title: Translation start sequences affect the efficiency of silencing of Agrobacterium tumefaciens T-DNA oncogenes.
abstract: Agrobacterium tumefaciens oncogenes cause transformed plant cells to overproduce auxin and cytokinin. Two oncogenes encode enzymes that convert tryptophan to indole-3-acetic acid (auxin): iaaM (tryptophan mono-oxygenase) and iaaH (indole-3-acetamide hydrolase). A third oncogene (ipt) encodes AMP isopentenyl transferase, which produces cytokinin (isopentenyl-AMP). Inactivation of ipt and iaaM (or iaaH) abolishes tumorigenesis. Because adequate means do not exist to control crown gall, we created resistant plants by introducing transgenes designed to elicit posttranscriptional gene silencing (PTGS) of iaaM and ipt. Transgenes that elicit silencing trigger sequence-specific destruction of the inducing RNA and messenger RNAs with related sequences. Although PTGS has proven effective against a variety of target genes, we found that a much higher percentage of transgenic lines silenced iaaM than ipt, suggesting that transgene sequences influenced the effectiveness of PTGS. Sequences required for oncogene silencing included a translation start site. A transgene encoding a translatable sense-strand RNA from the 5' end of iaaM silenced the iaaM oncogene, but deletion of the translation start site abolished the ability of the transgene to silence iaaM. Silencing A. tumefaciens T-DNA oncogenes is a new and effective method to produce plants resistant to crown gall disease.
authors.affiliation: Departments of Microbiology and Horticulture, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Hyewon
authors.initials: H
authors.lastname: Lee
authors.forename: Jodi L
authors.initials: JL
authors.lastname: Humann
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Pitrak
authors.forename: Josh T
authors.initials: JT
authors.lastname: Cuperus
authors.forename: T Dawn
authors.initials: TD
authors.lastname: Parks
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Whistler
authors.forename: Machteld C
authors.initials: MC
authors.lastname: Mok
authors.forename: L Walt
authors.initials: LW
authors.lastname: Ream
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics* / Q000254:growth & development; D018389:Codon, Nonsense / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics*; D009857:Oncogenes / Q000235:genetics*; D010641:Phenotype; D010941:Plant Tumors / Q000235:genetics / Q000382:microbiology; D010944:Plants / Q000235:genetics* / Q000382:microbiology; D030821:Plants, Genetically Modified; D034622:RNA Interference / Q000502:physiology*; D016372:RNA, Antisense / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D014170:Transformation, Genetic / Q000235:genetics
chemical_list: D018389:Codon, Nonsense; D004269:DNA, Bacterial; D016372:RNA, Antisense; D012333:RNA, Messenger; C036483:T-DNA