Leaf trichome formation is known to be regulated by the TTG, GL1, GL2, and GL3 genes in Arabidopsis. GL1 and GL3 encode proteins with Myb and bHLH domains, respectively. Overexpression of the AtmybL2 gene, which encodes a single Myb-like DNA-binding domain, repressed trichome development in transgenic Arabidopsis plants. The amount of GL2 transcription was clearly reduced in the transgenic plants. Consistent with this, overexpression of AtmybL2 decreased beta-glucuronidase (GUS) activity in transgenic plants carrying a GUS-reporter gene regulated by the GL2 promoter. These findings, together with the results from our yeast two-hybrid analysis, suggest that GL3 gene function and overexpression of AtmybL2 act synergistically to inhibit trichome formation by negatively regulating GL2 expression.