Trichome patterning on growing tissue

Leaves of Arabidopsis thaliana bear trichomes, or hairs, which are spaced in an approximately regular pattern on their adaxial side. Trichome cells differentiate in the fast-growing basal part of the leaf and do not divide. The regular spacing of trichomes is controlled by cell-to-cell interactions (Larkin et al., 1997). We created simulation models of these interactions to gain a better understanding of the patterning process. The models operate on a growing virtual leaf with dividing and differentiating cells. We show that, within the previously proposed class of reaction-diffusion processes (Hülskamp, 2004), trichome patterning is more readily generated by activatorinhibitor than activator-substrate models (Meinhardt and Gierer, 1974). We then report on current work, in which an activator-inhibitor model is being refined by taking into account present understanding of the genetic regulatory network that controls trichome differentiation in Arabidopsis.