BIO-ORANIC CHEMICAL REEARCH ON CELL SIGNALS IN BACTERIA

1.金针茅(Stigmatellaaurantiaca)子实体的形成：金针茅(Stigmatellaaurantiaca)在饥饿和光照条件下，细胞分泌的一种子实体诱导因子。两个基因relA和csgA被认为与另一种Mko价球菌的子实体形成有关，在这种情况下，还不知道是否有像豆醇酮这样的低分子因子。在本研究中，我们从橙色葡萄球菌中分离了这些基因的同源基因，并利用这些基因进行了细菌突变。在relA干扰的突变体中，豆醇酮的生产力丧失。不能通过添加豆瓣素恢复子实体的形成能力。因此，RelA不仅与豆醇酮的产量有关，还与植物的接受性要求有关。研究结果如下：1.CsgA基因能促进豆醇酮的合成，该基因的mRNA受饥饿诱导，但不受光照诱导。植物病原细菌的植物-病原菌相互作用。(1)丁香假单胞菌产生的植物毒素。紫丁香属植物毒素合成的基因簇。丁香属被分离出来，基因被破坏了。在突变菌的培养基中，未检测到毒素。当该突变体应用于感病植物时，细菌的生长受到抑制，病害症状明显减轻。燕麦假单胞菌Flagellin以种属特异性方式参与诱导水稻过敏反应(HR)。致病菌株和非致病菌株的细菌基因在大肠杆菌中得到了表达。这两种表达的蛋白质都能诱导水稻培养细胞产生HR。因此，鞭毛的特异性并不依赖于氨基酸序列的差异。

1. Fruiting body formation in Myxococcus, Stigmatellaaurantiaca.Stingmolone is a fruiting body inducing factor secreted from the cells of Stigmatella aurantiaca when the cells are starved and irradiated with light. Two genes, RelA and csgA are thought to be involved in fruiting body formation in another Mkococcus in which any low molecular weight factor like stigmolone has not been known. In this study, we isolated homologs to these genes from S. aurantiaca and made the bacterial mutants using these genes. In RelA disrupted mutant, the productivity of stigmolone was lost. The ability to form fruiting body could not be recovered by addition of stigmobne. So, RelA should be involved in requirement of receptability as well as productivity of stigmolone. The gene, csgA promoted the synthesis of stigmolone The Mrna of the gene was induced by starvation but not by light irradiation.2. Plant-pathogen interaction of phytopathogenic bacteria.(1) Phytotoxin produced by Pseudomonas syringae pv. syringae.The gene cluster for synthesis of Phytotoxin in P. syringe pv. syringae was isolated and the gene was disrupted. In the cultured medium of the mutant bacterium, the toxin was not detected. When the mutant was applied to a susceptive plant, the growth of the bacterium was inhibited and the disease symptom was much diminished. Then the toxin should be involved in the pathogenecity of the bacterium.(2) Flagellins of Pseudomonas avenaeFlagellin of P. avenae is involved in induction of the hypersensitive reaction (HR) to rice in strain species specific manner. The bacterial genes from pathogenic and non-pathogenic strains were expressed in E. coli. Both of the expressed proteins could similarly elicit HR to rice cultured cells. So it is concluded that the specificity of the flagelns does not depend on the difference of the amino acid sequences.