RT Journal Article SR Electronic T1 ARGONAUTE10 is required for cell fate specification and the control of formative cell divisions in the Arabidopsis root meristem JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.02.05.429893 DO 10.1101/2021.02.05.429893 A1 Nabila El Arbi A1 Ann-Kathrin Schürholz A1 Alexei Schiffner A1 Inés Hidalgo Prados A1 Friedrich Böhme A1 Christian Wenzl A1 Xinai Zhao A1 Jian Zeng A1 Jan U. Lohmann A1 Sebastian Wolf YR 2021 UL http://biorxiv.org/content/early/2021/02/05/2021.02.05.429893.abstract AB A key question in plant biology is how oriented cell divisions are integrated with patterning mechanisms to generate organs with adequate cell type allocation. In the root vasculature, a miRNA gradient controls the abundance of HD-ZIP III transcription factors, which in turn control cell fate and spatially restrict vascular cell proliferation to specific cells. Here, we show that a functional miRNA gradient requires an opposing gradient of ARGONAUTE10, which sequesters miRNAs to protect HD-ZIP III transcripts from degradation. In the absence of ARGONAUTE10, xylem precursor cells undergo periclinal divisions that lead to continuous strands of differentiated xylem elements at ectopic positions. Notably, periclinal daughter cells maintain xylem identity even when they are located outside of the xylem axis, resulting in disrupted tissue boundaries. We further demonstrate that ARGONAUTE10 and HD-ZIP IIIs buffer cytokinin signalling to control formative cell divisions, providing a framework for integration of phytohormone and miRNA-mediated patterning.Competing Interest StatementThe authors have declared no competing interest.