Unit Fruit Science, Technische Universität München, Dürnast 2, D-85354 Freising-Weihenstephan, Germany.
Plant Physiol Biochem. 2013 Nov;72:62-71. doi: 10.1016/j.plaphy.2013.03.011. Epub 2013 Mar 23.
Products containing the epiphytic yeast Aureobasidium pullulans are commercially available and applied by fruit growers to prevent several fungal and bacterial diseases of fruit trees. The proposed beneficial mechanisms relate to limitations of space and nutrients for the pathogens in presence of the rapidly proliferating yeast cells. These explanations ignore the potential of yeasts to elicit the plant's defense. Our experiments aim at clarifying if an autoclaved and centrifuged suspension of A. pullulans may induce defense mechanisms. As a model system, the biosynthesis and accumulation of stilbene phytoalexins in callus and shoots of grapevine Vitis vinifera grown in vitro was used. Yeast application to the plant tissue stimulated stilbene biosynthesis, sometimes at the cost of flavonoids. The expression of the gene encoding stilbene synthase was enhanced and the enzyme showed higher activity while chalcone synthase activity and expression was reduced in some cases. An accumulation of stilbenes was also found in transgenic apple trees (Malus domestica cv. Holsteiner Cox) harboring the stilbene synthase-gene under control of its own promoter. These results clearly show that the application of A. pullulans may induce defense mechanisms of the treated plants.
含有附生酵母出芽短梗霉的产品可从商业途径获得，并被果农应用于预防多种真菌和细菌性的果树疾病。所提出的有益机制与在快速增殖的酵母细胞存在的情况下病原体空间和营养限制有关。这些解释忽略了酵母引发植物防御的可能性。我们的实验旨在阐明经高压灭菌和离心的出芽短梗霉悬浮液是否可能诱导防御机制。作为一个模型系统，我们使用了在体外生长的葡萄属葡萄愈伤组织和芽中芪类植物抗毒素的生物合成和积累。酵母应用于植物组织刺激芪类生物合成，有时以黄酮类化合物为代价。编码芪合酶的基因表达增强，并且在某些情况下，酶表现出更高的活性，同时查尔酮合酶活性和表达降低。在携带受自身启动子控制的芪合酶基因的转基因苹果树上（Malus domestica cv. Holsteiner Cox）也发现了芪类物质的积累。这些结果清楚地表明，出芽短梗霉的应用可能诱导处理植物的防御机制。
