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INTRODUCTION

Aphids are phloem sap-sucking insects and are a serious destructive pest of several crop plants. Aphids are categorized as "generalists" or "specialists" depending on their host range. (Sulz.) is a generalist aphid with a broad host range while (Kalt.), a specialist aphid, has a narrow host range. Aphid infestation involves several sequential stages including host recognition and selection, overcoming primary plant defence barriers, feeding on phloem sap and detoxification of host defence responses. Information on the molecular basis of variations between generalist and specialist aphids with reference to the above processes is limited.

METHODS

In the current study, we generated transcriptome data of and from adult and nymph stages and analysed the differential expression of genes between adults of the generalist and specialist aphid and similarly, between nymphs of the two aphid species. We categorized these differentially expressed genes into nine different categories namely, chemosensation-related, plant cell wall degrading enzymes, detoxification-related, digestive enzymes, peptidases, carbohydrate-, lipid-, amino acid-metabolism and reproduction. We also identified putative effector molecules in both and from the transcriptome data.

RESULTS AND DISCUSSION

Gene expression analysis identified 7688 and 8194 differentially expressed unigenes at adult and nymph stages, respectively of and showed significantly higher levels of expression in a greater number of unigenes (5112 in adults and 5880 in nymphs) in contrast to the specialist, (2576 in adults and 2314 in nymphs) in both developmental stages. In addition, displayed a greater number (350 in adults and 331 in nymphs) of upregulated unigenes involved in important processes such as host recognition, plant cell wall degradation, detoxification, digestion and metabolism, which correlate with its dynamic and polyphagous nature in contrast to the specialist (337 in adults and 251 in nymphs). We also observed a greater number of putative effectors in (948 in adults and 283 in nymphs) than (797 in adults and 245 in nymphs). Based on our analysis, we conclude that the generalist aphid, has a more diversified and stronger arsenal of genes that influence its polyphagous feeding behaviour and effective response to plant defence mechanisms against insect-herbivory. Our study provides a compendium of such candidate genes that would be most useful in studies on aphid biology, evolution and control.

INTRODUCTION

METHODS

RESULTS AND DISCUSSION

引言

蚜虫是以韧皮部汁液为食的昆虫，是几种农作物的严重破坏性害虫。根据宿主范围，蚜虫可分为“多食性”或“寡食性”。（苏尔茨）是一种多食性蚜虫，宿主范围广泛，而（卡尔特）是一种寡食性蚜虫，宿主范围狭窄。蚜虫侵染涉及几个连续阶段，包括宿主识别与选择、克服植物初级防御屏障、取食韧皮部汁液以及对宿主防御反应进行解毒。关于多食性和寡食性蚜虫在上述过程中差异的分子基础的信息有限。

方法

在本研究中，我们生成了成年和若虫阶段的[多食性蚜虫名称]和[寡食性蚜虫名称]的转录组数据，并分析了多食性和寡食性蚜虫成虫之间以及两种蚜虫若虫之间基因的差异表达。我们将这些差异表达基因分为九个不同类别，即化学感应相关、植物细胞壁降解酶、解毒相关、消化酶、肽酶、碳水化合物、脂质、氨基酸代谢和繁殖。我们还从转录组数据中鉴定了[多食性蚜虫名称]和[寡食性蚜虫名称]中的假定效应分子。

结果与讨论

基因表达分析分别在成年和若虫阶段鉴定出7688个和8194个差异表达的单基因，[多食性蚜虫名称]在两个发育阶段的大量单基因（成年期5112个，若虫期5880个）中显示出显著更高的表达水平，相比之下，寡食性蚜虫[寡食性蚜虫名称]（成年期2576个，若虫期2314个）。此外，[多食性蚜虫名称]在参与宿主识别、植物细胞壁降解、解毒、消化和代谢等重要过程的上调单基因数量上更多（成年期350个，若虫期331个），这与其动态和多食性的特性相关，而寡食性蚜虫[寡食性蚜虫名称]则较少（成年期337个，若虫期251个）。我们还观察到[多食性蚜虫名称]中的假定效应分子数量比[寡食性蚜虫名称]更多（成年期948个，若虫期283个，而[寡食性蚜虫名称]分别为成年期797个和若虫期245个）。基于我们的分析，我们得出结论，多食性蚜虫[多食性蚜虫名称]拥有更多样化且更强的基因库，这些基因影响其多食性取食行为以及对植物抗虫防御机制的有效反应。我们的研究提供了这样一份候选基因清单，这在蚜虫生物学、进化和防治研究中将非常有用。