Arabidopsis PECTIN METHYLESTERASEs Contribute to Immunity against Pseudomonas syringae

Abstract

Pectins, major components of dicot cell walls, are synthesized in a heavily methylesterified form in the Golgi and are partially deesterified by pectin methylesterases (PMEs) upon export to the cell wall. PME activity is important for the virulence of the necrotrophic fungal pathogen Botrytis cinerea. Here, the roles of Arabidopsis PMEs in pattern-triggered immunity and immune responses to the necrotrophic fungus Alternaria brassicicola and the bacterial hemibiotroph Pseudomonas syringae pv maculicola ES4326 (Pma ES4326) were studied. Plant PME activity increased during pattern-triggered immunity and after inoculation with either pathogen. The increase of PME activity in response to pathogen treatment was concomitant with a decrease in pectin methylesterification. The pathogen-induced PME activity did not require salicylic acid or ethylene signaling, but was dependent on jasmonic acid signaling. In the case of induction by A. brassicicola, the ethylene response factor, but not the MYC2 branch of jasmonic acid signaling, contributed to induction of PME activity, whereas in the case of induction by Pma ES4326, both branches contributed. There are 66 PME genes in Arabidopsis, suggesting extensive genetic redundancy. Nevertheless, selected pme single, double, triple and quadruple mutants allowed significantly more growth of Pma ES4326 than wild-type plants, indicating a role of PMEs in resistance to this pathogen. No decreases in total PME activity were detected in these pme mutants, suggesting that the determinant of immunity is not total PME activity; rather, it is some specific effect of PMEs such as changes in the pattern of pectin methylesterification.The plant cell wall determines cell shape, facilitates cell-cell interaction, and provides mechanical strength to plant cells. De Bary (1886) first observed that a plant pathogen, Sclerotina sclerotiorum, degraded host cell walls during infection. Later, it was concluded that plant cell walls act as preformed structural barriers against pathogen entry, because it was noticed that many plant pathogens produced various types of cell wall-degrading enzymes and that some of those were required for optimal infection of host plants (Albersheim et al., 1969).Arabidopsis mesophyll cells are surrounded by primary cell walls consisting of three major components: cellulose, hemicelluloses, and pectins. Pectins make up approximately 50% of Arabidopsis leaf cell walls (Zablackis et al., 1995;Harholt et al., 2010). They are complex GalA-containing polysaccharides composed of homogalacturonan (HG), rhamnogalacturonan I and II, and xylogalacturonan (Mohnen, 2008). HG is typically the most abundant polysaccharide, constituting approximately 65% of the pectin (Mohnen, 2008;Harholt et al., 2010). HG is a linear homopolymer of 1,4-linked GalA and is synthesized in the Golgi in a highly methylesterified form (Caffall and Mohnen, 2009). Pectin methylesterases (PMEs) demethylesterify HG in the apoplast (Mohnen, 2008;Harholt et al., 2010). Demethylesterification of pectin is considered t...

PECTIN METHYLESTERASE48 Is Involved in Arabidopsis Pollen Grain Germination

“…The regulation of the DM of HG has been implicated in many aspects of plant development (Wolf et al, 2009a), including cell adhesion (Tieman and Handa, 1994;Wen et al, 1999;Mollet et al, 2000;Bouton et al, 2002;Mouille et al, 2007;Durand et al, 2009), adventitious rooting (Guénin et al, 2011), primordia emergence at the shoot apical meristem (Peaucelle et al, 2008(Peaucelle et al, , 2011, fruit ripening (Brummell and Harpster, 2001;Phan et al, 2007), and plant defense (Bethke et al, 2014). Although data have shown an important role for Figure 5.…”

Requirement for Pectin Methyl Esterase and Preference for Fragmented over Native Pectins for Wall-associated Kinase-activated, EDS1/PAD4-dependent Stress Response in Arabidopsis

“…Bromphenol blue was added, and the sample was heated at 80°C for 10 min and then separated by SDS-PAGE using 10% acrylamide gel and transferred to nitrocellulose membrane for 1500 mA h. Western blots were blocked with 5% (w/v) nonfat dry milk in Tris-buffered saline (TBS) supplemented with 3% Tween 20; incubated with peroxidase-antiperoxidase-soluble complex (Sigma) or the indicated antiserum and the appropriate secondary serum at 1:2500 dilution for 2 h each; and detected with chemiluminescence. PME Activity-The Ruthenium Red agar diffusion assay was adapted from Bethke et al (15). 0.1% pectin Ն85% esterified (Sigma P9561), 1% agarose, 12.5 mM citric acid, 50 mM Na 2 HPO 4 , pH 7.0, was microwaved, and 13 ml was poured per 10-cm Petri dish.…”

“…Pectins are also the target of numerous pathogens that digest the wall as they approach the plant cell, thereby generating de-esterified pectin fragments or oligogalacturonides (OGs) (13,14). Numerous studies demonstrate that OGs can activate a stress response by the plant, indicating that OGs signal pathogen presence (15).…”

Pectin Methylesterases: A Review

“…In a recent study on Arabidopsis PMEs, revealed that PMEs affect patterns of methylesterification in a way that impart pattern-triggered immunity to Pseudomonas syringae pv maculicola ES4326 (Pma ES4326) [79]. Oils from coconut germ, sunflower seed, palm kernel, rape seed are industrially extracted with organic solvents.…”

“…3.1.1.11), a methyl ester group hydrolytic enzyme is produced by plants, pathogenic fungi, and bacteria also constantly being used in the wine, juice, and other food industries [1]. In Arabidopsis PMEs, it was revealed that PMEs have unique patterns of methylesterification that provide immunity to Pseudomonas syringae pv maculicola ES4326 (Pma ES4326) [2]. Pectin methylesterase catalyzes reactions according to the double-displacement mechanisms, de-esterification through transferring the C 6 carboxyl groups in the pectin-PME complexes to water molecules altering the degree and pattern of methyl esterification and transacylation through transferring the C 6 carboxyl groups to the hydroxyl groups of another pectin molecules and resulting in the formation of high molecular weight pectins with new non-methoxy ester linkages [3][4][5][6][7][8].…”