Palm C J, Gaffney T, Kosuge T
Department of Plant Pathology, University of California, Davis 95616.
J Bacteriol. 1989 Feb;171(2):1002-9. doi: 10.1128/jb.171.2.1002-1009.1989.
Indoleacetic acid (IAA) production by the plant pathogen Pseudomonas syringae subsp. savastanoi is essential for tumor formation on olive and oleander. The bacterium produces IAA from tryptophan in reactions catalyzed by tryptophan monooxygenase and indoleacetamide hydrolase. The genetic determinants are, respectively, iaaM and iaaH. In oleander isolates, the genes encoding the IAA biosynthetic enzymes are located on a plasmid; in olive isolates, the genes occur on the chromosome. The IAA genes from the oleander isolate strain EW2009 are located within a 4-kilobase (kb) segment of the 52-kb plasmid pIAA1. Escherichia coli strains harboring a recombinant plasmid, pCJP3, which contains this 4-kb fragment, excreted IAA into culture media, and crude cell extracts had both tryptophan monooxygenase and indoleacetamide hydrolase activity. In vitro coupled transcription-translation of pCJP3 demonstrated that this fragment coded for proteins of 62 and 47 kilodaltons which correspond to tryptophan monooxygenase and indoleacetamide hydrolase, respectively. Expression of these genes was dependent upon a vector promoter in pCJP3. However, in the absence of a vector promoter, E. coli containing recombinant plasmids with additional pIAA1 DNA in front of iaaM had high levels of tryptophan monooxygenase. Northern (RNA) hybridization experiments verified that iaaM and iaaH are cotranscribed as a portion of a ca. 4- to 5-kb transcript in vivo. Southern hybridization experiments with IAA plasmids from different oleander strains of P. syringae subsp. savastanoi revealed that all IAA plasmids contained a region of at least 10 kb of homology, with the IAA genes at one end. Repetitive DNA and a copy of IS51 were found at the end of this region of homology.
植物病原菌丁香假单胞菌 savastanoi 亚种产生吲哚乙酸（IAA）对于在橄榄和夹竹桃上形成肿瘤至关重要。该细菌在色氨酸单加氧酶和吲哚乙酰胺水解酶催化的反应中由色氨酸产生 IAA。其遗传决定因素分别是 iaaM 和 iaaH。在夹竹桃分离株中，编码 IAA 生物合成酶的基因位于质粒上；在橄榄分离株中，这些基因存在于染色体上。夹竹桃分离株 EW2009 的 IAA 基因位于 52kb 质粒 pIAA1 的 4 千碱基（kb）片段内。携带包含该 4kb 片段的重组质粒 pCJP3 的大肠杆菌菌株将 IAA 分泌到培养基中，粗细胞提取物具有色氨酸单加氧酶和吲哚乙酰胺水解酶活性。pCJP3 的体外偶联转录 - 翻译表明该片段编码分别对应于色氨酸单加氧酶和吲哚乙酰胺水解酶的 62 和 47 千道尔顿的蛋白质。这些基因的表达依赖于 pCJP3 中的载体启动子。然而，在没有载体启动子的情况下，含有在 iaaM 前带有额外 pIAA1 DNA 的重组质粒的大肠杆菌具有高水平的色氨酸单加氧酶。Northern（RNA）杂交实验证实 iaaM 和 iaaH 在体内作为约 4 至 5kb 转录物的一部分共转录。用来自丁香假单胞菌 savastanoi 亚种不同夹竹桃菌株的 IAA 质粒进行的 Southern 杂交实验表明，所有 IAA 质粒都包含至少 10kb 的同源区域，IAA 基因位于一端。在该同源区域的末端发现了重复 DNA 和一个 IS51 拷贝。
