Abstract
Efficient induction of gain-of-function mutations is essential for functional assignment of genes whose loss-of-function mutations do not cause obvious phenotypic defects. In order to identify genes responsible for root morphogenesis, we are establishing a new activation tagging system that utilizes a yeast transcriptional activator GAL4 and its recognition sequence (UAS). In this system, a T-DNA containing five copies of 17-mer UAS is randomly inserted into the genome of GAL4:VP16-expressing Arabidopsis lines established by Jim Haseloff and coworkers. The simple transcriptional activation by GAL4:VP16-UAS interaction is expected to efficiently induce ectopic expression of tagged genes in a pattern defined by the GAL4:VP16 expression. Since the host lines also harbor a GFP reporter placed under the UAS, plants defective in root patterning can be easily screened in the primary transformants based on altered GFP expression. TAIL-PCR analysis of isolated mutants has identified several genes to which no biological functions have been assigned.
