Salivary enzymes are injected into xylem by the glassy-winged sharpshooter, a vector of Xylella fastidiosa
Salivary enzymes are injected into xylem by the glassy-winged sharpshooter, a vector of Xylella fastidiosa
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DOI：
10.1016/j.jinsphys.2012.04.011
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发表时间：
2012-07-01
影响因子：
2.2
通讯作者：
Alhaddad, Hasan
中科院分区：
文献类型：
--
作者：
Backus, Elaine A.;Andrews, Kim B.;Alhaddad, Hasan
一些植食性半翅目物种，例如玻璃翅神枪手 Homalodisca vitripennis (Germar)，完全依靠木质部液体生存。尽管了解甚少，但昆虫唾液生理学的各个方面可能促进木质部取食和植物病原体的传播。苛养木杆菌 (Xylella fastidiosa) 是一种限制木质部的细菌，可引起葡萄皮尔斯病和许多重要作物的其他焦枯病。 X. fastidiosa 定殖于 H. vitripennis 和其他木质部取食媒介的前前肠（precibarium 和 cibarium）。细菌形成致密的生物膜，部分由胞外多糖 (EPS) 基质锚定，据报道，胞外多糖具有 β-1,4-葡聚糖骨架。最近发表的证据支持以下关于在载体喂养期间接种 X. fastidiosa 的唾液分泌假说。昆虫将唾液分泌到植物中，然后迅速吸收唾液和植物成分的混合物。在前壁中的湍流流体运动过程中，细菌可能会被机械和酶促排出：然后混合物通过管心针被排出到植物细胞中，可能包括木质部导管。本研究发现，根据目前有关这些多糖结构的信息，从解剖的 H. vitripennis 唾液腺中提取的蛋白质含有多种酶活性，能够水解多糖中的糖苷键，例如 EPS 和植物细胞壁中发现的糖苷键。通过对唾液腺蛋白提取物进行几个简单的纯化步骤，可以在唾液腺蛋白提取物中富集其中一种酶，即 β-1,4-内切葡聚糖酶 (EGase)。然后，富含 EGase 的提取物被用来生成多克隆抗血清，用于对葡萄中神枪手唾液鞘中的酶进行免疫组织化学成像。结果表明，在神枪手进食过程中，含酶的胶凝唾液被注入木质部血管中，在一种情况下，唾液被蒸腾流带离注射部位。因此，本研究为唾液分泌假说提供了支持。由爱思唯尔有限公司出版
A few phytophagous hemipteran species such as the glassy-winged sharpshooter, Homalodisca vitripennis, (Germar), subsist entirely on xylem fluid. Although poorly understood, aspects of the insect's salivary physiology may facilitate both xylem-feeding and transmission of plant pathogens. Xylella fastidiosa is a xylem-limited bacterium that causes Pierce's disease of grape and other scorch diseases in many important crops. X. fastidiosa colonizes the anterior foregut (precibarium and cibarium) of H. vitripennis and other xylem-feeding vectors. Bacteria form a dense biofilm anchored in part by an exopolysaccharide (EPS) matrix that is reported to have a beta-1,4-glucan backbone. Recently published evidence supports the following, salivation-egestion hypothesis for the inoculation of X. fastidiosa during vector feeding. The insect secretes saliva into the plant and then rapidly takes up a mixture of saliva and plant constituents. During turbulent fluid movements in the precibarium, the bacteria may become mechanically and enzymatically dislodged: the mixture is then egested back out through the stylets into plant cells, possibly including xylem vessels. The present study found that proteins extracted from dissected H. vitripennis salivary glands contain several enzyme activities capable of hydrolyzing glycosidic linkages in polysaccharides such as those found in EPS and plant cell walls, based on current information about the structures of those polysaccharides. One of these enzymes, a beta-1,4-endoglucanase (EGase) was enriched in the salivary gland protein extract by subjecting the extract to a few, simple purification steps. The EGase-enriched extract was then used to generate a polyclonal antiserum that was used for immunohistochemical imaging of enzymes in sharpshooter salivary sheaths in grape. Results showed that enzyme-containing gelling saliva is injected into xylem vessels during sharpshooter feeding, in one case being carried by the transpiration stream away from the injection site. Thus, the present study provides support for the salivation-egestion hypothesis. Published by Elsevier Ltd.