Dear Editor,Forward genetic screens are commonly used as unbiased tools to isolate genes responsible for a phenotype of interest.In Arabidopsis thaliana,especially T-DNA activation tagging populations are frequently employed.These populations are generated using vectors containing multiple copies of the constitutive 35S promoters derived from cauliflower mosaic virus(35S CaMV)and often result in isolation of dominant gain-of-function alleles(Weigel et al.,2000;Nakazawa et al.,2003).