Search for: All records

Cell division is often regulated by extracellular signaling networks to ensure correct patterning during development. In Arabidopsis , the SHORT-ROOT (SHR)/SCARECROW (SCR) transcription factor dimer activates CYCLIND6 ; 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 for SHR -dependent formative divisions and CYCD6;1 expression, but not SHR -dependent ground tissue specification. Root-enriched CLE ligands bind the BAM1 extracellular domain and are necessary and sufficient to activate SHR -mediated divisions and CYCD6;1 expression. 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. 

In flowering plants, cell–cell communication plays a key role in reproductive success, as both pollination and fertilization require pathways that regulate interactions between many different cell types. Some of the most critical of these interactions are those between the pollen tube (PT) and the embryo sac, which ensure the delivery of sperm cells required for double fertilization. Synergid cells function to attract thePTthrough secretion of small peptides and inPTreception via membrane‐bound proteins associated with the endomembrane system and the cell surface. While many synergid‐expressed components regulatingPTattraction and reception have been identified, few tools exist to study the localization of membrane‐bound proteins and the components of the endomembrane system in this cell type. In this study, we describe the localization and distribution of seven fluorescent markers that labelled components of the secretory pathway in synergid cells ofArabidopsis thaliana. These markers were used in co‐localization experiments to investigate the subcellular distribution of the twoPTreception componentsLORELEI, aGPI‐anchored surface protein, andNORTIA, aMILDEW RESISTANCE LOCUSO protein, both found within the endomembrane system of the synergid cell. These secretory markers are useful tools for both reproductive and cell biologists, enabling the analysis of membrane‐associated trafficking within a haploid cell actively involved in polar transport.