title: Characterization of gamma irradiation-induced deletion mutations at a selectable locus in Arabidopsis.
abstract: Seeds of transgenic Arabidopsis, containing a negatively selectable suicide marker, a 35Stms2 construct introduced as a transgene, were gamma-irradiated at a range of doses from 20-120 krad. Batches of M2 seeds, from M1 plants irradiated at doses of 40, 45 and 60 krad, were screened by germinating them on medium containing NAM under conditions that selectively inhibited growth of plants expressing the tms2 gene product. Nine candidate loss-of-transgene mutants were isolated. The frequency of such mutations (0.0125 to 0.025%) did not vary significantly with irradiation dose or M1 pool size. DNA from the mutants and the parent was hybridized in Southern blots, using probes complementary to various regions of the transgene. All nine mutants were null for both the tms2 coding sequence and the 35S promoter. Six of the nine mutants were null for the entire transgene construct of 9 kbp. DNA from one mutant contained one of the T-DNA borders and gave a hybridization pattern consistent with a deletion at least 5 kbp. The two remaining mutant lines gave identical patterns of hybridization, consistent with a 5.6-kbp internal deletion within the transgene. From the Southern blots, and on the basis of lineage, the nine lines represent the progeny of either seven or eight independent mutations. We have established conditions capable of producing deletion mutations of at least 5 kbp, but without apparently introducing small deletions or rearrangements. Such deletion mutations are ideally suited for cloning by subtractive hybridization, and should also be readily detectable by RFLP analysis, facilitating map-based cloning procedures.
authors.affiliation: Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Glasgow University, Glasgow G12 8QQ, Scotland, UK.
authors.forename: E
authors.initials: E
authors.lastname: Cecchini
authors.forename: B J
authors.initials: BJ
authors.lastname: Mulligan
authors.forename: S N
authors.initials: SN
authors.lastname: Covey
authors.forename: J J
authors.initials: JJ
authors.lastname: Milner
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics; D000581:Amidohydrolases / Q000096:biosynthesis / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000528:radiation effects*; D017796:Caulimovirus; D002588:Cesium Radioisotopes; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D016296:Mutagenesis; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D017384:Sequence Deletion
chemical_list: D002588:Cesium Radioisotopes; D011994:Recombinant Proteins; D000581:Amidohydrolases; C058772:indole-3-acetamide hydrolase