Partial demethylation of oligogalacturonides by pectin methyl esterase 1 is required for eliciting defence responses in wild strawberry (Fragaria vesca)

Abstract

SummaryIn addition to the role of the cell wall as a physical barrier against pathogens, some of its constituents, such as pectin-derived oligogalacturonides (OGA), are essential components for elicitation of defence responses. To investigate how modifications of pectin alter defence responses, we expressed the fruit-specific Fragaria · ananassa pectin methyl esterase FaPE1 in the wild strawberry Fragaria vesca. Pectin from transgenic ripe fruits differed from the wild-type with regard to the degree and pattern of methyl esterification, as well as the average size of pectin polymers. Purified oligogalacturonides from the transgenic fruits showed a reduced degree of esterification compared to oligogalacturonides from wild-type fruits. This reduced esterification is necessary to elicit defence responses in strawberry. The transgenic F. vesca lines had constitutively activated pathogen defence responses, resulting in higher resistance to the necrotropic fungus Botrytis cinerea. Further studies in F. vesca and Nicotiana benthamiana leaves showed that the elicitation capacity of the oligogalacturonides is more specific than previously envisaged.

Antisense Down-Regulation of theFaPG1Gene Reveals an Unexpected Central Role for Polygalacturonase in Strawberry Fruit Softening

“…In the strawberry-ripening process, pectin breakdown fragments of [1/4]-alinked oligogalacturonides can, potentially, be released through the action of PG or other pectinolytic enzymes. These OGAs have been demonstrated to modify gene expression and to play a role in eliciting different cellular responses as a plant-pathogen interaction in strawberry fruits (Osorio et al, 2008). However, in our case, the absence of significant transcriptomic changes in the microarray studies does not support this explanation.…”

Arabidopsis PECTIN METHYLESTERASEs Contribute to Immunity against Pseudomonas syringae

“…Moreover, in wheat (Triticum aestivum) near-isogenic lines, a blockwise distribution of methylesters was detected in lines susceptible to Puccinia graminis compared with a more random distribution in resistant lines (Wiethölter et al, 2003). In addition, the elicitor activity of OGs is dependent on the degree and distribution of methylesters (Cabrera et al, 2008;Osorio et al, 2008). Thus, it is likely that patterns of methylesterification affect plant-pathogen interactions.…”

“…The degree and pattern of pectin methylesterification are important for pectin degradation and hence generation of OGs by pectolytic enzymes (Berger and Reid, 1979;Limberg et al, 2000aLimberg et al, , 2000b. The elicitor activity of OGs depends on their length and degree of esterification (Osorio et al, 2008;Ferrari et al, 2013). It has been shown that pectic fragments can be perceived by WALL-ASSOCIATED KINASE1 (WAK1) and WAK2 (Kohorn et al, 2009;Brutus et al, 2010).…”

Plant Cell Wall Polymers: Function, Structure and Biological Activity of Their Derivatives

“…Besides, the induction of lipoxigenase activity demonstrated the stimulation of the octadecanoid pathaway. Moreover, transgenic strawberries (Fragaria vesca L.) producing partially demethylated OGAs displayed an enhanced resistance against Botrytis cinerea [53]. Table 1 shows that OGAs modulate diverse growth and developmental processes in plants.…”