PHF7, a novel male gene influences female fecundity and population growth in Nilaparvata lugens Stål (Hemiptera: Delphacidae)

Molecular basis for PHF7-mediated ubiquitination of histone H3

The RING-type E3 ligase has been known for over two decades, yet its diverse modes of action are still the subject of active research. Plant homeodomain (PHD) finger protein 7 (PHF7) is a RING-type E3 ubiquitin ligase responsible for histone ubiquitination. PHF7 comprises three zinc finger domains: an extended PHD (ePHD), a RING domain, and a PHD. While the function of the RING domain is largely understood, the roles of the other two domains in E3 ligase activity remain elusive. Here, we present the crystal structure of PHF7 in complex with the E2 ubiquitin-conjugating enzyme (E2). Our structure shows that E2 is effectively captured between the RING domain and the C-terminal PHD, facilitating E2 recruitment through direct contact. In addition, through in vitro binding and functional assays, we demonstrate that the N-terminal ePHD recognizes the nucleosome via DNA binding, whereas the C-terminal PHD is involved in histone H3 recognition. Our results provide a molecular basis for the E3 ligase activity of PHF7 and uncover the specific yet collaborative contributions of each domain to the PHF7 ubiquitination activity.

The transcript integrity index (TII) provides a standard measure of sperm RNA

Standardizing RNA quality is key to interpreting RNA-seq data as a compromised sample can mask the underlying biology. The challenge remains when evaluating RNA quality in samples with high RNA fragmentation. For example, programmed fragmentation and cytoplasmic expulsion, integral to sperm maturation, is a prime example of the complexities of interpreting RNA-seq data, given that fragmentation can be random and\or targeted. To meet this challenge, we developed an algorithm that accurately measures RNA quality in samples with high fragmentation, such as spermatozoa. The integrity of 1,000 previously identified abundant sperm transcripts were independently visualized and evaluated using the Transcript Integrity Index (TII) algorithm to identify intact transcripts. Full-length transcripts from visual and the TII algorithm were evaluated for testis preference in humans using the GTEx tissues database. Samples were then filtered by the Interquartile Range (IQR), identifying those in which the greatest number of transcripts failed to pass the visual or TII thresholds. Transcript lists were overlapped, forming the set of intact transcripts used as TII standards. Each sample was re-evaluated as a function of this TII set of intact transcripts, with poor quality samples identified as those failing in the largest number of transcripts. While ontologically enriched in roles related to spermatogenesis and/or fertilization, samples did not segregate based on birth outcome. The TII algorithm proved an effective means to identify samples of similar quality from sperm, a cell type enriched in biologically fragmented RNAs. The algorithm should facilitate other studies using samples compromised by high levels of RNA fragmentation, such as Formalin-Fixed Paraffin-Embedded samples. Requisite to assessing male health, TII provides a solution to the long-sought-after standard that identifies samples of similar quality.

Direct reprogramming as a route to cardiac repair

Ischemic heart disease is the leading cause of morbidity, mortality, and healthcare expenditure worldwide due to an inability of the heart to regenerate following injury. Thus, novel heart failure therapies aimed at promoting cardiomyocyte regeneration are desperately needed. In recent years, direct reprogramming of resident cardiac fibroblasts to induced cardiac-like myocytes (iCMs) has emerged as a promising therapeutic strategy to repurpose the fibrotic response of the injured heart toward a functional myocardium. Direct cardiac reprogramming was initially achieved through the overexpression of the transcription factors (TFs) Gata4, Mef2c, and Tbx5 (GMT). However, this combination of TFs and other subsequent cocktails demonstrated limited success in reprogramming adult human and mouse fibroblasts, constraining the clinical translation of this therapy. Over the past decade, significant effort has been dedicated to optimizing reprogramming cocktails comprised of cardiac TFs, epigenetic factors, microRNAs, or small molecules to yield efficient cardiac cell fate conversion. Yet, efficient reprogramming of adult human fibroblasts remains a significant challenge. Underlying mechanisms identified to accelerate this process have been centered on epigenetic remodeling at cardiac gene regulatory regions. Further studies to achieve a refined understanding and directed means of overcoming epigenetic barriers are merited to more rapidly translate these promising therapies to the clinic.

Octopamine signaling is involved in the female postmating state in Nilaparvata lugens Stål (Hemiptera: Delphacidae)

Mating triggers physiological and behavioral changes in female insects. In many species, females experience postmating behavioral and physiological changes that define a post-mated state. These changes are comprised of several conditions, including long-term refractoriness to re-mating and increased production and laying of eggs. Here, we report that mating led to several changes in brown planthopper (BPH) females, including increased octopamine (OA), cAMP concentrations, and activities of several enzymes. Mating also led to changes in the expression of several genes acting in female physiology, including those in the cAMP/PKA signal transduction pathway. OA injections into virgin females led to similar changes. RNAi silencing of the gene encoding tyramine β-hydroxylase, involved in the final step in OA synthesis, led to decreased expression of these genes, and reduced the cAMP/PKA signaling. At the whole-organism level, the RNAi treatments led to reduced fecundity, body weights, and longevity. RNAi silencing of genes acting in OA signaling led to truncated ovarian development, egg maturation, and ovarian vitellogenin (Vg) uptake. The impact of these decreases is also registered at the population level, seen as decreased population growth. We infer that OA signaling modulates the postmating state in female BPH and possibly other hemipterans.

The fitness advantages of bistrifluron resistance related to chitin synthase A in Spodoptera litura (Fab.) (Noctuidae: Lepidoptera)

BACKGROUND

Spodoptera litura is one of the major agricultural pests in China, and it has developed serious resistance to many traditional chemical insecticides. In the present study, the bistrifluron-resistant (Bis-SEL) strain accompanied by a higher oviposition, 113.8-fold RR compared to the bistrifluron-susceptible (Bis-UNSEL) strain, was obtained by bidirectional screening. A comparison of their gonad coefficiency and genes related to oviposition or resistance was used to elucidate the resurgence mechanism.

RESULTS

The ovarian index, oviposition, and potential egg production in the Bis-SEL strain of female adults were significantly higher than those in the Bis-UNSEL strain, and the length of ovariole in the Bis-SEL strain was also significantly elongated. The protein contents of vitellogenin (Vg) and vitellogenin receptor (VgR) in the Bis-UNSEL strain were lower than those in the Bis-SEL strain, consistent with their gene expressions levels, and there was a significantly positive linear correlation between Vg and VgR protein contents, further confirming that resistant strains have high reproductive fitness. Moreover, the chitin synthase A in the Bis-SEL strain was clearly up-regulated, and a mutation (H866Y) near the QRRRW in the catalytic domain caused a rise in the hydrogen bond between UDP-GlcNAc and chitin synthase, and its chitin content was higher than that in the Bis-UNSEL strain. Nevertheless, the sensitivity of the Bis-SEL strain to bistrifluron was significantly recovered when it was knocked down though RNA interference.

CONCLUSION

The fitness advantages of bistrifluron resistance may be related to the up-regulation and mution of chitin synthase A. © 2021 Society of Chemical Industry.

Identification of putative abdominal vibration-related genes through transcriptome analyses in the brown planthopper (Nilaparvata lugens)

The sexually mature female brown planthoppers (BPHs) send out abdominal vibration (AV) signals through the rice so that the males can obtain intraspecific, gender, and localization information to prepare for mating. Destroying vibration signals is an alternative biological method for pest control. However, the regulatory mechanism of AV in female BPHs remains elusive, which presents an obstacle to pest control. We observed that before mating female BHPs emitted abdominal vibration signals that disappeared immediately after mating and reappeared after 6 days. Therefore, ovarian and brain samples of female BPHs from Unmated-6h⁺ (with AV), Mated-6h^- (without AV) and Mated-6d⁺ (with AV) individuals were collected for transcript analyses. By transcriptional sequencing analyses, 33 candidate genes that might involve in the regulation of female AV were obtained. After selecting 4 candidate genes of them for verification by RNA interference (RNAi), it was found that interference of juvenile hormone binding protein (JHBP) could greatly reduce the probability and frequency of AV for female BPHs. In general, this study identified AV-related candidate genes in female BPHs through transcriptome analyses and provided an important basis for future research on pest control in BPHs.

RNA Interference-Based Silencing of the Chitin Synthase 1 Gene for Reproductive and Developmental Disruptions in Panonychus citri

Simple Summary

The Chitin Synthase 1 gene, when suppressed with RNAi, imparts differences in the structural development, physiology, and synthesis of epidermal chitin, which ultimately leads to the mortality of the target pest. The results presented here will help to illuminate the molecular mechanism and function of the PcCHS1 gene, which regulates the egg-laying potential in adult citrus red mites. Using the leaf dip method, we found that dsRNA was potent and effective, and significantly reduced the egg-laying potential and hatching of citrus red mite eggs. These results show the potential utility of the PcCHS1 gene in the development of novel RNA interference strategies for controlling the citrus red mite.

Abstract

Chitin synthase 1 (CHS1) is an essential gene regulating chitin during different developmental stages of arthropods. In the current study, we explored for the first time the role of CHS1 gene regulation in the citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), by silencing its expression using (RNA interference) RNAi-based strategies. The results reveal that P. citri tested in different developmental stages, including larvae, protonymphs, deutonymphs, and adults fed on sweet orange leaves dipped in various concentrations (200, 400, 600, and 800 ng/μL) of dsRNA-PcCHS1, resulted in a continuous reduction in their gene expression, and the extent of transcript knockdown was positively correlated with the concentration of dsRNA. Concentration–mortality response assays revealed a mortality of more than 50% among all the studied developmental stages, except for adulthood. Furthermore, the target gene dsRNA-PcCHS1 treatment of larvae, protonymphs, deutonymphs, and females at a treatment rate of 800 ng/mL of dsRNA significantly decreased the egg-laying rates by 48.50%, 43.79%, 54%, and 39%, respectively, and the hatching rates were also considerably reduced by 64.70%, 70%, 64%, and 52.90%, respectively. Moreover, using the leaf dip method, we found that the RNA interference effectively reduced the PcCHS1 transcript levels by 42.50% and 42.06% in the eggs and adults, respectively. The results of this study demonstrate that the RNAi of PcCHS1 can dramatically reduce the survival and fecundity of P. citri, but the dsRNA concentrations and developmental stages can significantly influence the RNAi effects. These findings indicate the potential utility of the PcCHS1 gene in causing developmental irregularities, which could aid in the development of effective and novel RNAi-based strategies for controlling P. citri.

Frizzled 2 Functions in the Regulation of TOR-Mediated Embryonic Development and Fecundity in Cyrtorhinus lividipennis Reuter

The mirid bug, Cyrtorhinus lividipennis Reuter, is an important predator of rice planthoppers in Asia. In a previous study, C. lividipennis fed on gramineous weeds with brown planthopper (BPH) eggs had reduced development compared to those fed on rice with BPH eggs. In the current study, the concentrations of selected amino acids (AAs) were higher in rice than five gramineous species, which might explain the enhanced growth of C. lividipennis on rice. When C. lividipennis was fed on AA-deprived artificial diets, the Wnt/β-catenin pathway was inhibited. Furthermore, C. lividipennis females silenced for expression of Frizzled 2 (Fz2) showed a significant reduction in the Wnt/β-catenin and target of rapamycin (TOR) pathways. Silencing Fz2 led to decreased expression of the vitellogenin gene (Vg), lower Vg accumulation in oocytes, reduced soluble protein in ovaries and fat bodies, reduced titers of juvenile hormone, prolonged preoviposition periods, and lower predation capacity, body weight, and egg numbers as controlled to controls. Fz2 silencing resulted in undeveloped ovaries and the inhibition of oocyte growth in the ovarioles, resulting in decreased numbers of offspring and reduced hatching rates. The silencing of Fz2 also resulted in aberrant embryos with undeveloped eyespots and organs, suggesting that Fz2 is an essential gene for embryonic development, oogenesis, and egg maturation. In summary, this study established a potential link between Wnt and TOR pathways, which interact synergistically to regulate C. lividipennis reproduction in response to AA signals. These results provide valuable new information that can be applied to large-scale rearing of C. lividipennis predators, which is important for reducing planthopper damage in rice fields.

Identification and functional analysis of five genes that encode distinct isoforms of protein phosphatase 1 in Nilaparvata lugens

Ten distinct cDNAs encoding five different protein phosphatases 1 (PPP1) were cloned from Nilaparvata lugens. NlPPP1α and NlPPP1β are highly conserved whereas NlPPP1-Y, NlPPP1-Y1 and NlPPP1-Y2 are lowly conserved among insects. NlPPP1α and NlPPP1β exhibited a ubiquitous expression, while NlPPP1-Y, NlPPP1-Y1, and NlPPP1-Y2 were obviously detected from the 4th instar nymph to imago developmental stages in males, especially detected in internal reproductive organ and fat bodies of the male. Injection nymphs with dsRNA of NlPPP1α or NlPPP1β was able to reduce the target gene expression in a range of 71.5-91.0%, inducing a maximum mortality rate of 95.2% or 97.2% at 10th day after injection and eclosion ratio down by 65.5-100.0%. Injection with dsNlPPP1Ys targeted to NlPPP1-Y, NlPPP1-Y1and NlPPP1-Y2 was able to induce a maximum mortality rate of 95.5% at 10th day after injection, eclosion ratio down by 86.4%. Knock-down one of the male-biased NlPPP1 genes has no effect on survival and eclosion ratio. Injection of 4th instar nymph with dsNlPPP1Ys led to reduced oviposition amount and hatchability, down by 44.7% and 19.6% respectively. Knock-down of NlPPP1-Y1 or NlPPP1-Y2 gene did not significantly affect oviposition amount but significantly affected hatchability. The results indicate that the male-biased NlPPP1 genes have overlapping functions in N. lugens development, and NlPPP1-Y1 and NlPPP1-Y2 may play important roles in spermatogenesis and fertilization. The dsNlPPP1β and dsNlPPP1Ys in this study could be the preferred sequence in RNAi and low-conserved male-biased NlPPP1 genes could be potential target for N. lugens control.

Interactions between brown planthopper (Nilaparvata lugens) and salinity stressed rice (Oryza sativa) plant are cultivar-specific

Salinity stress triggers changes in plant morphology, physiology and molecular responses which can subsequently influence plant-insect interactions; however, these consequences remain poorly understood. We analyzed plant biomass, insect population growth rates, feeding behaviors and plant gene expression to characterize the mechanisms of the underlying interactions between the rice plant and brown planthopper (BPH) under salinity stress. Plant bioassays showed that plant growth and vigor losses were higher in control and low salinity conditions compared to high salinity stressed TN1 (salt-planthopper susceptible cultivar) in response to BPH feeding. In contrast, the losses were higher in the high salinity treated TPX (salt-planthopper resistant cultivar). BPH population growth was reduced on TN1, but increased on TPX under high salinity condition compared to the control. This cultivar-specific effect was reflected in BPH feeding behaviors on the corresponding plants. Quantification of abscisic acid (ABA) and salicylic acid (SA) signaling transcripts indicated that salinity-induced down-regulation of ABA signaling increased SA-dependent defense in TN1. While, up-regulation of ABA related genes in salinity stressed TPX resulted in the decrease in SA-signaling genes. Thus, ABA and SA antagonism might be a key element in the interaction between BPH and salinity stress. Taken together, we concluded that plant-planthopper interactions are markedly shaped by salinity and might be cultivar specific.

Triazophos-induced vertical transmission of rice stripe virus is associated with host vitellogenin in the small brown planthopper Laodelphax striatellus

BACKGROUND

Rice stripe virus (RSV) is one of the most serious rice diseases in East Asia. The small brown planthopper (SBPH), Laodelphax striatellus, is an economically important rice pest. SBPH transmits RSV horizontally and vertically, resulting in serious rice economic losses. Exposure to sublethal doses of insecticides can induce many physiological and cellular changes in insects. However, the mechanism underlying triazophos-induced RSV vertical transmission remains unclear. Here, we investigated the role of vitellogenin (Vg) in triazophos-induced RSV vertical transmission.

RESULTS

RSV vertical transmission rates were significantly induced by sublethal exposure to triazophos. The transcript abundance of viral RNA3 segment (RNA3) and capsid protein (CP) in the ovaries of SBPH were also significantly increased. Triazophos induced the expression level of Vg in L. striatellus (LsVg) and increased the contents of ovarian protein and fat body protein. Knockdown of Vg significantly reduced the expression levels of LsVg and Vg receptor (LsVgR), and decreased RSV accumulations in the ovaries. Double-stranded Vg (dsVg)-mediated down-regulation could be rescued by exposure to triazophos. Vertical transmission rate of the dsVg-injected group was significantly decreased compared with the dsGFP-injected group, and triazophos significantly rescued the RSV vertical transmission rate of the dsVg-injected group.

CONCLUSION

Our results indicate that triazophos-induced RSV vertical transmission is associated with Vg. This work will help us to further elucidate sublethal doses of insecticides-mediated effects and develop new strategies for pest control. © 2019 Society of Chemical Industry.

Pesticide-Induced Planthopper Population Resurgence in Rice Cropping Systems

Planthoppers are serious rice pests in Asia. Their population resurgence was first reported in the early 1960s, caused mainly by insecticides that indiscriminately killed beneficial arthropods and target pests. The subsequent resurgence involved two mechanisms, the loss of beneficial insects and insecticide-enhanced planthopper reproduction. In this review, we identify two forms of resurgence, acute and chronic. Acute resurgence is caused by traditional insecticides with rapid resurgence in the F₁ generation. Chronic resurgence follows application of modern pesticides, including fungicides and herbicides, with low natural enemy toxicity, coupled with stimulated planthopper reproduction. The chemical-driven syndrome of changes leads to later resurgence in the F₂ or later generations. Chronic resurgence poses new threats to global rice production. We review findings on the physiological and molecular mechanisms of chronic planthopper resurgence and suggest research directions that may help manage these new threats.

Male Selenoprotein F-Like (SPF-L) Influences Female Reproduction and Population Growth in Nilaparvata lugens (Hemiptera: Delphacidae)

Selenoproteins serve in anti-oxidant and cellular redox functions in almost all organisms. A recent study characterized a selenoprotein F-like (SPF-L) in the brown plant hopper’s (BPH), Nilaparvata lugens, male accessory glands (MAGs), raised the question of whether the SPF-L is associated with female fecundity. In this study, SPF-L mRNA was found to be enriched in the internal reproductive organ (IRO) of virgin males, also expressed relatively stably in virgin males and females, and dietary dsSPF-L-treatments led to reduced MAG protein and Arginine content. Knockdown of NlSPF-L in unmated males did not influence juvenile hormone (JH) III and ecdysteroid titers, however, dsSPF-L-treated mated males had increased JH III titer, and reduced ecdysteroid titer compared to controls. After mating with dsSPF-L-treated males, female partners had reduced fat body and ovary soluble proteins and JH III tier and vitellogenin (Vg) mRNA levels, but no alterations in ecdysteroid titer, body weight or longevity. The experimental females had prolonged pre-oviposition periods and they laid fewer eggs, which suffered reduced hatching rates and population growth index (PGI). Such mating also led to impaired IRO development in males and females, which was confirmed by immunofluorescence staining. We infer that SPF-L affects reproductive success of males and their partners.

Silencing pyruvate kinase (NlPYK) leads to reduced fecundity in brown planthoppers, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

Pyruvate kinase (PYK) operates in the glycolytic pathway, responsible for regulating the balance between glycolysis and gluconeogenesis. The previous work indicates PYK acts in development of Drosophila embryos and in embryonic muscle growth, from which it may be inferred that PYK acts in insect fecundity. More to the point, as a central enzyme in the glycolytic pathway, PYK acts in many energy-spending functions in most organisms. On the background findings that triazophos (TZP) stimulates fecundity via increase activities of several genes in brown planthoppers, Nilaparvata lugens, we investigated the combined influence of TZP and silencing a N. lugens PYK (NlPYK) on reproduction-linked biological performance parameters. Here, we report that TZP+dsNlPYK treatments led to reduced (by 26%) ovarian, but not fat body, protein content relative to controls. Ovarian (35%) and fat body (54%) soluble sugar contents were reduced. TZP+dsNlPYK treatments also led to reduced (by about 24%) fecundity, expressed as numbers of eggs laid. These data show directly that NlPYK acts in insect fecundity, probably via increases in glucose metabolism.