Abstract
Leaf trichomes in Arabidopsis develop through several distinct cellular processes, such as patterning, differentiation and growth. Here we report a novel trichome mutation in Arabidopsis, which in contrast to previously identified mutants, increases trichome cell size without altering its overall patterning or branching. We show that the corresponding gene encodes a GT-2-LIKE1 (GTL1) protein, a member of the trihelix transcription factor family. GTL1 is present within the nucleus during the post-branching stages of trichome development and its loss of function leads to a ploidy increase in trichomes that have completed branching. Our data further demonstrate that the gtl1 mutation modifies the expression of several cell cycle genes and partially rescues the ploidy defects in the cyclin-dependent kinase (CDK) inhibitor mutant siamese. Taken together, this study provides the genetic evidence for the requirement of transcriptional regulation in the repression of ploidy-dependent plant cell growth as well as for an involvement of GT-2-like trihelix proteins in this regulation.
