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) demethylesteriWes pectin, which is secreted into the cell wall in a highly methylesteriWed 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 diVerential expression of this gene. PuriWed 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.

Engineering the cell wall by reducing de-methyl-esterified homogalacturonan improves saccharification of plant tissues for bioconversion

“…This technology, unlike that involving PGs, is readily available for application purposes, because plants overexpressing PMEI have a normal growth and, in the case of Arabidopsis, even exhibit an increased biomass. Furthermore, since plants overexpressing PMEI display a higher resistance to microbial pathogens (13,23), crops with increased HGA methyl-esterification may also possess this additional desirable trait. Independently of the kind of genes that are used, we have shown that a reduction of the acidic HGA content ultimately determines an increased cell wall susceptibility to hydrolytic degradation.…”

Identification of Genes Involved in the Response of Arabidopsis to Simultaneous Biotic and Abiotic Stresses

“…Cell wall modifications can provide an increased physical barrier against potential pathogens, while improving tolerance to drought and oxidative stress and maintaining turgor during osmotic stress (Piro et al, 2003;Pelloux et al, 2007;An et al, 2008;Leucci et al, 2008). The observed up-regulation of cell wall modification proteins in response to combined nematode and dehydration stress may therefore be a general defensive mechanism activated to confer broad-spectrum tolerance against multiple stresses.…”

Cell wall integrity

“…For example, overexpression of pepper CaPMEI1 in Arabidopsis improved plant resistance to P. syringae possibly due to the antimicrobial activity of the protein and the activation of the salicylic acid pathway, although a possible contribution of altered cell wall esterification has not been excluded. 52 Moreover, CaPMEI overexpressing plants exhibited higher drought and oxidative stress tolerance. 52 Pectin acetylation can also affect plant resistance against invading pathogens.…”

“…52 Moreover, CaPMEI overexpressing plants exhibited higher drought and oxidative stress tolerance. 52 Pectin acetylation can also affect plant resistance against invading pathogens. Recent work demonstrated that reduction of pectin acetylation increased Arabidopsis resistance to microbial pathogens.…”

“…50 In addition to transcriptional control, PME activity is regulated by endogenous inhibitor proteins (PMEIs), which were discovered in kiwi fruit and subsequently identified in Arabidopsis, pepper, broccoli, wheat and tomato. [51][52][53][54][55][56][57][58][59] PMEIs function in apical meristem development, cell growth acceleration and pollen tube growth. 47,53,54,60 Also, overexpression of AtPMEI in Arabidopsis significantly increases the level of pectin methyesterification and improves leaf and root growth.…”