Pattern formation in plant embryogenesis: a reassessment.

Pattern formation in embryogenesis generates the basic body plan of flowering plants by establishing the diversity of position-dependent cell fates characteristic of the seedling. The concept of pattern formation, which was originally based on the analysis of Arabidopsis pattern mutants, is re-examined in the light of recent data that address the origin of the axis of polarity, the origin of the primary meristems as elements of the apical-basal pattern and the formation of the radial pattern of tissue layers. The available evidence from genetic, molecular and experimental approaches supports the notion that embryonic pattern formation occurs in steps involving communication between clonally unrelated cells.