Abstract
Arabidopsis root with its simple, consistent and well-defined pattern of cell division and growth is a highly tractable system for studying cellular development. The root apical meristem (RAM) of Arabidopsis, established post-embryonically is the main source of root cells. Complex bidirectional signaling between stem cells and mature root cells is required to maintain RAM activity. The Arabidopsis RAM comprises of a quiescent center (QC) and a niche of self-renewing stem cells that perform asymmetric (formative) cell divisions to generate daughter cells. These daughter cells subsequently divide symmetrically within delineated longitudinal cell files. The cells in the QC coordinate with neighboring stem cells to establish the balance between proliferation and differentiation in the meristem niche. The Arabidopsis primary root is composed of concentric rings of tissues (namely, the epidermis, the cortex, the endodermis and the pericycle, from the outside inwards) arranged in a radial axis that surrounds a central cylinder of vascular and procambial cells. Overlaid upon the radial organization of the root are three longitudinal zones viz, the meristem, the elongation zone and the differentiation zone, that describe cellular behavior. The boundaries of these domains are plastic and are largely regulated by antagonistic interactions between different phyto-hormones, which regulate the expression of key TFs. In this paper, we review the process of radial patterning in Arabidopsis thaliana post-embryonic root with an emphasis on genetic and molecular networks that determine the fate of each domain in the root.
Published Version
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