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.
Highlights d CLAVATA (CLV) signaling mediates continuous flower outgrowth in Arabidopsis thaliana d CLAVATA2/CORYNE function alongside CIK-family coreceptors d CLV signaling promotes auxin-mediated floral primordia growth in colder temperatures d High temperatures bypass CLV signaling, upregulating auxin through ELF3
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