Octave Stéphane, Roblin Gabriel, Vachaud Magali, Fleurat-Lessard Pierrette
Université de Poitiers, Laboratoire de Physiologie et Biochimie Végétales, UMR CNRS 6161, Bâtiment Botanique, 40 Avenue du Recteur Pineau, F-86022 Poitiers, France.
Funct Plant Biol. 2006 Mar;33(3):297-307. doi: 10.1071/FP05230.
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.
葡萄藤顶枯病是由真菌病原体宽顶葡萄座腔菌引起的一种对酿酒葡萄极具破坏性的病害。这种寄生于木材中的真菌会降解受感染葡萄藤主干和主蔓中的组织，并在叶片上引发症状。这些症状被认为是由病原体产生的有毒代谢物，特别是顶枯菌素所致。最近，我们在人工培养条件下分离出了该真菌分泌的多肽化合物。本研究的目的是通过将多肽和顶枯菌素施用于离体的茎杆，来检测其在叶片中诱导产生的效应，并将其与宽顶葡萄座腔菌在葡萄园里引起的叶片结构变化进行比较。在取自感染宽顶葡萄座腔菌的葡萄藤的叶片中，叶肉细胞的变化表明该真菌对远离感染区域的组织也有影响。叶肉细胞的大小减小了一半以上，淀粉含量降低，单宁丰富。质体、线粒体和细胞壁都发生了高度改变。在用宽顶葡萄座腔菌的多肽处理过的健康茎杆的叶片中，叶肉细胞的结构也发生了改变。细胞大小没有变化，但单宁含量增加，质体和线粒体的变化与在取自受感染葡萄藤的叶片中观察到的相似。主要影响是细胞壁完全紊乱。顶枯菌素对细胞器结构的影响较小，且不会改变细胞壁。在用多肽处理的茎杆中，与导管相关的细胞（VACs）也受到了损害。VACs的液泡中出现了大量单宁，线粒体、质体和保护层有明显变化，特别是在导管界面处的纹孔中。在这些纹孔中，保护层、初生壁和中层均发生了高度改变。相比之下，用顶枯菌素处理会诱导在未改变的果胶纤维素壁旁形成一个大型转运装置。这些结果表明，用宽顶葡萄座腔菌产生的多肽处理可能会导致叶片中叶肉细胞和茎杆中VACs发生变化，这与在自然感染的葡萄藤中观察到的变化相似。相对而言，强调了与顶枯菌素作用的差异。两种毒素可能在体内协同作用，导致病害期间观察到的退化现象。
