community assembly, thus probing the hypothesis that the same genes that influence hybrid lethality also influence phylosymbiosis.

动物的肠道容纳了一些微生物共生体的密集群落，过去十年的研究已经阐明了它们在宿主生物学中的惊人作用。在一些情况下，宿主-微生物群关联的保真度通过这些肠道细菌群落及其宏基因组的宿主特异性组成来反映。此外，肠道细菌群落关系可以概括宿主物种的进化相关性-一种称为“共生”的模式。值得注意的是，肠道细菌群落中细菌共生的破坏可能与杂交宿主中的严重疾病有关，并可能推动宿主物种形成。什么是宿主的遗传因素和机制，调节共生？这些基因如何影响与肠道微生物群相关的杂交条件？这一提议的中心假设是，细菌共生和微生物依赖性杂交致死是由于（1）肠道细菌异常迁移到血淋巴中，以及（2）杂交种中特定免疫基因的错误表达，否则这些基因将控制纯物种中的常驻细菌种群。Nasonia黄蜂模型系统是理想的测试这些假设，因为肠道微生物群已被观察到有助于严重的幼虫致死种间杂种。使用这个模型系统，我将解决以下两个目标：一：跟踪肠道细菌定植，并确定在杂交反应肠道定植高表达的宿主基因。奇异变形杆菌是Nasonia肠道微生物群的广泛成员，并导致非共生Nasonia杂种的过度黑化和死亡。该目标将使用GFP标记的奇异变形杆菌来检验以下假设：在纯物种中，细菌以良性的“游泳者”形态型存在，但在杂交种中分化为毒性更强的“成群”形态型，导致血淋巴黑化，随后死亡。用荧光显微镜观察奇异变形杆菌的增殖率和增殖部位。此外，在无菌和被微生物群定殖的黄蜂中的RNA-seq分析和qPCR将测试杂交体中的特定候选免疫基因参与宿主-微生物群相互作用中的致死性破坏的假设。负责杂种致死性和幼虫共生的候选基因将基于在Aim 1中从杂种和非杂种幼虫获得的表达谱而入围。这一目标将检验这样的假设，即当用于杂种致死性的重要候选基因被RNAi或CRISPR抑制时，杂种活力将恢复。此外，物种内相同基因的抑制将破坏共生群落的组装，从而探索影响杂种致死率的相同基因也影响共生的假设。