Collaborative Research: Dimensions: Integrating phylogenetics, ecophysiology and transcriptomics to understand the diversity of hornwort-cyanobacterium symbiosis

只有少数非凡的植物能与固氮细菌形成有益的伙伴关系。这些植物包括几种苔藓植物、蕨类植物、苏铁和一小群开花植物。由于豆类对作物的重要性，许多研究都集中在豆类与为它们固定氮的细菌——根瘤菌之间的关系上。对于植物和蓝藻之间更为广泛的伙伴关系，我们所知甚少。因为蓝藻通常比根瘤菌更少依赖于植物宿主，它们可能是一个很好的合作伙伴，在作物植物中进行有益的固氮工程。然而，我们目前对植物-蓝藻伙伴关系的理解很差。有益的蓝藻的物种和遗传多样性实际上尚未被探索。同样，参与这些伙伴关系的植物基因仍然未知。作为苔藓植物的三种分支之一，角苔是研究植物与蓝藻关系的一个杰出系统。本研究将调查角藻-蓝藻伙伴关系的系统发育，功能和遗传方面。在这样做的过程中，这项研究将探索一系列问题，这些问题将为这些独特的植物如何与它们的细菌伙伴相互作用来固定氮提供新的见解。培养博士后1人，研究生3人，本科生10人，高中生5人。与纽约州科学教师协会合作，将制作一个教育视频。本视频将展示各种形式的植物与蓝藻的关系。本研究的目的是首先揭示角苔和蓝藻的系统发育多样性。然后阐明共生固氮功能的多样性。最后，该研究将揭示角苔及其蓝藻共生体之间的遗传成分。研究人员将使用系统基因组学方法重建角草的生命树。然后，对于每个角苔样品，蓝藻群落的遗传多样性将被表征。比较角苔和蓝藻的多样性将有助于揭示寄主-共生体的特异性。该研究还将研究共同进化的模式，以及蓝藻共生在角苔进化中的作用。接下来，将通过种群和微观研究来测试角苔菌群多样性、环境变量和固氮率之间的相互作用。最后，将分离出多个纯角藻和蓝藻培养物。一旦分离，它们的共生关系将在实验室受控的环境条件下重建。时间过程RNA-seq数据将产生，以确定假定的基因是共生建立的核心，并与共生行为的变化有关。这项研究的结果将使植物-微生物相互作用的所有三种主要形式的比较，以充分表征共生的进化和遗传基础。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。

Only a few remarkable plants can form beneficial partnerships with nitrogen-fixing bacteria. These include a few species of bryophytes, ferns, cycads, and a small group of flowering plants. Because of their importance to crops, a lot of research has focused on the relationship between legumes and the bacteria that fix nitrogen for them - rhizobia. Much less is known about an even more widespread partnership between plants and cyanobacteria. Because cyanobacteria are generally less dependent on the plant host than rhizobia, they could be an excellent partner for engineering helpful nitrogen fixation into crop plants. However, our current understanding of plant-cyanobacterium partnerships is poor. The species and genetic diversity of helpful cyanobacteria is virtually unexplored. Similarly, the plant genes involved in these partnerships remain unknown. Hornworts, one of the three bryophyte lineages, are an outstanding system to study plant-cyanobacterial relationships. This study will investigate phylogenetic, functional, and genetic aspects of the hornwort-cyanobacterium partnership. In doing so, the research will explore an array of questions that will provide new insights into how these unique plants interact with their bacterial partners to fix nitrogen. One postdoctoral fellow, three graduate, ten undergraduate, and five high school students will be trained. In partnership with the Science Teachers Association of New York State, an educational video will be made. This video will showcase the various forms of plant-cyanobacterium relationships. The goals of this research are first to uncover the phylogenetic diversity of hornworts and cyanobionts. Then to elucidate the functional diversity of symbiotic nitrogen-fixation. Finally, the research will reveal the genetic components of the association between hornworts and their cyanobionts. The researchers will reconstruct the hornwort tree-of-life using a phylogenomic approach. Then, for each hornwort sample, the genetic diversity of the cyanobiont community will be characterized. Comparing the hornwort and cyanobiont diversity will shed light on host-symbiont specificity. The research will also study patterns of co-evolution, and the roles of cyanobacterial symbiosis in hornwort evolution. Next, population and microcosm studies will be used to test the interaction among hornwort microbiome diversity, environmental variables, and nitrogen-fixation rates. Finally, multiple pure hornwort and cyanobiont cultures will be isolated. Once isolated, their symbioses will be reconstituted under controlled environmental conditions in the laboratory. Time-course RNA-seq data will be generated to identify putative genes that are core for symbiosis establishment and linked to variation in symbiotic behaviors. The results of this research will enable comparisons across all three major forms of plant-microbe mutualistic interaction to fully characterize the evolutionary and genetic underpinnings of symbioses.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.