T‐DNA insertion mutagenesis in Arabidopsis: mutational spectrum

More than 8000 transformants of Arabidopsis have been generated by treating germinating seeds with cultures of Agrobacterium tumefaciens. Genetic characterization of a subset of the transformants indicates that they contain an average of 1.4 inserts each, as assayed by kanamycin resistance. Molecular analysis shows that the inserts are predominantly concatamers of T‐DNAs arranged as direct and inverted repeats. More recently these 8000 lines have been screened under a variety of growth conditions for visible alterations in phenotype. More than 1000 putative mutants were observed during the application of these screening procedures. These mutants fall into several general classes: seedling‐lethals, size variants, pigment, embryo‐defective, reduced‐fertility, dramatic (morphological), and physiological. The majority of the mutants (88%) segregate in a Mendelian manner for the mutant phenotype. An analysis of approximately 50 mutants in this group shows that > 80% are tagged with a functional insert. The wide spectrum of mutants observed suggests that it may be feasible to develop a comprehensive collection of mutant lines in which each gene is tagged by a T‐DNA insertion.