Unraveling the mechanisms by which novel fungal-plant associations evolve

阐明基因型和适应之间的联系是进化生物学研究的基础，但这仍然是一个难以实现的目标。昆虫病原罗伯茨绿僵菌(Metarhizium robertsii，MR)的少数菌株是根部定植的植物生长促进剂。这个项目将使用比较和进化的方法来研究新的共生体迅速出现的机制，这些方法将遗传筛选与菌株的转录图谱相结合，显示出一系列的互惠关系。快速进化是病原体、害虫和癌症的共同特征；尽管在大多数情况下，人们对其潜在机制知之甚少。MR是一个实验上非常容易处理的模型系统，用它来解决这些机制将涉及到许多基本问题，这些问题涉及到一些鲜为人知的主题，这些主题跨越了大部分分子进化，例如氨基酸与调控进化的相对重要性。此外，了解生态多样性对于预测真菌对气候变化和疾病暴发的反应结果尤为关键。通过关注最近适应性变化的遗传基础，该项目将解决入侵菌株如何与生物世界相互作用并适应新的自然环境的不确定性。绿僵菌真菌已经被用作生物杀虫剂，通过确定它们作为植物共生体的作用方式以及它们何时和为什么不起作用，这项工作将促进它们作为综合植物生长促进剂的更大作用。由于绿僵菌与许多重要的植物病原菌和生防真菌关系密切，因此这项工作的结果和结论将有许多应用。MR所利用的异常广泛的生态位允许在所有这些生活方式中访问基因功能，而MR种群中的内生关联光谱提供了一个模型，其中基因组变异可以与对特定生活方式的适应有关。通过关注最近适应性变化的遗传基础，该项目将解决入侵菌株如何与生物世界相互作用并适应新的自然环境的不确定性。通过比较和进化的方法，将显示一系列互惠关系的菌株的转录图谱与促进生长的菌株的遗传筛选相结合，将识别有助于植物联想的因素。这些互补的方法将检验这样一个假设，即植物关联性的快速变化是由基因表达的调控控制决定的。这项提议还将澄清中心的“未知数”，例如是否存在大量的效应器蛋白，它们是否与病原昆虫的相互作用具有重叠的功能，或者MR是否具有更有限的关键效应器，用于植物的定植。其他实验将表征这些效应器及其启动子，以进一步解决定义共生关系的潜在调控、代谢和生物合成差异。总的来说，这些实验将解决环境相互作用如何塑造有机体和基因组多样性，以及绿僵菌真菌快速进化和适应新栖息地的能力等基本问题。这一奖项反映了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。

Elucidating the connection between genotype and adaptation is fundamental to the study of evolutionary biology, yet it remains an elusive goal. A minority of strains of the insect pathogenic Metarhizium robertsii (Mr) are root colonizing plant growth promoters. This project will examine the mechanisms by which novel symbioses can rapidly emerge using comparative and evolutionary approaches that integrate a genetic screen with a transcriptional profiles of strains showing a spectrum of mutualistic associations. Rapid evolution is a trait shared with pathogens, pests and cancers; although in most cases the underlying mechanisms are poorly understood. Addressing these mechanisms with Mr, which is an experimentally very tractable model system, will involve asking many basic questions on poorly understood topics that span much of molecular evolution, such as the relative importance of amino-acid versus regulatory evolution. Moreover, understanding ecological diversification is particularly crucial for predicting the outcome of fungal responses to climate change and disease outbreaks. By focusing on the genetic basis of recent adaptive changes this project will address the uncertainty of how invasive strains could interplay with the biological world and adapt to a new natural environment. Metarhizium fungi are already deployed as biological insecticides, and by identifying how they work as plant symbionts, and when and why they do not, this work will facilitate their use in an expanded role as comprehensive plant growth promoters. As Metarhizium fungi are closely related to many important plant pathogens and biocontrol fungi, the results and conclusions from this work will have many applications.The unusually broad array of ecological niches exploited by Mr allows a genes function to be accessed in all these lifestyles, while the spectrum of endophytic associations in Mr populations provide a model where genomic variation can be related to adaptation to particular lifestyles. By focusing on the genetic basis of recent adaptive changes this project will address the uncertainty of how invasive strains could interplay with the biological world and adapt to a new natural environment. Identifying the factors that contribute to plant associations will be achieved by comparative and evolutionary approaches that integrate transcriptional profiles of strains showing a spectrum of mutualistic associations with a genetic screen of a growth promoting strain. These complementary methodologies will test the hypothesis that rapid changes in plant associations are determined by regulatory controls of gene expression. This proposal will also clarify central "unknowns" such as whether there are large sets of effector proteins, whether they have overlapping functions with the pathogenic insect interaction or whether Mr has a more limited repertoire of key effectors that are deployed to colonize plants. Additional experiments will characterize these effectors and their promoters to further address the underlying regulatory, metabolic and biosynthetic differences that define symbiotic associations. Collectively, these experiments will address fundamental questions on how environmental interactions shape organismal and genome diversity, as well as the capacity of Metarhizium fungi to rapidly evolve and adapt to new habitats.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.