REGULATION OF NODULATION GENES IN RHIZOBIUM MELILOTI

许多细菌与细菌建立致病或共生的相互作用 高等有机体。我们研究营养上的互惠互利 紫花苜蓿根瘤菌与寄主紫花苜蓿的相互作用。 这种宿主-微生物的联合是通过一系列有序的 步骤，这些步骤是唯一的，并且高度特定于交互 特定物种的。互动的早期步骤是 由一系列细菌结瘤(NOD)基因控制，其 表达是由一种小的黄酮类化合物木犀草素诱导的， 由主持人制作。此外，nod基因的诱导依赖于 在蛋白质上，Nodd。在草地早熟禾中，有三个节点基因编码 具有可区分的大小和性质的调节蛋白。 黄酮类(木犀草素)诱导剂的诱导作用 调控上游DNA序列、Nodd蛋白和RNA 将对聚合酶进行研究。木犀草素将被贴上标签，其 确定了受体蛋白。NodD和NodD3将被提纯并 确定Nodd介导黄酮基的特征 Nod基因的诱导，而NodD3导致构成nod基因 表情。RNA聚合酶将被提纯，并产生专门的Sigma 对影响nod基因的因素进行分离和鉴定。 表情。将使用删除分析来指示角色 可诱导结节基因上游的序列。的存在 除了Nodd之外的调控基因将进行基因测试， 这些基因的产物将被描述出来。具体的 假设Nodd结合黄酮类，并激活转录 通过与DNA的直接相互作用，将被详细分析。

Many bacteria establish pathogenic or symbiotic interactions with higher organisms. We study the nutritionally mutualistic interaction or Rhizobium meliloti with a host legume, alfalfa. This host-microbe association proceeds by a ordered series of steps, which are unique and are highly specific to the interaction of particular species. The early steps of the interaction are controlled by a series of bacterial nodulation (nod) genes, whose expression is induced by a small flavonoid compound, luteolin, produced by the host. In addition, induction of nod genes depends on a protein, NodD. In R. meliloti, three nodD genes encode regulatory proteins with distinguishable sizes and properties. The roles in induction of the flavone (luteolin) inducer, the regulatory upstream DNA sequences, the NodD protein, and RNA polymerase will be studied. Luteolin will be labelled and its receptor protein identified. NodD and NodD3 will be purified and characterized to determine the basis for NodD mediating flavone induction of nod genes, while NodD3 causes constitutive nod gene expression. RNA polymerase will be purified, and specialized sigma factors will be isolated and characterized for effects on nod gene expression. Deletion analysis will be used to indicate the roles of sequences upstream of inducible nod genes. The existence of regulatory genes besides nodD will be tested genetically, and the products of such genes will be characterized. The specific hypothesis that NodD binds flavone, and activates transcription through direct interaction with DNA, will be analyzed in detail.