Polypeptide metabolites secreted by the fungal pathogen Eutypa lata participate in Vitis vinifera cell structure damage observed in Eutypa dieback

Abstract

Eutypa dieback is a devastating disease of Vitis vinifera L. caused by the fungal pathogen Eutypa lata. This wood-inhabiting fungus degrades tissues in the trunk and cordons of infected vines and induces symptoms in the foliage. These symptoms have been attributed to the production of toxic metabolites by the pathogen, in particular eutypine. Recently, we have isolated polypeptide compounds secreted by the fungus in artificial culture. The aims of this study were to examine the effects induced in leaves by applying polypeptides and eutypine to detached canes and to compare this to the changes in leaf structure induced by E. lata in the vineyard. In leaves taken from vines infected with E. lata, the changes in mesophyll cells indicate that the fungus has an effect on tissue remote from the infected area. The size of mesophyll cells decreased by more than half, starch content was reduced and tannins were abundant. Plastids, mitochondria and cell walls were highly modified. In leaves taken from healthy canes treated with polypeptides of E. lata, the structure of mesophyll cells was also modified. The cell size did not change, but the tannin content increased and modifications in plastids and mitochondria were similar to those observed in leaves taken from infected vines. The major effect was the complete disorganisation of cell walls. Eutypine had less effect on organelle structure and did not modify the cell wall. In canes treated with polypeptides, vessel-associated cells (VACs) were also damaged. Abundant tannins occurred in the vacuoles of VACs and marked changes were noted in mitochondria, plastids and the protective layer, in particular in the pit at the vessel interface. In these pits, the protective layer, the primary wall and the middle lamella were all highly modified. In contrast, treatment with eutypine induced the development of a large transfer apparatus bordering the unmodified pectocellulose wall. These results illustrate that treatment with polypeptides produced by E. lata may cause changes in mesophyll cells in leaves and VACs in canes, that resemble changes observed in naturally infected vines. Comparatively, the differences with eutypine action were stressed. Both types of toxins may co-operate in vivo to produce the degeneration observed during the disease.

Toxicity of extracellular proteins from Diplodia seriata and Neofusicoccum parvum involved in grapevine Botryosphaeria dieback

“…This result was in agreement with studies on isolated proteins from E. lata, which induced, even at low concentrations, higher aggression levels than the characteristic toxins, i.e. eutypine and derivatives (Octave et al 2006a). We speculate that an additional interaction between extracellular proteins and other types of secondary metabolites (e.g.…”

“…We have observed a markedly distinctive toxic effect when equal protein concentrations are added to calli culture media. The effect was abolished when denatured proteins were used, indicating that the three-dimensional structure of these proteins is crucial for toxicity, as observed in several studies on E. lata (Octave et al 2005 and2006a), Pal and Pch (Luini et al 2010). In fact, Octave et al (2006a) demonstrated that proteins produced by E. lata, implicated in Eutypa dieback, may cause changes in mesophyll cells in leaves and vessel-associated cells in canes of Vitis vinifera cv.…”

“…Interestingly, an experiment on Eutypa dieback disease led to the identification of an electrophoretic pattern of proteins secreted by E. lata (Octave et al 2006a) that covers a large range of molecular weights from 6 to 200 kDa. These proteins are involved in cell structure damage and affect grapevine metabolism (Octave et al 2006b and.…”

Susceptibility of Cultivated and WildVitisspp. to Wood Infection by Fungal Trunk Pathogens

“…However, V. arizonica b42-26, which is resistant to the xylem-limited bacterium X. fastidiosa (30), was the most susceptible to E. lata and Eutypa sp. Tbat said, plant defense mechanisms against wood symptoms and foliar symptoms may differ (at least for Eutypa dieback and Esca) (39), because tbe foliar symptoms are tbougbt to result from the translocation of phytotoxic compounds from infected wood to the shoots and leaves (26), whereas the wood-canker symptoms are thought to result primarily from enzymatic decomposition of the wood (32). Because the center of origin for E. lata is thought to be Europe (41), co-evolution of the pathogen and V. vinifera may have enriched cultivars of this species for increased resistance to E. lata relative to the North American V. arizonica and V. aestivalis.…”

Identification of grapevine marker genes for early, non‐destructive Eutypa lata infection diagnosis

“…Antibodies have been raised against E. lata ascospores and hyphal material and used to identify the fungus by immunodiffusion and immunofluorescence (Francki & Carter, ). More recently, it has been shown that E. lata secretes various polypeptides (Octave et al ., ,b) and enzymes (Schmidt et al ., ) into its culture medium. Rabbit antibodies raised against these polypeptides were used to develop a sensitive and specific serological assay for the in planta identification of E .…”