Signaling network for stem cell maintenance and functioning in Arabidopsis shoot apical meristem

Abstract

The shoot apical meristem (SAM) domain, which contains a self-renewing population of undifferentiated pluripotent cells, produces all of a plant's post-embryonic aerial organs. Intra- and intercellular signaling networks are essential to the maintenance of SAM size and structure, and for coordinating the formation and patterning of new organs. A key regulatory system for meristem functioning consists of a non-cell-autonomous WUSCHIEL (WUS)-CLAVATA (CLV) regulatory loop and class I KNOX-related signaling in the shoot apex. Meristem activity is also dependent on short- and long-distance signaling from the organizing center, organ boundaries/primordia, and distant organs. Here, we provide an overview of SAM organization and present our current knowledge about the signaling network for stem cell maintenance and functioning in the vegetative SAM in Arabidopsis. Transcription factors belonging to the WOX, KNOX, HD-ZIP, MYB, SAND, AP2, and NAC domain protein families, as well as microRNA, play central roles in this network, along with hormonal cross-talk. We also discuss regulation at different levels, such as for protein interactions, and transcriptional and epigenetic controls. Our intent is to show how various signals are integrated to maintain a stem cell niche in the SAM.