CAREER: Investigating the mechanistic basis of host adaptation in close and distant relatives within Xanthomonas species complex

全球贸易增加、现代农业做法和全球气候变化使农业生态系统更容易面临新老疾病爆发的风险。这些影响粮食安全的疫情是一个重大的社会问题。为了控制疾病暴发，了解不同致病物种感染共同宿主或有时在新宿主上获得传染性的各种机制至关重要。虽然在单个致病物种中发现了特定宿主的潜在发病机制，但了解这些机制是否在感染共同宿主的不同物种中是保守的仍然是难以捉摸的。这个项目的目标是：1)了解不同致病菌在一个共同宿主上专门使用的各种机制；2)确定允许致病菌在一个新宿主上获得传染性的特征。这些知识将有助于解决植物和病原体之间复杂的相互作用，并促进有效策略的发展，以应对和管理病原体种群。教育目标包括通过为阿拉巴马州高需求学校的高中生和第一代少数民族本科生提供研究机会，培养STEM研究兴趣，提高公众对植物疾病爆发的认识，它们对植物健康的影响，最终对我们生活的影响。该项目将教育学生是什么使细菌致病，以及疾病是如何在现代农业时代出现的。植物致病菌寄主范围的界定一直是一个挑战。群体基因组学、关联分析和转录组学方法提出了一种新的范式，认为宿主范围是一个重叠的遗传连续体，涉及多个遗传决定因素，影响从小到大。然而，对所选候选者的功能验证还不足以揭示宿主范围的基础。利用黄单胞菌物种复合体作为模型系统，病理趋同和最近的宿主范围扩张都已被观察到，该项目将测试宿主范围决定因素并不局限于致病阶段的想法，但无症状的早期阶段在确定基本致病性决定因素的整体动态方面同样重要。利用正向和反向细菌遗传学、病原体转录组学、实验进化和高通量测序工具，该项目将测试以下假设；I)来自不同病原体物种的功能保守的基本决定因素与引起同一疾病的共同宿主的感染有关，尽管它们的时间动态可能因其他可变适应度决定因素的贡献而变化；Ii)亲缘物种在寄主选择压力和竞争物种存在下适应性性状的遗传交换是寄主范围扩大的原因。该项目将确定感染过程中的遗传决定因素，这些决定因素决定了不同致病物种之间的定性和定量差异。对解释新病原体谱系出现的适应性的理解将揭示病原体的弱点。该项目将促进对现代农业中寄主适应的遗传机制及其功能意义的认识。该项目由IOS-Plant biointeraction和Established Program to stimulation Competitive Research （EPSCoR）联合资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Increased global trade, modern agricultural practices and global climate change have predisposed agro-ecosystems to the increased risk of outbreaks of old and new diseases. These outbreaks impacting food security are a major societal concern. To manage disease outbreaks, understanding various mechanisms employed by diverse pathogenic species to infect a common host or, at times, to acquire infectivity on a new host is crucial. While molecular mechanisms underlying pathogenesis on a given host have been uncovered in individual pathogenic species, understanding whether these mechanisms are conserved across diverse species infecting common host remains elusive. The goals of this project are to 1) understand various mechanisms that diverse pathogenic bacteria use to specialize on a common host, 2) identify traits that allow pathogenic bacteria to acquire infectivity on a new host. This knowledge will help resolve complex interactions between plants and pathogens and foster development of effective strategies to respond and manage pathogen populations. The educational goals include fostering STEM research interests by providing research opportunities for high-school students from high-need schools in Alabama and first-generation minority undergraduate students, and raising public knowledge of emergence of plant disease outbreaks, their influence on plant health and, ultimately, on our lives. The project will educate students on what makes bacterium pathogenic and how diseases emerge in the modern era of agriculture. Conceptualizing host range of plant pathogenic bacteria has been a challenge. Population genomics, association analyses, and transcriptomics approaches have proposed a new paradigm stating host range as an overlapping genetic continuum involving multiple genetic determinants with small to major effect. However, functional validation of the select candidates has not been sufficient to uncover the basis of host range. Using Xanthomonas species complex as a model system where both pathological convergence as well as recent host range expansion have been observed, the project will test the idea that host range determinants are not restricted to the pathogenic phase, but asymptomatic early phase is equally important in determining overall dynamics of essential pathogenicity determinants. Deploying forward and reverse bacterial genetics, pathogen transcriptomics, experimental evolution and high-throughput sequencing tools, the project will test the following hypotheses; i) functionally conserved essential determinants from diverse pathogen species are involved in the infection of a common host causing the same disease, although their temporal dynamics may vary depending on contribution of other variable fitness determinants; ii) genetic exchange of adaptive traits in closely related species under host selection pressure and in presence of competing species is responsible for host range expansion. The project will identify genetic determinants during infection process that govern qualitative and quantitative differences across different pathogenic species. Understanding of the fitness adaptations that explain emergence of novel pathogen lineages will reveal pathogen weaknesses. This project will advance the knowledge of genetic mechanisms and their functional significance underlying host adaptation in modern agriculture.This project is jointly funded by IOS-Plant Biotic Interaction and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.