Stem Cell Basis of Shoot Branching.

During their postembryonic development, plants continuously form branches to conquer more space and adapt to changing environments. In seed plants, this is achieved by lateral branching, in which axillary meristems (AMs) initiate at the leaf axils to form axillary buds. The developmental potential of AMs to form shoot branches is the same as that of embryonic shoot apical meristems (SAMs). Recent studies in Arabidopsis thaliana have revealed the cellular origin of AMs and have identified transcription factors and phytohormones that regulate sequential steps leading to AM initiation. In particular, a group of meristematic cells detached from the SAM are key to AM initiation, which constitutes an excellent system for understanding stem cell fate and de novo meristem formation.