Generation of a Spacing Pattern: The Role of TRIPTYCHON in Trichome Patterning in Arabidopsis

Abstract

Trichomes in Arabidopsis are single-celled hairs that exhibit a regular spacing pattern. Here, the role of TRIPTYCHON (TRY) in the generation of this spacing pattern is studied. By using genetic mosaics, we demonstrate that the formation of trichome clusters in try mutants is not correlated with cell lineage, indicating that TRY is required to single out trichome cells in a process involving cellular interactions. The genetic interactions of TRY, GLABRA1 (GL1), and TRANSPARENT TESTA GLABRA (T TG) in trichome patterning are assessed by determining the cluster frequency in various genetic combinations. It is shown that TRY acts as a negative regulator of GL1- and TTG-dependent pathways. Furthermore, it is demonstrated that trichome initiation in ttg-1, a strong ttg allele, is rescued almost to wild-type levels in a try background in which GL1 is expressed under the control of the cauliflower mosaic virus 35S promoter, indicating that T TG acts upstream of GL1 and TRY. These findings are incorporated into a model to explain the generation of a trichome spacing pattern from a homogeneous population of epidermal cells.

Ectopic D-type cyclin expression induces not only DNA replication but also cell division in Arabidopsis trichomes

“…Plants were grown as described (8). The Arabidopsis ecotype Landsberg erecta (Ler) was used as a wild-type control.…”

The control of leaf development

“…These factors promote trichome formation and are predicted to activate their own expression. Factors which repress trichome formation have also been characterized, including TRIPTYCHON (TRY) and CAPRICE (CPC) (Schnittger et al, 1999;Schellmann et al, 2002). Surprisingly, these negative regulators are expressed at a relatively high level in the cells which form trichomes.…”

Signals from the cuticle affect epidermal cell differentiation

“…Three positive regulators, GLABRA1 (GL1), GLABRA2 (GL2) and TRANSPARENT TESTA GLABRA (TTG), and an inhibitor, TRIPTYCHON (TRY ), of trichome development have been identified (Koornneef et al, 1982;Larkin et al, 1993Larkin et al, , 1994Hülskamp et al, 1994). It has been postulated (Schnittger et al, 1999;Larkin et al, 1996) that GL1 and TTG create a positive feedback loop in cells predisposed to becoming trichomes, and as their expression increases the cell becomes committed to the trichome cell fate pathway. TRY, on the other hand, is expressed by the committed cell and is involved in inhibiting surrounding cells from becoming trichomes.…”