Pattern formation during de novo assembly of the Arabidopsis shoot meristem

Most multicellular organisms have a capacity to regenerate tissue after wounding. Few, however, have the ability to regenerate an entire new body from adult tissue. Induction of new shoot meristems from cultured root explants is a widely used, but poorly understood, process in which apical plant tissues are regenerated from adult somatic tissue through the de novo formation of shoot meristems. We characterize early patterning during de novo development of the Arabidopsis shoot meristem using fluorescent reporters of known gene and protein activities required for shoot meristem development and maintenance. We find that a small number of progenitor cells initiate development of new shoot meristems through stereotypical stages of reporter expression and activity of CUP- SHAPED COTYLEDON 2 ( CUC2), WUSCHEL ( WUS), PIN- FORMED 1 ( PIN1), SHOOT- MERISTEMLESS ( STM), FILAMENTOUS FLOWER ( FIL, also known as AFO), REVOLUTA ( REV), ARABIDOPSIS THALIANA MERISTEM L1 LAYER ( ATML1) and CLAVATA 3 ( CLV3). Furthermore, we demonstrate a functional requirement for WUS activity during de novo shoot meristem initiation. We propose that de novo shoot meristem induction is an easily accessible system for the study of patterning and selforganization in the well- studied model organism Arabidopsis.