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1. Mutation of an Arabidopsis Golgi membrane protein ELMO1 reduces cell adhesion

   https://doi.org/10.1242/dev.199420  

   Kohorn, Bruce D.; Zorensky, Frances D.; Dexter-Meldrum, Jacob; Chabout, Salem; Mouille, Gregory; Kohorn, Susan (May 2021, Development)

   null (Ed.)

   ABSTRACT 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. 

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2. Fundamental interactions between pectin and cellulose nanocrystals: a molecular dynamics simulation

   https://doi.org/10.1007/s10570-025-06611-x  

   Wu, Xiawa; Prasad, Anamika (July 2025, Cellulose)

   French, Alfred (Ed.)

   While the relative abundance of plant biopolymers can vary significantly depending on the cell type and maturation, pectin and cellulose nanocrystals are among the two key biopolymers found in many plants’ primary cell walls at the early growth stage. Nanocomposites that utilize cellulose nanocrystals have gained extensive interest over the years. Limited knowledge regarding pectin and the interaction between pectin and cellulose is available because pectin was considered a non-loading-bearing component with little interaction with cellulose. However, recent developments in primary cell wall structure have shifted, and pectin is viewed as a part of the reinforcement structure. Thus, understanding the role of pectin has become relevant in creating advanced bio-composites that mimic the structure of primary cell walls. This work aims to provide fundamental information on the interaction between pectin and cellulose nanocrystals using molecular dynamics simulations. A dry interaction is modeled to replicate their status in a composite, where water is removed via processing such as freeze-drying. Interphase models consisting of two cellulose nanocrystals and a homogalacturonan pectin molecule are created to simulate the interfacial structure, including binding potential energy and hydrogen bonds. Friction and adhesion responses are predicted by moving one cellulose nanocrystal against the other. The results show that a pectin molecule increases the friction at the interphase by 14 and 8 times between CNC (200) and (110) surfaces, respectively, which is correlated to the significantly increased binding energies and interfacial hydrogen bonds, regardless of pectin’s charge density. On the other hand, the adhesion force is increased by 1.1 times with a pectin molecule between the CNC (110) surfaces. Adhesion, however, reduces to 1/5 between CNC (200) surfaces with embedded pectin, which is attributed to disrupted$$\pi$$ $\pi$-$$\pi$$ $\pi$interaction. The simulation results reveal the atomistic level interaction between pectin and cellulose nanocrystals, which is essential for designing nanocomposites using pectin and cellulose nanocrystals as main components. 

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3. PECTIN METHYLESTERASE51 Affects Stomatal Dimensions, Rosette Area, and Root Length in Arabidopsis thaliana

   https://doi.org/10.1002/pld3.70066  

   Dunham, Angelica L.; Tamadaddi, Chetana; Marshall, Rayna; Anderson, Charles T. (April 2025, Plant Direct)

   ABSTRACT Pectins are abundant in the cell walls of eudicot plants and have been implicated in determining the development and biomechanics of stomatal guard cells, which expand and contract dynamically to open and close stomatal pores on the plant surface, modulating photosynthesis and water transport. Pectic homogalacturonan is delivered to the cell wall in a methylesterified form but can be demethylesterified in the wall by pectin methylesterases, increasing both its ability to form crosslinks via calcium and its susceptibility to degradation by endogenous pectinases. Although a few pectin methylesterases have been implicated in stomatal development and function, this large family of proteins has not been fully characterized with respect to how they modulate stomatal guard cells. Here, we characterized the function of PECTIN METHYLESTERASE51 (PME51), a pectin methylesterase–encoding gene that is expressed in developing guard cells, in stomatal morphogenesis in seedlings and adult plants ofArabidopsis thaliana. OverexpressingPME51led to smaller adult plants with smaller stomatal complexes and subtle changes in initial responses to opening and closure stimuli, whereas knocking outPME51resulted in smaller stomatal complexes and longer roots in seedlings. We observed changes in pectin labeling in knockout and overexpression plants that imply a specific function for PME51 in modulating the degree of methylesterification for homogalacturonan. Together, these findings expand our understanding of how pectin modification by pectin methylesterases affects the development and function of stomatal guard cells, which must maintain a balance of strength and flexibility to optimize plant growth. 

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

   https://doi.org/10.3390/plants10040690  

   Kohorn, Bruce D.; Dexter-Meldrum, Jacob; Zorensky, Frances D.; Chabout, Salem; Mouille, Gregory; Kohorn, Susan (April 2021, Plants)

   null (Ed.)

   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. 

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5. Coexpression of Fungal Cell Wall-Modifying Enzymes Reveals Their Additive Impact on Arabidopsis Resistance to the Fungal Pathogen, Botrytis cinerea

   https://doi.org/10.3390/biology10101070  

   Swaminathan, Sivakumar; Reem, Nathan T.; Lionetti, Vincenzo; Zabotina, Olga A. (October 2021, Biology)

   The plant cell wall (CW) is an outer cell skeleton that plays an important role in plant growth and protection against both biotic and abiotic stresses. Signals and molecules produced during host–pathogen interactions have been proven to be involved in plant stress responses initiating signal pathways. Based on our previous research findings, the present study explored the possibility of additively or synergistically increasing plant stress resistance by stacking beneficial genes. In order to prove our hypothesis, we generated transgenic Arabidopsis plants constitutively overexpressing three different Aspergillus nidulans CW-modifying enzymes: a xylan acetylesterase, a rhamnogalacturonan acetylesterase and a feruloylesterase. The two acetylesterases were expressed either together or in combination with the feruloylesterase to study the effect of CW polysaccharide deacetylation and deferuloylation on Arabidopsis defense reactions against a fungal pathogen, Botrytis cinerea. The transgenic Arabidopsis plants expressing two acetylesterases together showed higher CW deacetylation and increased resistance to B. cinerea in comparison to wild-type (WT) Col-0 and plants expressing single acetylesterases. While the expression of feruloylesterase alone compromised plant resistance, coexpression of feruloylesterase together with either one of the two acetylesterases restored plant resistance to the pathogen. These CW modifications induced several defense-related genes in uninfected healthy plants, confirming their impact on plant resistance. These results demonstrated that coexpression of complementary CW-modifying enzymes in different combinations have an additive effect on plant stress response by constitutively priming the plant defense pathways. These findings might be useful for generating valuable crops with higher protections against biotic stresses. 

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