Transposon tagging provides an effective method of isolating plant genes by identifying a mutation tagged by a DNA insertion, and then using the DNA tag to isolate the mutant gene (reviewed m ref. I ). The first examples of this approach in plants involved transposon tagging in maize and Antirrhinum using endogenous transposons. More recently, maize transposons were shown to be active in a wide range of plant species, and in some of these have facilitated the use of transposon tagging (2 ‐5 ). In Arabidopsis, Actzvator/Dissoclation (AC/ Ds) have been used to isolate recessive loss-of-function mutations (6 —8 ), dommant gain of function mutations (9 ) and to isolate genes based on then patterns of expression (10 ,11 ).