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

只有少数了不起的植物可以与固氮菌形成有益的合作伙伴关系。这些植物包括一些苔藓植物、蕨类植物、苏铁和一小群开花植物。由于它们对农作物的重要性，许多研究都集中在豆类与为它们固定氮素的细菌--根瘤菌--之间的关系。关于植物和蓝藻之间更广泛的合作伙伴关系，人们知之甚少。由于蓝藻通常比根瘤菌对植物宿主的依赖程度较低，它们可能是在作物中进行有益的固氮工程的极佳合作伙伴。然而，我们目前对植物-蓝藻伙伴关系的理解很差。有帮助的蓝藻的种类和遗传多样性几乎是未知的。同样，参与这些伙伴关系的植物基因仍然未知。金鱼藻是苔藓植物三大谱系之一，是研究植物-蓝藻关系的优秀系统。这项研究将调查角藻-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固定氮提供新的见解。将培养1名博士后、3名研究生、10名本科生和5名高中生。将与纽约州科学教师协会合作，制作一部教育视频。这个视频将展示各种形式的植物与蓝藻的关系。这项研究的目标是首先揭示角藻和蓝藻的系统发育多样性。阐明了共生固氮的功能多样性。最后，这项研究将揭示金鱼藻和它们的蓝藻之间联系的遗传成分。研究人员将使用系统基因组学方法重建金鱼藻生命树。然后，对于每个金鱼藻样本，将对蓝藻群落的遗传多样性进行表征。比较角藻和蓝藻的多样性将有助于了解寄主-共生体的专一性。这项研究还将研究共同进化的模式，以及蓝藻共生在角藻进化中的作用。下一步，将利用种群和微观世界研究来测试金鱼藻微生物群落多样性、环境变量和固氮率之间的相互作用。最后，将分离出多种纯金线虫和蓝藻培养物。一旦分离，它们的共生体将在实验室受控的环境条件下重新构建。将产生时间进程的RNA-SEQ数据，以确定对共生建立起核心作用并与共生行为变化有关的假定基因。这项研究的结果将能够对所有三种主要形式的植物-微生物相互作用进行比较，以充分描述共生的进化和遗传基础。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。

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.