AC DS TRANSPOSON MUTAGENESIS IN ARABIDOPSIS-THALIANA - MUTANT SPECTRUM AND FREQUENCY OF DS INSERTION MUTANTS/

Using a two-component Ac/Ds system consisting of a stabilized Ac eleme nt (Ac-c1) and a nonautonomous element (Ds(A)), 650 families of plants carrying independent germinal Ds(A) excisions/transpositions were iso lated. Progenies of 559 of these Ac-c1/Ds(A) families, together with 4 3 families of plants selected for excision/transposition of wild-type (wt) Ac were subjected to a broad screening program for mutants exhibi ting visible alterations. This resulted in the identification of 48 mu tants showing a wide variety of mutant phenotypes, including embryo le thality (24 mutants), chlorophyll defects (5 mutants), defective seedl ings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutan ts), altered leaf morphology (2 mutants), dark green, unexpanded roset te leaves (3 mutants), and aberrant flower or shoot morphology (4 muta nts). To test whether these mutants were due to transposon Insertions, a series of Southern blot experiments was performed on 28 families, c omparing in each case several mutant plants with others showing the wi ld-type phenotype. A preliminary analysis revealed in 4 of the 28 fami lies analyzed a common, novel Ds(A) fragment in all mutant plants, whi ch was present only in heterozygous plants with wt phenotype, as expec ted for Ds(A) insertion mutations. These four mutants included two sho wing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences. and one with curly growth of stems, leaves and siliques. Further evidence for Ds(A) insertion mutations was obta ined for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the Ds(A) insertion could be separated from the mutant locus by genetic recombination.