Emerging Frontier 03: Functional Analyses of the Genome of the Phenotypically Complex, Multicellular Cyanobacterium Nostoc Punctiforme

本项目的实验核心是蓝藻发菜的功能基因组分析。斑点拟青霉9.25Mbp基因组的鸟枪测序工作已经完成，其注释数据库可在http://www.jgi.doe.gov上查阅。斑点毛藻具有非常广泛的生态位、生理特性和细胞发育选择，包括在自由生活和植物共生生长状态下不寻常的固氮能力。固氮作用发生在末端分化的细胞中，称为异形胞。除了异形胞外，点状核型营养细胞还可以瞬间分化为休眠细胞，称为无动细胞和运动细丝，称为原基细胞。工作假说是，控制细胞分化、替代和共生相互作用的调控元件和途径在蓝藻中是唯一进化的。因此，除了计算分析外，还需要功能分析来确定基因组中存在的发育遗传元件和调控电路。了解这些回路是如何在点状新月形藻中整合的，对于复杂生物体中发育途径的进化具有重要意义。该项目将利用全球基因表达分析的高通量基因组方法，使用DNA微阵列和突变。产生的资源，包括基因组中存在的所有单独扩增的基因，将提供给国家和国际蓝藻社区。首席研究员、技术人员、博士后研究员、研究生和本科生将参与开发这些新方法并将其应用于这种复杂的蓝藻；因此，该项目提供了一个综合培训机会。

The experimental core of this project is functional genomic analyses of the cyanobacterium Nostoc punctiforme. The shotgun sequencing of the 9.25 Mbp genome of N. punctiforme has been completed and an annotated database is available at http://www.jgi.doe.gov . N. punctiforme has an extraordinarily wide range of ecological niches, physiological properties and cellular developmental alternatives, including the unusual ability of fixing nitrogen in both free-living and plant-associated symbiotic growth states. Nitrogen fixation occurs in terminally differentiated cells called heterocysts. In addition to heterocysts, N. punctiforme vegetative cells can transiently differentiate into resting cells termed akinetes and motile filaments called hormogonia. The working hypothesis is that the regulatory elements and pathways governing cellular differentiation alternatives and symbiotic interactions of N. punctiforme uniquely evolved in cyanobacteria. Therefore, functional, in addition to computational, analyses are required to identify the developmental genetic elements and regulatory circuits present in the genome. Understanding how these circuits are integrated in N. punctiforme has implications on the evolution of developmental pathways in complex organisms. This project will utilize high throughput genomic methodologies of global gene expression assays, using DNA microarrays, and mutagenesis. The resources generated, including all of the individually amplified genes present in the genome, will be made available to the national and international cyanobacterial community. Researchers at the level of principle investigators, technicians, postdoctoral fellows, graduate and undergraduate students, will interact in developing and applying these new methodologies to this complex cyanobacterium; thus, the project affords an integrative training opportunity.