Abstract
In the Arabidopsis root, stem cell activity is dependent on a short-range signal from the quiescent center (QC), a group of mitotically less active cells surrounded by the stem cells. QC specification and stem cell maintenance requires SCR and SHR, GRAS-family transcription factors involved in radial patterning, as well as the phytohormone auxin. We identified PLETHORA1 (PLT1), which is mainly expressed in the QC and surrounding stem cells. PLT1 and its closest homolog PLT2 encode putative transcription factors of the AP2/EREBP family. Genetic analysis showed that PLT1 and PLT2 are required for QC specification and stem cell maintenance in the root. The PLT genes are suggested to act independently with the radial pathway represented by SCR and SHR and act downstream of auxin. Moreover, ectopic expression studies suggest that the PLT genes are also involved in embryonic specification of hypocotyl and root identity.
