Mutation of an Arabidopsis Golgi membrane protein ELMO1 reduces cell adhesion

Plant growth, morphogenesis and development involve cellular adhesion, a process dependent on the composition and structure of the extracellular matrix or cell wall. Pectin in the cell wall is thought to play an essential role in adhesion, and its modification and cleavage are suggested to be highly regulated so as to change adhesive properties. To increase our understanding of plant cell adhesion, a population of ethyl methanesulfonate-mutagenized Arabidopsis were screened for hypocotyl adhesion defects using the pectin binding dye Ruthenium Red that penetrates defective but not wild-type (WT) hypocotyl cell walls. Genomic sequencing was used to identify a mutant allele of ELMO1 which encodes a 20 kDa Golgi membrane protein that has no predicted enzymatic domains. ELMO1 colocalizes with several Golgi markers and elmo1-/- plants can be rescued by an ELMO1-GFP fusion. elmo1-/- exhibits reduced mannose content relative to WT but no other cell wall changes and can be rescued to WT phenotype by mutants in ESMERALDA1, which also suppresses other adhesion mutants. elmo1 describes a previously unidentified role for the ELMO1 protein in plant cell adhesion

Cell adhesion in plants is under the control of putative O-fucosyltransferases

Cell-to-cell adhesion in plants is mediated by the cell wall and the presence of a pectin-rich middle lamella. However, we know very little about how the plant actually controls and maintains cell adhesion during growth and development and how it deals with the dynamic cell wall remodeling that takes place. Here we investigate the molecular mechanisms that control cell adhesion in plants. We carried out a genetic suppressor screen and a genetic analysis of cell adhesion-defective Arabidopsis thaliana mutants. We identified a genetic suppressor of a cell adhesion defect affecting a putative O-fucosyltransferase. Furthermore, we show that the state of cell adhesion is not directly linked with pectin content in the cell wall but instead is associated with altered pectin-related signaling. Our results suggest that cell adhesion is under the control of a feedback signal from the state of the pectin in the cell wall. Such a mechanism could be necessary for the control and maintenance of cell adhesion during growth and development

Cell adhesion in plants is under the control of putative O-fucosyltransferases

Cell-to-cell adhesion in plants is mediated by the cell wall and the presence of a pectin-rich middle lamella. However, we know very little about how the plant actually controls and maintains cell adhesion during growth and development and how it deals with the dynamic cell wall remodeling that takes place. Here we investigate the molecular mechanisms that control cell adhesion in plants. We carried out a genetic suppressor screen and a genetic analysis of cell adhesion-defective Arabidopsis thaliana mutants. We identified a genetic suppressor of a cell adhesion defect affecting a putative O-fucosyltransferase. Furthermore, we show that the state of cell adhesion is not directly linked with pectin content in the cell wall but instead is associated with altered pectin-related signaling. Our results suggest that cell adhesion is under the control of a feedback signal from the state of the pectin in the cell wall. Such a mechanism could be necessary for the control and maintenance of cell adhesion during growth and development

Identification OligoGalacturonides (OGs) involved in the control of cell adhesion

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Galacturonic acid oxidation: a radical way to stick together

The middle lamellae (ML) of plant cells, enriched in Homogalacturonan (HG) is considered to function as a crucial ‘glue’ responsible for cell-cell cohesion (for review see 1 ). Mutants with defective HG content exhibit cell adhesion defects 2,3 . Despite advances, the mechanisms governing cell adhesion during plant development remain elusive. We previously hypothesized that cell-cell cohesion relies on cell wall integrity signaling, yet the specifics remain undefined 4 . OligoGalacturonans (OG), degradation products of HG, are prime candidates for ‘informing’ cells about ML status and thereby influencing cell adhesion. This integrity signal is crucial for adhesion homeostasis 4 . OGs serve as signaling molecules, recognized by membrane-bound cell wall receptors. Notably, restoring adhesion in qua2-1 mutants by modulating pectin response gene expression in esmd/qua2 mutants underscores potential OGs’ importance 4–6 . Deciphering the diversity and role of endogenous OGs is imperative for understanding cell adhesion modulation. Our study aims to identify compounds in this signalling pathway that regulate cell adhesion. We focused on characterizing HG degradation products in dark-grown hypocotyls. Our findings highlight various oligomers, along with two key monomers: galacturonic acid and its oxidized form, galactaric acid. These monomers appear to play a pivotal role in controlling cell adhesion by indirectly enhancing the crosslinking of extensin, a cell wall structural protein. This crosslinking leads to the densification of extensin-based cell wall networks, ultimately restoring cell adhesion in defective mutants. Our research sheds light on the intricate interplay between HG degradation product monomer and cell adhesion mechanisms

Fine-Tuning and Remodelling of Pectins Play a Key Role in the Maintenance of Cell Adhesion

Plant cell adhesion is essential for development and stress response, mediated by pectin-rich middle lamella deposition between cell walls. However, the precise control mechanism of cell adhesion remains unclear. The qua2-1 and esmd1-1 mutants provide a better understanding of this process and suggest a signaling pathway triggering the loss and restoration of adhesion via cell wall modifications. This study attempts to characterize the potential regulatory role of endogenous oligogalacturonides (OGs) and pectin modifications in the control of cell adhesion in Arabidopsis. From dark-grown hypocotyls, our extraction revealed seven distinct endogenous OGs with varying polymerization and modifications. Abundance variations of OGs were observed among wild type, qua2-1 , esmd1-1 , and qua2-1/esmd1-1 mutants. The structure of homogalacturonans was analyzed by enzymatic fingerprint, in order to identify changes in esterification patterns. Expression analysis of pectin-modifying enzymes showed significant variations in PME , PMEI , and PAE genes. Gene expressions correlate with homogalacturonans modifications and cell adhesion phenotypes. This study enhances our understanding of a feedback loop between the endogenous OGs, homogalacturonans esterification fine tuning, and pectin remodeling enzymes expression in controlling cell adhesion

Pectin Dependent Cell Adhesion Restored by a Mutant Microtubule Organizing Membrane Protein

The cellulose- and pectin-rich plant cell wall defines cell structure, mediates defense against pathogens, and facilitates plant cell adhesion. An adhesion mutant screen of Arabidopsis hypocotyls identified a new allele of QUASIMODO2 (QUA2), a gene required for pectin accumulation and whose mutants have reduced pectin content and adhesion defects. A suppressor of qua2 was also isolated and describes a null allele of SABRE (SAB), which encodes a previously described plasma membrane protein required for longitudinal cellular expansion that organizes the tubulin cytoskeleton. sab mutants have increased pectin content, increased levels of expression of pectin methylesterases and extensins, and reduced cell surface area relative to qua2 and Wild Type, contributing to a restoration of cell adhesion

FINE-TUNING AND REMODELLING OF PECTINS PLAY A KEY ROLE IN THE MAINTENANCE OF CELL ADHESION

International audiencePlant cell adhesion is essential for development and stress response, mediated by pectin-rich middle lamella deposition between cell walls. However, the precise control mechanism of cell adhesion remains unclear. The qua2-1 and esmd1-1 mutants provide a better understanding of this process and suggest a signaling pathway triggering the loss and restoration of adhesion via cell wall modifications. This study attempts to characterize the potential regulatory role of endogenous oligogalacturonides (OGs) and pectin modifications in the control of cell adhesion in Arabidopsis. From dark-grown hypocotyls, our extraction revealed seven distinct endogenous OGs with varying polymerization and modifications. Abundance variations of OGs were observed among wild type, qua2-1, esmd1-1, and qua2-1/esmd1-1 mutants. The structure of homogalacturonans was analyzed by enzymatic fingerprint, in order to identify changes in esterification patterns. Expression analysis of pectin-modifying enzymes showed significant variations in PME, PMEI, and PAE genes. Gene expressions correlate with homogalacturonans modifications and cell adhesion phenotypes. This study enhances our understanding of a feedback loop between the endogenous OGs, homogalacturonans esterification fine tuning, and pectin remodeling enzymes expression in controlling cell adhesion

EB1 contributes to microtubule bundling and organization, along with root growth, in Arabidopsis thaliana

Microtubules are involved in plant development and adaptation to their environment, but the sustaining molecular mechanisms remain elusive. Microtubule-end-binding 1 (EB1) proteins participate in directional root growth in Arabidopsis thaliana. However, a connection to the underlying microtubule array has not been established yet. We show here that EB1 proteins contribute to the organization of cortical microtubules in growing epidermal plant cells, without significant modulation of microtubule dynamics. Using super-resolution stimulated emission depletion (STED) microscopy and an original quantification approach, we also demonstrate a significant reduction of apparent microtubule bundling in cytoplasmic-EB1-deficient plants, suggesting a function for EB1 in the interaction between adjacent microtubules. Furthermore, we observed root growth defects in EB1-deficient plants, which are not related to cell division impairment. Altogether, our results support a role for EB1 proteins in root development, in part by maintaining the organization of cortical microtubules. This article has an associated First Person interview with the first author of the paper

Disruption of the Sugar Transporters AtSWEET11 and AtSWEET12 Affects Vascular Development and Freezing Tolerance in Arabidopsis

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