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The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama is the leading vector of Candidatus Liberibacter asiaticus ( C Las), the causative agent of citrus Huanglongbing (HLB) disease. The distribution and dynamics of C Las within ACP are critical to understanding how the transmission, spread and infection of C Las occurs within its host vector in nature. In this study, the distribution and titer changes of C Las in various tissues of ACP 5 th instar nymphs and adults were examined by fluorescence in situ hybridization (FISH) and real-time quantitative PCR (qPCR) techniques. Results demonstrated that 100% of ACP 5 th instar nymphs and adults were infected with C Las following feeding on infected plants, and that C Las had widespread distribution in most of the tissues of ACP. The titers of C Las within the midgut, salivary glands and hemolymph tissues were the highest in both 5 th instar nymphs and adults. When compared with adults, the titers of C Las in these three tissues of 5 th instar nymphs were significantly higher, while in the mycetome, ovary and testes they were significantly lower than those of adults. FISH visualization further confirmed these findings. Dynamic analysis of C Las demonstrated that it was present across all the developmental ages of ACP adults. There was a discernible upward trend in the presence of C Las with advancing age in most tissues of ACP adults, including the midgut, hemolymph, salivary glands, foot, head, cuticula and muscle. Our findings have significant implications for the comprehensive understanding of the transmission, dissemination and infestation of C Las, which is of much importance for developing novel strategies to halt the spread of C Las, and therefore contribute to the efficient prevention and control of HLB., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Guo, Kong, Mukangango, Hu, Liu, Sang and Qiu.)

Huanglongbing (HLB), a devastating citrus disease caused by Candidatus Liberibacter asiaticus, is efficiently vectored by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Tamarixia radiata (Waterston) plays a crucial role as an ectoparasitoid, preying on D. citri nymphs. By collecting and identifying headspace volatiles from fifth instar nymphs of D. citri using a gas chromatograph-mass spectrometer (GC-MS), we obtained a collection of 9 volatile compounds. These compounds were subsequently chosen to investigate the electrophysiological and behavioral responses of female T. radiata. At a concentration of 10 μg/μl, 9 compounds were compared with cis-3-hexen-1-ol (control), resulting in trans-2-nonenal inducing the highest relative electroantennogram (EAG) value, followed by hexanal, heptanal, n-heptadecane, tetradecanal, n-tetradecane, n-pentadecane, 1-tetradecanol, and 1-dodecanol. The top 5 EAG responses of female T. radiata to these compounds were further investigated through EAG dose-response experiments. The results showed positive dose-responses as concentrations increased from 0.01 to 10 μg/μl. In Y-tube olfactometer bioassays, female T. radiata exhibited a preference for specific compounds. They were significantly attracted to tetradecanal at a concentration of 10 µg/µl and trans-2-nonenal at 0.01 µg/µl, while no significant attraction was observed toward hexanal, heptanal, or n-heptadecane. Our report is the first to demonstrate that volatiles produced by D. citri nymphs attract T. radiata, which suggests that this parasitoid may utilize nymph volatiles to locate its host., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America.)

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is the key vector insect transmitting the Candidatus Liberibacter asiaticus ( C Las) bacterium that causes the devastating citrus greening disease (Huanglongbing, HLB) worldwide. The D. citri salivary glands (SG) exhibit an important barrier against the transmission of HLB pathogen. However, knowledge on the molecular mechanism of SG defence against C Las infection is still limited. In the present study, we compared the SG transcriptomic response of C Las-free and C Las-infected D. citri using an illumine paired-end RNA sequencing. In total of 861 differentially expressed genes (DEGs) in the SG upon C Las infection, including 202 upregulated DEGs and 659 downregulated DEGs were identified. Functional annotation analysis showed that most of the DEGs were associated with cellular processes, metabolic processes, and the immune response. Gene ontology and Kyoto Encyclopaedia of Genes and Genomes enrichment analyses revealed that these DEGs were enriched in pathways involving carbohydrate metabolism, amino acid metabolism, the immune system, the digestive system, the lysosome, and endocytosis. A total of 16 DEGs were randomly selected to further validate the accuracy of RNA-Seq dataset by reverse-transcription quantitative polymerase chain reaction. This study provides substantial transcriptomic information regarding the SG of D. citri in response to C Las infection, which may shed light on the molecular interaction between D. citri and C Las, and provides new ideas for the prevention and control of citrus psyllid.

The Asian citrus psyllid, Diaphorina citri Kuwayama, is among the most important pests of citrus. It is the main vector of the Huanglongbing (HLB) pathogen Candidatus Liberibacter asiaticus (CLas), which causes severe losses in citrus crops. Control of D. citri is therefore of paramount importance to reduce the spread of HLB. In this regard, using RNA interference (RNAi) to silence target genes is a useful strategy to control psyllids. In this study, using RNAi, we examined the biological functions of the V-ATPase subunit E (V-ATP-E) gene of D. citri, including its effect on acquisition of CLas. The amino acid sequence of V-ATP-E from D. citri had high homology with proteins from other insects. V-ATP-E was expressed at all D. citri life stages analyzed, and the expression level in mature adults was higher than that of teneral adults. Silencing of V-ATP-E resulted in a significant increase in mortality, reduced body weight, and induced cell apoptosis of the D. citri midgut. The reduced expression of V-ATP-E was indicated to inhibit CLas passing through the midgut and into the hemolymph, leading to a majority of CLas being confined to the midgut. In addition, double-stranded RNA of D. citri V-ATP-E was safe to non-target parasitic wasps. These results suggest that V-ATP-E is an effective RNAi target that can be used in D. citri control to block CLas infection., (© 2022 Institute of Zoology, Chinese Academy of Sciences.)

Blue light with a wavelength of 400-470 nm is the composition of the visible light. However, in recent years, blue light contributed the most significance to light pollution due to the artificial light at night. Previously, we have demonstrated that the Asian citrus psyllid (ACP), Diaphorina citri, an important pest in citrus production, has significant positive phototaxis with a light-emitting diode light of 400 nm. In this study, ACP with positive phototactic behavior to 400 nm light (PH) and non-phototactic behavior to 400 nm light (NP) were collected, individually. Transcriptome dynamics of head tissues of PH and NP groups were captured by using RNA-sequencing technology, respectively. Forty-three to 46 million clean reads with high-quality values were obtained, and 1773 differential expressed genes (DEGs) were detected. Compared with the NP group, there were 841 up-regulated DEGs and 932 down-regulated DEGs in the PH group. Eight pathways were significantly enriched in the PH group in the KEGG database, while 43 up-regulated pathways and 25 down-regulated pathways were significantly enriched in the PH group in the GO database. The DGE approach was reliable validated by real time quantitative PCR. Results indicated that the blue light acted as an abiotic stress causing physiological and biochemical responses such as oxidative stress, protein denaturation, inflammation and tumor development in ACPs. Additionally, the light was absorbed by photoreceptors of ACPs, and converted into electrical signal to regulate neuromodulation. This study provides basic information for understanding the molecular mechanisms of ACP in response to blue light and provides a reference for further studies to elucidate phototactic behavior., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Diaphorina citri is an important vector of Citrus Huanglongbing (HLB) disease. After feeding on young host plant shoots, the population of D. citri can increase significantly. Females also only lay eggs on young shoots. However, there are few studies on the mechanism of this phenomenon. Exogenous nutrient signals can affect the insulin signaling system of D. citri after feeding on young shoots. In this study, the expression of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system of D. citri was upregulated after feeding on young shoots. After being silenced by RNA interference technology, the results showed that the number of oviposited eggs of D. citri was significantly decreased and the ovarian development was inhibited with severe vacuolation. In addition, detection using quantitative reverse transcription-polymerase chain reaction showed that the upstream regulatory gene DcRheb of the target of rapamycin (TOR) pathway and the downstream reproduction-related DcVg gene were also significantly downregulated. These results suggest that feeding upon young shoots may upregulate the expression levels of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system. The signal will be through upregulating the expression of DcRheb, an upstream gene of the TOR signaling pathway. This in turn influences yolk metabolism, which eventually causes the ovaries of female D. citri to mature and therefore initiate oviposition behavior., (© 2022 The Authors. Insect Science published by John Wiley & Sons Australia, Ltd on behalf of Institute of Zoology, Chinese Academy of Sciences.)

Cardinium and Wolbachia are maternally inherited bacterial symbionts of arthropods that can manipulate host reproduction by increasing the fitness of infected females. Here, we report that Cardinium and Wolbachia coinfection induced male-killing and cytoplasmic incompatibility (CI) when they coexisted in a cryptic species of whitefly, Bemisia tabaci Asia II7. Cardinium and Wolbachia symbionts were either singly or simultaneously localized in the bacteriocytes placed in the abdomen of B. tabaci nymphs and adults. Cardinium-Wolbachia coinfection induced male-killing and resulted in a higher female sex ratio in the intraspecific amphigenetic progeny of Asia II7 I CWH and I CWL lines; interestingly, male-killing induction was enhanced with increased Cardinium titer. Moreover, single infection of Wolbachia induced partial CI in the Asia II7 I W line and resulted in reduced fecundity, higher embryonic mortality, and lower female sex ratio. The uninfected Asia II7 I U line had significantly higher fecundity, lower embryonic and nymphal mortalities, and a lower level of CI than both the Wolbachia-infected Asia II7 I W line and the Cardinium-Wolbachia-coinfected Asia II7 I CWH line. Our findings indicate that Cardinium-Wolbachia coinfection induced male-killing, which may have had antagonistic effects on Wolbachia-induced CI in the Asia II7 whiteflies. For the first time, our study revealed that B. tabaci Asia II7 reproduction is co-manipulated by Cardinium and Wolbachia endosymbionts., (© 2020 Institute of Zoology, Chinese Academy of Sciences.)

The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a severe agricultural pest that harbors at least seven endosymbionts. Many important aspects of the symbiosis mechanism between these bacterial endosymbionts and their hosts are poorly understood, such as endosymbiont proliferation dynamics, spatial distribution and titer regulation during host development. In this study, infection by bacterial endosymbionts in the whitefly B. tabaci Middle East-Asia Minor-1 (MEAM1, formerly B biotype) South China population, their infection titers in various stages of whitefly host development and their spatial localization were investigated. Results revealed that the MEAM1 B. tabaci harbors the primary symbiont Portiera and secondary symbionts Rickettsia and Hamiltonella. The titers of these three endosymbionts increased with the development of their B. tabaci host. Significant proliferation of Portiera and Hamiltonella mainly occurred during the second to fourth instar nymphal stages, while Rickettsia proliferated mainly during adult eclosion. Fluorescence in situ hybridization analysis of B. tabaci adults revealed three novel infection patterns of Rickettsia: assemblage in the bacteriocytes that scattered through the entire abdomen of the female host, localization in wax glands and localization in the colleterial gland. These novel infection patterns may help to uncover the function of Rickettsia in its insect hosts.