Asian Citrus Psyllid Expression Profiles Suggest <i>Candidatus</i> Liberibacter Asiaticus-Mediated Alteration of Adult Nutrition and Metabolism, and of Nymphal Development and Immunity

The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the insect vector of the fastidious bacterium Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening disease, or Huanglongbing (HLB). The widespread invasiveness of the psyllid vector and HLB in citrus trees worldwide has underscored the need for non-traditional approaches to manage the disease. One tenable solution is through the deployment of RNA interference technology to silence protein-protein interactions essential for ACP-mediated CLas invasion and transmission. To identify psyllid interactor-bacterial effector combinations associated with psyllid-CLas interactions, cDNA libraries were constructed from CLas-infected and CLas-free ACP adults and nymphs, and analyzed for differential expression. Library assemblies comprised 24,039,255 reads and yielded 45,976 consensus contigs. They were annotated (UniProt), classified using Gene Ontology, and subjected to in silico expression analyses using the Transcriptome Computational Workbench (TCW) (http://www.sohomoptera.org/ACPPoP/). Functional-biological pathway interpretations were carried out using the Kyoto Encyclopedia of Genes and Genomes databases. Differentially expressed contigs in adults and/or nymphs represented genes and/or metabolic/pathogenesis pathways involved in adhesion, biofilm formation, development-related, immunity, nutrition, stress, and virulence. Notably, contigs involved in gene silencing and transposon-related responses were documented in a psyllid for the first time. This is the first comparative transcriptomic analysis of ACP adults and nymphs infected and uninfected with CLas. The results provide key initial insights into host-parasite interactions involving CLas effectors that contribute to invasion-virulence, and to host nutritional exploitation and immune-related responses that appear to be essential for successful ACP-mediated circulative, propagative CLas transmission.亚洲柑橘木虱（Asian citrus psyllid，ACP）*Diaphorina citri* Kuwayama（半翅目：木虱科）是难培养细菌亚洲韧皮部杆菌（Candidatus Liberibacter asiaticus，CLas）的昆虫媒介，该细菌是柑橘黄龙病（citrus greening disease，又名Huanglongbing，HLB）的致病原。该木虱媒介与HLB在全球柑橘种植区的广泛扩散，凸显了采用非传统手段防控该病害的迫切需求。一种可行的防控策略是利用RNA干扰（RNA interference，RNAi）技术，沉默ACP介导CLas入侵与传播所必需的蛋白质-蛋白质相互作用。为筛选与木虱-CLas互作相关的木虱互作蛋白-细菌效应蛋白组合，研究人员从感染CLas与未感染CLas的ACP成虫和若虫中构建互补DNA（complementary DNA，cDNA）文库，并开展差异表达分析。该文库的组装共获得24,039,255条读段（reads），并得到45,976个一致性重叠群（consensus contigs）。研究人员对其进行了UniProt注释、基因本体论（Gene Ontology，GO）分类，并利用转录组计算工作台（Transcriptome Computational Workbench，TCW，http://www.sohomoptera.org/ACPPoP/）开展了计算机模拟表达分析。研究人员利用京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes，KEGG）数据库进行功能生物学通路注释。成虫和/或若虫中差异表达的一致性重叠群，对应参与黏附、生物被膜形成、发育相关过程、免疫、营养、应激以及毒力的基因和/或代谢/致病通路。值得注意的是，本研究首次在木虱中记录了参与基因沉默以及转座子相关应答的一致性重叠群。本研究是首次针对感染与未感染CLas的ACP成虫和若虫开展的比较转录组学分析。本研究结果为解析CLas效应蛋白介导的宿主-寄生物互作（该互作与入侵毒力相关），以及宿主营养利用与免疫相关应答提供了关键的初步见解——而这些过程似乎是ACP介导的循环性、增殖性CLas成功传播所必需的。