Thomashow L S, Reeves S, Thomashow M F
Proc Natl Acad Sci U S A. 1984 Aug;81(16):5071-5. doi: 10.1073/pnas.81.16.5071.
Stable incorporation of tumor-inducing (Ti) plasmid sequences, the T-DNA, into the genomes of dicotyledonous plants results in the formation of crown gall tumors. Previous genetic studies have suggested that the products of the genes encoding transcripts 1 and 2, which are encoded by the TL-DNA region of pTiA6, are responsible for inducing the auxin-independent phenotype of crown gall tissues. Here we report the construction of a plasmid, pMTlacT2, which directs the synthesis of the Mr 49,800 polypeptide encoded by the transcript 2 gene. Cell-free extracts prepared from Escherichia coli harboring this plasmid converted indoleacetamide to indoleacetic acid, the natural auxin of plants; extracts prepared from plasmidless strains of E. coli or strains harboring the cloning vehicle pBR322 did not carry out this reaction. We conclude that the transcript 2 gene of pTiA6 codes for an enzyme that participates in auxin biosynthesis, probably an indoleacetamide hydrolase.
肿瘤诱导（Ti）质粒序列（即T-DNA）稳定整合到双子叶植物基因组中会导致冠瘿瘤的形成。先前的遗传学研究表明，由pTiA6的TL-DNA区域编码的转录本1和转录本2的基因产物负责诱导冠瘿组织的生长素非依赖型表型。在此，我们报道了一种质粒pMTlacT2的构建，该质粒指导由转录本2基因编码的49,800道尔顿多肽的合成。从携带该质粒的大肠杆菌制备的无细胞提取物将吲哚乙酰胺转化为植物天然生长素吲哚乙酸；从不含质粒的大肠杆菌菌株或携带克隆载体pBR322的菌株制备的提取物则不进行此反应。我们得出结论，pTiA6的转录本2基因编码一种参与生长素生物合成的酶，可能是吲哚乙酰胺水解酶。
