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受到新旧疾病暴发风险的影响。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普通宿主或有时在新宿主上获得感染力的各种机制是至关重要的。虽然在特定宿主上潜在的致病分子机制已经在单个致病物种中发现，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)了解不同的病原菌用来专门针对一个共同宿主的各种机制，2)识别允许病原菌在新的宿主上获得感染力的特征。这一知识将有助于解决植物和病原体之间的复杂相互作用，并促进有效战略的发展，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族裔本科生提供研究机会来培养STEM研究兴趣，并提高公众对植物病害爆发的出现及其对植物健康的影响，最终对我们的生活的影响的知识。该项目将教育学生了解细菌是如何致病的，以及疾病是如何在现代农业时代出现的。对植物病原菌的寄主范围进行概念化一直是一个挑战。种群基因组学、关联分析和转录组学方法提出了一种新的范式，将寄主范围描述为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，对选定候选者的功能验证还不足以揭示寄主范围的基础。利用Xanthomonas物种复合体作为一个既观察到病理收敛又观察到最近寄主范围扩大的模式系统，该项目将测试寄主范围决定因素不仅限于致病阶段，但无症状早期阶段在确定基本致病决定因素的整体动态方面同样重要的想法。运用正向和反向细菌遗传学、病原体转录学、实验进化和高通量测序工具，该项目将检验以下假设：i)来自不同病原体物种的功能保守的基本决定因素与导致相同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合度决定因素的贡献而不同；ii)在宿主选择压力下和竞争物种的存在下，密切相关物种之间的适应特征的遗传交换是宿主范围扩大的原因。该项目将确定感染过程中控制不同致病物种之间质量和数量差异的遗传决定因素。理解解释新病原体谱系出现的适应性适应将揭示病原体的弱点。该项目将推进现代农业中寄主适应背后的遗传机制及其功能意义的知识。该项目由iOS-植物生物相互作用和已建立的刺激竞争研究计划(EPSCoR)联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.