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 only 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. In addition, studies of GTL1 and its closest orthologues in Arabidopsis provide further genetic evidence that these proteins are involved in the transcriptional regulation of plant cell growth beyond trichome development.
