van Bel Aart J E, Will Torsten
Institute of General Botany, Justus-Liebig-University Giessen, Germany.
Institute of Phytopathology, Justus-Liebig-UniversityGiessen, Germany; Institute for Resistance Research and Stress Tolerance, Federal Research Centre for Cultivated Plants, Julius-Kühn InstituteQuedlinburg, Germany.
Front Plant Sci. 2016 Dec 15;7:1840. doi: 10.3389/fpls.2016.01840. eCollection 2016.
Gel and watery saliva are regarded as key players in aphid-pIant interactions. The salivary composition seems to be influenced by the variable environment encountered by the stylet tip. Milieu sensing has been postulated to provide information needed for proper stylet navigation and for the required switches between gel and watery saliva secretion during stylet progress. Both the chemical and physical factors involved in sensing of the stylet's environment are discussed. To investigate the salivary proteome, proteins were collected from dissected gland extracts or artificial diets in a range of studies. We discuss the advantages and disadvantages of either collection method. Several proteins were identified by functional assays or by use of proteomic tools, while most of their functions still remain unknown. These studies disclosed the presence of at least two proteins carrying numerous sulfhydryl groups that may act as the structural backbone of the salivary sheath. Furthermore, cell-wall degrading proteins such a pectinases, pectin methylesterases, polygalacturonases, and cellulases as well as diverse Ca-binding proteins (e.g., regucalcin, ARMET proteins) were detected. Suppression of the plant defense may be a common goal of salivary proteins. Salivary proteases are likely involved in the breakdown of sieve-element proteins to invalidate plant defense or to increase the availability of organic N compounds. Salivary polyphenoloxidases, peroxidases and oxidoreductases were suggested to detoxify, e.g., plant phenols. During the last years, an increasing number of salivary proteins have been categorized under the term 'effector'. Effectors may act in the suppression (C002 or MIF cytokine) or the induction (e.g., Mp10 or Mp 42) of plant defense, respectively. A remarkable component of watery saliva seems the protein GroEL that originates from , the obligate symbiont of aphids and probably reflects an excretory product that induces plant defense responses. Furthermore, chitin fragments in the saliva may trigger defense reactions (e.g., callose deposition). The functions of identified proteins and protein classes are discussed with regard to physical and chemical characteristics of apoplasmic and symplasmic plant compartments.
凝胶状唾液和水样唾液被认为是蚜虫与植物相互作用中的关键因素。唾液成分似乎受口针尖端所遇到的多变环境影响。推测环境感知可为口针正确导航以及口针推进过程中凝胶状唾液和水样唾液分泌所需的转换提供所需信息。本文讨论了参与口针环境感知的化学和物理因素。为研究唾液蛋白质组，在一系列研究中从解剖的腺体提取物或人工饲料中收集蛋白质。我们讨论了每种收集方法的优缺点。通过功能测定或蛋白质组学工具鉴定了几种蛋白质，但其大多数功能仍不清楚。这些研究揭示了至少两种带有大量巯基的蛋白质的存在，它们可能作为唾液鞘的结构骨架。此外，还检测到细胞壁降解蛋白，如果胶酶、果胶甲酯酶、多聚半乳糖醛酸酶和纤维素酶，以及多种钙结合蛋白（如调节钙素、ARMET蛋白）。抑制植物防御可能是唾液蛋白的共同目标。唾液蛋白酶可能参与筛管分子蛋白的分解，以使植物防御失效或增加有机氮化合物的可用性。唾液多酚氧化酶、过氧化物酶和氧化还原酶被认为可使植物酚类物质解毒。在过去几年中，越来越多的唾液蛋白被归类为“效应子”。效应子可能分别作用于植物防御的抑制（如C002或MIF细胞因子）或诱导（如Mp10或Mp42）。水样唾液的一个显著成分似乎是源自蚜虫专性共生菌的蛋白质GroEL，它可能反映了一种诱导植物防御反应的排泄产物。此外，唾液中的几丁质片段可能引发防御反应（如胼胝质沉积）。本文根据质外体和共质体植物区室的物理和化学特性讨论了已鉴定蛋白质和蛋白质类别的功能。
