Evolution of Aromatic Biosynthesis and Regulation in Prokaryotes

Jensen博士建议利用寡核苷酸序列编目。核糖体RNA在进化过程中的强保守性是构建可靠的原核生物系统发育树的基础。rRNA的缓慢变化可以通过寡核苷酸编目以SAB值的形式量化，从而提供了一个进化尺度，可以测量其他基因产物系统的进化。这是第一次有可能在原核生物中重建生物化学途径排列和生物化学途径调控的进化事件。我们建议获得的数据，将允许这样的进化推论，以作出有关途径的芳香族氨基酸的生物合成。这将在原核生物的一个庞大但易于管理的分支中进行，即“紫色”细菌。已经获得的数据允许构建一个工作模型，用于推断(i)酪氨酸途径辅助因子特异性，（ii） DAHP合成酶同工酶，（iii）苯丙氨酸途径及其调控，以及（iv）酪氨酸途径及其调控的进化。由于新的编目数据确定了树上的分支位置，其中的间隙限制了解释，我们将继续分析这些生物。在分化程度较浅的情况下，rRNA/DNA杂交可能更适合于识别与近期生化变化的微调实例相关的进化分化点。

Dr. Jensen proposes to utilize the cataloging of oligonucleotide sequence. The strong conservation of ribosomal RNA through evolutionary time is the basis for assembly of a credible phylogenetic tree for prokaryotes. Slow changes in rRNA can be quantitated in the form of SAB values by oligonucleotide cataloging, thus providing an evolutionary scale against which the evolution of other gene-product systems can be measured. It is possible now for the first time to reconstruct in prokaryotes the events in the evolution of biochemical-pathway arrangement and biochemical-pathway regulation. We propose to obtain data that will permit such evolutionary deductions to be made with respect to the pathway for biosynthesis of aromatic amino acids. This will be carried out in a large but manageable division of prokaryotes, the "purple" bacteria. Data already obtained allow construction of a working model for deductions about the evolution of (i) tyrosine-pathway cofactor specificity, (ii) DAHP synthase isozymes, (iii) the phenylalanine pathway and its regulation, and (iv) the tyrosine pathway and its regulation. As new cataloging data identify brance positions on the tree where gaps limit interpretations, we will proceed with analysis of these organisms. At shallow levels of divergence, rRNA/DNA hybridization will probably be more appropriate for identification of evolutionary points of divergence in correlation with fine-tuned instances of recent biochemical change.