Probable transcription factor required for the initiation of inflorescence trichomes in response to gibberellin and cytokinin. Acts upstream of GIS, GIS2, ZFP8, and the trichome initiation factors GL1 and GL3. Binds the promoter region of GIS and GIS2, which may be direct targets of GIS3. Decreased number of trichomes in cauline leaves, lateral branches, sepals and main stems. Plants over-expressing GIS3 have increased trichome densities in sepals, cauline leaves, lateral branches, main inflorescence stems, and have ectopic trichomes on carpels.