BAM1/2 receptor kinase signaling drives CLE peptide-mediated formative cell divisions in Arabidopsis roots

Abstract

Cell division is often regulated by extracellular signaling networks to ensure correct patterning during development. InArabidopsis, the SHORT-ROOT (SHR)/SCARECROW (SCR) transcription factor dimer activatesCYCLIND6;1(CYCD6;1) to drive formative divisions during root ground tissue development. Here, we show plasma-membrane-localized BARELY ANY MERISTEM1/2 (BAM1/2) family receptor kinases are required forSHR-dependent formative divisions andCYCD6;1expression, but notSHR-dependent ground tissue specification. Root-enriched CLE ligands bind the BAM1 extracellular domain and are necessary and sufficient to activateSHR-mediated divisions andCYCD6;1expression. Correspondingly, BAM-CLE signaling contributes to the restriction of formative divisions to the distal root region. Additionally, genetic analysis reveals that BAM-CLE and SHR converge to regulate additional cell divisions outside of the ground tissues. Our work identifies an extracellular signaling pathway regulating formative root divisions and provides a framework to explore this pathway in patterning and evolution.

The receptor-like kinases BAM1 and BAM2 are required for root xylem patterning

“…In Arabidopsis roots, BAM1 is strongly expressed in the stele (SI Appendix, Fig. S1) (10). We reasoned that, considering this expression pattern, if BAM1 regulates movement of miRNAs, it could mediate the cell-to-cell spread of miR165/6, hence acting…”

Control of Arabidopsis shoot stem cell homeostasis by two antagonistic CLE peptide signalling pathways

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