Regulation of epidermal cell fate in Arabidopsis roots: the importance of multiple feedback loops

Abstract

The specification of distinct cell types in multicellular organisms is accomplished via establishment of differential gene expression. A major question is the nature of the mechanisms that establish this differential expression in time and space. In plants, the formation of the hair and non-hair cell types in the root epidermis has been used as a model to understand regulation of cell specification. Recent findings show surprising complexity in the number and the types of regulatory interactions between the multiple transcription factor genes/proteins influencing root epidermis cell fate. Here, we describe this regulatory network and the importance of the multiple feedback loops for its establishment and maintenance.

Keywords: Arabidopsis thaliana; feedback loops; pattern formation; root hairs; transcription factors.

Figure 1

Molecular genetic regulation of cell fate specification in the Arabidopsis root epidermis. Root-hair specific gene expression occurs in differentiating epidermal cells located in a cleft between adjacent cortical cells (right-most cell). Gene regulatory activity is indicated by solid lines with arrows (positive transcriptional effect) or bars (negative transcriptional effect). Dotted lines represent the movement of proteins within or between cells. The downstream genes shown here are taken from Bruex et al. (2012) and defined as hair or non-hair genes based on their accumulation in the root epidermis in either cpc try (non-hair) mutants vs. ttg1, wer myb23, or gl3 egl3 (hairy) mutants.