Control of Cellular Differentiation in Symbiotically Competent Cyanobacteria

*9514787 Meek该计划的长期目标是识别、表征和操纵蓝藻发菜中与细胞分化有关的基因。ATCC 29133菌株是一株能区分动态丝、无动体(孢子)和异形胞的菌株，它们是固定氮气的部位。发菜29133也是一种兼性异养菌，可以通过配子体与苔藓植物花斑苔藓建立共生关系。花生菌产生胞外代谢产物，进而刺激念珠藻的异形胞和异形胞的分化。到10倍或更高的水平比在没有它的情况下看到的。在先前的资助中开发的生理和分子遗传技术以及目前手中的转座子突变体构成了这一提议的方法学和生物学基础。在以下两个方面提出了具体目标。我..。异型囊泡的成熟依赖于信号级联调控系统。Nostoc 29133：：Tn5-1063株UCD311(Fox~Sym+)插入DevR的分析，编码仅受体域的反应调节蛋白。生化和遗传分析，以确定潜在的磷和磷受体的DevR。该项目将确定参与杂胞体发育的两组分调控系统的成员。2.精原细胞分化是基因表达差异的结果。原神经节特异消减文库的建立和分析；原生孢子形成过程中发生突变的发菜29133突变体的转座产生；这些突变体和宇宙克隆的遗传特征。该项目是了解细胞如何从DNA复制和生物量增加解偶联分裂形成原生细胞，然后在完成细胞生命周期后返回营养生长状态的初步努力。***

*** 9514787 Meeks The long-term goal of this program is to identify, characterize and manipulate genes involved in cellular differentiation in the cyanobacterium Nostoc sp. strain ATCC 29133, a strain that can differentiate motile hormogonial filaments, akinetes (spores) and heterocysts, which are the sites of N2 fixation. Nostoc 29133 is also a facultative heterotroph that can establish a symbiotic association, via hormogonia, with the bryophyte Anthoceros punctatus. Anthoceros produces extracellular metabolites that sequentially stimulate hormogonia and heterocyst differentiation of Nostoc spp. to 10-fold or higher levels than those seen in its absence. The physiological and molecular genetic techniques developed in the prior grant and the transposon mutants currently in hand form the methodological and biological foundation of this proposal. Specific objectives are proposed in the following two areas. I . Heterocyst maturation is dependent on a signal cascade regulatory system. Analysis of Nostoc 29133: :Tn5-1063 strain UCD 311 (Fox~Sym+) with an insertion devR, encoding a receiver-domain-only response regulator protein. Biochemical and genetic assays to identify potential phosphodonors and phosphoreceivers of DevR. This project will identify members of a two component regulatory system involved in heterocyst development. 2. Hormogonia differentiation is a consequence of differential gene expression. Establishment and analysis of a hormogonia-specific subtractive cDNA library; generation by transposition of mutants of Nostoc 29133 altered in hormogonia formation; genetic characterization of such mutants and of cosmic clones from cDNA analysis. This project is the initial effort in understanding how cells divide uncoupled from DNA replication and biomass increase to form hormogonia and then return to the vegetative growth state in completing a cellular life cycle. ***