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BACKGROUND The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a notorious pest that transmits the causal agent of huanglongbing (also called citrus greening disease). Resistance to insecticide in this destructive pest poses a serious threat to the citrus industry. To date, no systemic studies on genes coding for detoxification enzymes has been carried out on D. citri. RESULTS: Multiple transcriptomes were generated through deep sequencing of RNA libraries. Candidate genes potentially involved in detoxification including cytochrome P450 monooxygenases (CYPs), glutathione S‐transferases (GSTs), and esterases (ESTs) were systematically identified by searching the transcriptomes and a draft genome assembly. A total of 49, 14 and 20 genes were found encoding CYPs, GSTs, and ESTs, respectively, in D. citri. The total numbers of candidate detoxification genes were much smaller than the counterparts reported in other insect species, which may reflect the strict oligophagy of this insect species. Developmental stage‐ and tissue‐specific expression patterns of the identified genes as well as their responses to insecticide treatments identified a small set of genes that could participate in detoxifying plant secondary metabolites and insecticides. CONCLUSION: Our studies represent the most comprehensive investigation to date on identification, characterization and expression profiling of detoxification genes in D. citri. The information revealed in this study shall be useful in designing strategies to manage this important insect pest. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), can cause direct damage to citrus trees and is the main vector for the devastating disease, citrus greening disease or huanglongbing. Most molecular studies on this important insect pest use real-time reverse-transcription quantitative polymerase chain reaction (RT-qPCR) to quantify gene expression, including analyzing molecular basis for insecticide resistance in field populations. One critical factor to cause inaccuracy in RT-qPCR results is the lack of appropriate internal reference genes for optimal data normalization. In this study, the expression levels of 10 selected reference genes were evaluated in different tissue samples of psyllid adults and in the insects treated with different temperatures and insecticides. Data were analyzed using different computational algorithms, including Delta Ct, BestKeeper, NormFinder, geNorm, and RefFinder. According to our results, at least two reference genes should be used for the normalization of RT-qPCR data in this insect. The best choices of reference genes for different samples are as follows: ACT1 and Ferritin for different tissue samples, RPS20 and Ferritin for samples treated with different temperatures, TBP and EF1α for samples treated with imidacloprid, and Ferritin and TBP for samples treated with beta-cypermethrin. The reference genes identified in this study should be useful for future studies to analyze the expression patterns of target genes, especially for genes linked with temperature adaptability and insecticide resistance in this insect species in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • The metabolic changes in D. citri induced by two host plants were analyzed. • Six aquaporin genes in D. citri were identified. • The expression of osmotic regulation genes in D. citri altered by different plants. The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a worldwide citrus pest. It transmits the pathogen Candidatus Liberibacter spp. of Huanglongbing (HLB), causing severe economic losses to the citrus industry. Several genera of plants in the Rutaceae family are the hosts of D. citri. However, the impact of these hosts on the metabolism and osmotic regulation gene expression of the pest remains unexplored. In this study, the contents of total sugars, sucrose, fructose, and glucose in young shoots, old leaves, and young leaves of 'Shatangju' mandarin and Murraya exotica were analyzed. Metabolomic analysis found that sucrose and trehalose were more abundant in the gut samples of D. citri adults fed on M. exotica when compared to what's in 'Shatangju' mandarin. A total of six aquaporin genes were identified in D. citri through the genome and transcriptome data. Subsequently, the expression patterns of these genes were investigated with respect to their developmental stage and tissue specificity. Additionally, the expression levels of osmotic regulation and trehalose metabolism genes in adults fed on different plants were evaluated. Our results provide useful information on the transfer of sugar between plants and D. citri. Our results preliminary revealed the sugar metabolism regulation mechanism in D. citri adults. [ABSTRACT FROM AUTHOR]

• A strain of entomopathogenic fungus Clonostachys rosea was characterized. • C. rosea induced mortality in Diaphorina citri adults. • A total of 259 DEGs were identified in D. citri adults after inoculation with C. rosea. • Unigenes encoding proteins involved in immunity, apoptosis and cuticle were changed significantly. Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a serious pest of citrus. The insect also transmits Candidatus Liberibacter asiaticus, the pathogen of a devastating citrus disease called Huanglongbing. Clonostachys rosea is a versatile fungus that possesses nematicidal and insecticidal activities. The effect of C. rosea against D. citri remains unclear. Here we examined the pathogenicity of C. rosea against D. citri adults. A mortality rate of 46.67% was observed in adults treated with 1 × 108 conidia/mL spore suspension. Comparative transcriptomic analyses identified 259 differentially-expressed genes (DEGs) between controls and samples treated with fungi. Among the DEGs, 183 were up-regulated and 76 down-regulated. Genes with altered expression included those involved in immunity, apoptosis and cuticle formation. Our preliminary observation indicated that C. rosea is virulent against ACP adults and has the potential as a biological control agent for ACP management in the field. [ABSTRACT FROM AUTHOR]

• 118, 399 unigenes were obtained from the transcriptome data of Diaphorina citri adults. • 722 differentially expression genes were identified after heat stress. • HSPs, detoxification genes and cathepsins up-regulated after heat stress. • The protein synthesis and processing, metabolism and immunity pathways were enriched. The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a serious pest that feeds on plant phloem sap of citrus trees, and transmits Candidatus Liberibacter asiaticus, a bacterium that induces the destructive disease called Huanglongbing. Increasing evidence suggests that high temperatures could affect various biological traits, including size, longevity, mortality, behavior and metabolism of D. citri. However, the relevant mechanisms of heat stress remain unclear. In this study, a large set of transcriptomic data derived from D. citri adults were generated and differentially expressed genes (DEGs) after heat stress were identified by RNA sequencing. A total of 118, 399 unigenes were obtained, from which 37, 665 were mapped to sequences from at least one database. Seven hundreds and twenty-two unigenes were affected by high temperature of 40 °C for 4 h, in which 486 up-regulated and 236 down-regulated, and part of heat shock proteins, antioxidant and detoxification genes and cathepsins were identified as the DEGs. KEGG pathway enrichment analysis demonstrated that part of genes involved in protein synthesis and processing, metabolism, immunity, and signal transduction were differentially expressed under heat stress. Furthermore, the mRNA expression levels of 20 DEGs were confirmed by qRT-PCR, which verified the accuracy of high-throughput sequencing. Our results revealed that the response of D. citri adults to high temperatures is associated with a range of changes involved in various physiological and biochemical processes. Our data provide a basis for future research to improve our understanding on the molecular mechanism for heat responses in D. citri adults. [ABSTRACT FROM AUTHOR]