Selection and Validation of Reference Genes for RT-qPCR Analysis of the Ladybird Beetle Henosepilachna vigintioctomaculata

A critical role for the nuclear protein Akirin in larval development in Henosepilachna vigintioctopunctata

Akirin is a nuclear protein that controls development in vertebrates and invertebrates. The function of Akirin has not been assessed in any Coleopteran insects. We found that high levels of akirin transcripts in Henosepilachna vigintioctopunctata, a serious Coleopteran potato defoliator (hereafter Hvakirin), were present at prepupal, pupal and adult stages, especially in larval foregut and fat body. RNA interference (RNAi) targeting Hvakirin impaired larval development. The Hvakirin RNAi larvae arrested development at the final larval instar stage. They remained as stunted larvae, gradually blackened and finally died. Moreover, the remodelling of gut and fat body was inhibited in the Hvakirin depleted larvae. Two layers of cuticles, old and newly formed, were noted in the dsegfp-injected animals. In contrast, only a layer of cuticle was found in the dsakirin-injected beetles, indicating the arrest of larval development. Furthermore, the expression of three transforming growth factor-β cascade genes (Hvsmox, Hvmyo and Hvbabo), a 20-hydroxyecdysone (20E) receptor gene (HvEcR) and six 20E response genes (HvHR3, HvHR4, HvE75, HvBrC, HvE93 and Hvftz-f1) was significantly repressed, consistent with decreased 20E signalling. Conversely, the transcription of a juvenile hormone (JH) biosynthesis gene (Hvjhamt), a JH receptor gene (HvMet) and two JH response genes (HvKr-h1 and HvHairy) was greatly enhanced. Our findings suggest a critical role of Akirin in larval development in H. vigintioctopunctata.

RNA Interference-Mediated Suppression of Ecdysone Signaling Inhibits Choriogenesis in Two Coleoptera Species

During choriogenesis in insects, chorion (eggshell) is formed by surrounding follicular epithelial cells in ovarioles. However, the regulatory endocrine factor(s) activating choriogenesis and the effect of chemical components on eggshell deserve further exploration. In two representative coleopterans, a coccinellid Henosepilachna vigintioctopunctata and a chrysomelid Leptinotarsa decemlineata, genes encoding the 20-hydroxyecdysone (20E) receptor heterodimer, ecdysone receptor (EcR) and ultraspiracle (USP), and two chitin biosynthesis enzymes UDP-N-acetylglucosamine pyrophosphorylase (UAP) and chitin synthase (ChS1), were highly expressed in ovaries of the young females. RNA interference (RNAi)-aided knockdown of either HvEcR or Hvusp in H. vigintioctopunctata inhibited oviposition, suppressed the expression of HvChS1, and lessened the positive signal of Calcofluor staining on the chorions, which suggests the reduction of a chitin-like substance (CLS) deposited on eggshells. Similarly, RNAi of LdEcR or Ldusp in L. decemlineata constrained oviposition, decreased the expression of LdUAP1 and LdChS1, and reduced CLS contents in the resultant ovaries. Knockdown of LdUAP1 or LdChS1 caused similar defective phenotypes, i.e., reduced oviposition and CLS contents in the L. decemlineata ovaries. These results, for the first time, indicate that 20E signaling activates choriogenesis in two coleopteran species. Moreover, our findings suggest the deposition of a CLS on the chorions.

Molecular characterization of the cytochrome P450 enzyme CYP18A1 in Henosepilachna vigintioctopunctata

In insects, the expression of 20E response genes that initiate metamorphosis is triggered by a pulse of 20-hydroxyecdysone (20E). The 20E pulse is generated through two processes: synthesis, which increases its level, and inactivation, which decreases its titer. CYP18A1 functions as an ecdysteroid 26-hydroxylase and plays a role in 20E removal in several representative insects. However, applying 20E degradation activity of CYP18A1 to other insects remains a significant challenge. In this study, we discovered high levels of Hvcyp18a1 during the larval and late pupal stages, particularly in the larval epidermis and fat body of Henosepilachna vigintioctopunctata, a damaging Coleopteran pest of potatoes. RNA interference (RNAi) targeting Hvcyp18a1 disrupted the pupation. Approximately 75% of the Hvcyp18a1 RNAi larvae experienced developmental arrest and remained as stunted prepupae. Subsequently, they gradually turned black and eventually died. Among the Hvcyp18a1-depleted animals that successfully pupated, around half became malformed pupae with swollen elytra and hindwings. The emerged adults from these deformed pupae appeared misshapen, with shriveled elytra and hindwings, and were wrapped in the pupal exuviae. Furthermore, RNAi of Hvcyp18a1 increased the expression of a 20E receptor gene (HvEcR) and four 20E response transcripts (HvE75, HvHR3, HvBrC, and HvαFTZ-F1), while decreased the transcription of HvβFTZ-F1. Our findings confirm the vital role of CYP18A1 in the pupation, potentially involved in the degradation of 20E in H. vigintioctopunctata.

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.

Twist is required for muscle development of the adult legs in Henosepilachna vigintioctopunctata

Although muscle development has been widely studied in Drosophila melanogaster, it was a great challenge to apply to developmental processes of other insect muscles. This study was focused on the functional characterization of a basic helix-loop-helix transcription factor gene twist in an herbivorous ladybird Henosepilachna vigintioctopunctata. Its transcript (Hvtwist) levels were detected in all developmental stages. RNA interference (RNAi)-aided knockdown of Hvtwist at the penultimate larval instar stage impaired pupation, and caused a deformed adult in the legs. The tarsi were malformed and did not support the bodies in an upright position. The climbing ability was impaired. Moreover, around 50% of the impaired adults had a malformed elytrum. In addition, they consumed less foliage and did not lay eggs. A hematoxylin-eosin staining of the leg demonstrated that the tibial extensor (TE) and the tibial flexor (TF) muscles were originated from the femurs while levator and depressor muscles of the tarsus (TL and TD) were located in the tibia in the control adults, in which tarsal segments were devoid of muscles. RNAi treatment specific to Hvtwist expression markedly impaired TE and TF muscles in the femurs, and prevented the development of TL and TD muscles in the tibia. Therefore, our findings demonstrate Twist plays a vital role in the myogenesis in H. vigintioctopunctata adult legs.

Selection and validation of optimal reference genes for RT-qPCR analyses in Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae)

Aphidoletes aphidimyza is a predator that is an important biological agent used to control agricultural and forestry aphids. Although many studies have investigated its biological and ecological characteristics, few molecular studies have been reported. The current study was performed to identify suitable reference genes to facilitate future gene expression and function analyses via quantitative reverse transcription PCR. Eight reference genes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), RPS13, RPL8, RPS3, α-Tub, β-actin, RPL32, and elongation factor 1 alpha (EF1-α) were selected. Their expression levels were determined under four different experimental conditions (developmental stages, adult tissues, sugar treatment, and starvation treatment) using qRT-PCR technology. The stability was evaluated with five methods (Ct value, geNorm, NormFinder, BestKeeper, and RefFinder). The results showed that GAPDH, RPL32, and EF1-α were ranked as the best reference gene combinations for measuring gene expression levels among different developing stages and in various starvation treatments. RPL8 and RPS3 were recommended to normalize the gene expression levels among different adult tissues. RPL32, β-actin, and EF1-α were recommended sugar-feeding conditions. To validate the utility of the selected reference pair, RPL8, and RPS3, we estimated the tissue-biased expression level of a chemosensory protein gene (AaphCSP1). As expected, AaphCSP1 is highly expressed in the antennae and lowly expressed in the abdomen. These findings will lay the foundation for future research on the molecular physiology and biochemistry of A. aphidimyza.

Screening and validation of the optimal panel of reference genes in colonic epithelium and relative cancer cell lines

Real-time quantitative polymerase chain reaction (RT-qPCR) is the most common method to determine mRNA expression, and Minimum Information for Publication of RT-qPCR Experiments (MIQE) proposes that a panel of reference genes for RT-qPCR is conducive to obtaining accurate results. This study aimed to screen and verify the optimal panel of reference genes in colorectal cancer (CRC) and normal colonic cell lines. In the study, eight candidate reference genes (GAPDH, ACTB, 18S, PPIA, B2M, SDHA, GUSB, and YWHAZ) were selected for RT-qPCR to detect their expression in NCM460, HT29, HCT116, SW480, SW620, DLD-1, LOVO and RKO cell lines. The stability of reference genes and the optimal panel were evaluated by geNorm, NormFinder, and BestKeeper software. As results, the expression levels of candidate reference genes differed in the colonic epithelial cell lines, and the number of optimal panel of reference genes is two. B2M and YWHAZ were the two most stable reference genes for NCM460, HCT116, SW620, LOVO, and RKO cell lines, while only one of B2M and YWHAZ was most stable in HT29 and SW480 cells. In DLD-1 cells, the stability of B2M and YWHAZ ranked 3rd and 6th, PPIA and GUSB were the most stable two. Furthermore, the YWHZA + B2M performed smaller intragroup differences than other panel or single reference gene. In conclusion, this study indicates the optimal panel of reference genes is YWHZA + B2M for the NCM460, HCT116, SW620, LOVO, RKO, SW480, and HT29 cell lines, but it is PPIA + GUSB in DLD-1 cell lines.

RNAi-Mediated Functional Analysis Reveals the Regulation of Oocyte Vitellogenesis by Ecdysone Signaling in Two Coleoptera Species

Coleoptera is the largest taxa of animals by far. The robust reproductive capacity is one of the main reasons for such domination. Successful female reproduction partially relies on effective vitellogenesis. However, the hormone regulation of vitellogenesis remains to be explored. In the present paper, in vitro culture of Leptinotarsa decemlineata 1-day-old adult fat bodies in the 20E-contained median did not activate juvenile hormone production and insulin-like peptide pathways, but significantly stimulated the expression of two LdVg genes, in a cycloheximide-dependent pattern. In vivo RNA interference (RNAi) of either ecdysone receptor (LdEcR) or ultraspiracle (Ldusp) by injection of corresponding dsRNA into 1-day-old female adults inhibited oocyte development, dramatically repressed the transcription of LdVg genes in fat bodies and of LdVgR in ovaries; application of JH into the LdEcR or Ldusp RNAi L. decemlineata females did not restore the oocyte development, partially rescued the decreased LdVg mRNA levels but over-compensated LdVgR expression levels. The same RNAi experiments were performed in another Coleoptera species, Henosepilachna vigintioctopunctata. Little yolk substances were seen in the misshapen oocytes in the HvEcR or Hvusp RNAi ovaries, in contrast to larger amounts of yolk granules in the normal oocytes. Correspondingly, the transcript levels of HvVg in the fat bodies and ovaries decreased significantly in the HvEcR and Hvusp RNAi samples. Our results here show that 20E signaling is indispensable in the activation of vitellogenesis in the developing oocytes of the two beetle species.

Requirement of Snakeskin for normal functions of midgut and Malpighian tubules in Henosepilachna vigintioctopunctata

Septate junctions (SJs) are located between epithelial cells and play crucial roles in epithelial barrier formation and epithelia cell homeostasis. Nevertheless, the molecular constituents, especially those related to smooth SJs (sSJs), have not been well explored in non-Drosophilid insects. A putative integral membrane protein Snakeskin (Ssk) was identified in a Coleoptera foliar pest Henosepilachna vigintioctopunctata. RNA interference-aided knockdown of Hvssk at the third-instar larval stage arrested larval development. Most resultant larvae failed to shed larval exuviae until their death. Silence of Hvssk at the fourth-instar larvae inhibited the growth and reduced foliage consumption. Dissection and microscopic observation revealed that compromised expression of Hvssk caused obvious phenotypic defects in the midgut. A great number of morphologically abnormal columnar epithelial cells accumulated throughout the midgut lumen. Moreover, numerous vesicles were observed in the malformed cells of the Malpighian tubules (Mt). All the Hvssk depleted larvae remained as prepupae; they gradually darkened and eventually died. Furthermore, depletion of Hvssk at the pupal stage suppressed adult feeding and shortened adult lifespan. These findings demonstrated that Ssk plays a vital role in the integrity and function of both midguts and Mt, and established the conservative roles of Ssk in the formation of epithelial barrier and the homeostasis of epithelial cells in H. vigintioctopunctata.

RNAi-based silencing of proteasome 20S subunit alpha 2 affected the survival and development of Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a notorious pest of solanaceous plants in Asia, which is mainly managed by chemical pesticides. RNA interference (RNAi) technique is considered to be a promising and effective alternative for pest control. In this study, we selected the proteasome 20S subunit alpha 2 (Prosα2) gene, a cellular protein involved in many proteins regulatory processes, to explore the RNAi efficiency in H. vigintioctopunctata. The obtained results confirmed the significant lethal effects of HvProsα2 silencing on the H. vigintioctopunctata 1st instar larvae at concentrations of 100, 50, and 5 ng/μL. Ingestion of the bacterially expressed dsHvProsα2 caused high mortality in both larvae and adults. Moreover, silencing of HvProsα2 resulted in feeding disorders, growth delay, and abnormal intestinal development of the larvae. Overall, HvProsα2 acts as an important regulator for the growth and development of H. vigintioctopunctata, and can serve as a candidate target gene for the RNAi-based control of H. vigintioctopunctata.

Dusky-like Is Critical for Morphogenesis of the Cellular Protuberances and Formation of the Cuticle in Henosepilachna vigintioctopunctata

Dusky-like (Dyl) is a transmembrane protein containing a zona pellucida domain. Its physiological roles during metamorphosis have been well explored in Drosophila melanogaster and have also been documented in Tribolium castaneum. However, Dyl has undergone a functional shift between Diptera and Coleoptera insects. Further investigation of Dyl in other insects will be helpful to further clarify its function in insect growth and development. Henosepilachna vigintioctopunctata is an important Coleoptera that causes enormous economic losses in agriculture in China. In this study, we found that the expression of Hvdyl was detectable in embryos, larvae, prepupae, pupae, and adults. We knocked down Hvdyl in third- and fourth-instar larvae and pupae with RNA interference (RNAi). RNAi of Hvdyl mainly caused two phenotypic defects. Firstly, the growth of epidermal cellular protuberances was suppressed. Injection of dsdyl (double-stranded dusky-like RNA) at the third-instar larval stage truncated the scoli throughout the thorax and abdomen and shortened the setae on the head capsules and mouthparts of the fourth-instar larvae. Introduction of dsdyl at the third- and fourth-instar stages led to misshapen pupal setae. The setae were shortened or became black nodules. Treatment with dsdyl at the larval and pupal stages resulted in deformed adults with completely suppressed wing hairs. Moreover, the knockdown of Hvdyl at the third-instar stage caused deformed larval mouthparts at the fourth-instar period. As a result, foliage consumption was inhibited, and larval growth was slowed. The results indicate that Dyl is associated with the growth of cellular protuberances throughout development and with the formation of the cuticle in H. vigintioctopunctata.

Complete protection from Henosepilachna vigintioctopunctata by expressing long double-stranded RNAs in potato plastids

RNA interference (RNAi) has emerged as a powerful technology for pest management. Previously, we have shown that plastid-mediated RNAi (PM-RNAi) can be utilized to control the Colorado potato beetle, an insect pest in the Chrysomelidae family; however, whether this technology is suitable for controlling pests in the Coccinellidae remained unknown. The coccinellid 28-spotted potato ladybird (Henosepilachna vigintioctopunctata; HV) is a serious pest of solanaceous crops. In this study, we identified three efficient target genes (β-Actin, SRP54, and SNAP) for RNAi using in vitro double-stranded RNAs (dsRNAs) fed to HV, and found that dsRNAs targeting β-Actin messenger RNA (dsACT) induced more potent RNAi than those targeting the other two genes. We next generated transplastomic and nuclear transgenic potato (Solanum tuberosum) plants expressing HV dsACT. Long dsACT stably accumulated to up to 0.7% of the total cellular RNA in the transplastomic plants, at least three orders of magnitude higher than in the nuclear transgenic plants. Notably, the transplastomic plants also exhibited a significantly stronger resistance to HV, killing all larvae within 6 d. Our data demonstrate the potential of PM-RNAi as an efficient pest control measure for HV, extending the application range of this technology to Coccinellidae pests.

I Choose You: Selecting Accurate Reference Genes for qPCR Expression Analysis in Reproductive Tissues in Arabidopsis thaliana

Quantitative real-time polymerase chain reaction (qPCR) is a widely used method to analyse the gene expression pattern in the reproductive tissues along with detecting gene levels in mutant backgrounds. This technique requires stable reference genes to normalise the expression level of target genes. Nonetheless, a considerable number of publications continue to present qPCR results normalised to a single reference gene and, to our knowledge, no comparative evaluation of multiple reference genes has been carried out in specific reproductive tissues of Arabidopsis thaliana. Herein, we assessed the expression stability levels of ten candidate reference genes (UBC9, ACT7, GAPC-2, RCE1, PP2AA3, TUA2, SAC52, YLS8, SAMDC and HIS3.3) in two conditional sets: one across flower development and the other using inflorescences from different genotypes. The stability analysis was performed using the RefFinder tool, which combines four statistical algorithms (geNorm, NormFinder, BestKeeper and the comparative ΔCt method). Our results showed that RCE1, SAC52 and TUA2 had the most stable expression in different flower developmental stages while YLS8, HIS3.3 and ACT7 were the top-ranking reference genes for normalisation in mutant studies. Furthermore, we validated our results by analysing the expression pattern of genes involved in reproduction and examining the expression of these genes in published mutant backgrounds. Overall, we provided a pool of appropriate reference genes for expression studies in reproductive tissues of A. thaliana, which will facilitate further gene expression studies in this context. More importantly, we presented a framework that will promote a consistent and accurate analysis of gene expression in any scientific field. Simultaneously, we highlighted the relevance of clearly defining and describing the experimental conditions associated with qPCR to improve scientific reproducibility.

RNAi-Based Biopesticides Against 28-Spotted Ladybeetle Henosepilachna vigintioctopunctata Does Not Harm the Insect Predator Propylea japonica

RNA interference (RNAi)-mediated control of the notorious pest Henosepilachna vigintioctopunctata is an emerging environment friendly research area. However, the characterization of key target genes in H. vigintioctopunctata is crucial for this. Additionally, assessing the risk of RNAi to nontarget organisms (NTOs) is necessary for environmental safety. In this study, the potential of RNAi technology in controlling H. vigintioctopunctata infestation has been investigated by the oral delivery of double-stranded RNA (dsRNA). The results revealed that the silencing of six genes, including HvABCH1, HvHel25E, HvProsbeta5, HvProsalpha6, HvProsbeta6, and HvSrp54k, was highly lethal to H. vigintioctopunctata. The LC50 values of the dsRNAs used to silence these six genes were found to be less than 13 ng/μL. Moreover, the use of the bacterially expressed dsRNAs caused high mortality in the lab and field populations of H. vigintioctopunctata. Further, administration of HvHel25E and HvSrp54k dsRNAs in the predatory lady beetle Propylea japonica confirmed no transcriptional or organismal levels effects. This risk-assessment result ensured no off-target RNAi effects on the NTOs. Overall, the findings of the study suggested that HvABCH1, HvHel25E, HvProsbeta5, HvProsalpha6, HvProsbeta6, and HvSrp54k can be novel promising molecular targets with high specificity for H. vigintioctopunctata management with negligible effects on the NTOs.

Disruption of tetrahydrobiopterin (BH4) biosynthesis pathway affects cuticle pigmentation in Henosepilachna vigintioctopunctata

Tetrahydrobiopterin (BH4) is produced from guanosine triphosphate (GTP) under catalyzation of GTP cyclohydrolase I (GTPCH), 6-pyruvoyltetrahydropterin synthase (PTPS) and sepiapterin reductase (SR), among others. In Drosophila melanogaster, BH4 and other pteridines are required for cuticle tanning and eye pigmentation. In this study, two Hvgtpch (Hvgtpch-a and Hvgtpch-b), an Hvptps and an Hvsr transcripts were identified in a serious defoliator Henosepilachna vigintioctopunctata. Hvgtpch-a and Hvgtpch-b were highly expressed just before and/or right after the molt, in contrast to Hvptps and Hvsr. RNA interference (RNAi) by injection of a dsgtpch targeting the common fragment of Hvgtpch-a and Hvgtpch-b into the third instar larvae caused albino fourth-instar larvae and pupae. Around 80% of the Hvgtpch RNAi larvae failed to pupate. The remaining 20% of Hvgtpch RNAi pupated beetles did not completely remove the larval/pupal exuviae after emerged as adults and eventually died. Depletion of Hvgtpch at the fourth instar stage resulted in under-pigmented pupae and adults, with significantly low pupation and emergence rates. The Hvgtpch RNAi adults rarely moved and fed on plant leaves; they died within a week after emergence. Silence of Hvptps or Hvsr at the third- and fourth-instar stages led to similar but less serious phenotypes, with lowest influence in the Hvsr RNAi ladybirds. Moreover, RNAi of Hvgtpch, Hvptps or Hvsr did not affect coloration of the larval ocelli and pupal/adult compound eyes. Therefore, our results demonstrated that pteridines are involved in melanin formation but not in eye pigmentation in H. vigintioctopunctata. Moreover, our findings will enable the development of a dsgtpch-based pesticide to control H. vigintioctopunctata larvae.

Requirement of Myoglianin for metamorphosis in the beetle Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a serious defoliating beetle attacking Solanaceae and Cucurbitaceae plants in many Asian countries. In the present paper, we identified a putative myoglianin (myo) gene. Hvmyo was actively transcribed throughout development, from embryo to adult. RNA interference (RNAi)-aided knockdown of Hvmyo delayed larval development by more than 2 days, reduced larval body size, inhibited the growth of antennae, wings and legs and disturbed gut purge. Knockdown of Hvmyo impaired the larval-pupal transition. All the Hvmyo RNAi larvae arrested at the larval stage or formed misshapen pupae or adults. The deformed pupae and adults were partially wrapped with exuviae, bearing separated wings. Moreover, the expression levels of five ecdysteroidogenesis genes (Hvspo, Hvphm, Hvdib, Hvsad and Hvshd), a prothocicotropic hormone (PTTH)/Torso pathway gene (Hvtorso), two 20E receptor genes (HvEcR and HvUSP), and two 20E signalling genes (HvE93 and HvFTZ-F1) were as a result of HvMyo RNAi significantly lowered. Conversely, the expression of a JH biosynthesis gene (Hvjhamt), a JH receptor gene HvMet and a JH signalling gene HvKr-h1 was greatly enhanced. Although ingestion of 20E and Hal rescued the 20E signal, it could not alleviate larval performance and defective phenotypes. Our results suggest that Myo exerts four distinctive roles in ecdysteroidogenesis, JH production, organ growth and larva-pupa-adult transformation in H. vigintioctopunctata.

Knockdown of Ecdysone-Induced Protein 93F Causes Abnormal Pupae and Adults in the Eggplant Lady Beetle

Ecdysone-induced protein 93F (E93) plays triple roles during post-embryonic development in insects whose juvenile instars are more than four. However, it only acts as a specifier of adult structures in Drosophila flies whose larval instars are fixed at three. In this study, we determined the functions of E93 in the eggplant lady beetle (Henosepilachna vigintioctopunctata), which has four larval instars. We uncovered that E93 was abundantly expressed at the prepupal and pupal stages. A precocious inhibition of the juvenile hormone signal by RNA interference (RNAi) of HvKr-h1 or HvHairy, two vital downstream developmental effectors, at the penultimate instar larval stage increased the expression of E93, Conversely, ingestion of JH by the third-instar larvae stimulated the expression of HvKr-h1 but repressed the transcription of either HvE93X1 or HvE93X2. However, disturbance of the JH signal neither drove premature metamorphosis nor caused supernumerary instars. In contrast, depletion of E93 at the third- and fourth-instar larval and prepupal stages severely impaired pupation and caused a larval-pupal mixed phenotype: pupal spines and larval scoli were simultaneously presented on the cuticle. RNAi of E93 at the pupal stage affected adult eclosion. When the beetles had suffered from a dsE93 injection at the fourth-instar larval and pupal stages, a few resultant adults emerged, with separated elytra, abnormally folded hindwings, a small body size and short appendages. Taken together, our results suggest the larval instars are fixed in H. vigintioctopunctata; E93 serves as a repressor of larval characters and a specifier of adult structures during the larval–pupal–adult transition.

On the trail of iron uptake in ancestral Cyanobacteria on early Earth

Cyanobacteria oxygenated Earth's atmosphere ~2.4 billion years ago, during the Great Oxygenation Event (GOE), through oxygenic photosynthesis. Their high iron requirement was presumably met by high levels of Fe(II) in the anoxic Archean environment. We found that many deeply branching Cyanobacteria, including two Gloeobacter and four Pseudanabaena spp., cannot synthesize the Fe(II) specific transporter, FeoB. Phylogenetic and relaxed molecular clock analyses find evidence that FeoB and the Fe(III) transporters, cFTR1 and FutB, were present in Proterozoic, but not earlier Archaean lineages of Cyanobacteria. Furthermore Pseudanabaena sp. PCC7367, an early diverging marine, benthic strain grown under simulated Archean conditions, constitutively expressed cftr1, even after the addition of Fe(II). Our genetic profiling suggests that, prior to the GOE, ancestral Cyanobacteria may have utilized alternative metal iron transporters such as ZIP, NRAMP, or FicI, and possibly also scavenged exogenous siderophore bound Fe(III), as they only acquired the necessary Fe(II) and Fe(III) transporters during the Proterozoic. Given that Cyanobacteria arose 3.3-3.6 billion years ago, it is possible that limitations in iron uptake may have contributed to the delay in their expansion during the Archean, and hence the oxygenation of the early Earth.

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.

Tyrosine hydroxylase involved in cuticle tanning and reproduction in the 28-spotted potato ladybeetle, Henosepilachna vigintioctopunctata

BACKGROUND

Tyrosine hydroxylase (TH), a melanin synthesis pathway enzyme hydroxylating tyrosine into 3,4-dihydroxyphenylalanine, is involved in the pigmentation and sclerotization of insect cuticles. However, the role of TH in 28-spotted potato ladybeetle (Henosepilachna vigintioctopunctata), an emerging pest of the solanaceous crops has been explored to a limited extent. In this study, we integrated dietary RNA interference (RNAi) and hematoxylin and eosin (H&E) staining with various bioassays to analyze the role of tyrosine hydroxylase (HvTH) throughout the developmental processes of Henosepilachna vigintioctopunctata.

RESULTS

The results revealed that ingestion of dsHvTH led to cuticle tanning impairment, arrested larval feeding in the first and second instars of Henosepilachna vigintioctopunctata, and subsequently resulted in 100% mortality. The H&E staining assays revealed that dsHvTH prevented new abdominal cuticle formation. A pharmacological study using 3-iodo-tyrosine (3-IT), a HvTH inhibitor, disrupted larval-larval-pupal cuticle tanning during the third-fourth instar larval development and eventually failed to pupate. Similarly, dsHvTH fed to fourth instars hindered larval-pupal-adult cuticle tanning, and the eclose adults were 100% malformed. Ingestion of dsHvTH or 3-IT significantly down-regulated HvTH, HvDDC, Hvebony, and Hvlaccase2 expression and reduced dopamine levels. Finally, HvTH silencing in adult females substantially reduced the offspring hatching rates.

CONCLUSIONS

The collective results of the study suggested that HvTH plays conserved roles in larval-pupal-adult cuticle melanization and sclerotization while exhibiting a novel function in Henosepilachna vigintioctopunctata reproduction. © 2022 Society of Chemical Industry.

Silencing uridine diphosphate N-acetylglucosamine pyrophosphorylase gene impairs larval development in Henosepilachna vigintioctopunctata

BACKGROUND

Uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) diphosphorylase (UAP) catalyzes the formation of UDP-GlcNAc, the precursor for the production of chitin in ectodermally derived epidermal cells and midgut, for GlcNAcylation of proteins and for generation of glycosyl-phosphatidyl-inositol anchors in all tissues in Drosophila melanogaster.

RESULTS

Here, we identified a putative HvUAP gene in Henosepilachna vigintioctopunctata. Knockdown of HvUAP at the second-, third- and fourth-instar stages impaired larval development. Most resultant HvUAP hypomorphs showed arrested development at the third-, fourth-instar larval or prepupal stages, and became paralyzed, depending on the age when treated. Some HvUAP-silenced larvae had weak and soft scoli. A portion of HvUAP-depleted beetles formed misshapen pupae. No HvUAP RNA interference pupae successfully emerged as adults. Dissection and microscopic observation revealed that knockdown of HvUAP affected gut growth and food ingestion, reduced cuticle thickness, and negatively affected the formation of newly generated cuticle layers during ecdysis. Furthermore, HvUAP deficiency inhibited development of the tracheal respiratory system and thinned tracheal taenidia.

CONCLUSION

The phenotypical defects in HvUAP hypomorphs suggest that HvUAP is involved in the production of chitin. Moreover, our findings will enable the development of a double-stranded RNA-based pesticide to control H. vigintioctopunctata. © 2021 Society of Chemical Industry.

Oral RNAi toxicity assay suggests clathrin heavy chain as a promising molecular target for controlling the 28-spotted potato ladybird, Henosepilachna vigintioctopunctata

BACKGROUND

Use of RNA interference (RNAi) technology in effective pest management has been explored for decades. Henosepilachna vigintioctopunctata is a major solanaceous crop pest in Asia. In this study, the effects of the RNAi-mediated silencing of clathrin heavy chain in H. vigintioctopunctata were investigated.

RESULTS

Feeding either the in vitro-synthesized or the bacterially expressed double-stranded RNAs (dsRNAs) significantly impaired the normal physiology of H. vigintioctopunctata instars and adults. However, the bacterially expressed dsHvChc caused higher mortality than the in vitro-synthesized ones in the larvae and adults. Moreover, on evaluating the potential risk of dsHvChc on Propylea japonica, significant transcriptional effects of dsHvChc1 were observed, while the organismal level effects were not significant. On the contrary, dsHvChc2 did not affect P. japonica at either level. A similar test revealed significant transcriptional effects of dsPjChc1 on H. vigintioctopunctata, while staying ineffective at the organismal levels. Conversely, dsPjChc2 did not affect H. vigintioctopunctata at either level. Importantly, no effect of dsPjChc1 exposure on H. vigintioctopunctata suggested that other factors besides the 21-nucleotide (nt) matches between sequences were responsible. Finally, ingestion of dsHvmChc1 derived from H. vigintioctomaculata, containing 265-nt matches with dsHvChc1, caused 100% mortality in H. vigintioctopunctata.

CONCLUSIONS

We conclude that (i) species with numerous 21-nt matches in homologous genes are more likely to be susceptible to dsRNA; (ii) dsRNA can be safely designed to avoid negative effects on non-target organisms at both transcriptional and organismal levels; (iii) HvChc can be used as an efficient RNAi target gene to effectively manage H. vigintioctopunctata. © 2021 Society of Chemical Industry.

Silencing tyrosine hydroxylase or dopa decarboxylase gene disrupts cuticle tanning during larva-pupa-adult transformation in Henosepilachna vigintioctopunctata

BACKGROUND

The 28-spotted potato ladybird, Henosepilachna vigintioctopunctata, is a notorious defoliator of many solanaceous and cucurbitaceous plants. Tyrosine hydroxylase (TH) and dopa decarboxylase (DDC) are responsible for cuticle tanning pathway in insects.

RESULTS

We identified HvTH and HvDDC in H. vigintioctopunctata, and found that high levels of them were accumulated just before or right after molting. Injection of dsHvTH or feeding 3-iodo-tyrosine (3-IT) at the third instar larval stage repressed tanning of the larval cuticle, reduced larval feeding, inhibited larval growth, and consequently caused 100% of larval mortality. Knockdown of HvDDC at the third instar larval stage hardly affected the coloration of larval head, and partially inhibited pigmentation of larval bodies and around 80% of the HvDDC RNAi larvae developed into albino pupae and adults. Moreover, depletion of HvTH or HvDDC at the fourth instar larval stage resulted in albino pupae and adults. The HvTH or HvDDC hypomorph adults fully or partially failed to remove the larval/pupal exuviae, possessed pale and abnormal wings, and poorly tanned heads and bodies, and eventually, struggled for several days without feeding on leaves before death.

CONCLUSION

These results show that TH and DDC play key roles in larval and adult cuticle tanning and development in H. vigintioctopunctata. Also, these findings suggest that dopa- and dopamine-originated pigments are essential for larval and adult feeding behavior and the molting process during emergence. © 2022 Society of Chemical Industry.

Identification and Validation of Reference Genes for Expression Analysis Using qRT-PCR in Cimex hemipterus (Hemiptera: Cimicidae)

The tropical bed bug, Cimex hemipterus (F.) (Hemiptera: Cimicidae) is an important public-health pest that feeds on the blood of humans and some other animals. To explore the function of the target genes of C. hemipterus, it is essential to select suitable reference genes for the accurate quantification of gene expression. Here, we selected 10 frequently used reference genes in insects and evaluated their stability in C. hemipterus under various biotic (developmental stage, sex, and tissue) and abiotic (gas stimulation and temperature) conditions through RefFinder (which integrates four computational programs: geNorm, NormFinder, BestKeeper, and ∆Ct). Results indicate that the optimal combination of reference genes for each experimental condition was as follows: RPL8 and EF1α for the developmental stage (eggs, early instar nymphs, late instar nymphs, and adults), RPL8 and RPS16 for adult sex, RPL8 and RPL11 for adult tissue (head, thorax, abdomen, and legs), RPL8 and β-tubulin for gas stimulation (air and carbon dioxide), and RPL8 and NADH for temperature (0, 5, 17, 30, and 37 °C). Finally, the expression pattern of the HSP70 and GR21 genes were analyzed, and the results highlight the importance of appropriate reference-gene selection. Our results provide a comprehensive list of optimal reference genes from C. hemipterus for the first time, which will contribute to accurately analyzing the expression of target genes.

Smad on X is vital for larval-pupal transition in a herbivorous ladybird beetle

Insect development is regulated by a combination of juvenile hormone (JH) and 20-hydroxyecdysone (20E). Production of both JH and 20E is regulated by transforming growth factor-β (TGFβ) signaling. TGFβ can be classified into two branches, the Activin and Bone Morphogenetic Protein (BMP) pathways. In Drosophila melanogaster, BMP signaling is critical for JH synthesis, whereas Activin signal is required to generate the large pulse of 20E necessary for entering metamorphosis. However, to which extent the roles of these signals are conserved remains unknown. Here we studied the role of an Activin component Smad on X (Smox) in post-embryonic development in a defoliating ladybird Henosepilachna vigintioctopunctata. RNA interference (RNAi)-aided knockdown of Hvsmox inhibited larval growth, and impaired larval development. All Hvmyo RNAi larvae arrested at the fourth-instar larval stage. Moreover, knockdown of Hvsmox delayed gut and Malpighian tubules remodeling. Furthermore, the expression of a JH biosynthesis gene (Hvjhamt), a JH receptor gene HvMet and a JH response gene HvKr-h1 was greatly enhanced. Conversely, the expression levels of an ecdysteroidogenesis gene (Hvspo), a 20E receptor gene (HvEcR) and six 20E response genes (HvBrC, HvE74, HvE75, HvE93, HvHR3 and HvHR4) were significantly lowered. Knockdown of HvMet partially restored the negative phenotypes in the Hvsmox RNAi beetles. Our results suggest that Smox exerts regulative roles in JH production, ecdysteroidogenesis and organ remodeling, thus contributing to modulate the larva-pupa-adult transformation in H. vigintioctopunctata.

Selection of reference genes for quantitative real-time PCR normalization in the coffee white stem borer, Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae)

The coffee white stem borer, Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae), is a major destructive pest of Coffea arabica L. (Gentianales: Rubiaceae), widely planted in many Asian countries, including China. Quantitative real-time polymerase chain reaction (qRT-PCR) is a common method for quantitative analysis of gene transcription levels. To obtain accurate and reliable qRT-PCR results, it is necessary to select suitable reference genes to different experimental conditions for normalizing the target gene expression. However, the stability of the expression of reference genes in X. quadripes has rarely been studied. In this study, the expression stability of nine candidate reference genes were investigated under biotic and abiotic conditions for use in qRT-PCR's normalization. By integrating the results of four algorithms of NormFinder, BestKeeper, geNorm, and RefFinder, the optimal reference gene combinations in different experimental conditions were performed as follows: RPL10a and EIF3D were the optimal reference genes for developmental stage samples, EIF4E, RPL10a, and RPS27a for tissue samples, V-ATP and EF1α for the sex samples, EIF3D and V-ATP for temperature treatment, RPS27a and RPL10a for insecticide stress, and RPL10a, RPS27a, and EF1α for all the samples. This study will help to obtain the stable internal reference genes under biotic and abiotic conditions and lay the foundation for in-depth functional research of target genes or genomics on olfactory molecular mechanisms, temperature adaptability, and insecticide resistance in X. quadripes.

Vacuolar ATPase subunit F is critical for larval survival in Henosepilachna vigintioctopunctata

Vacuolar ATPase (vATPase) is an important proton pump in insect tissues including gut and Malpighian tubule. Subunit F, one of the 16 subunits of the vATPase holoenzyme, is not well characterized. Here, we found that two HvvATPaseF isoforms were highly expressed in the hindgut and Malpighian tubules (MT) in the 28-spotted lady-beetle Henosepilachna vigintioctopunctata, an agricultural pest that feeds on Solanaceae and Cucurbitaceae. Knockdown of both HvvATPaseF variants by RNA interference (RNAi) delayed larval growth and negatively affected ecdysis and adult emergence. In the midgut, RNAi treatment resulted in the disappearance of peritrophic membrane, the reduction in the size and the impaired integrity of the gut, which was associated with sparse principle cells and an increase in TUNEL- and EdU-positive cells. Whereas the MT were opaque and the tubule lumens were full of urine in dsegfp-fed larvae, the tubules were clear and the tubule lumens were empty in the dsvATPaseF-fed larvae. HvvATPaseF knockdown was also associated with a decrease in the abundance of the fat body and the levels of glucose, trehalose, triglyceride, total soluble amino acids and proteins, and an increase in glycogen. Consistent with the known effects of sugars on chitin formation, both the expression level of a chitin biosynthesis gene and the thickness of the head capsule cuticle were reduced in the HvvATPaseF-depleted beetles. Our results demonstrated that subunit F plays an essential role in H. vigintioctopunctata development.

RNAi suppression of the nuclear receptor FTZ-F1 impaired ecdysis, pupation, and reproduction in the 28-spotted potato ladybeetle, Henosepilachna vigintioctopunctata

Fushi-tarazu factor 1 (FTZF1) is an ecdysone-inducible transcription factor that plays a vital role during the metamorphosis in insects. In this study, we functionally characterized HvFTZ-F1 in H. vigintioctopunctata, a dreadful solanaceous crop pest, by using a dietary RNA interference technique. The HvFTZ-F1 expression levels were elevated in the 1st and 2nd-instars before molting and declined immediately after ecdysis. The HvFTZ-F1 silencing led to high mortality in the 1st instars, while the expression of the osmosis-regulative gene, HvAQPAn.G, was significantly increased in the 1st instars. HvFTZ-F1 silencing downregulated the Halloween and 20E-related genes, decreased the ecdysteroids titer, suppressed the expression of pigmentation-related genes, and reduced the catecholamines titer. In the 4th instars, HvFTZ-F1 silencing caused 100% mortality by arresting the development at the prepupal stage and preventing new abdominal cuticle formation. In the female adults, HvFTZ-F1 silencing caused an evident decrease in fecundity, prolonged the pre-oviposition period, reduced the number of eggs and hatching rate, severely atrophied the ovaries. Moreover, the 20E-related genes and the dopamine synthesis genes were suppressed in the dsHvFTZ-F1-treated females. Overall, our results revealed that HvFTZ-F1 regulates ecdysis, pupation, and reproduction in H. vigintioctopunctata, thereby could be a promising molecular target for the development of RNAi-based biopesticides to control H. vigintioctopunctata.

Dissecting the Isoform-Specific Roles of FTZ-F1 in the Larval–Larval and Larval–Pupal Ecdyses in Henosepilachna vigintioctopunctata

Simple Summary

Fushi Tarazu Factor-1 (FTZ-F1) plays a crucial regulatory role in molting in insects. It is hypothesized that, by alternative transcription start and splicing, the FTZ-F1 gene generates two isomers (α- and βFTZ-F1) that exert isoform-specific roles in non-Drosophilid insects. In the present paper, we first unveiled that the same post-transcriptional processing in FTZ-F1 occurred in coleopterans, lepidopterans, dipterans and hymenopterans. We then found that αFTZ-F1 and βFTZ-F1 were actively transcribed throughout the development, from embryo to adult, in Henosepilachna vigintioctopunctata. Moreover, by RNA interference, we confirmed that both FTZ-F1 isoforms act as regulators in larval–larval molting and βFTZ-F1 is involved in the regulation of the larval–pupal transition.

Abstract

Fushi Tarazu Factor 1 (FTZ-F1), a member of the nuclear receptor superfamily, is the downstream factor of 20-hydroxyecdysone signaling. In Drosophila melanogaster, alternative transcription start and splicing in the FTZ-F1 gene generate αFTZ-F1 and βFTZ-F1 isoforms, which are vital for pair-rule segmentation in early embryogenesis and post-embryonic development, respectively. However, whether the same mRNA isoforms are present and exert the conservative roles remains to be clarified in other insects. In the present paper, we first mined the genomic data of representative insect species and unveiled that the same post-transcriptional processing in FTZ-F1 occurred in coleopterans, lepidopterans, dipterans and hymenopterans. Our expression data in Henosepilachna vigintioctopunctata, a serious polyphagous defoliator damaging a wide range of crops in Solanaceae and Cucurbitaceae, showed that both αFTZ-F1 and βFTZ-F1 were actively transcribed throughout the development, from embryo to adult. The RNA interference-aided knockdown of both isoforms completely arrested larval ecdysis from the third to the fourth instar, in contrast to the depletion of either isoform. In contrast, silencing βFTZ-F1, rather than αFTZ-F1, severely impaired the larval–pupal transformation. We accordingly propose that both FTZ-F1 isoforms are essential but mutually interchangeable for larval–larval molting, while βFTZ-F1 is necessary for the larval–pupal transition and sufficient to exert the role of both FTZ-F1s during larval–pupal metamorphosis in H. vigintioctopunctata.

Silencing of Adc and Ebony Causes Abnormal Darkening of Cuticle in Henosepilachna vigintioctopunctata

N-β-alanyldopamine (NBAD) is a precursor of N-acylquinone sclerotin utilized for cross-linking between cuticular proteins for cuticle during insect molting. The importance of NBAD in cuticle tanning has not been well compared among different developing stages of insects. Henosepilachna vigintioctopunctata, a typical polyphagous pest feeding on a large number of Solanaceae and Cucurbitaceae plants in Asian countries, displays diverse cuticle pigmentation patterns among developing stages and body regions. Here, we found that the expression of three genes (Hvadc, Hvebony, and Hvtan) involved in NBAD biosynthesis peaked in the 4-day-old pupae or 0-day-old adults of H. vigintioctopunctata. At the first, second, third, and fourth larval instar and pupal stage, their transcript levels were high just before and/or right after the molting. Moreover, they were more abundantly transcribed at the larval heads than in the bodies. RNA interference (RNAi) of either Hvadc or Hvebony at the third instar larvae selectively deepened the color of the larval head capsules, antennae, mouthpart, scoli, strumae, and legs; and depletion of the two genes blackened the pupal head capsules, antennae, mouthpart, and legs. However, the knockdown of either Hvadc or Hvebony darkened the whole bodies of the adults. Conversely, RNAi of Hvtan at the third instar stage had little influence on the pigmentation in the larvae, pupae, and adults. These findings demonstrated that Adc and Ebony are important in cuticle pigmentation of H. vigintioctopunctata and suggested that larger quantities of NBAD were present in adults and play more important roles in pigmentation than larvae/pupae.

Yellow-b, -c, -d, and -h are required for normal body coloration of Henosepilachna vigintioctopunctata

The involvement of yellow genes y-b, y-c, y-e, and y-h in cuticle tanning has poorly been clarified. In the present paper, six putative yellow (y-y, y-b, y-c, y-e y-f, and y-h) genes were identified in Henosepilachna vigintioctopunctata. Hvy-b, Hvy-c, Hvy-e, and Hvy-h were abundantly transcribed at early larval and late pupal stages, especially in the epidermis. Accordingly, RNA interference (RNAi) experiments were performed by an injection of dsy-b, dsy-c, dsy-e, or dsy-h into the second instar larvae and 1-day-old pupae. The head capsule, scoli and strumae, and legs in the fourth-instar larvae became blacker; the blackish spots in the pupae were darkened and widened after RNAi of Hvy-b, compared with those of dsegfp-treated controls. Depletion of Hvy-b at the 1-day-old pupal stage expanded two pair of black markings on the sternum of the metathorax, and darkened the black patched on the sterna of the abdomen segments I-VI in the resultant adults. Depletion of Hvy-e caused darker pigmented adult body and elytral cuticles than those of dsegfp-introduced controls. However, there was no obvious difference in pigmentation of the black markings. Hvy-h-deficient larvae displayed dark yellow body color, whereas the body color of the dsegfp-injected control was pale yellow. There was no obvious difference in coloration of larval specific-black markings or pupal cuticle between dsHvy-h- and dsegfp-treated animals. Moreover, silence of Hvy-c at the second instar larval stage lightened black markings in the resulting larvae and pupae, but had no influence on pale yellow body color. Our results demonstrated their different roles of the four yellow genes during body pigmentation: HvY-b and HvY-c, respectively, inhibit and facilitate the coloration within dark markings, whereas HvY-e and HvY-h, respectively, repress the pigmentation in adult and larval body cuticles outside the black patches in H. vigintioctopunctata.

Reference Genes for Expression Analyses by qRT-PCR in Phthorimaea operculella (Lepidoptera: Gelechiidae)

Due to a lack of effective internal references, studies on functional genes in Phthorimaea operculella, a serious Lepidopteran pest attacking potatoes worldwide, have been greatly limited. To select suitable endogenous controls, ten housekeeping genes of actin (ACT), α-tubulin (α-TUB), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), elongation factor 1α (EF1α), 18S and 28S ribosomal RNA (18S, 28S), ribosomal protein genes RPL4, RPL13 and RPL27 and superoxide dismutase (SOD) were tested. Their expression levels were determined under three different experimental conditions (developmental stages, tissues/organs and temperatures) using qRT-PCR technology. The stability was evaluated with five methods (Ct value, geNorm, NormFinder, BestKeeper and RefFinder). The results clarified that RPL13, EF1α and RPL27 are ranked as the best reference gene combination for measuring gene expression levels among different developing stages and under various temperatures; EF1α and RPL13 are recommended to normalize the gene expression levels among diverse tissues. EF1α and RPL13 are the best reference genes in all the experimental conditions. To validate the utility of the selected reference pair, EF1α and RPL13, we estimated the tissue-biased expression level of chitin synthase A gene (PoChSA). As expected, PoChSA was abundantly expressed in ectodermally derived epidermal cells, and lowly transcribed in the midgut. These findings will lay the foundation for future research on the molecular physiology and biochemistry of P. operculella.

Stability of Nuclear and Mitochondrial Reference Genes in Selected Tissues of the Ambrosia Beetle Xylosandrus germanus

The fungus-farming ambrosia beetle Xylosandrus germanus (Blandford) uses a pouch-like structure (i.e., mycangium) to transport spores of its nutritional fungal mutualist. Our current study sought to identify reference genes necessary for future transcriptome analyses aimed at characterizing gene expression within the mycangium. Complementary DNA was synthesized using selected tissue types from laboratory-reared and field-collected X. germanus consisting of the whole body, head + thorax, deflated or inflated mycangium + scutellum, inflated mycangium, and thorax + abdomen. Quantitative reverse-transcription PCR reactions were performed using primers for 28S ribosomal RNA (28S rRNA), arginine kinase (AK), carbamoyl-phosphate synthetase 2-aspartate transcarbamylase-dihydroorotase (CAD), mitochondrial cytochrome oxidase 1 (CO1), and elongation factor-1α (EF1α). Reference gene stability was analyzed using GeNorm, NormFinder, BestKeeper, ΔCt, and a comprehensive final ranking by RefFinder. The gene CO1 was identified as the primary reference gene since it was generally ranked in first or second position among the tissue types containing the mycangium. Reference gene AK was identified as a secondary reference gene. In contrast, EF1α was generally ranked in the last or penultimate place. Identification of two stable reference genes will aid in normalizing the expression of target genes for subsequent gene expression studies of X. germanus' mycangium.

Evaluation of Reference Genes in Glenea cantor (Fabricius) by Using qRT-PCR

Kapok is the main host of Glenea cantor (Fabricius), which causes serious damage and is difficult to control. In severe cases, it often causes the kapok trees to die continuously, which seriously affects the results of urban landscaping. To provide reference for the functional research on related genes in G. cantor, we screened the stable expression of candidate reference genes at different developmental stages (i.e., eggs, larvae, pupae, and adults), in various adult tissues (i.e., head, thorax, abdomen, feet, antennae, and wings), and sexes (i.e., male pupae, female pupae, male adults, and female adults). In this study, 12 candidate reference genes (i.e., ACTINLIKE, ACTININ, TUB, RPL36, RPL32, RPS20, TBP, GAPDH, 18S rRNA, EF1A1, EF1A2, and UBQ) were evaluated using different adult tissues, developmental stages, and sexes. RefFinder, geNorm, NormFinder, and BestKeeper were used to evaluate and comprehensively analyze the stability of the expression of the candidate reference genes. The results show that RPL32 and EF1A1 were the most suitable reference genes in the different adult tissues, and RPL36 and EF1A1 were best at the different developmental stages. RPL36 and EF1A2 were the best fit for the qRT-PCR reference genes in the different sexes, while RPL36 and EF1A1 were the most appropriate qRT-PCR reference genes in all samples. Results from geNorm showed that the optimal number of reference genes was two. We also surveyed the expression of cellulase at the different developmental stages and in the different adult tissues. Results further verified the reliability of the reference genes, and confirmed the best reference genes under the different experimental conditions. This study provides a useful tool for molecular biological studies on G. cantor.

RNA interference-mediated silencing of vATPase subunits A and E affect survival and development of the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata

RNA interference (RNAi) has emerged as a powerful tool for developing novel management strategies for controlling insect pests. The 28-spotted ladybeetle, Henosepilachna vigintioctopunctata is one of the most important pests attacking solanaceous plants in Asia. In this study, the potential of dietary RNAi to manage H. vigintioctopunctata was investigated using both in vitro synthesized and bacterially expressed double-stranded RNAs (dsRNAs) of HvvATPase A and HvvATPase E. The expression levels of HvvATPase A and HvvATPase E were higher in Malpighian tubules than in other tissue types. The silencing of HvvATPase A and HvvATPase E led to significant mortality in H. vigintioctopunctata larvae. In addition, the ingestion of HvvATPase A and HvvATPase E significantly deterred feeding behavior and subsequently arrested the development of H. vigintioctopunctata. Notably, the bacterially expressed dsRNAs consistently caused higher mortality in larvae and adults. Finally, the nontarget effects of the dsRNAs of H. vigintioctopunctata on the predatory ladybeetle Propylaea japonica were evaluated. P. japonica 1st instar larvae were administered vATPase A and vATPase E dsRNAs from H. vigintioctopunctata and P. japonica under the worst-case scenario, in which dsGFP served as negative control. There were significant effects of dsHvvATPase A on P. japonica at the transcriptional level but not at the organismal level, whereas dsHvvATPase E did not effect P. japonica at either the transcriptional or the organismal level. Collectively, the results of the study suggest that HvvATPase A and HvvATPase E can act as novel molecular targets for the control of H. vigintioctopunctata.

Knockdown of Vacuolar ATPase Subunit G Gene Affects Larval Survival and Impaired Pupation and Adult Emergence in Henosepilachna vigintioctopunctata

Simple Summary

Vacuolar ATPase (vATPase), a proton pump driven by ATP hydrolysis, acts as a membrane energizer to motivate the movement of ions and nutrients across the cellular membrane in insect guts and Malpighian tubules, among others. The vATPase holoenzyme contains 16 subunits. Out of these subunits, mammalian G subunit includes three isoforms (G1-G3) which are encoded by three distinctive genes. The physiological role of a specific G isoform can be compensated by others. Thus, current experimental evidence on the in vivo function of G is rather limited among eight V₁ subunits. In the present paper, particular attention was paid to an insect model, Henosepilachna vigintioctopunctata ladybird, a serious defoliator of Solanaceae and Cucurbitaceae plants in many Asian countries. Given that the beetle is sensitive to RNA interference (RNAi), HvvATPaseG gene was knocked down by ingestion of its corresponding dsRNA at the fourth-instar larval stage. Silence of HvvATPaseG affected larval growth and survival, impaired pupation and adult emergence. Our results provide a basis for further functional research on the vATPase G subunit in insects and suggest new ideas for the management of H. vigintioctopunctata.

Abstract

The vATPase holoenzyme consists of two functional subcomplexes, the cytoplasmic (peripheral) V₁ and the membrane-embedded V₀. Both V₁ and V₀ sectors contain eight subunits, with stoichiometry of A₃B₃CDE₃FG₃H in V₁ and ac₈c’c”def(Voa1p) in V₀ respectively. However, the function of G subunit has not been characterized in any non-Drosophilid insect species. In the present paper, we uncovered that HvvATPaseG was actively transcribed from embryo to adult in a Coleopteran pest Henosepilachna vigintioctopunctata. Its mRNA levels peaked in larval hindgut and Malpighian tubules. RNA interference (RNAi)-mediated knockdown of HvvATPaseG significantly reduced larval feeding, affected chitin biosynthesis, destroyed midgut integrity, damaged midgut peritrophic membrane, and retarded larval growth. The function of Malpighian tubules was damaged, the contents of glucose, trehalose, lipid, total soluble amino acids and protein were lowered and the fat bodies were lessened in the HvvATPaseG RNAi larvae, compared with those in the PBS- and dsegfp-fed beetles. In contrast, the amount of glycogen was dramatically increased in the HvvATPaseG depletion ladybirds. As a result, the development was arrested, pupation was inhibited and adult emergence was impaired in the HvvATPaseG hypomorphs. Our results demonstrated that G subunit plays a critical role during larval development in H. vigintioctopunctata.

RNAi for chitin synthase 1 rather than 2 causes growth delay and molting defect in Henosepilachna vigintioctopunctata

Chitin synthase (CHS) plays a critical role in chitin synthesis and excretion. In most insects, CHSs have been segregated into 1 and 2 classes. CHS1 is responsible for chitin production in the ectodermally-derived epidermal cells. CHS2 is dedicated to chitin biosynthesis in the midgut peritrophic matrix (PM). Henosepilachna vigintioctopunctata is a serious pest of Solanaceae and Cucurbitaceae plants. In this study, we identified HvCHS1 and HvCHS2. We found that HvCHS1 was abundantly transcribed in the larval tracheae and epidermis, whereas HvCHS2 was mainly expressed in the guts. Escherichia coli HT115 expressed double stranded RNAs targeting HvCHS1 and HvCHS2 (dsCHS1 and dsCHS2) were used to immerse potato foliage and the treated leaves were provided to the newly-molted fourth- and third-instar larvae. Ingestion of dsCHS1 by the fourth-instar larvae significantly diminished the target mRNA level and had slight influence on the expression of HvCHS2. In contrast, consumption of dsCHS2 significantly lowered the target mRNA level but triggered the transcription of HvCHS1. Knockdown of HvCHS1, rather than HvCHS2, arrested larval development and impaired larva-pupa-adult transition. A large proportion of HvCHS1 hypomorphs became stunting prepupae, deformed pupae or misshapen adults. Moreover, knockdown of HvCHS1 damaged gut integrity, decreased cuticle thickness, and delayed the formation of newly-generated cuticle layer during ecdysis. Furthermore, depletion of HvCHS1 inhibited the development of trachea system and thinned tracheal taenidia. Ingestion of dsCHS1 at the third-instar stage caused similar but severe negative effects. Our results demonstrated that HvCHS1 is responsible for chitin biosynthesis during ecdysis. Moreover, HvCHS1 is a potential amenable target gene and young larvae are more susceptible to dsRNA.

Assessment on effects of transplastomic potato plants expressing Colorado potato beetle β-Actin double-stranded RNAs for three non-target pests

RNA interference has been proved as an efficient technology for pest control through the silencing of essential genes of targeted insects. We had previously shown that the expression of double-stranded RNAs (dsRNAs) in plastids of plants offers a great potential for efficiently controlling Colorado potato beetle (CPB, Leptinotarsa decemlineata) (Coleoptera, Chrysomelidae). However, whether these transplastomic plants have an impact on other non-target pests was not investigated. In this study, we evaluated the potential effects of transplastomic plants expression dsRNAs target CPB β-Actin (referred to as ACT plants) on three other potato pests: Myzus persicae (Hemiptera, Aphididae), Henosepilachna vigintioctopunctata (Coleoptera, Coccinellidae), and Spodoptera litura (Lepidoptera, Noctuidae). Although no effects on M. persicae or S. litura were observed by feeding ACT plants, we found that feeding H. vigintioctopunctata with ACT plants can result in its growth retardation and suppressing the gene expression of HvACT, which has 91.7% identity to CPB β-Actin and shared 66 potential 21-mer matches. Taking together, these results indicated that ACT plants had cross-resistance to H. vigintioctopunctata, another coleopteran insect with the highly conserved nucleotide sequence of β-Actin gene. It also provided an opportunity to simultaneously control L. decemlineata and H. vigintioctopunctata by RNAi induced by intermediate dsRNAs with optimized sequences.

Determination of the panel of reference genes for quantitative real-time PCR in fetal and adult rat intestines

In quantitative real-time PCR (qRT-PCR) detection, the stability of reference genes varies with different organs, tissue locations, sex and developmental stages. This study aimed to screen out and determine the optimal panel of reference genes of the intestine in pre- and post-natal rats of different sex. We used qRT-PCR to detect the mRNA expression of six commonly used reference genes (ACTB, GAPDH, HPRT1, B2M, RPLPO and SDHA) in rat intestines at gestational day 21 (GD21) and postnatal week 12 (PW12). Using GeNorm, BestKeeper and NormFinder software comprehensively analyzed the stability of candidate reference genes and screened out stable reference genes. Further, we used the pathological model of prenatal dexamethasone exposure (PDE) to verify the stability of the selected panel of reference genes. Based on the results of the software analysis, the optimal panel of reference genes in the fetal rat intestine was SDHA + ACTB, and the adult rat small intestine and colon were ACTB + HPRT1 and RPLP0 + GAPDH, respectively. There was no significant sex difference in the above results. Besides, in the PDE model, the results were consistent with those under physiological conditions. Therefore, the stability of intestinal reference genes in fetal rats and adult rats was different, and the intestinal reference genes of adult rats were intestinal segments-specific. The selected panel of reference genes was still stable under pathological conditions. This study determined the optimal panel of reference genes of pre- and post-natal rat intestines and provided reliable reference genes for the qRT-PCR analysis of rat intestines.

RNAi of vacuolar-type H+-ATPase genes causes growth delay and molting defect in Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is one of the most serious insect pests to a large number of nightshades and cucurbits. RNA interference (RNAi) triggered by double-stranded RNA (dsRNA) offers a reduced risk approach to control the beetle. Identification of amenable target genes and determination of appropriate life stage for dsRNA treatment are two critical steps in order to improve RNAi efficiency. In the present paper, we identified three vATPase genes, namely HvvATPaseC, HvvATPaseE and HvvATPaseH. We found that the three transcripts were widely expressed in the eggs, first- to fourth-instar larvae, prepupae, pupae and adults. They were abundantly transcribed in the hindgut and Malpighian tubules, in contrast to the epidermis and fat body. Three days' ingestion of dsvATPaseC, dsvATPaseE and dsvATPaseH by the fourth-instar larvae significantly decreased corresponding transcript level by 90.1, 88.9 and 97.2%, greatly reduced larval fresh weight by 28.0, 29.9 and 28.0%, and caused 66.7, 100 and 78.7% larval lethality respectively. Comparably, 3 days' exposure of the third-instar larvae to dsvATPaseC significantly reduced HvvATPaseC mRNA level by 89.5%, decreased approximately 80% of the larval fresh weight, and killed 100% of the treated larvae. Therefore, the three vATPase genes, especially HvvATPaseE, are potential amenable target genes and young larvae are more susceptible to dsRNA. Our findings will enable the development of the dsRNA-based pesticide to control H. vigintioctopunctata.

Disruption of kynurenine pathway reveals physiological importance of tryptophan catabolism in Henosepilachna vigintioctopunctata

Kynurenine pathway is critically important to catabolize tryptophan, to produce eye chromes, and to protect nervous system in insects. However, several issues related to tryptophan degradation remain to be clarified. In the present paper, we identified three genes (karmoisin, vermilion and cardinal) involved in kynurenine pathway in Henosepilachna vigintioctopunctata. The karmoisin and cardinal were highly expressed in the pupae and adults having compound eyes. Consistently, high-performance liquid chromatography result showed that three ommochrome peaks were present in adult heads rather than bodies (thoraces, legs, wings and abdomens). RNA interference (RNAi)-aided knockdown of vermilion caused accumulation of tryptophan in both adult heads and bodies, disappearance of ommochromes in the heads and a complete loss of eye color in both pupae and adults. Depletion of cardinal brought about excess of 3-hydroxykynurenine and insufficient ommochromes in the heads and decolored eyes. RNAi of karmoisin resulted in a decrease in ommochromes in the heads, and a partial loss of eye color. Moreover, a portion of karmoisin-, vermilion- or cardinal-silenced adults exhibited negative phototaxis, whereas control beetles showed positive phototaxis. Furthermore, dysfunctions of tryptophan catabolism impaired climbing ability. Our findings clearly illustrated several issues related to kynurenine pathway and provided a new insight into the physiological importance of tryptophan catabolism in H. vigintioctopunctata.

Evaluation of candidate reference genes for gene expression analysis in the brassica leaf beetle, Phaedon brassicae (Coleoptera: Chrysomelidae)

The brassica leaf beetle Phaedon brassicae is a notorious defoliator of cruciferous vegetables. However, few molecular studies of this pest have been conducted due to limited sequence data. Recently, RNA sequencing has offered a powerful platform to generate numerous transcriptomic data, which require RT-qPCR to validate target gene expression. The selection of reliable reference genes to normalize RT-qPCR data is a prerequisite for gene expression analysis. In the present study, the expression stabilities of eight candidate reference genes under biotic conditions (development stages and various tissues) and abiotic perturbations (thermal stress and pesticide exposure) were evaluated using four different statistical algorithms. The optimal suites of reference genes were recommended for the respective experimental conditions. For tissue expression analysis, RPL32 and EF-1α were recommended as the suitable reference genes. RPL19 and TBP were the optimal reference genes across different developmental stages. RPL32 and TBP were identified as the most suitable references for thermal stress. Furthermore, RPL32 and RPL19 were ranked as the best references for insecticide exposure. This work provides a systematic exploration of the optimal reference genes for the respective experimental conditions, and our findings would facilitate molecular studies of P. brassicae.

Identification and Evaluation of Suitable Reference Genes for RT-qPCR Analysis in Hippodamia variegata (Coleoptera: Coccinellidae) Under Different Biotic and Abiotic Conditions

Reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) is an accurate and convenient technique for quantifying expression levels of the target genes. Selection of the appropriate reference gene is of the vital importance for RT-qPCR analysis. Hippodamia variegata is one of the most important predatory natural enemies of aphids. Recently, transcriptome and genome sequencings of H. variegata facilitate the gene functional studies. However, there has been rare investigation on the detection of stably expressed reference genes in H. variegata. In the current study, by using five analytical tools (Delta Ct, geNorm, NormFinder, BestKeeper, and RefFinder), eight candidate reference genes, namely, Actin, EF1α, RPL7, RPL18, RPS23, Tubulin-α, Tubulin-β, and TufA, were evaluated under four experimental conditions including developmental stages, tissues, temperatures, and diets. As a result, a specific set of reference genes were recommended for each experimental condition. These findings will help to improve the accuracy and reliability of RT-qPCR data, and lay a foundation for further exploration on the gene function of H. variegata.

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.

RNA interference targeting ecdysone receptor blocks the larval-pupal transition in Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a serious insect pest which attacks a large number of nightshades and cucurbits in Asian countries, Brazil and Australia. Prolonged application of traditional pesticides has caused environmental pollution and exerted deleterious effects on human health. Finding new approaches with high target specificity and low environmental contamination has become an urgent task. RNA interference (RNAi) induced by double-stranded RNA (dsRNA) is expected to be applicable to managing this pest. Here we evaluated the effects of Escherichia coli-expressed dsRNAs targeting ecdysone receptor (EcR) gene via dietary delivery in laboratory and foliar spraying in a greenhouse. The target transcript was successfully knocked down when the 4th-instar larvae had fed on potato foliage dipped with dsEcR in a laboratory bioassay. Around 85% of the HvEcR RNAi larvae remained as prepupae or became abnormal pupae, and failed to emerge into adults. Ingestion of dsEcR-immersed foliage by the 3rd-instar larvae effectuated a comparable RNAi response and brought about more severe defects: all the resultant larvae arrested development, remained as prepupae and finally died. For assay in the greenhouse, a dsEcR-contained E. coli suspension was directly sprayed to the foliage of greenhouse-growing potato plants and the 3rd- and 4th-instar larvae were transferred to the leaves. High RNAi efficacy was obtained and identical RNAi phenotypes were observed in treated larvae. In addition, spraying dsEcR reduced leaf damage. Our results indicate a possibility of practical application of dsEcR as an environmentally friendly RNA pesticide to control H. vigintioctopunctata larvae.

Selection of reference genes for quantitative PCR analysis in poultry red mite (Dermanyssus gallinae)

Poultry red mites (PRMs, Dermanyssus gallinae) are harmful ectoparasites that affect farmed chickens and cause serious economic losses in the poultry industry worldwide. Acaricides are used for PRM control; however, some PRMs have developed acaricide-resistant properties, which have indicated the need for different approaches for PRM control. Therefore, it is necessary to elucidate the biological status of PRMs to develop alternative PRM control strategies. Quantitative polymerase chain reaction (qPCR) allows analysis of the biological status at the transcript level. However, reference genes are preferable for accurate comparison of expression level changes given the large variation in the quality of the PRM samples collected in each farm. This study aimed to identify candidate reference genes with stable expression levels in the different blood feeding states and life stages of PRMs. First, we selected candidates based on the following criteria: sufficient expression intensity and no significant expression difference between fed and starved states. We selected and characterized seven candidate reference genes. Among them, we evaluated the gene expression stability between the starved and fed states using RefFinder; moreover, we compared their expression levels in each life-stage and identified two reference genes, Elongation factor 1-alpha (ELF1A)-like and apolipophorins-like. Finally, we evaluated the utility of the candidates as reference genes, and the use of ELF1A-like and apolipophorins-like successfully normalized ATP synthase subunit g -like gene expression. Thus, ELF1A-like and apolipophorins-like could be suitable reference genes in PRMs.

Comprehensive evaluation of candidate reference genes for quantitative real-time PCR-based analysis in Caucasian clover

The forage species Caucasian clover (Trifolium ambiguum M. Bieb.), a groundcover plant, is resistant to both cold and drought. However, reference genes for qRT-PCR-based analysis of Caucasian clover are lacking. In this study, 12 reference genes were selected on the basis of transcriptomic data. These genes were used to determine the most stably expressed genes in various organs of Caucasian clover under cold, salt and drought stress for qRT-PCR-based analysis. Reference gene stability was analyzed by geNorm, NormFinder, BestKeeper, the ∆Ct method and RefFinder. Under salt stress, RCD1 and PPIL3 were the most stable reference genes in the leaves, and NLI1 and RCD1 were the most stable references genes in the roots. Under low-temperature stress, APA and EFTu-GTP were the most stable reference genes in the leaves, and the RCD1 and NLI2 genes were highly stable in the roots. Under 10% PEG-6000 stress, NLI1 and NLI2 were highly stable in the leaves, and RCD1 and PPIL3 were the most stable in the roots. Overall, RCD1 and NLI2 were the most stable reference genes in organs under normal conditions and across all samples. The most and least stable reference genes were validated by assessing their appropriateness for normalization via WRKY genes.

Selection and Validation of the Optimal Panel of Reference Genes for RT-qPCR Analysis in the Developing Rat Cartilage

Real-time fluorescence quantitative PCR (RT-qPCR) is widely used to detect gene expression levels, and selection of reference genes is crucial to the accuracy of RT-qPCR results. Minimum Information for Publication of RT-qPCR Experiments (MIQE) proposes that using the panel of reference genes for RT-qPCR is conducive to obtaining accurate experimental results. However, the selection of the panel of reference genes for RT-qPCR in rat developing cartilage has not been well documented. In this study, we selected eight reference genes commonly used in rat cartilage from literature (GAPDH, ACTB, 18S, GUSB, HPRT1, RPL4, RPL5, and SDHA) as candidates. Then, we screened out the optimal panel of reference genes in female and male rat cartilage of fetus (GD20), juvenile (PW6), and puberty (PW12) in physiology with stability analysis software of genes expression. Finally, we verified the reliability of the selected panel of reference genes with the rat model of intrauterine growth retardation (IUGR) induced by prenatal dexamethasone exposure (PDE). The results showed that the optimal panel of reference genes in cartilage at GD20, PW6, and PW12 in physiology was RPL4 + RPL5, which was consistent with the IUGR model, and there was no significant gender difference. Further, the results of standardizing the target genes showed that RPL4 + RPL5 performed smaller intragroup differences than other panels of reference genes or single reference genes. In conclusion, we found that the optimal panel of reference genes in female and male rat developing cartilage was RPL4 + RPL5, and there was no noticeable difference before and after birth.

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.

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.