Zhang Hui, Lin Ruixun, Liu Qian, Lu Jianjun, Qiao Gexia, Huang Xiaolei
State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China.
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
Front Plant Sci. 2023 Jan 11;13:1098751. doi: 10.3389/fpls.2022.1098751. eCollection 2022.
Salivary glands and their secreted proteins play an important role in the feeding process of sap-sucking aphids. The determination of saliva composition is an important step in understanding host plant adaptation of aphids. Pseudoregma bambucicola is a severe bamboo pest in subtropical areas and the only aphid species that can exclusively feed on hard stalks of bamboos. How this species can penetrate and degrade hard bamboo cell walls and utilize a very specialized niche are important unanswered questions.
In this study, comprehensive analyses based on transcriptome sequencing, RT-qPCR, liquid chromatography-tandem spectrometry (LC-MS/MS) and bioinformatics were conducted on dissected salivary glands and secreted saliva of P. bambucicola to characterize the overall gene expression and salivary protein composition, and to identify putative effector proteins important for aphid-plant interactions.
Some secretory proteins homologous to known aphid effectors important for aphid-plant interactions, such as digestive enzymes, detoxifying and antioxidant enzymes and some effectors modulating plant defenses, are also detected in salivary gland transcriptome and salivary gland and/or saliva secretomes in P. bambucicola. This indicates that these effectors are probably be essential for enabling P. bambucicola feeding on bamboo host. Although several plant cell wall degrading enzymes (PCWDEs) can be identified from transcriptome, most of the enzymes identified in salivary glands showed low expression levels and they only represent a small fraction of the complete set of enzymes for degrading cellulose and hemicellulose. In addition, our data show that P. bambucicola has no its own ability to produce pectinases. Overall, our analyses indicate that P. bambucicola may lose its own ability to express and secrete key PCWDEs, and its adaptation to unique feeding habit may depend on its symbiotic bacteria.
唾液腺及其分泌的蛋白质在吸食树液的蚜虫取食过程中发挥着重要作用。确定唾液成分是了解蚜虫对寄主植物适应性的重要一步。竹伪角蚜是亚热带地区一种严重的竹子害虫，也是唯一一种能够专一取食竹子硬茎的蚜虫物种。该物种如何穿透并降解坚硬的竹细胞壁以及利用非常特殊的生态位，是尚未得到解答的重要问题。
在本研究中，对竹伪角蚜解剖后的唾液腺和分泌的唾液进行了基于转录组测序、逆转录定量聚合酶链反应（RT-qPCR）、液相色谱-串联质谱（LC-MS/MS）和生物信息学的综合分析，以表征整体基因表达和唾液蛋白质组成，并鉴定对蚜虫与植物相互作用重要的假定效应蛋白。
在竹伪角蚜的唾液腺转录组以及唾液腺和/或唾液分泌组中，也检测到了一些与已知对蚜虫与植物相互作用重要的蚜虫效应蛋白同源的分泌蛋白，如消化酶、解毒和抗氧化酶以及一些调节植物防御的效应蛋白。这表明这些效应蛋白可能对于竹伪角蚜取食竹寄主至关重要。尽管从转录组中可以鉴定出几种植物细胞壁降解酶（PCWDEs），但在唾液腺中鉴定出的大多数酶表达水平较低，它们仅占降解纤维素和半纤维素的完整酶集的一小部分。此外，我们的数据表明竹伪角蚜没有自身产生果胶酶的能力。总体而言，我们的分析表明竹伪角蚜可能失去了自身表达和分泌关键PCWDEs的能力，其对独特取食习性的适应可能依赖于其共生细菌。
