Factors involved in asymmetric cell division in the Arabidopsis root meristem

Abstract

The root of the flowering plant Arabidopsis thaliana has a simple, yet well-defined pattern of tissue layers. Single concentric layers of epidermis, cortex, endodermis and pericycle encircle the stele, while columella and lateral root cap compose the basal tissue of the root. These layers arise from the so-called stem cell niche, which is located at the tip of the root. The endodermis and cortex cell layers arise from the cortex/endodermis initial (CEI) and the asymmetric division of it's daughter cell (Da).

The genes SHORT-ROOT and SCARECROW play a key role in patterning of the endodermis and cortex. The endodermis is absent when SHORT-ROOT is mutated; asymmetric division of the Da does not take place. SCARECROW has been shown to be essential for the asymmetric division of the Da as well. Mutation of this gene inhibits division of the Da, and the resulting single layer has mixed identity. SCARECROW has been found to be a direct target of SHORT-ROOT. All of the above suggests that SHORT-ROOT is necessary for initiating endodermal cell fate, while SCARECROW is needed for the asymmetric division of the CEI.

There are indications that the recently discovered gene SCARECROW-LIKE23 plays a role in root patterning as well. In this thesis, an experiment in order to characterize SCARECROW-LIKE23 is described. Yet unpublished, some results indicate that SCARECROW-LIKE23 acts in the same pathway of root patterning as SHORT-ROOT and SCARECROW.