Microbial ecology of sea star wasting disease

从2013年6月开始到现在（2015年5月），超过20种海星（海星总科，棘皮动物）受到海星星星消耗病（SSWD）的影响，影响了从阿拉斯加中部到下加利福尼亚的种群。 这种疾病导致这些关键捕食者的数量大大减少或消失，这可能会导致底栖生物群落结构的深刻变化。最近的工作已经确定了海洋星星相关浓核病毒（SSaDV）作为最有可能的病原体的疾病。SSaDV与居住在世界各地其他棘皮动物中的浓核病毒有关，并且已经在西海岸小行星种群中存在了至少72年。 因此，在我们理解SSaDV如何实际上引起SSWD症状，特别是棘皮动物宿主，浓核病毒和微生物组成分如何相互作用方面，仍然存在重大的知识差距。该项目将解决三个主要问题：1）病毒感染是否会改变海洋星星微生物组的组成？2)病毒基因组的变异及其相关的毒力是什么？幼虫扩散是否会在栖息地之间传播疾病？ 该项目将通过对宿主、病原体和相关微生物的时间进程测量、历史和当代病毒株之间的基因组-基因组比较，以及通过针对水族馆和自然界中的幼虫和幼年小行星的实验来解决这些假设。这项工作将支持在生物海洋学和疾病生态学技术方面培训一名研究生（招聘对象是代表性不足的少数群体）和几名本科生。将通过在太平洋沿岸两个著名的公共水族馆（西雅图和温哥华水族馆）开展的公共外联活动、通过一个专门介绍该项目的网站以及通过公开讲座和媒体曝光来传播信息。 本项目将解决与海洋星星损耗病（SSWD）有关的三个基本问题：1）SSaDV如何引起SSWD症状以及疾病如何从初次感染发展到动物死亡：2）SSaDV当前的基因型与历史上存在的基因型如何不同，以及毒力与基因组多态性相关;和3）是幼虫和少年小行星的差异受SSaDV，广播产卵bipinarria的一个可行的机制之间的遥远的栖息地之间的SSaDV传播。第一个问题将通过用SSaDV实验性接种幼稚海星来解决，然后通过16 S rRNA测序和定量PCR监测宿主转录（即通过RNAseq的转录组学），微生物组组成，以及使用定量PCR的病毒载量和流行率。第二个问题将通过扩增SSaDV和相关浓核病毒的整个基因组来解决，然后进行基因组-基因组比较以鉴定关键蛋白质编码区域中的多态性DNA。第三个问题将通过在小行星产卵种群附近的实地地点收集浮游生物中的bipinarria，以及对捕获的幼海星进行时间过程观测，并使用定量聚合酶链反应监测其细菌和病毒载量来解决。这项工作将主要在萨利希海地区进行，从阿拉斯加沃茨收集SSaDV -幼稚小行星。

Beginning in June 2013 and continuing to present (May 2015), over 20 species of sea stars (Asteroidea, Echinodermata) have been affected by sea star wasting disease (SSWD), affecting populations from central Alaska to Baja California. The disease has lead to greatly reduced abundance or disappearance of these keystone predators, which may result in profound alteration to benthic community structure. Recent work has identified the sea star associated densovirus (SSaDV) as the most likely causative agent of the disease. SSaDV is related to densoviruses inhabiting other echinoderms worldwide, and has been present in West Coast asteroid populations for at least 72 years. Hence, there remain significant knowledge gaps in our understanding of how SSaDV actually elicits SSWD symptoms, especially how the echinoderm host, densovirus and microbiome constituents interact. This project will address three major questions: 1) does viral infection change the composition of the sea star microbiome?, 2) what is the variation of viral genomes and their associated virulence?, and 3) does larval dispersal spread the disease between habitats? This project will address these hypotheses through time-course measurements of host, pathogen and associated microorganisms, genome-genome comparisons between historical and contemporary viral strains, and through experiments targeting larvae and juvenile asteroids in aquaria and in nature. This work will support training of a graduate student (recruitment targeting an under-represented minority) and several undergraduates in biological oceanographic and disease ecology techniques. Information will be disseminated through public outreach activities at two high-profile Pacific coast public aquariums (the Seattle and Vancouver Aquariums), through a website dedicated to the project, and through public talks and media exposure. This project will address three fundamental questions relating to Sea Star Wasting Disease (SSWD): 1) How does SSaDV causes SSWD symptoms and how does the disease progress from primary infection through animal mortality; 2) How do current genotypes of SSaDV vary from those present historically, and is virulence related to genome polymorphisms; and 3) Are larvae and juvenile asteroids differentially affected by SSaDV, and are broadcast-spawned bipinarria a viable mechanism for SSaDV dispersal between distant habitats. The first question will be addressed by experimental inoculation of naïve sea stars with SSaDV, then time-course monitoring of host transcription (i.e. transcriptomics via RNAseq), microbiome composition via 16S rRNA sequencing and quantitative PCR, and viral load and prevalence using quantitatice PCR. The second question will be addressed by amplifying the entire genome of SSaDV and related densoviruses, then perform genome-genome comparisons to identify polymorphic DNA in key protein-encoding regions. The third question will be addressed by collecting bipinarria from plankton at field locations adjacent to spawning asteroid populations, and by performing time-course observations of captive juvenile sea stars and monitoring their bacterial and viral loads using quantitative PCR. This work will be performed primarily in the Salish Sea region, with SSaDV - naïve asteroids collected from Alaskan waters.