Biology subjects

Etchells, P.

Publications and source records attributed to Etchells, P..

3 recordsLinked to original sources

bioRxiv2024

A receptor kinase complex refines cambium activity in Arabidopsis

In plant development, key receptor kinases are often active in disparate cell types, with each requiring vastly different signalling outputs. The ERECTA (ER) receptor kinase and its homologs ERL1 and ERL2 exemplify this pleiotropy. In Arabidopsis, they influence stomatal patterning, shoot meristem function, ovule morphogenesis, xylem fiber differentiation, and cell division in the vascular cambium1-6. Such diverse expression and functionality raises the question of how ER signalling can specify such distinct cell behaviours. One mechanism is via cell-type specific interactions with co-receptors, ligands, or other proteins that modulate signalling. However, little is known about ER interactors in the vascular cambium, a bifacial stem cell niche that generates phloem and xylem (Figure 1A). Combinatorial mutations between ER, ERL1 and ERL2 and receptor kinases of a second family, PXY, PXL1, and PXL2, show severe cambial defects5,7, but the mechanism underpinning these phenotypes is not known. Here we discovered that PXY proteins form protein complexes with ER and ERL2. PXY signalling can be manipulated by altering levels of its cognate ligand, TDIF. In genetic analysis, plant lines in which TDIF levels were altered had dramatic phenotypic changes that required the presence of ER or ERL2. Our results demonstrate that PXY signalling mediated cambium regulation depends on ER signalling and explains ER function in the cambium. Because the cambium produces xylem, which constitutes the wood in vascular plants, our findings position PXY-ER complexes at the centre of the accumulation of this versatile biomaterial and essential carbon sink. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=168 SRC="FIGDIR/small/594489v1_fig1.gif" ALT="Figure 1"> View larger version (79K): org.highwire.dtl.DTLVardef@289bb6org.highwire.dtl.DTLVardef@6d0fdorg.highwire.dtl.DTLVardef@1829836org.highwire.dtl.DTLVardef@d70b3b_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO PXY forms heterodimers with ER and ERL2 (A) Transverse sections of a wild type hypocotyl showing the region of secondary growth. Black rectangle marks the area of cambium shown in the diagrammatic representation on the lower left. (B-D) Localisation of PXY-CFP (B), ER-YFP (C) and overlap (D) in Nicotiana epidermal cells. (E) FRET signal. (F) Graph showing FRET efficiencies of PXY-CFP and ER/ERL1/ERL2-YFP pairs. (G-H) Coimmunoprecipitation of PXY-FLAG with ER-HA or ERL2-HA and vice versa in Arabidopsis cells. Scales (A) are 50 M. C_FIG

plant biology↗

bioRxiv2023

Identification of cambium stem cell factors and their positioning mechanism

Wood constitutes the majority of terrestrial biomass. Composed of xylem, it arises from one side of the vascular cambium, a bifacial stem cell niche that also produces phloem on the opposing side. It is currently unknown which molecular factors endow cambium stem cell identity. Here we show that TDIF ligand-activated PXY receptors promote the expression of CAMBIUM AINTEGUMENTA-LIKE (CAIL) transcription factors to define cambium stem cell identity in the Arabidopsis root. By sequestrating the phloem-originated TDIF, xylem-dependent PXY confines the TDIF signaling front, resulting in the activation of CAIL expression and stem cell identity in only a narrow domain. Our findings show how signals emanating from cells on opposing sides ensure robust yet dynamically adjustable positioning of a bifacial stem cell.

plant biology↗

bioRxiv2018

Paralogues of the PXY and ER receptor kinases enforce radial patterning in plant vascular tissue.

Plant cell walls do not allow cells to migrate, thus plant growth and development is entirely the consequence of changes to cell division and cell elongation. Where tissues are arranged in concentric rings, expansion of inner tissue, such as that which occurs during vascular development, must be coordinated with cell division and/or expansion of the outer tissue layers, endodermis, cortex, and epidermis, in order for tissue integrity to be maintained. Little is known of how coordination between cell layers occurs, but non-cell autonomous signalling could provide an explanation. Endodermis-derived EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) ligands have been shown to signal to the ERECTA (ER) receptor kinase present in the phloem. ER interacts with PHLOEM INTERCALLATED WITH XYLEM (PXY), a receptor present in the procambium. The PXY ligand, TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF) is derived from CLE41 which is expressed in the phloem. These factors therefore represent a mechanism by which intertissue signalling could occur to control radial expansion between vascular and non-vascular tissue in plant stems. Here we show that ER regulates expression of PXY paralogues, PXL1 and PXL2, and that in turn PXY, PXL1 and PXL2 together with ER, regulate the expression of ERL1 and ERL2, genes paralogous to ER. PXY, PXL1, PXL2 and ER also regulate the expression of ER-ligands. Genetic analysis of these six receptor kinase genes demonstrated that they are required to control organisation, proliferation and cell size across multiple tissue layers. Taken together, our experiments demonstrate that ER signalling attenuates PXL expression in the stem, thus influencing vascular expansion and patterning. We anticipate that similar regulatory relationships, where tissue growth is controlled via cell signals moving across different tissue layers, will coordinate tissue layer expansion throughout the plant body.

plant biology↗