Immediate targets of ETTIN suggest a key role for pectin methylesterase inhibitors in the control of Arabidopsis gynecium development.
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SUBMITTER: Andres-Robin A
PROVIDER: S-EPMC8570713 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Plant cell walls are complex and dynamic structures that play important roles in growth and development, as well as in response to stresses. Pectin is a major polysaccharide of cell walls rich in galacturonic acid (GalA). Homogalacturonan (HG) is considered the most abundant pectic polymer in plant cell walls and is partially methylesterified at the C6 atom of galacturonic acid. Its degree (and pattern) of methylation (DM) has been shown to affect biomechanical properties of the cell wall by making pectin susceptible for enzymatic de-polymerization and enabling gel formation. Pectin methylesterases (PMEs) catalyze the removal of methyl-groups from the HG backbone and their activity is modulated by a family of proteinaceous inhibitors known as pectin methylesterase inhibitors (PMEIs). As such, the interplay between PME and PMEI can be considered as a determinant of cell adhesion, cell wall porosity and elasticity, as well as a source of signaling molecules released upon cell wall stress. This review aims to highlight recent updates in our understanding of the PMEI gene family, their regulation and structure, interaction with PMEs, as well as their function in response to stress and during development.
| S-EPMC6213510 | biostudies-literature
Project description:Plant infection by a virus is a complex process influenced by virus-encoded factors and host components which support replication and movement. Critical factors for a successful tobamovirus infection are the viral movement protein (MP) and the host pectin methylesterase (PME), an important plant counterpart that cooperates with MP to sustain viral spread. The activity of PME is modulated by endogenous protein inhibitors (pectin methylesterase inhibitors, PMEIs). PMEIs are targeted to the extracellular matrix and typically inhibit plant PMEs by forming a specific and stable stoichiometric 1:1 complex. PMEIs counteract the action of plant PMEs and therefore may affect plant susceptibility to virus. To test this hypothesis, we overexpressed genes encoding two well-characterized PMEIs in tobacco and Arabidopsis plants. Here, we report that, in tobacco plants constitutively expressing a PMEI from Actinidia chinensis (AcPMEI), systemic movement of Tobacco mosaic virus (TMV) is limited and viral symptoms are reduced. A delayed movement of Turnip vein clearing virus (TVCV) and a reduced susceptibility to the virus were also observed in Arabidopsis plants overexpressing AtPMEI-2. Our results provide evidence that PMEIs are able to limit tobamovirus movement and to reduce plant susceptibility to the virus.
| S-EPMC6638747 | biostudies-literature
Project description:The degree of methylesterification (DM) of homogalacturonans (HGs), the main constituent of pectins in Arabidopsis thaliana, can be modified by pectin methylesterases (PMEs). Regulation of PME activity occurs through interaction with PME inhibitors (PMEIs) and subtilases (SBTs). Considering the size of the gene families encoding PMEs, PMEIs and SBTs, it is highly likely that specific pairs mediate localized changes in pectin structure with consequences on cell wall rheology and plant development. We previously reported that PME17, a group 2 PME expressed in root, could be processed by SBT3.5, a co-expressed subtilisin-like serine protease, to mediate changes in pectin properties and root growth. Here, we further report that a PMEI, PMEI4, is co-expressed with PME17 and is likely to regulate its activity. This sheds new light on the possible interplay of specific PMEs, PMEIs and SBTs in the fine-tuning of pectin structure.
| S-EPMC4622950 | biostudies-other
Project description:Pectin methylesterases (PMEs) catalyze the demethylesterification of pectin, one of the main polysaccharides in the plant cell wall, and are of critical importance in plant development. PME activity generates highly negatively charged pectin and mutates the physiochemical properties of the plant cell wall such that remodeling of the plant cell can occur. PMEs are therefore tightly regulated by proteinaceous inhibitors (PMEIs), some of which become active upon changes in cellular pH. Nevertheless, a detailed picture of how this pH-dependent inhibition of PME occurs at the molecular level is missing. Herein, using an interdisciplinary approach that included homology modeling, MD simulations, and biophysical and biochemical characterizations, we investigated the molecular basis of PME3 inhibition by PMEI7 in Arabidopsis thaliana Our complementary approach uncovered how changes in the protonation of amino acids at the complex interface shift the network of interacting residues between intermolecular and intramolecular. These shifts ultimately regulate the stability of the PME3-PMEI7 complex and the inhibition of the PME as a function of the pH. These findings suggest a general model of how pH-dependent proteinaceous inhibitors function. Moreover, they enhance our understanding of how PMEs may be regulated by pH and provide new insights into how this regulation may control the physical properties and structure of the plant cell wall.
| S-EPMC5766959 | biostudies-literature
Project description:The hydrolysis of p-nitrophenyl acetate catalysed by pectin methylesterase is competitively inhibited by pectin and does not require metal ions to occur. The results suggest that the activastion by metal ions may be explained by assuming that they interact with the substrate rather than with the enzyme. With pectin used as substrate, metal ions are required in order to allow the hydrolysis to occur in the presence of pectin methylesterase. This is explained by the existence of 'blocks' of carboxy groups on pectin that may trap enzyme molecules and thus prevent the enzyme reaction occurring. Metal ions may interact with these negatively charged groups, thus allowing the enzyme to interact with the ester bonds to be cleaved. At high concentrations, however, metal ions inhibit the enzyme reaction. This is again understandable on the basis of the view that some carboxy groups must be adjacent to the ester bond to be cleaved in order to allow the reaction to proceed. Indeed, if these groups are blocked by metal ions, the enzyme reaction cannot occur, and this is the reason for the apparent inhibition of the reaction by high concentrations of metal ions. Methylene Blue, which may be bound to pectin, may replace metal ions in the 'activation' and 'inhibition' of the enzyme reaction. A kinetic model based on these results has been proposed and fits the kinetic data very well. All the available results favour the view that metal ions do not affect the reaction through a direct interaction with enzyme, but rather with pectin.
| S-EPMC1151611 | biostudies-other
Project description:Pectin methylesterases (PMEs) catalyze the demethylesterification of homogalacturonan domains of pectin in plant cell walls and are regulated by endogenous pectin methylesterase inhibitors (PMEIs). In Arabidopsis dark-grown hypocotyls, one PME (AtPME3) and one PMEI (AtPMEI7) were identified as potential interacting proteins. Using RT-quantitative PCR analysis and gene promoter::GUS fusions, we first showed that AtPME3 and AtPMEI7 genes had overlapping patterns of expression in etiolated hypocotyls. The two proteins were identified in hypocotyl cell wall extracts by proteomics. To investigate the potential interaction between AtPME3 and AtPMEI7, both proteins were expressed in a heterologous system and purified by affinity chromatography. The activity of recombinant AtPME3 was characterized on homogalacturonans (HGs) with distinct degrees/patterns of methylesterification. AtPME3 showed the highest activity at pH 7.5 on HG substrates with a degree of methylesterification between 60 and 80% and a random distribution of methyl esters. On the best HG substrate, AtPME3 generates long non-methylesterified stretches and leaves short highly methylesterified zones, indicating that it acts as a processive enzyme. The recombinant AtPMEI7 and AtPME3 interaction reduces the level of demethylesterification of the HG substrate but does not inhibit the processivity of the enzyme. These data suggest that the AtPME3·AtPMEI7 complex is not covalently linked and could, depending on the pH, be alternately formed and dissociated. Docking analysis indicated that the inhibition of AtPME3 could occur via the interaction of AtPMEI7 with a PME ligand-binding cleft structure. All of these data indicate that AtPME3 and AtPMEI7 could be partners involved in the fine tuning of HG methylesterification during plant development.
| S-EPMC4645611 | biostudies-literature
Project description:Rice weevils (Sitophilus oryzae) use a pectin methylesterase (EC 3.1.1.11), along with other enzymes, to digest cell walls in cereal grains. The enzyme is a right-handed ?-helix protein, but is circularly permuted relative to plant and bacterial pectin methylesterases, as shown by the crystal structure determination reported here. This is the first structure of an animal pectin methylesterase. Diffraction data were collected to 1.8?Å resolution some time ago for this crystal form, but structure solution required the use of molecular-replacement techniques that have been developed and similar structures that have been deposited in the last 15 years. Comparison of the structure of the rice weevil pectin methylesterase with that from Dickeya dandantii (formerly Erwinia chrysanthemi) indicates that the reaction mechanisms are the same for the insect, plant and bacterial pectin methylesterases. The similarity of the structure of the rice weevil enzyme to the Escherichia coli lipoprotein YbhC suggests that the evolutionary origin of the rice weevil enzyme was a bacterial lipoprotein, the gene for which was transferred to a primitive ancestor of modern weevils and other Curculionidae. Structural comparison of the rice weevil pectin methylesterase with plant and bacterial enzymes demonstrates that the rice weevil protein is circularly permuted relative to the plant and bacterial molecules.
| S-EPMC4231848 | biostudies-literature
Project description:Invertases (INVs) and pectin methylesterases (PMEs) are essential enzymes coordinating carbohydrate metabolism, stress responses, and sugar signaling. INVs catalyzes the cleavage of sucrose into glucose and fructose, exerting a pivotal role in sucrose metabolism, cellulose biosynthesis, nitrogen uptake, reactive oxygen species scavenging as well as osmotic stress adaptation. PMEs exert a dynamic control of pectin methylesterification to manage cell adhesion, cell wall porosity, and elasticity, as well as perception and signaling of stresses. INV and PME activities can be regulated by specific proteinaceous inhibitors, named INV inhibitors (INVIs) and PME Inhibitors (PMEIs). Despite targeting different enzymes, INVIs and PMEIs belong to the same large protein family named "Plant Invertase/Pectin Methylesterase Inhibitor Superfamily." INVIs and PMEIs, while showing a low aa sequence identity, they share several structural properties. The two inhibitors showed mainly alpha-helices in their secondary structure and both form a non-covalent 1:1 complex with their enzymatic counterpart. Some PMEI members are organized in a gene cluster with specific PMEs. Although the most important physiological information was obtained in Arabidopsis thaliana, there are now several characterized INVI/PMEIs in different plant species. This review provides an integrated and updated overview of this fascinating superfamily, from the specific activity of characterized isoforms to their specific functions in plant physiology. We also highlight INVI/PMEIs as biotechnological tools to control different aspects of plant growth and defense. Some isoforms are discussed in view of their potential applications to improve industrial processes. A review of the nomenclature of some isoforms is carried out to eliminate confusion about the identity and the names of some INVI/PMEI member. Open questions, shortcoming, and opportunities for future research are also presented.
| S-EPMC8990755 | biostudies-literature
Project description:BackgroundPectin methylesterases (PMEs) catalyze the demethylesterification of homogalacturonans in the cell wall; their activity is regulated in part by pectin methylesterase inhibitors (PMEIs). PME activity may result in either rigidification or loosening of the cell wall, depending on the mode of demethylesterification. The activity of PMEs in the middle lamella is expected to affect intrusive elongation of phloem fibers, and their adhesion to adjacent cells. Length and extractability of phloem fibers are qualities important for their industrial uses in textiles and composites. As only three flax PMEs had been previously described, we were motivated to characterize the PME and PMEI gene families of flax.ResultsWe identified 105 putative flax PMEs (LuPMEs) and 95 putative PMEIs (LuPMEIs) within the whole-genome assembly. We found experimental evidence for the transcription of 77/105 LuPMEs and 83/95 LuPMEIs, and surveyed the transcript abundance of these in 12 different tissues and stages of development. Six major monophyletic groups of LuPMEs could be defined based on the inferred relationships of flax genes and their presumed orthologs from other species. We searched the LuPMEs and LuPMEIs for conserved residues previously reported to be important for their tertiary structure and function. In the LuPMEs, the most highly conserved residues were catalytic residues while in the LuPMEIs, cysteines forming disulfude bridges between helices α2 and α3 were most highly conserved. In general, the conservation of critical residues was higher in the genes with evidence of transcript expression than in those for which no expression was detected.ConclusionsThe LuPMEs and LuPMEIs comprise large families with complex patterns of transcript expression and a wide range of physical characteristics. We observed that multiple PMEs and PMEIs are expressed in partially overlapping domains, indicative of several genes acting redundantly during most processes. The potential for functional redundancy was highlighted also by the phylogenetic analyses. We were able to identify a subset of PME and PMEIs that appeared particularly relevant to fiber development, which may provide a basis for the improvement of key traits in industrial feedstocks and a better understanding of the physiological roles of PMEs and PMEIs in general.
| S-EPMC4008260 | biostudies-literature
Project description:DUF538 (domain of unknown function 538) proteins are known as a group of putative hypothetical proteins in a wide range of plant species. They have been identified from some plants challenged with various environmental stresses. However, a little is known about their functional properties. They have been newly predicted to have binding capacity and esterase-type hydrolytic activity towards bacterial lipopolysaccharides and chlorophyll molecules as carboxylic compounds in plants. In the present study, the binding ability and the methylesterase activity of DUF538 proteins towards pectin molecules were also predicted. Their similarities to pectin methylesterases and their binding ability to pectin molecule were predicted using bioinformatic tools as well as the experimental method. A probable cooperation was speculated between DUF538 and pectin methylesterase protein families in cell wall associated defense responses in plants.
| S-EPMC7113335 | biostudies-literature