Reference gene selection for qRT-PCR analysis in the sweetpotato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae)

Evaluation of reference genes and expression patterns of CONSTANS-LIKE genes in Tetrastigma hemsleyanum under different photoperiods

CONSTANS-LIKE (COL ) genes are a key signalling molecule that regulates plant growth and development during the photoperiod. Our preliminary experiments showed that the photoperiod greatly influence the formation of Tetrastigma hemsleyanum root tubers. In this study, we examined the oscillation patterns and expression characteristics of COL genes in leaves of T. hemsleyanum under different photoperiod conditions. Six genes were selected as candidate reference genes for further analyses: (1) 18S ribosomal RNA (18S rRNA ); (2) α-tubulin (TUBA ); (3) 30S ribosomal RNA (30S rRNA ); (4) TATA binding protein (TBP ); (5) elongation factor 1α (EF-1α ); and (6) RNA polymerase II (RPII ). The geNorm, NormFinder, and BestKeeper software programs were used to evaluate expression stability. Two ThCOL genes were screened in the T. hemsleyanum transcriptome library, and their expression patterns under different photoperiod conditions were analysed using quantitative reverse transcription PCR. The genes EF-1α , TUBA , and 18S rRNA were used to analyse the expression profiles of CONSTANS genes (ThCOL4 and ThCOL5 ) under different photoperiods. The expression peaks of ThCOL4 and ThCOL5 appeared at different times, demonstrating that their oscillation patterns were influenced by the photoperiod. We speculate that these two ThCOL genes may be involved in different biological processes.

Variations in the expression of odorant binding and chemosensory proteins in the developmental stages of whitefly Bemisia tabaci Asia II-1

The cotton whitefly, Bemisia tabaci, is considered as a species complex with 46 cryptic species, with Asia II-1 being predominant in Asia. This study addresses a significant knowledge gap in the characterization of odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) in Asia II-1. We explored the expression patterns of OBPs and CSPs throughout their developmental stages and compared the motif patterns of these proteins. Significant differences in expression patterns were observed for the 14 OBPs and 14 CSPs of B. tabaci Asia II-1, with OBP8 and CSP4 showing higher expression across the developmental stages. Phylogenetic analysis reveals that OBP8 and CSP4 form distinct clades, with OBP8 appearing to be an ancestral gene, giving rise to the evolution of other odorant-binding proteins in B. tabaci. The genomic distribution of OBPs and CSPs highlights gene clustering on the chromosomes, suggesting functional conservation and evolutionary events following the birth-and-death model. Molecular docking studies indicate strong binding affinities of OBP8 and CSP4 with various odour compounds like β-caryophyllene, α-pinene, β-pinene and limonene, reinforcing their roles in host recognition and reproductive functions. This study elaborates on our understanding of the putative roles of different OBPs and CSPs in B. tabaci Asia II-1, hitherto unexplored. The dynamics of the expression of OBPs and CSPs and their interactions with odour compounds offer scope for developing innovative methods for controlling this global invasive pest.

Silencing of catalase reduces unfavorable low-temperature tolerance capacity in whiteflies

BACKGROUND

Temperature is a primary factor that determines the eco-geographical distribution and population development of invasive insects. Temperature stress leads to various negative effects, including excess reactive oxygen species (ROS), and catalase (CAT) is a key enzyme against ROS in the antioxidant pathway. The whitefly Bemisia tabaci MED is a typical invasive pest that causes damage worldwide. Our previous studies have shown that CAT promotes whitefly adaptation to high temperature by eliminating ROS. However, the mechanism underlying the low-temperature adaptation of whiteflies is still unknown.

RESULTS

In this study, we investigated the role of CAT in the low-temperature tolerance of B. tabaci MED by analyzing its survival rate, reproduction, and ROS levels at 25 °C (as a control, suitable temperature), 20 °C (moderately decreased temperature), and 4 °C (severely decreased temperature). Silencing of BtCAT1, BtCAT2, or BtCAT3 reduced the viability of whiteflies under a short-term severely decreased temperature (4 °C), which manifested as decreases in survival and fecundity accompanied by significant increases in ROS levels. Moreover, even at a moderately decreased temperature (20 °C), silencing of BtCAT1 led to high ROS levels and low survival rates in adults.

CONCLUSION

Silencing of BtCATs significantly increased the sensitivity of B. tabaci MED to low temperatures. BtCAT1 is likely more essential than other BtCATs for low-temperature tolerance in whiteflies. © 2024 Society of Chemical Industry.

Effect of High Temperature on Abamectin and Thiamethoxam Tolerance in Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae)

Bemisia tabaci (Gennadius) is one of the most important invasive species in China, with strong insecticide resistance and thermotolerance. In this study, we investigated the effects of elevated temperature on the tolerance of B. tabaci MEMA1 to abamectin (AB) and thianethixam (TH) insecticides. We firstly cloned two new CYP450 genes from B. tabaci MEAM1, including one CYP6 family gene (BtCYP6k1) and one CYP305 family gene (BtCYP305a1). The expression patterns of the two BtCYP450 genes were compared in response to high-temperature stress and insecticide exposure, and RNAi was then used to demonstrate the role that these two genes play in insecticide tolerance. The results showed that expression of the two BtCYP450 genes could be induced by exposure to elevated temperature or insecticide, but this gene expression could be inhibited to a certain extent when insects were exposed to the combined effects of high temperature and insecticide treatment. For AB treatment, the expression of the two BtCYP450 genes reached the lowest level when insects were exposed to a temperature of 41 °C and treated with AB (combined effects of temperature and insecticide). In contrast, TH treatment showed a general decrease in the expression of the two BtCYP450 genes with exposure to elevated temperatures. These findings suggest that insecticide tolerance in B. tabaci MEAM1 could be mediated by high temperatures. This study provides a prospective method for the more effective application of insecticides for the control of B. tabaci in the field.

Stability evaluation of candidate reference genes for real-time qPCR normalization in Rhyzopertha dominica (Coleoptera: Bostrycidae)

Rhyzopertha dominica is a serious stored grain insect pest around the world. Real-time quantitative polymerase chain reaction (RT-qPCR) is a widely used experimental method in molecular biology for detecting the expression of target genes. As appropriate reference genes are essential for normalizing gene expression, the selection of suitable reference genes is the basis of RT-qPCR experiments. In this study, the expression profiles of 7 candidate reference genes of rps3, rps6, rps13, actin, gadph, tubulin, and 18S rRNA were analyzed under 4 different experimental conditions. The expression stability of candidate genes was evaluated using the ΔCt, GeNorm, BestKeeper, NormFinder, and RefFinder methods. The results revealed that different reference genes were suitable for various experiments. Specifically, rps3 and rps6 were appropriate for the developmental stages and all samples: 18S rRNA and rps13 for temperature-related experiments, actin and rps6 for sex-related experiments, and rps6 and gadph for starvation stress. Our results lay essential groundwork for the normalization of RT-qPCR analyses and contribute to genomic and gene functional research of R. dominica.

Transcriptomic Identification and Characterization of Trehalose-6-Phosphate Synthase in Fat Body of the Oriental Fruit Fly, Bactrocera dorsalis

The destructive agricultural pest oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), has been causing huge damage to the fruits and vegetable industry. Although many pertinent studies have been conducted on B. dorsalis, the functions of fat body still remain largely unknown. To this end, the comparative transcriptome analysis between fat body and carcass was performed in an attempt to provide insights into functions of fat body of B. dorsalis in the present study. A total of 1431 upregulated and 2511 downregulated unigenes were discovered in the fat body vs carcass comparison, respectively. The enrichment analysis of differentially expressed genes (DEG) revealed that most of the enriched pathways were related to metabolism. The reliability of DEG analysis was validated by qRT-PCR measurements of 12 genes in starch and sucrose metabolism pathway, including the trehalose-6-phosphate synthase (BdTPS) which was highly expressed in eggs, 5 d-old adults, and fat body. The RNAi of BdTPS significantly affected trehalose and chitin metabolism, larval growth, and larva-pupa metamorphosis. Collectively, the findings in this study enriched our understanding of fat body functions in metabolism and demonstrated the indispensable roles of BdTPS in trehalose-related physiological pathways.

Comprehensive Assessment of Reference Gene Expression within the Whitefly Dialeurodes citri Using RT-qPCR

The citrus whitefly, Dialeurodes citri, is a destructive pest that infests citrus plants. It is a major vector in transmitting plant viruses such as citrus yellow vein clearing virus (CYVCV), which has caused severe economic losses worldwide, and therefore efficient control of this pest is economically important. However, the scope of genetic studies primarily focused on D. citri is restricted, something that has potentially limited further study of efficient control options. To explore the functionalities of D. citri target genes, screening for specific reference genes using RT-qPCR under different experimental conditions is essential for the furtherance of biological studies concerning D. citri. The eight candidate reference genes were evaluated by dedicated algorithms (geNorm, Normfinder, BestKeeper and ΔCt method) under five specific experimental conditions (developmental stage, sex, tissue, population and temperature). In addition, the RefFinder software, a comprehensive evaluation platform integrating all of the above algorithms, ranked the expression stability of eight candidate reference genes. The results showed that the best reference genes under different experimental settings were V-ATP-A and RPS18 at different developmental stages; α-tubulin, 18S and V-ATP-A in both sexes; EF1A and α-tubulin in different tissues; Actin and Argk under different populations; and RPS18 and RPL13 in different temperatures. The validation of selected reference genes was further identified using heat shock protein (Hsp) 70 as a reporter gene. Our study, for the first time, provides a detailed compilation of internal reference genes for D. citri that are suitable for RT-qPCR analysis, which is robust groundwork for comprehensive investigation of the functional target genes of D. citri.

Dual mutations in the whitefly nicotinic acetylcholine receptor β1 subunit confer target-site resistance to multiple neonicotinoid insecticides

Neonicotinoid insecticides, which target insect nicotinic acetylcholine receptors (nAChRs), have been widely and intensively used to control the whitefly, Bemisia tabaci, a highly damaging, globally distributed, crop pest. This has inevitably led to the emergence of populations with resistance to neonicotinoids. However, to date, there have been no reports of target-site resistance involving mutation of B. tabaci nAChR genes. Here we characterize the nAChR subunit gene family of B. tabaci and identify dual mutations (A58T&R79E) in one of these genes (BTβ1) that confer resistance to multiple neonicotinoids. Transgenic D. melanogaster, where the native nAChR Dβ1 was replaced with BTβ1A58T&R79E, were significantly more resistant to neonicotinoids than flies where Dβ1 were replaced with the wildtype BTβ1 sequence, demonstrating the causal role of the mutations in resistance. The two mutations identified in this study replace two amino acids that are highly conserved in >200 insect species. Three-dimensional modelling suggests a molecular mechanism for this resistance, whereby A58T forms a hydrogen bond with the R79E side chain, which positions its negatively-charged carboxylate group to electrostatically repulse a neonicotinoid at the orthosteric site. Together these findings describe the first case of target-site resistance to neonicotinoids in B. tabaci and provide insight into the molecular determinants of neonicotinoid binding and selectivity.

Evaluation of Reference Genes for Quantitative Real-Time PCR Analysis in the Bean Bug, Riptortus pedestris (Hemiptera: Alydidae)

Quantitative real-time PCR (qRT-PCR) is widely accepted as a precise and convenient method for quantitatively analyzing the expression of functional genes. The data normalization strongly depends upon stable reference genes. The bean bug, Riptortus pedestris (Hemiptera: Alydidae), is a significant pest of leguminous crops and broadly distributed across Southeast Asia. In this study, a total of 16 candidate reference genes (RPL32, RPS23, SDHA, UBQ, UCCR, GST, TATA-box, HSP70, GAPDH, RPL7A, SOD, RPS3, Actin, α-tubulin, AK, and EF1) were carefully chosen in R. pedestris, and their expression levels were assessed across various conditions, including different developmental stages, diverse tissues, temperature treatments, adult age, molting time, and mating status. Following this, the stability of these reference genes was evaluated using four algorithms (ΔCt, GeNorm, NormFinder, and BestKeeper). Ultimately, the comprehensive rankings were determined using the online tool RefFinder. Our results demonstrate that the reference gene for qRT-PCR analysis in R. pedestris is contingent upon the specific experimental conditions. RPL7A and EF1 are optimal reference genes for developmental stages. Furthermore, α-tubulin and EF1 exhibit the most stable expression across various adult tissues. RPL32 and RPL7A exhibit the most stable expression for adult age. For nymph age, RPL32 and SOD display the most stable expression. For temperature conditions, RPS23 and RPL7A were identified as the most suitable for monitoring gene expression. Lastly, we verified the practicability of evaluating expression levels of odorant-binding protein 37 (RpedOBP37) and cytochrome P450 6a2 (RpedCYP6) throughout developmental stages, tissues, and temperature conditions. These findings are a significant addition to the qRT-PCR analysis studies on R. pedestris, serving as a fundamental groundwork for future investigations on stable reference genes in R. pedestris as well as other organisms.

Catalase promotes whitefly adaptation to high temperature by eliminating reactive oxygen species

Thermal stress usually leads to excessive production of reactive oxygen species (ROS) in all aerobic organisms. Catalases (CAT) are the key antioxidant enzymes, which act as the first line of defense against ROS in the antioxidant pathway. The highly invasive and widely distributed whitefly Bemisia tabaci MED damages plants by feeding as well as by transmitting many plant viruses. Previous studies have shown that strong adaptability to high temperature helps explain the spread of MED around the world. However, the mechanism underlying high temperature adaptation of this pest is not well understood. In this study, 6 CAT genes were identified from the MED genome and transcriptome dataset, among which BtCAT1, BtCAT2, and BtCAT3 were found to be highly expressed in adults. The expression of BtCAT1, BtCAT2, or BtCAT3 increased with induction temperature and induction time. The MED was exposed with mean high temperature (30 °C or 35 °C) and a short-term extremely high temperature (39 °C or 41 °C) after the silencing of BtCAT1, BtCAT2, or BtCAT3 to significantly increased ROS levels by at least 0.5 times and significantly decreased survival rate and fecundity of MED adults. The ROS level in the treated specimens gradually returned to a normal level after 24 h at 25 °C, but the survival rate still declined significantly. Taken together, our results demonstrate that CAT could help B. tabaci adapt to long-term mean high temperatures and short-term extremely high temperatures by eliminating excessive ROS.

20E biosynthesis gene CYP306A1 confers resistance to imidacloprid in the nymph stage of Bemisia tabaci by detoxification metabolism

BACKGROUND

Difference in physiology level between the immature and mature stages of insects likely contribute to different mechanisms of insecticide resistance. It is well acknowledged that insect 20-hydroxyecdysone (20E) plays an important role in many biological processes in the immature stage, whether 20E confers insecticide resistance at this specific stage is still poorly understood. By gene cloning, reverse transcription quantitative real-time PCR, RNA interference (RNAi) and in vitro metabolism experiments, this study aimed to investigate the potential role of 20E-related genes in conferring imidacloprid (IMD) resistance in the immature stage of the whitefly Bemisia tabaci Mediterranean.

RESULTS

After identification of low to moderate IMD resistance in the whitefly, we found CYP306A1 of the six 20E-related genes was overexpressed in the nymph stage of the three resistant strains compared to a laboratory reference susceptible strain, but not in the adult stage. Further exposure to IMD resulted in an increase in CYP306A1 expression in the nymph stage. These results together imply that CYP306A1 may be implicated in IMD resistance in the nymph stage of the whitefly. RNAi knockdown of CYP306A1 increased the mortality of nymphs after treatment with IMD in bioassay, suggesting a pivotal role of CYP306A1 in conferring IMD resistance in the nymph stage. Additionally, our metabolism experiments in vivo showed that the content of IMD reduced by 20% along with cytochrome P450 reductase and heterologously expressed CYP306A1, which provides additional evidence for the important function of CYP306A1 in metabolizing IMD that leads to the resistance.

CONCLUSION

This study uncovers a novel function of the 20E biosynthesis gene CYP306A1 in metabolizing imidacloprid, thus contributing to such resistance in the immature stage of the insect. These findings not only advance our understanding of 20E-mediated insecticide resistance, but also provide a new target for sustainable pest control of global insect pests such as whitefly. © 2023 Society of Chemical Industry.

Knockdown of the Nicotinic Acetylcholine Receptor β1 Subunit Decreases the Susceptibility to Five Neonicotinoid Insecticides in Whitefly (Bemisia tabaci)

The sweet potato whitefly, Bemisia tabaci, (Gennadius) (Hemiptera:Aleyrodidae) is a global pest of crops. Neonicotinoids are efficient insecticides used for control of this pest. Insecticidal targets of neonicotinoids are insect nicotinic acetylcholine receptors (nAChRs). Here, we characterized and cloned the full length of the nAChR β1 subunit (BTβ1) in B. tabaci and confirmed the consistency of BTβ1 in B. tabaci MEAM1 and MED. Expression levels of BTβ1 in different developmental stages and body parts of adults were investigated and compared in B. tabaci MED. dsRNA was prepared to knock down BTβ1 in adult B. tabaci and significantly decreases the susceptibility to five neonicotinoid insecticides, including imidacloprid, clothianidin, thiacloprid, nitenpyram, and dinotefuran. This study indicated BTβ1 as a notable site influencing the susceptibility of B. tabaci to neonicotinoids.

Zinc finger protein 330 regulates Ramie mosaic virus infection in the whitefly Bemisia tabaci MED

BACKGROUND

The whitefly, Bemisia tabaci (Gennadius) is one of the most economically important pests that cause serious damage to agricultural production by transmitting plant pathogenic viruses. Approximately 90% of the virus species transmitted by the whitefly are members of the genus begomovirus. Ramie mosaic virus (RaMoV) is a new bipartite begomovirus that causes severe damage to ramie and several other economic crops in China. In previous studies, we have demonstrated that RaMoV had no obvious direct or indirect effects on B. tabaci. However, whether B. tabaci affects RaMoV infection and the molecular mechanisms of their interaction remain unclear.

RESULTS

Here, we identified a zinc finger protein 330 (ZNF330) in B. tabaci MED interacted with the coat protein (CP) of RaMoV by the yeast two-hybrid assay. Then the interaction between ZNF330 and RaMoV CP was further verified by glutathione S-transferase (GST) pull-down assay. The expression of ZNF330 gene was continuously induced after RaMoV infection. ZNF330 negatively regulated RaMoV replication in the B. tabaci MED. Furthermore, the longevity and fecundity of RaMoV-infected female adults were significantly decreased after silencing of ZNF330.

CONCLUSIONS

Our results indicated that the ZNF330 protein was involved in the negative regulation of RaMoV replication in the B. tabaci MED. High viral accumulation caused by ZNF330 silencing is detrimental to fecundity and longevity of the B. tabaci MED. These findings provided a new insight into identifying the binding partners in whitefly with viral CP and fully understanding the complex interactions between begomoviruses and their whitefly vector. © 2023 Society of Chemical Industry.

Resistance to dinotefuran in Bemisia tabaci in China: status and characteristics

BACKGROUND

Bemisia tabaci (Gennadius) is a serious agricultural pest worldwide. Neonicotinoids are the most important new class of synthetic insecticides used in the management of B. tabaci. However, B. tabaci populations have developed resistance to various active ingredients in neonicotinoids following long-term and widespread application.

RESULTS

Dinotefuran exhibited high toxicity against most B. tabaci field populations. One population (Din-R) with a high level of resistance to dinotefuran (255.6-fold) was first identified in the field. The Din-R population exhibited medium to high levels of resistance to all the tested neonicotinoid insecticides and a high level of resistance to spinetoram. Genetic inheritance analysis revealed that resistance to dinotefuran was incompletely recessive and polygenic. The synergist piperonyl butoxide significantly increased the toxicity of dinotefuran to Din-R. P450 activity in the Din-R population was 2.19-fold higher than in the susceptible population. RNA-sequencing analysis showed that 12 P450 genes were significantly upregulated in the Din-R population, of which CYP6DW5, CYP6JM1 and CYP306A1 were found to exhibit more than 3.00-fold higher expression in Din-R when using a reverse transcription quantitative real-time polymerase chain reaction. Expression of eight P450 genes was obviously induced by dinotefuran, and CYP6DW5 showed the highest expression level. After knockdown of CYP6DW5 in Din-R, the toxicity of dinotefuran increased significantly.

CONCLUSION

P450 had a crucial role in dinotefuran resistance in B. tabaci, and CYP6DW5 was involved in the resistance. These results provide important information for the management of resistance in B. tabaci and improve our understanding of the resistance mechanism of dinotefuran. © 2022 Society of Chemical Industry.

Reference genes selection for expression studies in Maconellicoccus hirsutus (Green) (Pseudococcidae: Hemiptera) under specific experimental conditions

BACKGROUND

Maconellicoccus hirsutus is a destructive pest which causes severe losses of agricultural and horticultural crops. For the management of M. hirsutus, many insecticides have been used and it has been exposed to insufficient dosage or uneven spray coverage which resulted in the development of insecticide resistance. Xenobiotic metabolism can be better understood with the help of gene expression studies by unveiling the underlying molecular mechanisms. The qRT-PCR is the simplest method to analyse gene expression, however, it highly relies on suitable reference genes concerning the different experimental conditions.

METHODS AND RESULTS

We evaluated the stability of five reference genes in two sets of experimental conditions viz. developmental stages (nymphs and adults) and agrochemical stress (GA3 and Buprofezin sprayed) against M. hirsutus, using different softwares-NormFinder, geNorm, BestKeeper, and RefFinder. The study revealed that ATP51a and GAPDH can be used as reference genes for gene expression studies when exposed to Gibberellic acid. Additionally, the study revealed that the ideal pair of reference genes for data validation in M. hirsutus treated with Buprofezin was GAPDH and β-tubulin. The ideal reference gene combination for various developmental stages was found to be 28S and Actin.

CONCLUSION

According to the study, GAPDH can be utilized as a reliable reference gene in the agrochemical (GA3 and Buprofezin) exposure set. The genes can be utilized as a suitable reference for qRT-PCR gene expression studies of xenobiotic metabolism to understand the underlying molecular mechanism, which will help further to design suitable management strategies.

Identification and validation of reference genes for normalization of gene expression analysis using qRT-PCR in Megalurothrips usitatus (thysanoptera: thripidae)

Introduction: Gene expression analysis by reverse transcription quantitative polymerase chain reaction (qRT-PCR) has been widely used in research including insects. The selection of appropriate reference genes is the key to obtaining accurate and reliable results from qRT-PCR. However, studies on the expression stability of reference genes in Megalurothrips usitatus remain lacking. Methods: In this study, qRT-PCR was used to analyze the expression stability of candidate reference genes in M. usitatus. The expression levels of six candidate reference gene transcription of M. usitatus were analyzed. GeNorm, NormFinder, BestKeeper, and ΔCt were used to analyze the expression stability of M. usitatus treated with biological factors (developmental period treatment) and abiotic factors (light, temperature, insecticide treatment, respectively). Comprehensive stability ranking of candidate reference genes was recommended by RefFinder. Results and Discussion: Results showed that ribosomal protein S (RPS) was the most suitable expression in insecticide treatment. Ribosomal protein L (RPL) was the most suitable expression at developmental stage and light treatment, whereas elongation factor was the most suitable expression in temperature treatment. RefFinder was used to comprehensively analyze the above four treatments, and the results showed that RPL and actin (ACT) showed high stability in each treatment. Therefore, this study identified these two genes as reference genes in the qRT-PCR analysis of different treatment conditions of M. usitatus. Ourfindings will be beneficial for improving the accuracy of qRT-PCR analysis for future functional analysis of the target gene expression in M. usitatus.

Selection and validation of reference genes for RT-qPCR-based analyses of Anastatus japonicus Ashmead (Hymenoptera: Helicopteridae)

RT-qPCR remains a vital approach for molecular biology studies aimed at quantifying gene expression in a range of physiological or pathological settings. However, the use of appropriate reference genes is essential to attain meaningful RT-qPCR results. Anastatus japonicus Ashmead (Hymenoptera: Helicopteridae) is an important egg parasitoid wasp and natural enemy of fruit bugs and forest caterpillars. While recent transcriptomic studies have analyzed gene expression profiles in A. japonicus specimens, offering a robust foundation for functional research focused on this parasitoid, no validated A. japonicus reference genes have yet been established, hampering further research efforts. Accordingly, this study sought to address this issue by screening for the most stable internal reference genes in A. japonicus samples to permit reliable RT-qPCR analyses. The utility of eight candidate reference genes (ACTIN, TATA, GAPDH, TUB, RPL13, RPS6, EF1α, RPS3a) was assessed under four different conditions by comparing developmental stages (larvae, pupae, adults), tissues (abdomen, chest, head), sex (male or female adults), or diapause states (diapause induction for 25, 35, 45, or 55 days, or diapause termination). RefFinder was used to calculate gene stability based on the integration of four algorithms (BestKeeper, Normfinder, geNorm, and ΔCt method) to determine the optimal RT-qPCR reference gene. Based on this approach, RPS6 and RPL13 were found to be the most reliable reference genes when assessing different stages of development, while ACTIN and EF1α were optimal when comparing adults of different sexes, RPL13 and EF1α were optimal when analyzing different tissues, and TATA and ACTIN were optimal for different diapause states. These results provide a valuable foundation for future RT-qPCR analyses of A. japonicus gene expression and function under a range of experimental conditions.

Cytochrome P450 Gene, CYP6CX3, Is Involved in the Resistance to Cyantraniliprole in Bemisia tabaci

Bemisia tabaci is an important agricultural sucking pest, and it develops serious resistance to various insecticides. Although cytochrome P450 was involved in the resistance to cyantraniliprole, limited studies have been conducted on B. tabaci. In the present study, piperonyl butoxide significantly increased the toxicity of cyantraniliprole. P450 activities in two resistant populations were 1.97- and 2.17-fold higher than that in the susceptible population. Among 79 P450 genes, CYP6CX3 expressions in two resistant populations were 3.08- and 3.67-fold higher than that in the susceptible population. When CYP6CX3 was knocked down, the toxicity of cyantraniliprole increased significantly. The LC₅₀ value of cyantraniliprole to the Drosophila melanogaster line overexpressing B. tabaci CYP6CX3 increased 7.34-fold. The content of cyantraniliprole was decreased by 25.74 ± 4.27% after mixing with CYP6CX3 and CPR for 2 h. These results suggested that the overexpression of CYP6CX3 was likely involved in the resistance to cyantraniliprole in B. tabaci.

Knockdown of heat shock transcription factor 1 decreases temperature stress tolerance in Bemisia tabaci MED

The primary function of heat shock transcription factor (HSF) in the heat shock response is to activate the transcription of genes encoding heat shock proteins (HSPs). The phloem-feeding insect Bemisia tabaci (Gennadius) is an important pest of cotton, vegetables and ornamentals that transmits several plant viruses and causes enormous agricultural losses. In this study, the gene encoding HSF (Bthsf1) was characterized in MED B. tabaci. The full-length cDNA encoded a protein of 652 amino acids with an isoelectric point of 5.55. The BtHSF1 deduced amino acid sequence showed strong similarity to HSF in other insects. Expression analyses using quantitative real-time PCR indicated that Bthsf1 was significantly up-regulated in B. tabaci adults and pupae during thermal stress. Although Bthsf1 was induced by both hot and cold stress, the amplitude of expression was greater in the former. Bthsf1 had distinct, significant differences in expression pattern during different duration of high but not low temperature stress. Oral ingestion of dsBthsf1 repressed the expression of Bthsf1 and four heat shock proteins (Bthsp90, Bthsp70-3, Bthsp20 and Bthsp19.5) in MED B. tabaci during hot and cold stress. In conclusion, our results show that Bthsf1 is differentially expressed during high and low temperature stress and regulates the transcription of multiple hsps in MED B. tabaci.

Assessment of Suitable Reference Genes for qRT-PCR Normalization in Eocanthecona furcellata (Wolff)

Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) is a widely used tool for measuring gene expression; however, its accuracy relies on normalizing the data to one or more stable reference genes. Eocanthecona furcellata (Wolff) is a polyphagous predatory natural enemy insect that preferentially feeds on more than 40 types of agricultural and forestry pests, such as those belonging to the orders Lepidoptera, Coleoptera, and Hymenoptera. However, to our knowledge, the selection of stable reference genes has not been reported in detail thus far. In this study, nine E. furcellata candidate reference genes (β-1-TUB, RPL4, RPL32, RPS17, RPS25, SDHA, GAPDH2, EF2, and UBQ) were selected based on transcriptome sequencing results. The expression of these genes in various samples was examined at different developmental stages, in the tissues of male and female adults, and after temperature and starvation treatments. Five algorithms were used, including ΔCt, geNorm, NormFinder, BestKeeper, and RefFinder, to evaluate reference gene expression stability. The results revealed that the most stable reference genes were RPL32 and RPS25 at different developmental stages; RPS17, RPL4, and EF2 for female adult tissue samples; RPS17 and RPL32 for male adult tissue samples; RPS17 and RPL32 for various temperature treatments of nymphs; RPS17 and RPS25 for nymph samples under starvation stress; and RPS17 and RPL32 for all samples. Overall, we obtained a stable expression of reference genes under different conditions in E. furcellata, which provides a basis for future molecular studies on this organism.

Identification of Endogenous Genes for Normalizing Titer Variation of Citrus Tristeza Virus in Aphids at Different Post-acquisition Feeding Times

Citrus tristeza virus (CTV) is efficiently transmitted in a semi-persistent manner by the brown citrus aphid (Toxoptera citricida (Kirkaldy)). Currently, the most sensitive method for detecting plant viruses in insect vectors is reverse-transcription quantitative polymerase chain reaction (RT-qPCR). In this study, the elongation factor-1 alpha (EF-1α) gene and acidic p0 ribosomal protein (RPAP0) gene were confirmed to be suitable reference genes for RT-qPCR normalization in viruliferous T. citricida aphids using the geNorm, NormFinder, and BestKeeper tools. Then the relative CTV titer in aphids (T. citricida) at different post-acquisition feeding times on healthy plants was quantified by RT-qPCR using EF-1α and RPAP0 as reference genes. The relative CTV titer retained in the aphids gradually decreased with increasing feeding time. During the first 0.5 h of feeding time on healthy plants, the remaining CTV titer in aphids showed about 80% rapid loss for the highly transmissible isolate CT11A and 40% loss for the poorly transmissible isolate CTLJ. The relative CTV titer in aphids during more than 12 h post-acquisition times for CT11A was significantly lower than at the other feeding times, which is similar to the trend found for CTLJ. To our knowledge, this is the first report about the relative titer variation of CTV remaining in T. citricida at different post-acquisition feeding times on healthy plants.

Selection of stable reference genes for quantitative real-time PCR in the Varroa mite, Varroa destructor

To investigate the acaricide toxicity and resistance mechanisms in the Varroa mite, it is essential to understand the genetic responses of Varroa mites to acaricides, which are usually evaluated by transcriptional profiling based on quantitative real-time polymerase chain reaction (qPCR). In this study, to select reference genes showing consistent expression patterns regardless of the acaricide treatment or the type of tissue, Varroa mites treated with each of the three representative acaricides (coumaphos, fluvalinate, and amitraz) were processed for transcriptomic analysis, from which eight genes (NADH dehydrogenase [NADHD], glyceraldehyde-3-phosphate dehydrogenase [GAPDH], eukaryotic translation elongation factor 1 α 1 [eEF1A1], eukaryotic translation elongation factor 2 [eEF2], ribosomal protein L5 [RpL5], Actin, tubulin α-1D chain [α-tubulin], and Rab1) were selected as candidates. The transcription profiles of these genes, depending on the treatment of the three acaricides or across different tissues (cuticle, legs, gut/fat bodies, and synganglion), were analyzed using qPCR with four validation programs, BestKeeper, geNorm, NormFinder, and RefFinder. Following acaricide treatment, eEF1A1 and NADHD showed the least variation in their expression levels, whereas the expression levels of α-tubulin and RpL5 were the most stable across different tissue groups. Rab1/GAPDH and Actin/eEF2 showed the least stable expression patterns following acaricide treatments and across different tissues, respectively, requiring precautions for use. When vitellogenin gene expression was analyzed by different reference genes, its expression profiles varied significantly depending on the reference genes, highlighting the importance of proper reference gene use. Thus, it is recommended using eEF1A1 and NADHD as reference genes for the comparison of the effects of acaricide on the whole body, whereas α-tubulin and RpL5 are recommended for investigating the tissue-specific expression profiles of target genes.

Involvement of Laccase2 in Cuticle Sclerotization of the Whitefly, Bemisia tabaci Middle East–Asia Minor 1

Cuticle sclerotization is critical for insect survival. Laccase2 (Lac2) is a phenol oxidase that plays a key role in cuticle formation and pigmentation in a variety of insects. However, the function of Lac2 in whitefly, Bemisia tabaci, remains unclear. In this study, we identified a BtLac2 gene in B. tabaci MEAM1 and found that BtLac2 was expressed in all stages. It was highly expressed in the egg stage, followed by nymph and adult. Moreover, the expression of BtLac2 was higher in the cuticle than in other tissues. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate, extended the development duration of nymphs, and decreased the emergence rate of adults. This result demonstrates that BtLac2 plays an important role in the cuticle hardening of B. tabaci and suggests a potential management strategy using RNAi to knock down BtLac2 expression.

Selection and Evaluation of Reference Genes for miRNA Expression Analysis in Bemisia tabaci Under Insecticide Tolerance

A growing number of studies have focused on the microRNA (miRNA) expression in Bemisia tabaci, one devastating agricultural insect pest of the tropical and subtropical areas for which the primary means of control are insecticides. In studying the genetic underpinnings of insecticide resistance, the choice of stable reference genes for normalizing data plays a key role to acquire unbiased expression profile results from quantitative real-time PCR (qPCR) analysis. Expression profiles of 11 selected reference genes were determined systematically in B. tabaci exposure to 11 insecticides. Furthermore, we assessed the stability of all the selected candidates in relation to other variables including sex, tissue type, and developmental stage. Candidate reference gene validation was conducted by analyzing the let-7-5p expression under various experimental treatments. Five programs BestKeeper, NormFinder, geNorm, △Ct, and RefFinder were applied to verify the accuracy of the selected candidates. Our results displayed that the best choices of the selected candidates for pymetrozine, sulfoxaflor, flonicamid, cyantraniliprole, afidopyropen, and deltamethrin treatment were miR-1-3p and miR-100-5p, U6 and miR-100-5p were best for chlorpyrifos and imidacloprid treatments, and U6 and miR-1-3p were best for flupyradifurone and β-cypermethrin treatments. The reference genes miR-624, miR-252, and miR-275 worked best in adult tissues, miR-100-5p and miR-1-3p worked best in either sex, and miR-624 and miR-11 were best to use across developmental stages. Not even one reference gene was found to be suitable for all experimental conditions. Our results contributed to the growing body of the literature on qPCR reference gene selection under various experimental conditions and facilitate further investigation on gene expression changes in B. tabaci, resulting from pesticide exposure.

Selection of Reference Genes for RT-qPCR Analysis in the Hawthorn Spider Mite, Amphitetranychus viennensis (Acarina: Tetranychidae), Under Acaricide Treatments

Hawthorn spider mite, Amphitetranychus viennensis Zacher, one of the most damaging arthropod pests for Rosaceaous fruit trees and ornamentals, has developed resistance to most of the commercially available acaricides. To understand the molecular basis of acaricide resistance, a standardized protocol for real-time quantitative reverse transcription PCR (RT-qPCR) following the MIQE (minimum information for publication of quantitative real time PCR experiments) guidelines is needed. In this study, we screened for the internal references in A. viennensis to study in acaricide resistance. In total, 10 candidate reference genes, including EF1A, 28S rRNA, 18S rRNA, α-tubulin, Actin3, RPS9, GAPDH, V-ATPase B, RPL13, and V-ATPase A, were assessed under the treatments of four commonly used acaricides with distinct mode-of-actions (MOAs). Based on the Insecticide Resistance Action Committee MOA classification, avermectin, bifenazate, spirodiclofen, and fenpropathrin belong to group 6, 20D, 23, and 3A, respectively. The expression profiles of these candidate genes were evaluated using geNorm, Normfinder, BestKeeper, and ∆Ct methods, respectively. Eventually, different sets of reference genes were recommended for each acaricide according to RefFinder, a comprehensive platform integrating all four above-mentioned algorithms. Specifically, the top three recommendations were 1) 28S, V-ATPase A, and Actin 3 for avermectin, 2) GAPDH, RPS9, and 28S for bifenazate, 3) Actin 3, V-ATPase B, and α-tubulin for spirodiclofen, and 4) Actin 3, α-tubulin, and V-ATPase A for fenpropathrin. Although unique sets of genes are proposed for each acaricide, α-tubulin, EF1A, and GAPDH are the most consistently stably expressed reference genes when A. viennensis was challenged chemically. Our findings lay the foundation for the study of acaricide resistance in the phytophagous mites in general, and in the hawthorn spider mite, A. viennensis, in particular.

Selection and Validation of Reliable Reference Genes for qRT-PCR Normalization of Bursaphelenchus xylophilus from Different Temperature Conditions and Developmental Stages

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) is a powerful technique for studying gene expression. The key to quantitative accuracy depends on the stability of the reference genes used for data normalization under different experimental conditions. Pine wood nematode (PWN; Bursaphelenchus xylophilus) is the causal agent of the devastating pine wilt disease (PWD). Extensive and prompt research is needed to understand the molecular mechanism of PWD, but identification of the reference PWN genes for standardized qRT-PCR has not been reported yet. We have analyzed eight candidate reference genes of PWN across different temperature conditions and developmental stages. Delta Ct method, GeNorm, NormFinder, BestKeeper, and RefFinder algorithms were used to evaluate the stability of expression of these genes. Finally, we use arginine kinase gene (AK) in different temperatures and heat shock protein 90 (HSP90) in different developmental stages to confirm the stability of these genes. UBCE and EF1γ were most stable across different temperature treatments, whereas EF1γ and Actin were most stable across different developmental stages. In general, these results indicate that EF1γ is the most stable gene for qRT-PCR under different conditions. The systematic analysis of qRT-PCR reference gene selection will be helpful for future functional analysis and exploration of B. xylophilus genetic resources.

Silencing of the BtTPS genes by transgenic plant-mediated RNAi to control Bemisia tabaci MED

BACKGROUND

Whitefly (Bemisia tabaci) is a typical pest that causes severe damage to hundreds of agricultural crops. The trehalose-6-phosphate synthase (TPS) genes, as the key genes in the insect trehalose synthesis pathway, are important for insect growth and development. The whitefly TPS genes may be a main reason for the severe damage and may represent potential targets for the control of whiteflies.

RESULTS

In this study, we identified and cloned three TPS genes from B. tabaci MED and found that the BtTPS1 and BtTPS2 genes showed higher expression levels than the BtTPS3 gene. Then, RNA interference (RNAi) of BtTPS1 and BtTPS2 resulted in significant mortality and influenced the expression of related genes involved in energy metabolism and chitin biosynthesis in whitefly adults. Finally, the transgenic tobacco plants showed a significant effect on B. tabaci, and knockdown of BtTPS1 or BtTPS2 led to retarded growth and low hatchability in whitefly nymphs, and caused 90% mortality and decreased the fecundity in whitefly adults. Additionally, the transgenic tobacco with combinatorial RNAi of BtTPS1 and BtTPS2 showed a better efficacy against whiteflies than individual silencing.

CONCLUSION

Our results suggest that silencing of the BtTPS genes can compromise the growth and development of whiteflies, offering not only a new option for whitefly control but also a secure and environmentally friendly management strategy.

Transcriptional analysis of Bemisia tabaci MEAM1 cryptic species under the selection pressure of neonicotinoids imidacloprid, acetamiprid and thiamethoxam

BACKGROUND

Neonicotinoids are widely applied in the control of the destructive agricultural pest Bemisia tabaci, and resistance against these chemicals has become a common, severe problem in the control of whiteflies. To investigate the molecular mechanism underlying resistance against nenonicotinoids in whiteflies, RNA-seq technology was applied, and the variation in the transcriptomic profiles of susceptible whiteflies and whiteflies selected by imidacloprid, acetamiprid and thiamethoxam treatment was characterized.

RESULTS

A total of 90.86 GB of clean sequence data were obtained from the 4 transcriptomes. Among the 16,069 assembled genes, 584, 110 and 147 genes were upregulated in the imidacloprid-selected strain (IMI), acetamiprid-selected strain (ACE), and thiamethoxam (THI)-selected strain, respectively, relative to the susceptible strain. Detoxification-related genes including P450s, cuticle protein genes, GSTs, UGTs and molecular chaperone HSP70s were overexpressed in the selected resistant strains, especially in the IMI strain. Five genes were downregulated in all three selected resistant strains, including 2 UDP-glucuronosyltransferase 2B18-like genes (LOC 109030370 and LOC 109032577).

CONCLUSIONS

Ten generations of selection with the three neonicotinoids induced different resistance levels and gene expression profiles, mainly involving cuticle protein and P450 genes, in the three selected resistant whitefly strains. The results provide a reference for research on resistance and cross-resistance against neonicotinoids in B. tabaci.

Genome-wide identification and analysis of sulfatase and sulfatase modifying factor genes in Bemisia tabaci (Hemiptera: Aleyrodidae)

The invasive pest whitefly (Bemisia tabaci) is a complex species, of which Middle East-Minor Asia 1 (MEAM1) and Mediterranean (MED) are the two most damaging members. Previous research showed that cabbage is frequently infested with MEAM1 but seldomly with MED, and this difference in performance is associated with glucosinolate (GS) content. Some insects can modify GS using glucosinolate sulfatase (SULF), the activity of which is regulated by sulfatase modifying factor 1 (SUMF1); therefore, to increase our understanding of different performances of MEAM1 and MED on cabbage plants, we identified and compared nine putative SULFs and one SUMF in MEAM1 and MED. We found that the lengths of two genes, BtSulf2 and BtSulf4, differed between MEAM1 and MED. The messenger RNA levels of BtSulf4 increased more than 20-fold after MEAM1 and MED adults were exposed to GS, but BtSulf2 expression was only induced by GS in MEAM1. Knockdown of BtSulf2 and BtSulf4 in MEAM1 resulted in a substantial increase in the mortality of GS-treated adults but not in MED. These results indicate that differences in BtSulf2 and BtSulf4 sequences and/or expression may explain why MEAM1 performs better than MED on cabbage. Our results provide a basis for future functional research on SULF and SUMF in B. tabaci.

Suppression of Bta11975, an α-glucosidase, by RNA interference reduces transmission of tomato chlorosis virus by Bemisia tabaci

BACKGROUND

Tomato chlorosis virus (ToCV) is mainly vectored by Bemisia tabaci in China, which has a worldwide distribution, and greatly reduces the yields of tomato and other vegetables. At present, control of ToCV has been focused mainly by the use of insecticides to control whitefly populations. Transcriptome sequencing showed high expression of the B. tabaci Bta11975 gene, an α-glucosidase (AGLU) during ToCV acquisition by whitefly Mediterranean (MED) species. To investigate the role of Bta11975 gene in ToCV acquisition and transmission by B. tabaci MED, we used RNA interference (RNAi) to reduce the expression of the Bta11975 gene.

RESULTS

The relative expression of the Bta11975 gene was correlated with the ToCV content in B. tabaci. The AGLU is highly expressed in primary salivary gland and gut. After the Bta11975 gene was silenced, the gene expression of B. tabaci was reduced and B. tabaci mortality was increased. Besides, ToCV acquisition by B. tabaci at 48 and 72 h AAP was reduced, and ToCV transmission was significantly reduced by 25 or 50 of B. tabaci.

CONCLUSIONS

These results indicate that suppression of expression of the Bta11975 gene in B. tabaci MED by RNAi can reduce acquisition and transmission of ToCV by B. tabaci MED.

Case Study Using Recommended Reference Genes Actin and 18S for Reverse-Transcription Quantitative Real-Time PCR Analysis in Myzus persicae

Myzus persicae is a globally important pest with the ability to adjust to a wide range of environmental situations, and many molecular technologies have been developed and applied to understand the biology and/or control this pest insect directly. Reverse-transcription quantitative real-time PCR (RT-qPCR) is a primary molecular technology that is used to quantify gene expression. Choosing a stable reference gene is significantly important for precisely clarifying the expression level of the target gene. Actin and 18S have been recommended as stable compounds for real-time RT-qPCR in M. persicae under the tested biotic and abiotic conditions. In this study, we checked the stability of Actin and 18S by analyzing the relative expression levels of the cytochrome 450 monooxygenase family member genes CYP6CY3 and CYP6-1, carboxylesterase gene E4 and vacuolar protein sorting gene VPS11 via RT-qPCR under various conditions. The expression levels of these four target genes were normalized using both Actin and 18S individually and the combination of these two genes. Our results confirmed that Actin and 18S can be used as reference genes to normalize the expression of target genes under insecticide treatment and starvation in M. persicae. However, at the developmental stages of M. persicae, the expression of the four tested target genes was normalized stably by Actin but not 18S, with the latter presenting a problematic change with the developmental stages. Thus, the stability of reference genes in response to diverse biotic and abiotic factors should be evaluated before each RT-qPCR experiment.

Expression stability of candidate RT-qPCR housekeeping genes in Spodoptera frugiperda (Lepidoptera: Noctuidae)

Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) is commonly used to quantify gene expression. For normalization, the expression of each gene is compared with a reference "housekeeping" gene that is stably expressed under relevant stress. Unfortunately, there have been no reports on the stability of such reference genes under various treatments of the Spodoptera frugiperda. In this study, we used five tools (RefFinder, GeNorm, NormFinder, BestKeeper, and ΔCt methods) to evaluate the stability of 12 candidate reference genes (RPS18, β-tubulin, GAPDH, RPS7, RPS15, RPL7, RPL32, Actin-5C, EF1-α, EF1-γ, RPL27, and ACE) in different instars, tissues, and treatments (high and low temperature, UV-A, and emamectin benzoate). Several ribosomal proteins (RPS7, RPS15, RPL32, RPS18, and RPL7), GAPDH, Actin-5C, and β-tubulin, were relatively stable, suggesting that they are ideal housekeeping genes for various treatments. ACE was extremely unstable under various experimental treatments, rendering it unsuitable as an internal reference. This study identified the reference housekeeping genes stably expressed by S. frugiperda under different treatments, thus setting a foundation for further exploration of the physiological and biochemical mechanisms.

Identification and Evaluation of Reference Genes for Quantitative PCR Normalization in Alligator Weed Flea Beetle (Coleoptera: Chrysomelidae)

Stably expressed reference genes are critical internal standards for the quantification of gene transcription levels using quantitative real-time PCR. Housekeeping genes are commonly used as reference genes but their expressions were variable depending on experimental conditions in many insect species studied. Here we report the identification and evaluation of 10 housekeeping genes in alligator weed flea beetle, Agasicles hygrophila Selman & Vogt (Coleoptera: Chrysomelidae), a biocontrol agent of alligator weed. The 10 housekeeping genes are: beta-actin (Actin), ribosomal protein L13A (PRL13a), succinate dehydrogenase complex subunit A (SDHA), ribosomal protein S20 (RPS20), ribosomal protein S13 (RPS13), glyceraldehyde phosphate dehydrogenase (GAPDH), TATA-box-binding protein (TBP), ribosomal protein L32 (RPL32), tubulin alpha-1 chain (TUBULIN), and elongation factor-1 alpha (ELF). Five programs, geNorm, NormFinder, BestKeeper, ΔCt method, and RefFinder, were used to evaluate the expression stability of the 10 genes among various A. hygrophila body parts and with different nutrient types (starvation, diet types). The expression stability analysis showed that RPS32 and RPL13a were reliable reference genes for the study of gene transcription in different body parts; Actin and RPL13a were optimal reference genes for different nutrient types. The selections of reference genes were validated using a CarE gene (GeneBank No: KX353552). The results of this study provide useful bases for studies of gene expression in various aspects relating to A. hygrophila.

CircMTO1 inhibits ox-LDL-stimulated vascular smooth muscle cell proliferation and migration via regulating the miR-182-5p/RASA1 axis

Background

Circular RNAs (circRNAs) play critical roles in the development of atherosclerosis (AS). This study investigated the role of circMTO1 in the progression of AS.

Methods

Serum samples from AS patients and healthy volunteers and vascular smooth muscle cells (VSMCs) were used as the study materials. The expressions of circMTO1 and miR-182-5p were measured by RT-qPCR. The effects of circMTO1, miR-182-5p, and RASA1 on VSMC proliferation and apoptosis were examined by MTT and BrdU assays and wound healing and flow cytometric analyses, respectively. Downstream target genes of circMTO1 and miR-182-5p were predicted using target gene prediction and screening and confirmed using a luciferase reporter assay. RASA1 expression was detected by RT-qPCR and Western blot.

Results

circMTO1 expression was decreased, while miR-182-5p expression was increased in human AS sera and oxidized low-density lipoprotein (ox-LDL)-stimulated VSMCs. CircMTO1 overexpression inhibited the proliferation and promoted the apoptosis of ox-LDL-stimulated VSMCs. CircMTO1 was found to be served as a sponge of miR-182-5p and RASA1 as a target of miR-182-5p. Moreover, circMTO1 acted as a ceRNA of miR-182-5p to enhance RASA1 expression. Furthermore, miR-182-5p overexpression and RASA1 knockdown reversed the effects of circMTO1 overexpression on the proliferation, migration, and apoptosis of ox-LDL-stimulated VSMCs.

Conclusion

CircMTO1 inhibited the proliferation and promoted the apoptosis of ox-LDL-stimulated VSMCs by regulating miR-182-5p/RASA1 axis. These results suggest that circMTO1 has potential in AS treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00330-2.

Selection and Validation of Reference Genes For qRT-PCR Analysis of Rhopalosiphum padi (Hemiptera: Aphididae)

Rhopalosiphum padi (L.) (Hemiptera: Aphididae) is an important cosmopolitan pest in cereal crops. Reference genes can significantly affect qRT-PCR results. Therefore, selecting appropriate reference genes is a key prerequisite for qRT-PCR analyses. This study was conducted to identify suitable qRT-PCR reference genes in R. padi. We systematically analyzed the expression profiles of 11 commonly used reference genes. The ΔCt method, the BestKeeper, NormFinder, geNorm algorithms, and the RefFinder online tool were used to evaluate the suitability of these genes under diverse experimental conditions. The data indicated that the most appropriate sets of reference genes were β-actin and GAPDH (for developmental stages), AK and TATA (for populations), RPS18 and RPL13 (for tissues), TATA and GAPDH (for wing dimorphism), EF-1α and RPS6 (for antibiotic treatments), GAPDH and β-actin (for insecticide treatments), GAPDH, TATA, RPS18 (for starvation-induced stress), TATA, RPS6, and AK (for temperatures), and TATA and GAPDH (for all conditions). Our study findings, which revealed the reference genes suitable for various experimental conditions, will facilitate the standardization of qRT-PCR programs, while also improving the accuracy of qRT-PCR analyses, with implications for future research on R. padi gene functions.

MiRNA-1271-5p regulates osteogenic differentiation of human bone marrow-derived mesenchymal stem cells by targeting forkhead box O1 (FOXO1)

Forkhead box O1 (FOXO1) is a key regulator of osteogenesis. The aim of this study was to identify the mechanisms of microRNAs (miRNAs) targeting FOXO1 in osteogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs). Three miRNA target prediction programs were used to search for potential miRNAs that target FOXO1. Quantitative real-time polymerase chain reaction was conducted to detect the expression of miR-1271-5p and FOXO1 during osteogenic differentiation. Target gene prediction and screening, luciferase reporter assay was used to verify the downstream target gene of miR-1271-5p. The expression levels of FOXO1 and Runx2 were detected by RT-qPCR and Western blot analysis. Alkaline phosphatase (ALP) activity and matrix mineralization were detected by biochemical methods. The expression levels of Runx2, ALP, and osteocalcin were detected by RT-qPCR. Our results showed that miR-1271-5p was downregulated during osteogenic induction. And the expression levels of miR-1271-5p were higher in osteoporotic tissues than that in adjacent nonosteoporotic tissues. The expression levels of FOXO1 were lower in osteoporotic tissues than that in adjacent nonosteoporotic tissues. And a negative correlation was found between miR-1271-5p and FOXO1 in osteoporotic tissues. Overexpression of miR-1271-5p downregulated FOXO1 and inhibited osteogenic differentiation in hMSCs. Overexpression of miR-1271-5p downregulated the expression of osteogenic markers and reduced ALP activity. In addition, ectopic expression of FOXO1 reversed the effect of miR-1271-5p on osteogenic differentiation. In conclusion, miR-1271-5p functioned as a therapeutic target of osteogenic differentiation in hMSCs by inhibiting FOXO1, which provides valuable insights into the use of miR-1271-5p as a target in the treatment of osteoporosis and other bone metabolic diseases.

Whitefly hijacks a plant detoxification gene that neutralizes plant toxins

Plants protect themselves with a vast array of toxic secondary metabolites, yet most plants serve as food for insects. The evolutionary processes that allow herbivorous insects to resist plant defenses remain largely unknown. The whitefly Bemisia tabaci is a cosmopolitan, highly polyphagous agricultural pest that vectors several serious plant pathogenic viruses and is an excellent model to probe the molecular mechanisms involved in overcoming plant defenses. Here, we show that, through an exceptional horizontal gene transfer event, the whitefly has acquired the plant-derived phenolic glucoside malonyltransferase gene BtPMaT1. This gene enables whiteflies to neutralize phenolic glucosides. This was confirmed by genetically transforming tomato plants to produce small interfering RNAs that silence BtPMaT1, thus impairing the whiteflies' detoxification ability. These findings reveal an evolutionary scenario whereby herbivores harness the genetic toolkit of their host plants to develop resistance to plant defenses and how this can be exploited for crop protection.

Genome-Wide Identification and Analysis of Chitinase-Like Gene Family in Bemisia tabaci (Hemiptera: Aleyrodidae)

Chitinases are of great importance in chitin degradation and remodeling in insects. However, the genome-wide distribution of chitinase-like gene family in Bemsia tabaci, a destructive pest worldwide, is still elusive. With the help of bioinformatics, we annotated 14 genes that encode putative chitinase-like proteins, including ten chitinases (Cht), three imaginal disk growth factors (IDGF), and one endo-β-N-acetylglucosaminidase (ENGase) in the genome of the whitefly, B. tabaci. These genes were phylogenetically grouped into eight clades, among which 13 genes were classified in the glycoside hydrolase family 18 groups and one in the ENGase group. Afterwards, developmental expression analysis suggested that BtCht10, BtCht5, and BtCht7 were highly expressed in nymphal stages and exhibit similar expression patterns, implying their underlying role in nymph ecdysis. Notably, nymphs exhibited a lower rate of survival when challenged by dsRNA targeting these three genes via a nanomaterial-promoted RNAi method. In addition, silencing of BtCht10 significantly resulted in a longer duration of development compared to control nymphs. These results indicate a key role of BtCht10, BtCht5, and BtCht7 in B. tabaci nymph molting. Our research depicts the differences of chitinase-like family genes in structure and function and identified potential targets for RNAi-based whitefly management.

Two Deoxythymidine Triphosphate Synthesis-Related Genes Regulate Obligate Symbiont Density and Reproduction in the Whitefly Bemisia tabaci MED

Deoxythymidine triphosphate (dTTP) is essential for DNA synthesis and cellular growth in all organisms. Here, genetic capacity analysis of the pyrimidine pathway in insects and their symbionts revealed that dTTP is a kind of metabolic input in several host insect/obligate symbiont symbiosis systems, including Bemisia tabaci MED/Candidatus Portiera aleyrodidarum (hereafter Portiera). As such, the roles of dTTP on both sides of the symbiosis system were investigated in B. tabaci MED/Portiera. Dietary RNA interference (RNAi) showed that suppressing dTTP production significantly reduced the density of Portiera, significantly repressed the expression levels of horizontally transferred essential amino acid (EAA) synthesis-related genes, and significantly decreased the reproduction of B. tabaci MED adults as well as the hatchability of their offspring. Our results revealed the regulatory role of dTTP in B. tabaci MED/Portiera and showed that dTTP synthesis-related genes could be potential targets for controlling B. tabaci as well as other sucking pests.

Vector Transmission of Tomato Yellow Leaf Curl Thailand Virus by the Whitefly Bemisia tabaci: Circulative or Propagative?

Viruses that cause tomato yellow leaf curl disease are part of a group of viruses of the genus Begomovirus, family Geminiviridae. Tomato-infecting begomoviruses cause epidemics in tomato crops in tropical, subtropical, and Mediterranean climates, and they are exclusively transmitted by Bemisia tabaci in the field. The objective of the present study was to examine the transmission biology of the tomato yellow leaf curl Thailand virus (TYLCTHV) by B. tabaci, including virus-infected tissues, virus translocation, virus replication, and transovarial transmission. The results demonstrated that the virus translocates from the alimentary gut to the salivary glands via the hemolymph, without apparent replication when acquired by B. tabaci. Furthermore, the virus was detected in 10% of the first-generation progeny of viruliferous females, but the progeny was unable to cause the viral infection of host plants. There was no evidence of transovarial transmission of TYLCTHV in B. tabaci. When combined with the current literature, our results suggest that B. tabaci transmits TYLCTHV in a persistent-circulative mode. The present study enhances our understanding of virus-vector interaction and the transmission biology of TYLCTHV in B. tabaci.

Genome-wide identification of neuropeptides and their receptor genes in Bemisia tabaci and their transcript accumulation change in response to temperature stresses

Insect neuropeptides play an important role in regulating physiological functions such as growth, development, behavior and reproduction. We identified temperature-sensitive neuropeptides and receptor genes of the cotton whitefly, Bemisia tabaci. We identified 38 neuropeptide precursor genes and 35 neuropeptide receptors and constructed a phylogenetic tree using additional data from other insects. As temperature adaptability enables B. tabaci to colonize a diversity of habitats, we performed quantitative polymerase chain reaction with two temperature stresses (low = 4 °C and high = 40 °C) to screen for temperature-sensitive neuropeptides. We found many neuropeptides and receptors that may be involved in the temperature adaptability of B. tabaci. This study is the first to identify B. tabaci neuropeptides and their receptors, and it will help to reveal the roles of neuropeptides in temperature adaptation of B. tabaci.

Tomato Chlorosis Virus Infection Facilitates Bemisia tabaci MED Reproduction by Elevating Vitellogenin Expression

Simple Summary

The sweet potato whitefly, Bemisia tabaci, is a polyphagous, global invasive insect pest. It can damage vegetables and crops directly by feeding and indirectly by transmitting plant viruses. Previously, we showed that virus infection of host plants can promote B. tabaci MED (Q biotype) reproduction. Here, using a whitefly-tomato chlorosis virus (ToCV)-tomato system, we investigated how ToCV modulates B. tabaci reproduction to facilitate its spread. ToCV infection significantly increased whitefly fecundity and the relative expression of vitellogenin gene (Vg). Both ovarian development and fecundity of whitefly were suppressed when Vg expression was silenced with or without ToCV infection. These combined results reveal that ToCV infection increases B. tabaci MED fecundity via elevated vitellogenin gene expression.

Abstract

Transmission of plant pathogenic viruses mostly relies on insect vectors. Plant virus could enhance its transmission by modulating the vector. Previously, we showed that feeding on virus infected plants can promote the reproduction of the sweet potato whitefly, Bemisia tabaci MED (Q biotype). In this study, using a whitefly-Tomato chlorosis virus (ToCV)-tomato system, we investigated how ToCV modulates B. tabaci MED reproduction to facilitate its spread. Here, we hypothesized that ToCV-infected tomato plants would increase B. tabaci MED fecundity via elevated vitellogenin (Vg) gene expression. As a result, fecundity and the relative expression of B. tabaci MED Vg was measured on ToCV-infected and uninfected tomato plants on days 4, 8, 12, 16, 20 and 24. The role of Vg on B. tabaci MED reproduction was examined in the presence and absence of ToCV using dietary RNAi. ToCV infection significantly increased B. tabaci MED fecundity on days 12, 16 and 20, and elevated Vg expression on days 8, 12 and 16. Both ovarian development and fecundity of B. tabaci MED were suppressed when Vg was silenced with or without ToCV infection. These combined results suggest that ToCV infection increases B. tabaci MED fecundity via elevated Vg expression.

Plant flavonoids enhance the tolerance to thiamethoxam and flupyradifurone in whitefly Bemisia tabaci (Hemiptera: Aleyrodidae)

The sweetpotato whitefly Bemisia tabaci is a polyphagous crop pest distributed worldwide and frequent exposure to many different defensive secondary metabolites in its host plants. To counteract these defensive plant secondary metabolites, B. tabaci elevate their production of detoxification enzymes, including cytochrome P450 monooxygenases. Besides their tolerance to phytotoxin, B. tabaci have quickly developed resistance to various insecticides in the field. However, the relationship between host plant secondary metabolites and insecticide resistance in B. tabaci is not fully understood. In this study, the influence of plant flavonoid ingestion on B. tabaci tolerance to thiamethoxam and flupyradifurone insecticides and its possible mechanism were examined. Eight plant flavonoids were screened to evaluate their effects on B. tabaci adult sensitivity to thiamethoxam and flupyradifurone. Of which rutin, quercetin, kaempferol, myricetin and catechin significantly reduced adult sensitivity to thiamethoxam and flupyradifurone. Application of cytochrome P450 inhibitor piperonyl butoxide significantly increased the mortality of B. tabaci adults treated with thiamethoxam and flupyradifurone. Moreover, flavonoid ingestion predominantly enhanced the activity of cytochrome P450 enzyme in B. tabaci adults. Meanwhile, the expression level of three cytochrome P450 genes, CYP6CM1, CYP6CX4 and CYP4C64 were induced by the flavonoids in B. tabaci adults. In conclusion, plant flavonoids enhanced the tolerance to thiamethoxam and flupyradifurone in B. tabaci and cytochrome P450s may contribute the flavonoid adaptation. The reduced sensitivity of thiamethoxam and flupyradifurone in flavonoid-fed B. tabaci adults suggested that previous exposure to the host plant-derived flavonoids is likely to compromise the efficacy of insecticides.

Selection and validation of experimental condition-specific reference genes for qRT-PCR in Metopolophium dirhodum (Walker) (Hemiptera: Aphididae)

Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) is one of the most common aphid pests of winter cereals. To facilitate accurate gene expression analyses with qRT-PCR assays, the expression stability of candidate reference genes under specific experimental conditions must be verified before they can be used to normalize target gene expression levels. In this study, 10 candidate reference genes in M. dirhodum were analyzed by qRT-PCR under various experimental conditions. Their expression stability was evaluated with delta Ct, BestKeeper, geNorm, and NormFinder methods, and the final stability ranking was determined with RefFinder. The results indicate that the most appropriate sets of internal controls were SDHB and RPL8 across geographic population; RPL8, Actin, and GAPDH across developmental stage; SDHB and NADH across body part; RPL8 and Actin across wing dimorphism and temperature; RPL4 and EF1A across starvation stress; AK and RPL4 across insecticide treatments; RPL8 and NADH across antibiotic treatments; RPL8, RPL4, Actin, and NADH across all samples. The results of this study provide useful insights for establishing a standardized qRT-PCR procedure for M. dirhodum and may be relevant for identifying appropriate reference genes for molecular analyses of related insects.

Genome-Wide Identification and Expression Analysis of Udp-Glucuronosyltransferases in the Whitefly Bemisia Tabaci (Gennadius) (HemipterA: Aleyrodidae)

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is an important agricultural pest worldwide. Uridine diphosphate (UDP)-glucuronosyltransferases (UGTs) are one of the largest and most ubiquitous groups of proteins. Because of their role in detoxification, insect UGTs are attracting increasing attention. In this study, we identified and analyzed UGT genes in B. tabaci MEAM1 to investigate their potential roles in host adaptation and reproductive capacity. Based on phylogenetic and structural analyses, we identified 76 UGT genes in the B. tabaci MEAM1 genome. RNA-seq and real-time quantitative PCR (RT-qPCR) revealed differential expression patterns of these genes at different developmental stages and in association with four host plants (cabbage, cucumber, cotton and tomato). RNA interference results of selected UGTs showed that, when UGT352A1, UGT352B1, and UGT354A1 were respectively silenced by feeding on dsRNA, the fecundity of B. tabaci MEAM1 was reduced, suggesting that the expressions of these three UGT genes in this species may be associated with host-related fecundity. Together, our results provide detailed UGTs data in B.tabaci and help guide future studies on the mechanisms of host adaptation by B.tabaci.

Evaluation of reference genes for quantitative real-time PCR normalization in the scarab beetle Holotrichia oblita

Quantitative real-time polymerase chain reaction (qPT-PCR) is commonly used to analyze gene expression, however, the accuracy of the normalized results is affected by the expression stability of reference genes. Holotrichia oblita (Coleoptera: Scarabaeidae) causes serious damage to crops. Reliable reference genes in H. oblita are needed for qRT-PCR analysis. Therefore, we evaluated 13 reference genes under biotic and abiotic conditions. RefFinder provided a comprehensive stability ranking, and geNorm suggested the optimal number of reference genes for normalization. RPL13a and RPL18 were the most suitable reference genes for developmental stages, tissues, and temperature treatments; RPL13a and RPS3 were the most suitable for pesticide and photoperiod treatments; RPS18 and RPL18 were the most suitable for the two sexes. We validated the normalized results using odorant-binding protein genes as target genes in different tissues. Compared with the selected suitable reference genes, the expression of OBP1 in antennae, abdomen, and wings, and OBP2 in antennae and wings were overestimated due to the instability of ACTb. These results identified several reliable reference genes in H. oblita for normalization, and are valuable for future molecular studies.

Comprehensive Assessment of Candidate Reference Genes for Gene Expression Studies Using RT-qPCR in Tamarixia radiata, a Predominant Parasitoid of Diaphorina citri

Tamarixia radiata (Waterston) is a predominant parasitoid of the Asian citrus psyllid (ACP), a destructive citrus pest and vector of huanglongbing (HLB) disease in the fields of southern China. To explore the functioning of target genes in T. radiata, the screening of specific reference genes is critical for carrying out the reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) under different experimental conditions. However, no reference gene(s) for T. radiata has yet been reported. Here, we selected seven housekeeping genes of T. radiate and evaluated their stability under the six conditions (developmental stage, sex, tissue, population, temperature, diet) by using RefFinder software, which contains four different programs (geNorm, ΔCt, BestKeeper, and NormFinder). Pairwise variation was analyzed by geNorm software to determine the optimal number of reference genes during the RT-qPCR analysis. The results reveal better reference genes for differing research foci: 18S and EF1A for the developmental stage; PRS18 and EF1A for sex, PRS18 and RPL13 for different tissues (head, thorax, abdomen); EF1A and ArgK between two populations; β-tubulin and EF1A for different temperatures (5, 15, 25, 35 °C); and ArgK and PRS18 for different feeding diets. Furthermore, when the two optimal and two most inappropriate reference genes were chosen in different temperatures and tissue treatments, respectively, the corresponding expression patterns of HSP70 (as the reporter gene) differed substantially. Our study provides, for the first time, a more comprehensive list of optimal reference genes from T. radiata for use in RT-qPCR analysis, which should prove beneficial for subsequent functional investigations of target gene(s) in this natural enemy of ACP.

NEAT1/miR-140-3p/MAPK1 mediates the viability and survival of coronary endothelial cells and affects coronary atherosclerotic heart disease

Studies have shown that long non-coding RNAs (lncRNA) play critical roles in coronary atherosclerotic heart disease (CAD). However, the function of lncRNA nuclear enriched abundant transcript 1 (NEAT1) in CAD is unclear. In this study, we aimed to investigate the functions of lncRNA NEAT1 in CAD. RT-PCR and western blot analysis were carried out to examine the expressions of related RNAs. Colony formation assay, cell proliferation assay, apoptosis assay, and dual-luciferase reporter assay were conducted to investigate the abilities of colony migration, cell proliferation, apoptosis, and targeting. The results showed that NEAT1 was up-regulated in CAD blood samples and in human coronary endothelial cells (HCAECs). Transfection of pcNEAT1 significantly inhibited the survival rate of HCAECs and induced apoptosis of HCAECs. MiR-140-3p was down-regulated in HCAECs. NEAT1 directly targeted miR-140-3p, and the expression of miR-140-3p was inversely correlated with the expression of NEAT1 in CAD patients. In addition, co-transfection of NEAT1 with miR-140-3p mimic reversed the effect of pcNEAT1 on cell viability and apoptosis. mitogen-activated protein kinase 1 (MAPK1) was proved to be a target gene of miR-140-3p, and the miR-140-3p mimic was shown to reduce the expression of MAPK1 in HCAECs. pcNEAT1 significantly increased the expression level of MAPK1, while shNEAT1 significantly reduced the expression level of MAPK1. Our results revealed that lncRNA NEAT1 increased cell viability and inhibited CAD cell apoptosis possibly by activating the miR-140-3p/MAPK1 pathway, and lncRNA NEAT1 might serve as a potential therapeutic target for CAD.

A Chemosensory Protein BtabCSP11 Mediates Reproduction in Bemisia tabaci

The olfactory system serves a vital role in the evolution and survival of insects, being involved in behaviors such as host seeking, foraging, mating, and oviposition. Odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are involved in the olfactory recognition process. In this study, BtabCSP11, a CSP11 gene from the whitefly Bemisia tabaci, was cloned and characterized. The open reading frame of BtabCSP11 encodes 136 amino acids, with four highly conserved cysteine residues. The temporal and spatial expression profiles showed that BtabCSP11 was highly expressed in the abdomens of B. tabaci females. Dietary RNA interference (RNAi)-based functional analysis showed substantially reduced fecundity in parthenogenetically reproduced females, suggesting a potential role of BtabCSP11 in B. tabaci reproduction. These combined results expand the function of CSPs beyond chemosensation.

Genome-wide identification and analysis of nuclear receptors genes for lethal screening against Bemisia tabaci Q

BACKGROUND

Nuclear receptors (NRs) play an essential role in diverse biological processes, such as insect metamorphosis. Here, transcriptome analysis and functional studies were used to determine whether NRs are involved in metamorphosis of whitefly Bemisia tabaci Q, a serious pest to crops, and to find some potential insecticide targets.

RESULTS

Twenty NRs were identified in the Bemisia tabaci Q genome and categorized into the NR0-NR6 subfamilies. The phylogenetic tree of NRs from Bemisia tabaci Q and other representative species was constructed, which provided evolutionary insight into their genetic distances. The results of spatiotemporal gene expression indicated that the majority of NR gene expression was higher in the head than the abdomen and higher in eggs than adults. Further functional analysis using RNA interference (RNAi) showed that NR genes play an important role in Bemisia tabaci Q pupation and eclosion. With respect to high mortality and effects on growth, this was reflected in the unable to become pupa when the third-stage nymph treated with double-stranded RNA (dsRNA) and the developmental time delay (4-7 days) when pupae were treated with dsRNA for the 12 NR genes during molting compared with the development time in the control.

CONCLUSION

This study provides insight into NR functions during the metamorphosis stages of Bemisia tabaci Q. Several candidate genes could be potential insecticide targets for whitefly pest control due to their important roles in insect development. © 2020 Society of Chemical Industry.