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

杜克大学的弗朗索瓦·卢佐尼博士和希思奥布莱恩先生获得了一笔赠款，用于研究地衣共生体中的蓝藻。 蓝藻，以前被称为蓝绿藻，是一组光合细菌。 除了在水生和陆地生态系统中是重要的光收集器之外，蓝细菌还与各种其他生物体形成共生关系，包括植物中负责光合作用的叶绿体的内共生起源。 与叶绿体不同，地衣共生体是藻类或蓝细菌生活在真菌中的一种联合体，并为真菌提供来自光合作用的能量。与叶绿体不同，这些光合共生体不会从父母传给后代，必须在每一代重新获得。 这项研究将使用来自不同地衣的蓝藻的DNA序列比较，以及自由生活的蓝藻来追踪这些蓝藻如何在不同的地衣和环境中代代相传。 本研究还将尝试通过比较这些序列与已建立分类学的参考菌株的序列来确定它们的同一性，这项研究将对我们理解蓝藻系统学和蓝藻共生体的生活史做出重大贡献。 这可能提供了一些见解，植物叶绿体如何从自由生活的蓝细菌形成，从而产生了所有现代植物。 与不同地衣物种相关的地衣光合生物多样性的知识也将进一步研究地衣，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.