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Pepper pectin methylesterase inhibitor protein CaPMEI1 is required for antifungal activity, basal disease resistance and abiotic stress tolerance.

ABSTRACT: Pectin is one of the main components of the plant cell wall that functions as the primary barrier against pathogens. Among the extracellular pectinolytic enzymes, pectin methylesterase (PME) demethylesterifies pectin, which is secreted into the cell wall in a highly methylesterified form. Here, we isolated and functionally characterized the pepper (Capsicum annuum L.) gene CaPMEI1, which encodes a pectin methylesterase inhibitor protein (PMEI), in pepper leaves infected by Xanthomonas campestris pv. vesicatoria (Xcv). CaPMEI1 transcripts are localized in the xylem of vascular bundles in leaf tissues, and pathogens and abiotic stresses can induce differential expression of this gene. Purified recombinant CaPMEI1 protein not only inhibits PME, but also exhibits antifungal activity against some plant pathogenic fungi. Virus-induced gene silencing of CaPMEI1 in pepper confers enhanced susceptibility to Xcv, accompanied by suppressed expression of some defense-related genes. Transgenic Arabidopsis CaPMEI1-overexpression lines exhibit enhanced resistance to Pseudomonas syringae pv. tomato, mannitol and methyl viologen, but not to the biotrophic pathogen Hyaloperonospora parasitica. Together, these results suggest that CaPMEI1, an antifungal protein, may be involved in basal disease resistance, as well as in drought and oxidative stress tolerance in plants.

SUBMITTER: An SH

PROVIDER: S-EPMC2413075 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Pepper pectin methylesterase inhibitor protein CaPMEI1 is required for antifungal activity, basal disease resistance and abiotic stress tolerance.

An Soo Hyun SH Sohn Kee Hoon KH Choi Hyong Woo HW Choi Hyong Woo HW Hwang In Sun IS Lee Sung Chul SC Hwang Byung Kook BK

Planta 20080308 1

Pectin is one of the main components of the plant cell wall that functions as the primary barrier against pathogens. Among the extracellular pectinolytic enzymes, pectin methylesterase (PME) demethylesterifies pectin, which is secreted into the cell wall in a highly methylesterified form. Here, we isolated and functionally characterized the pepper (Capsicum annuum L.) gene CaPMEI1, which encodes a pectin methylesterase inhibitor protein (PMEI), in pepper leaves infected by Xanthomonas campestris ...[more]

PMID: 18327607

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Project description:The mechanical damage that often precedes the penetration of a leaf by a pathogen promotes the activation of pectin methylesterase (PME); the activation of PME leads to the emission of methanol, resulting in a "priming" effect on intact leaves, which is accompanied by an increased sensitivity to Tobacco mosaic virus (TMV) and resistance to bacteria. In this study, we revealed that mRNA levels of the methanol-inducible gene encoding Nicotiana benthamiana aldose 1-epimerase-like protein (NbAELP) in the leaves of intact plants are very low compared with roots. However, stress and pathogen attack increased the accumulation of the NbAELP mRNA in the leaves. Using transiently transformed plants, we obtained data to support the mechanism underlying AELP/PME-related negative feedback The insertion of the NbAELP promoter sequence (proNbAELP) into the N. benthamiana genome resulted in the co-suppression of the natural NbAELP gene expression, accompanied by a reduction in the NbAELP mRNA content and increased PME synthesis. Knockdown of NbAELP resulted in high activity of PME in the cell wall and a decrease in the leaf glucose level, creating unfavorable conditions for Agrobacterium tumefaciens reproduction in injected leaves. Our results showed that NbAELP is capable of binding the TMV movement protein (MPTMV) in vitro and is likely to affect the cellular nucleocytoplasmic transport, which may explain the sensitivity of NbAELP knockdown plants to TMV. Although NbAELP was primarily detected in the cell wall, the influence of this protein on cellular PME mRNA levels might be associated with reduced transcriptional activity of the PME gene in the nucleus. To confirm this hypothesis, we isolated the N. tabacum PME gene promoter (proNtPME) and showed the inhibition of proNtPME-directed GFP and GUS expression in leaves when co-agroinjected with the NbAELP-encoding plasmid. We hypothesized that plant wounding and/or pathogen attack lead to PME activation and increased methanol emission, followed by increased NbAELP expression, which results in reversion of PME mRNA level and methanol emission to levels found in the intact plant.

Project description:BACKGROUND: Pectin 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. RESULTS: We 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 ?2 and ?3 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. CONCLUSIONS: The 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.

Dataset Information

Pepper pectin methylesterase inhibitor protein CaPMEI1 is required for antifungal activity, basal disease resistance and abiotic stress tolerance.

Publications

Pepper pectin methylesterase inhibitor protein CaPMEI1 is required for antifungal activity, basal disease resistance and abiotic stress tolerance.

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