Regulated accumulation of the SCRAMBLED receptor and positiondependent cell type patterning in arabidopsis

Abstract

SCRAMBLED (SCM), a leucine-rich repeat receptor-like kinase, mediates positional signaling and cell-type pattern formation in the epidermis of Arabidopsis roots. The precise mechanism of SCM action has been unclear. In a recent report, we find that accumulation of the SCM-GFP fusion protein varies in a cell-type-specific manner during root epidermis development. At early stages, SCM-GFP accumulates equally in both root-hair cells and nonhair cells, but at later stages of epidermis development, it accumulates preferentially in roothair cells. The importance of epidermal production of SCM was demonstrated by epidermis-specific SCM-GFP silencing, which caused an epidermal patterning defect. Further, the expression of SCM-GFP by a root-hair-cell promoter complements the scm-2 epidermal defect completely, whereas a non-hair-cell promoter complements the scm-2 epidermal phenotype partially. From these results we conclude that the spatial distribution of a positional cue and the accumulation of the SCM receptor are both required for optimal positional signaling in epidermal patterning. © 2009 Landes Bioscience.