Evaluation of tolerance to Pierce's disease and Botrytis in transgenic plants of Vitis vinifera L. expressing the pear PGIP gene

Abstract

SUMMARY Polygalacturonase-inhibiting proteins (PGIPs) are plant cell-wall proteins that specifically inhibit fungal endo-polygalacturonases (PGs) that contribute to the aggressive decomposition of susceptible plant tissues. The inhibition of fungal PGs by PGIPs suggests that PGIPs have a role in plant tolerance to fungal infections and this has been observed in transgenic plants expressing PGIPs. Xylella fastidiosa, the causal agent of Pierce's disease (PD) in grapevines, has genes that encode cell-wall-degrading enzymes, including a putative PG. Therefore, we hypothesized that PGIP expression could confer tolerance against this bacterium as well as against the fungal pathogen Botrytis cinerea. To test this hypothesis, Vitis vinifera cvs. 'Thompson Seedless' and 'Chardonnay' were transformed to express pear fruit PGIP-encoding gene (pPGIP) under the control of the CaMV 35S promoter. Substantial pear PGIP (pPGIP) activity was found in crude extracts from leaves and in xylem exudate of transgenic lines obtained from independent transformation events, but not in untransformed controls. pPGIP activity was detected in xylem exudate of untransformed scions grafted on to transgenic rootstocks expressing pPGIP. Leaves of transgenic plants infected with B. cinerea had reduced rates of lesion expansion. The development of PD was delayed in some transgenic lines with increased pPGIP activity. PD-tolerant transgenic lines had reduced leaf scorching, lower Xylella titres and better re-growth after pruning than the untransformed controls.

Vegetable Grafting: The Implications of a Growing Agronomic Imperative for Vegetable Fruit Quality and Nutritive Value

“…However, movement of proteins across graft unions is not restricted to the phloem path as it was demonstrated in transgrafting pathogen resistant, genetically engineered rootstocks with wild type scions. Rootstocks expressing transgenic polygalacturonase inhibiting protein (PGIP) as components of the defense against invasion with pathogens, onto which non-expressing scions were grafted, do not export the respective encoding nucleic acid rather than the PGIP protein itself via the xylem system (Aguero et al, 2005). Furthermore, the PGIP protein in the wild-type scion tissue grafted onto PGIP-expressing genetically engineered rootstocks reduced pathogen damage in scion tissues (Haroldsen et al, 2012).…”

Plant cell wall dynamics and wall-related susceptibility in plant–pathogen interactions

“…Against microbial and insect PGs, plants produce cell wall-associated polygalacturonase-inhibiting proteins (PGIPs; Spadoni et al, 2006). The over expression of PGIPs improves the resistance to fungal and bacterial necrotrophs in different plants (Aguero et al, 2005; Ferrari et al, 2012). The PG-PGIP interaction results in the accumulation of elicitor-active oligogalacturonides (OGs) that are perceived in Arabidopsis by the receptor Wall Associated Kinase 1 (WAK1; Brutus et al, 2010) to activate the plant immune responses (Ferrari et al, 2013).…”

Exogenous application of methyl jasmonate induces a defense response and resistance against Sclerotinia sclerotiorum in dry bean plants

“…Both a significant increase in the PG-inhibitory activity and a decrease in the susceptibility to B. cinerea have been found in transgenic tomato (Powell et al, 2000) and grapevine (Aguero et al, 2005) plants that overexpress a pear pgip. Additionally, Arabidopsis and wheat are protected by the transgenic expression of a bean PGIP in greenhouse trials against the fungi Fusarium graminearum and Bipolaris sorokiniana (Janni et al, 2008;Ferrari et al, 2012).…”