REGULATION OF NODULATION GENES IN RHIZOBIUM MELILOTI

许多细菌建立致病或共生相互作用， 更高的生物。 我们研究的是 苜蓿根瘤菌与寄主豆科植物苜蓿相互作用 这种宿主-微生物联合通过一系列有序的 步骤，这些步骤是独特的，对相互作用具有高度特异性 特定的物种。 互动的早期步骤是 由一系列的细菌转化（nod）基因控制， 表达是由一种小的类黄酮化合物，毛地黄黄酮， 由主持人制作。 此外，nod基因的诱导依赖于 一种蛋白质，NodD。 In R.苜蓿属植物中，三个CCLD基因编码 具有可区分的大小和性质的调节蛋白。 本文综述了黄酮类诱导剂（毛地黄黄酮）、 调控上游DNA序列、NodD蛋白和RNA 将研究聚合酶。 将标记木犀草素， 受体蛋白鉴定。 NodD和NodD 3将被纯化， 确定了NodD介导黄酮的基础 诱导结瘤基因，而NodD 3引起组成型结瘤基因 表情 RNA聚合酶将被纯化，并专门 将分离和表征对nod基因的影响的因素 表情 删除分析将用于指示角色 诱导型nod基因上游的序列。 的存在 除了BHD之外的调节基因将被遗传测试， 这些基因的产物将被表征。 具体 假设NodD结合黄酮并激活转录 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.