GLABROUS1 overexpression and TRIPTYCHON alter the cell cycle and trichome cell fate in Arabidopsis

Cellular competence, initiation cues, and inhibition signals control the di stribution of trichomes on the Arabidopsis leaf. The GLABROUS1 (GLI) gene h as a dual role in that it is required for trichome initiation, but GLI over expression reduces trichome number. We have found that a mutation in the TR IPTYCHON (TRY) gene partially suppresses the GLI overexpression phenotype b ut not in a way that indicates that TRY directly controls an epidermal inhi bition pathway. Surprisingly, cauliflower mosaic virus 35S::GLI try plants contain a subclass of trichomes derived from the subepidermal layer. Altere d cell cycle control was also detected in 35S::GLI and try plants. A mutati on in TRY led to increased epidermal and mesophyll cell number, a reduction in endoreduplication in the epidermis, and an increase in endoreduplicatio n in trichomes. GL1 overexpression also reduced endoreduplication levels in both the epidermis and trichomes; however, in the presence of try, it syne rgistically enhanced trichome endoreduplication. Interactions with the COTY LEDON TRICHOME1 (COM) gene indicate that GLI and TRY control trichome devel opment and may be involved in cell cycle control during leaf development.