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先生获得了一笔赠款，用于研究地衣共生中的蓝藻。蓝藻，以前被称为蓝绿藻，是一组光合细菌。蓝藻除了在水生和陆地生态系统中都是重要的光收获者外，还与各种其他生物形成共生关系，包括植物中负责光合作用的叶绿体的内共生起源。与叶绿体不同的是，地衣共生是藻类或蓝藻生活在真菌中，并为真菌提供光合作用产生的能量。与叶绿体不同，这些光合共生体不能从亲代遗传给后代，每一代都必须重新获得。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，以追踪这些蓝藻如何在不同的地衣和环境中代代相传。它还将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来确定它们的身份。这项研究将使我们的蓝藻系统学和蓝藻共生的生活史的理解显著贡献。这可能会对植物叶绿体如何从自由生活的蓝藻中形成，从而产生所有现代植物提供一些见解。了解与不同地衣物种相关的地衣光合生物多样性也将进一步研究地衣，目前，只有约5%的物种知道光合伙伴的身份。

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.