DISSERTATION RESEARCH: Phylogenetics of Nostoc and the Evolution of Specificity and Selectivity in Cyanolichen Symbioses

杜克大学的Francois Lutzoni博士和Heath O‘Brien先生获得了研究地衣共生中蓝藻的资助。蓝藻，以前被称为蓝藻，是一组光合作用细菌。除了在水生和陆地生态系统中都是重要的光收集器外，蓝藻还与许多其他生物形成共生关系，包括负责植物光合作用的叶绿体的内生共生起源。与叶绿体不同，地衣共生是藻类或蓝藻生活在真菌中并通过光合作用为其提供能量的组合。与叶绿体不同，这些光合作用共生体不会从父母传给后代，必须每一代重新获得。这项研究将使用来自不同地衣的蓝藻以及自由生活的蓝藻的DNA序列比较来追踪这些蓝藻如何在不同的地衣和环境中世代移动。通过将这些序列与已建立分类的参考菌株的序列进行比较，以确定它们的同源性。这项研究将对我们理解蓝藻的系统学和蓝藻共生体的生活史做出重要贡献。这可能为植物叶绿体是如何由自由生活的蓝藻形成的，从而形成所有现代植物提供了一些见解。了解与不同地衣物种相关的地衣光生物的多样性也将进一步促进地衣的研究，目前只有大约5%的物种知道光合作用伙伴的身份。

A grant has been awarded to Dr. Francois Lutzoni and Mr. Heath O'Brien at Duke University to study cyanobacteria in the lichen symbiosis. Cyanobacteria, previously known as blue-green algae, are a group of photosynthetic bacteria. In addition to being important light harvesters in both aquatic and terrestrial ecosystems, cyanobacteria form symbiotic associations with a variety of other organisms, including the endosymbiotic origin of the chloroplasts responsible for photosynthesis in plants. Not unlike chloroplasts, the lichen symbiosis is an association in which algae or cyanobacteria live within a fungus and provide it with energy derived from photosynthesis. Unlike chloroplasts, these photosynthetic symbionts are not passed on from parents to their offspring and must be re-acquired anew each generation. This study will use DNA sequence comparisons of cyanobacteria from different lichens, as well as free-living cyanobacteria to trace how these cyanobacteria move among different lichens and the environment from generation to generation. It will also attempt to determine their identity by comparing these sequences to ones obtained from reference strains with established taxonomy.This study will make a significant contribution to our understanding of both cyanobacterial systematics and the life-history of cyanobacterial symbioses. This may provide some insight into how the plant chloroplast could have formed from free-living cyanobacteria, giving rise to all modern plants. Knowledge of the diversity of lichen photobionts associated with different lichen species will also further the study of lichens, where at present, the identity of the photosynthetic partner is known for only about 5% of species.