Suppressing male spermatogenesis-associated protein 5-like gene expression reduces vitellogenin gene expression and fecundity in Nilaparvata lugens Stål

Roles of spermary-specific carboxylesterases in Nilaparvata lugens reproduction: Opposite between insecticide-induced upregulation and resistance-associated overexpression

Seminal fluid proteins (SFPs) in insect males are critical for reproduction, being transported into female ovary. In Nilaparvata lugens, a significant rice pest, seven spermary-specific carboxylesterases (CarEs) were found abundantly in SFPs, with over-expression in males of an imidacloprid-resistant (RES) strain compared to a susceptible (SUS) strain. This study aimed to evaluate roles of spermary-specific CarEs in N. lugens reproduction, especially in the reproduction disadvantage in RES. Sublethal doses of three insecticides significantly impacted N. lugens reproduction, concomitant with up-regulation of these CarE genes in males. When RNAi against these CarE genes in SUS males did not affect reproduction, RNAi suppression of insecticide-induced up-regulation worsened the reproductive decline caused by insecticides, indicating a reproduction benefit from the transient up-regulation induced by insecticides. However, constitutive overexpression of these CarEs in RES males did not enhance reproduction and instead imposed a fitness cost. RNAi against part CarE genes in RES males increased reproduction. Collectively, the transient up-regulation and constitutive overexpression of these spermary-expressed CarE genes had the opposite effects on N. lugens reproduction. We need to find a balance between these opposite effects in insect pest control and insecticide resistance management, especially for insecticides targeting reproduction.

Alginate oligosaccharide supplementation improves boar semen quality under heat stress

Heat stress is a serious problem that affects animal husbandry by reducing growth and reproductive performance of animals. Adding plant extracts to the diet is an effective way to help overcome this problem. Alginate oligosaccharide (AOS) is a natural non-toxic antioxidant with multiple biological activities. This study analyzed the potential mechanism of AOS in alleviating heat stress and improving semen quality in boars through a combination of multiple omics tools. The results indicated that AOS could significantly increase sperm motility (P < 0.001) and sperm concentration (P < 0.05). At the same time, AOS improved the antioxidant capacity of blood and semen, and increased blood testosterone (P < 0.05) level. AOS could improve the metabolites in sperm, change the composition of gut microbiota, increase the relative abundance of beneficial bacteria such as Pseudomonas (P < 0.01), Escherichia-Shigella (P < 0.05), Bifidobacterium (P < 0.01), reduce the relative abundance of harmful bacteria such as Prevotella_9 (P < 0.05), Prevotellaceae_UCG-001 (P < 0.01), and increase the content of short chain fatty acids. Proteomic results showed that AOS increased proteins related to spermatogenesis, while decreasing heat shock protein 70 (P < 0.05) and heat shock protein 90 (P < 0.01). These results were verified using immunofluorescence staining technology. There was a good correlation among sperm quality, sperm metabolome, sperm proteome, and gut microbiota. In conclusion, AOS can be used as a feed additive to increase the semen quality of boars to enhance reproductive performance under heat stress.

Redox mechanisms of environmental toxicants on male reproductive function

Humans and wildlife, including domesticated animals, are exposed to a myriad of environmental contaminants that are derived from various human activities, including agricultural, household, cosmetic, pharmaceutical, and industrial products. Excessive exposure to pesticides, heavy metals, and phthalates consequently causes the overproduction of reactive oxygen species. The equilibrium between reactive oxygen species and the antioxidant system is preserved to maintain cellular redox homeostasis. Mitochondria play a key role in cellular function and cell survival. Mitochondria are vulnerable to damage that can be provoked by environmental exposures. Once the mitochondrial metabolism is damaged, it interferes with energy metabolism and eventually causes the overproduction of free radicals. Furthermore, it also perceives inflammation signals to generate an inflammatory response, which is involved in pathophysiological mechanisms. A depleted antioxidant system provokes oxidative stress that triggers inflammation and regulates epigenetic function and apoptotic events. Apart from that, these chemicals influence steroidogenesis, deteriorate sperm quality, and damage male reproductive organs. It is strongly believed that redox signaling molecules are the key regulators that mediate reproductive toxicity. This review article aims to spotlight the redox toxicology of environmental chemicals on male reproduction function and its fertility prognosis. Furthermore, we shed light on the influence of redox signaling and metabolism in modulating the response of environmental toxins to reproductive function. Additionally, we emphasize the supporting evidence from diverse cellular and animal studies.

Genomic screening of allelic and genotypic transmission ratio distortion in horse

The phenomenon in which the expected Mendelian inheritance is altered is known as transmission ratio distortion (TRD). The TRD analysis relies on the study of the transmission of one of the two alleles from a heterozygous parent to the offspring. These distortions are due to biological mechanisms affecting gametogenesis, embryo development and/or postnatal viability, among others. In this study, TRD phenomenon was characterized in horses using SNP-by-SNP model by TRDscan v.2.0 software. A total of 1,041 Pura Raza Español breed horses were genotyped with 554,634 SNPs. Among them, 277 horses genotyped in trios (stallion-mare-offspring) were used to perform the TRD analysis. Our results revealed 140 and 42 SNPs with allelic and genotypic patterns, respectively. Among them, 63 displayed stallion-TRD and 41 exhibited mare-TRD, while 36 SNPs showed overall TRD. In addition, 42 SNPs exhibited heterosis pattern. Functional analyses revealed that the annotated genes located within the TRD regions identified were associated with biological processes and molecular functions related to spermatogenesis, oocyte division, embryonic development, and hormonal activity. A total of 10 functional candidate genes related to fertility were found. To our knowledge, this is the most extensive study performed to evaluate the presence of alleles and functional candidate genes with transmission ratio distortion affecting reproductive performance in the domestic horse.

Hominoid SVA-lncRNA AK057321 targets human-specific SVA retrotransposons in SCN8A and CDK5RAP2 to initiate neuronal maturation

SINE-VNTR-Alu (SVA) retrotransposons arose and expanded in the genome of hominoid primates concurrent with the slowing of brain maturation. We report genes with intronic SVA transposons are enriched for neurodevelopmental disease and transcribed into long non-coding SVA-lncRNAs. Human-specific SVAs in microcephaly CDK5RAP2 and epilepsy SCN8A gene introns repress their expression via transcription factor ZNF91 to delay neuronal maturation. Deleting the SVA in CDK5RAP2 initiates multi-dimensional and in SCN8A selective sodium current neuronal maturation by upregulating these genes. SVA-lncRNA AK057321 forms RNA:DNA heteroduplexes with the genomic SVAs and upregulates these genes to initiate neuronal maturation. SVA-lncRNA AK057321 also promotes species-specific cortex and cerebellum-enriched expression upregulating human genes with intronic SVAs (e.g., HTT, CHAF1B and KCNJ6) but not mouse orthologs. The diversity of neuronal genes with intronic SVAs suggest this hominoid-specific SVA transposon-based gene regulatory mechanism may act at multiple steps to specialize and achieve neoteny of the human brain.

Characterization of MicroRNAs Associated with Reproduction in the Brown Planthopper, Nilaparvata lugens

Insects have a robust capacity to produce offspring for propagation, and the reproductive events of female insects have been achieved at the molecular and physiological levels via regulatory gene pathways. However, the roles of MicroRNAs (miRNAs) in the reproductive development of the brown planthopper (BPH), Nilaparvata lugens, remain largely unexplored. To understand the roles of miRNAs in reproductive development, miRNAs were identified by Solexa sequencing in short-winged (SW) female adults of BPH. Small RNA libraries derived from three developmental phases (1 day, 3 days, and 5 days after emergence) were constructed and sequenced. We identified 905 miRNAs, including 263 known and 642 novel miRNAs. Among them, a total of 43 miRNAs were differentially expressed in the three developmental phases, and 14,568 putative targets for 43 differentially expressed miRNAs (DEMs) were predicted by TargetScan and miRanda. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the predicted miRNA targets illustrated the putative roles for these DEMs in reproduction. The progress events were annotated, including oogenesis, lipid biosynthetic process, and related pathways such as apoptosis, ABC transporters, and amino acid metabolism. Four highly abundant DEMs (miR-9a-5p, miR-34-5p, miR-275-3p, and miR-317-3p) were further screened, and miR-34-5p was confirmed to be involved in the regulation of reproduction. Overexpression of miR-34-5p via injecting its mimics reduced fecundity and decreased Vg expression. Moreover, target genes prediction for miR-34-5p showed they might be involved in 20E signaling cascades, apoptosis, and gonadal development, including hormone receptor 4 (HR4), caspase-1 (Cp-1), and spermatogenesis-associated protein 20 (SPATA20). These findings provide a valuable resource for future studies on the role of miRNAs in BPH reproductive development.

Heavy metal and metalloid - induced reproductive toxicity

Heavy metals and metalloid exposure are among the most common factors responsible for reproductive toxicity in human beings. Several studies have indicated that numerous metals and metalloids can display severe adverse properties on the human reproductive system. Metals like lead, silver, cadmium, uranium, vanadium, and mercury and metalloids like arsenic have been known to induce reproductive toxicity. Moderate to minute quantities of lead may affect several reproductive parameters and even affect semen quality. The ecological and industrial exposures to the various heavy metals and metalloids have disastrous effects on the reproductive system ensuing in infertility. This work emphasizes the mechanism and pathophysiology of the aforementioned heavy metals and metalloids in reproductive toxicity. Additionally, this work aims to cover the classical protective mechanisms of zinc, melatonin, chelation therapy, and other trending methods to prevent heavy metal-induced reproductive toxicity.

Molecular Characterization and RNA Interference Analysis of SLC26A10 From Nilaparvata lugens (Stål)

SLC26A10 is a member of the SLC26 gene family, but its role in insects is still unclear. We cloned the SLC26A10 gene of Nilaparvata lugens (NlSLC26A10) and found NlSLC26A10 contained 11 transmembrane regions and a STAS domain. Expression pattern analysis showed NlSLC26A10 expression was more upregulated in adults than in nymphs, highest in the ovary. After injection of double-stranded RNA (dsRNA) of NlSLC26A10, the mRNA level of NlSLC26A10 significantly decreased and, consequently, the ovarian development of adult females was hindered; the amount and the hatchability of eggs and yeast-like symbionts in mature oocytes decreased. Further study showed that NlSLC26A10 might result in decreased juvenile hormone level and vitellogenin expression. These results indicate that NlSLC26A10 plays an essential role in the reproduction of N. lugens.

The octopamine receptor, OA2B2, modulates stress resistance and reproduction in Nilaparvata lugens Stål (Hemiptera: Delphacidae)

The brown planthopper (BPH), Nilaparvata lugens (Stål) is a resurgent pest of rice crops throughout Asia. We recently discovered that octopamine (OA) and OA2B2 operate in the BPH mating system, where it mediates a wide range of molecular, physiological and behavioural changes. Here, we report on outcomes of experiments designed to test the hypothesis that OA/OA2B2 signalling mediates responses to three abiotic stressors, starvation, high temperature (37 °C), and induced oxidative stress. We found per os RNAi-mediated OA2B2 silencing led to significantly decreased survival, measured in days, following exposure to each of these stressors. We selected a biologically costly process, reproductive biology, as a biotic stressor. Silencing of OA2B2 led to decreased total protein content in ovaries and fat bodies, downregulated expression of vitellogenin (Vg) and Vg receptor (VgR), inhibited fat body Vg protein synthesis, shortened the oviposition period, prolonged the preoviposition period, reduced the number of laid eggs, body weight and female longevity. In addition, the silencing treatments also led to inhibited ovarian development, and ovarian Vg uptake, reduced numbers of egg masses and offspring and lower hatching rates and population growth index. These data support our hypothesis that OA2B2 acts in mediating BPH resistance to biotic and abiotic stressors.

Effects of imidacloprid and thiamethoxam on the development and reproduction of the soybean aphid Aphis glycines

The soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) is a primary pest of soybeans and poses a serious threat to soybean production. Our studies were conducted to understand the effects of different concentrations of insecticides (imidacloprid and thiamethoxam) on A. glycines and provided critical information for its effective management. Here, we found that the mean generation time and adult and total pre-nymphiposition periods of the LC50 imidacloprid- and thiamethoxam-treatment groups were significantly longer than those of the control group, although the adult pre-nymphiposition period in LC30 imidacloprid and thiamethoxam treatment groups was significantly shorter than that of the control group. Additionally, the mean fecundity per female adult, net reproductive rate, intrinsic rate of increase, and finite rate of increase of the LC30 imidacloprid-treatment group were significantly lower than those of the control group and higher than those of the LC50 imidacloprid-treatment group (P < 0.05). Moreover, both insecticides exerted stress effects on A. glycines, and specimens treated with the two insecticides at the LC50 showed a significant decrease in their growth rates relative to those treated with the insecticides at LC30. These results provide a reference for exploring the effects of imidacloprid and thiamethoxam on A. glycines population dynamics in the field and offer insight to agricultural producers on the potential of low-lethal concentrations of insecticides to stimulate insect reproduction during insecticide application.

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.

Effects of SPATA6 on proliferation, apoptosis and steroidogenesis of Hu sheep Leydig cells in vitro

This study aimed to investigate the expression pattern of spermatogenesis associated protein 6 (SPATA6) in Hu sheep testis and to ascertain the effects of SPATA6 on sheep Leydig cells (LCs) function linked to spermatogenesis. In the present study, we detected a 1970 bp cDNA fragment of SPATA6 included a 1467 bp coding sequence which encoded 487 amino acids. Meanwhile, sheep SPATA6 shared 51.70%-97.41% amino acid sequences with its orthologs compared with other species. In addition, SPATA6 was highly expressed in testis and localized in cytoplasm and nucleus of LCs as well as spermatogenic cells at different stages. Compared to the negative control (NC), SPATA6 interference promoted apoptosis of LCs with the increase of BAX/BCL-2 mRNA and protein levels, while the results of SPATA6 overexpression were on the contrary. Meanwhile, cell cycle was blocked at G2/M phase and CDK1 and CCNB1 were down-regulated after SPATA6 interference. SPATA6 overexpression induced cell cycle transfer G0/G1 into S and G2/M phase with upregulation of CDK1, CDK4, CCND1 and CCND2. Moreover, the secretion of testosterone hormone and the expression of StAR in LCs with SPATA6 overexpression were significantly promoted. Overall, our data suggest that SPATA6 is an important functional molecule of spermatogenesis, via regulating the proliferation, apoptosis and testosterone biosynthesis of Hu sheep LCs. These findings will enhance the understanding of the roles of SPATA6 in sheep spermatogenesis.

CRISPR/Cas9-induced vitellogenin knockout lead to incomplete embryonic development in Plutella xylostella

Vitellogenin (Vg) is important for insect egg maturation and embryo development. In the present study, we characterized the molecular structure and expression profile of Vg gene, and analyzed its reproductive functions in diamondback moth, Plutella xylostella (L.), a destructive pest of cruciferous crops, using CRISPR/Cas9 system. The P. xylostella Vg (PxVg) included all conserved domains and motifs that were commonly found in most insect Vgs except for the polyserine tract. PxVg gene was highly expressed in female pupae and adults. PxVg protein was detected in eggs and female adults. PxVg was mainly expressed in the fat body and its protein was detected in most tissues, except in the midgut. CRISPR/Cas9-induced PxVg knockout successfully constructed a homozygous mutant strain with a 5-base pair nucleotide deletion. No PxVg protein was found in the mutant individuals and in their ovaries. There were no significant differences between wild (WT) and mutant (Mut-5) types of P. xylostella in terms of ovariole length and the number of fully developed oocytes in newly emerged females. No significant difference was observed in the number of eggs laid within two days, but there was a lower egg hatchability (84% for WT vs. 47% for Mut-5). This is the first study presenting the functions of Vg in ovary development, egg maturation, oviposition and embryonic development of P. xylostella. Our results suggest that the reproductive functions of Vg may be species-specific in insects. It is possible that Vg may not be the major egg yolk protein precursor in P. xylostella. Other "functional Vgs" closely involved in the yolk formation and oogenesis would need to be further explored in P. xylostella.

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.

Increased DNA methylation in the spermatogenesis-associated (SPATA) genes correlates with infertility

BACKGROUND

Spermatogenesis-associated (SPATA) family of genes plays important roles in spermatogenesis, sperm maturation or fertilization. The knockout studies in mice have demonstrated that SPATA genes are crucial for fertility. Gene expression and genetic polymorphism studies have further suggested their correlation with infertility; however, methylation analysis of SPATA genes in human male infertility has not yet been undertaken.

OBJECTIVES

To analyze the methylation status of SPATA4, SPATA5 and SPATA6 genes in oligozoospermic male infertility.

MATERIALS AND METHODS

In the present study, we have analyzed DNA methylation pattern in the promoter regions of SPATA4, SPATA5 and SPATA6 genes in oligozoospermic patients and compared it with normozoospermic fertile controls. Semen samples were obtained from 30 oligozoospermic infertile and 19 normozoospermic fertile controls, and DNA methylation levels of the target gene promoters were analyzed by amplicon based deep sequencing methylation analysis using MiSeq.

RESULTS

SPATA4 (P < 0.0008), SPATA5 (P = 0.009) and SPATA6 (Promoter, P < 0.0005; Exon 1, P = 0.0128) genes were significantly hypermethylated in oligozoospermic patients in comparison to controls. This is the first study reporting a higher methylation in the promoters of SPATA4, SPATA5 and SPATA6 in oligozoospermic infertile individuals in comparison to the normozoospermic fertile controls.

DISCUSSION

Altered methylation of SPATA genes would affect pathways involved in sperm production or affect various processes linked to sperm fertility.

CONCLUSION

In conclusion, hypermethylation in the SPATA4, SPATA5 and SPATA6 genes correlates with oligozoospermic infertility.

Comparative Transcriptome Analysis of Gonads for the Identification of Sex-Related Genes in Giant Freshwater Prawns (Macrobrachium Rosenbergii) Using RNA Sequencing

The giant freshwater prawn (Macrobrachium rosenbergii) exhibits sex dimorphism between the male and female individuals. To date, the molecular mechanism governing gonadal development was unclear, and limited data were available on the gonad transcriptome of M. rosenbergii. Here, we conducted comprehensive gonadal transcriptomic analysis of female (ZW), super female (WW), and male (ZZ) M. rosenbergii for gene discovery. A total of 70.33 gigabases (Gb) of sequences were generated. There were 115,338 unigenes assembled with a mean size of 1196 base pair (bp) and N50 of 2195 bp. Alignment against the National Center for Biotechnology Information (NCBI) non-redundant nucleotide/protein sequence database (NR and NT), the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, SwissProt database, Protein family (Pfam), Gene ontology (GO), and the eukaryotic orthologous group (KOG) database, 36,282 unigenes were annotated at least in one database. Comparative transcriptome analysis observed that 10,641, 16,903, and 3393 genes were significantly differentially expressed in ZW vs. ZZ, WW vs. ZZ, and WW vs. ZW samples, respectively. Enrichment analysis of differentially expressed genes (DEGs) resulted in 268, 153, and 42 significantly enriched GO terms, respectively, and a total of 56 significantly enriched KEGG pathways. Additionally, 23 putative sex-related genes, including Gtsf1, IR, HSP21, MRPINK, Mrr, and other potentially promising candidate genes were identified. Moreover, 56,241 simple sequence repeats (SSRs) were identified. Our findings provide a valuable archive for further functional analyses of sex-related genes and future discoveries of underlying molecular mechanisms of gonadal development and sex determination.

Vitellogenin expression in the oilseed rape pest Meligethes aeneus

When investigating insecticide resistance of pest insects, for example, the pollen beetle Meligethes aeneus, it is relevant to differentiate toxicological and molecular genetic data between male and female specimens. A molecular sex determination method would allow resistance testing to be run without prior sorting of the samples. A one-step quantitative RT-PCR method for quantification of the yolk protein vitellogenin expression in the pollen beetle was established. The expression level of vitellogenin relative to tubulin was determined. Pollen beetles were tested at different time points during their development to determine if vitellogenin is a reliable molecular marker for detection of sexually mature females. The differentiation between females and males by relative expression of vitellogenin to tubulin is conditional regarding the life cycle. Sexually mature females and males could easily be distinguished, whereas immature specimens could not be seperated. Vitellogenin expression is a successful marker for identification of sexually mature pollen beetles. Females from the spring populations showed vitellogenin expression when the temperature was above 10.2°C. Further, detailed observations of vitellogenin throughout the spring indicated a strong relationship between daily temperatures and vitellogenin expression, which is an indicator of oviposition ability.

Transcriptome profiling of the honeybee parasite Varroa destructor provides new biological insights into the mite adult life cycle

Background

The parasite Varroa destructor represents a significant threat to honeybee colonies. Indeed, development of Varroa infestation within colonies, if left untreated, often leads to the death of the colony. Although its impact on bees has been extensively studied, less is known about its biology and the functional processes governing its adult life cycle and adaptation to its host. We therefore developed a full life cycle transcriptomic catalogue in adult Varroa females and included pairwise comparisons with males, artificially-reared and non-reproducing females (10 life cycle stages and conditions in total).

Results

Extensive remodeling of the Varroa transcriptome was observed, with an upregulation of energetic and chitin metabolic processes during the initial and final phases of the life cycle (e.g. phoretic and post-oviposition stages), whereas during reproductive stages in brood cells genes showing functions related to transcriptional regulation were overexpressed. Several neurotransmitter and neuropeptide receptors involved in behavioural regulation, as well as active compounds of salivary glands, were also expressed at a higher level outside the reproductive stages. No difference was detected between artificially-reared phoretic females and their counterparts in colonies, or between females who failed to reproduce and females who successfully reproduced, indicating that phoretic individuals can be reared outside host colonies without impacting their physiology and that mechanisms underlying reproductive failure occur before oogenesis.

Conclusions

We discuss how these new findings reveal the remarkable adaptation of Varroa to its host biology and notably to the switch from living on adults to reproducing in sealed brood cells. By spanning the entire adult life cycle, our work captures the dynamic changes in the parasite gene expression and serves as a unique resource for deciphering Varroa biology and identifying new targets for mite control.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4668-z) contains supplementary material, which is available to authorized users.

Vitellogenin and its receptor play essential roles in the development and reproduction of the brown citrus aphid, Aphis (Toxoptera) citricidus

Vitellogenin (Vg) and its receptor (VgR) play a key role in the reproductive process and development of insects. Aphids are a group of high-fecundity insect species with pseudoplacental viviparity, but the roles of their Vg and VgR genes have not been investigated yet. The brown citrus aphid, Aphis (Toxoptera) citricidus, is a major insect pest of citrus and the main vector of Citrus tristeza closterovirus. In this study, we identified and characterized these two genes, designated as AcVg and AcVgR, from the brown citrus aphid. We found that AcVg has lost the DUF1943 domain that is present in other insect Vgs. Silencing of AcVg and AcVgR led to a delay in the nymph-adult transition, a prolonged prereproductive period, and a shortened reproductive period, which in turn resulted in slower embryonic development and fewer new-born nymphs. Interestingly, silencing of AcVg decreased the transcript level of AcVgR, but silencing of AcVgR resulted in increased transcript levels of AcVg. In addition, silencing of Vg/VgR had similar phenotypes between alate and apterous morphs, suggesting that the functions of these two genes are the same in the two wing morphs of the aphid. Our results demonstrate that Vg and VgR are involved in various aspects of aphid development and reproduction. Further studies on the synthesis of Vg could help to elucidate the reproductive mechanism and provide information that will be useful for developing new pest control strategies.

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

PHF7 exhibits male-specific expression in early germ cells, germline stem cells and spermatogonia in insects, and its expression promotes spermatogenesis in germ cells when they are present in a male soma. However, the influence of male-specific PHF7 on female reproductive biology via mating remains unclear. Thus, we investigated the potential impacts of male PHF7, existed in seminal fluid of Nilaparvata lugens (NlPHF7), on fecundity and population growth via mating. Our results revealed that suppressing male NlPHF7 expression by RNAi led to decreases in body weight, soluble accessory gland protein content, arginine content, and reproductive organ development in males, resulting in significant reduction of oviposition periods and fecundity in females, and significant decrease in body weight, fat body and ovarian protein content, yeast-like symbionts abundance, ovarian development and vitellogenin gene expression in their female mating partners. Similarly, suppression of NlPHF7 expression in males mated with the control female reduced population growth and egg hatching rate, but did not influence gender ratio. We infer that NlPHF7 play a role important in stimulating female fecundity via mating. This study provides valuable information by identifying a potentially effective target gene for managing BPH population through RNAi.

Inductions of reproduction and population growth in the generalist predator Cyrtorhinus lividipennis (Hemiptera: Miridae) exposed to sub-lethal concentrations of insecticides

BACKGROUND

The miridbug, Cyrtorhinus lividipennis, is a significant predacious enemy of rice planthoppers. The effects of sub-lethal concentrations of triazophos, deltamethrin and imidacloprid on fecundity, egg hatchability, expression levels of genes associated with reproduction, and population growth in C. lividipennis were investigated.

RESULTS

The fecundities for three pair combinations (♀_c × ♂_t , ♀_t × ♂_c and ♀_t × ♂_t ) treated with sub-lethal concentrations of the insecticides triazophos, deltamethrin and imidacloprid (LC₁₀ and LC₂₀ ) showed a significant increase compared to the untreated pairs (♀_c × ♂_c ). However, sub-lethal concentration treatments did not affect the egg hatchability. The ClVg expression levels of female adults exposed to triazophos, deltamethrin and imidacloprid (LC₂₀ ) increased by 52.6, 48.9 and 91.2%, respectively. The ClSPATA13 expression level of adult males exposed to triazophos, deltamethrim and imidacloprid (LC₂₀ ) increased by 80.7, 41.3 and 48.3%, respectively. Furthermore, sub-lethal concentrations of insecticides (LC₂₀ ) caused increased population numbers in C. lividipennis.

CONCLUSION

Sub-lethal concentrations of triazophos, deltamethrin and imidacloprid stimulated reproduction and enhanced population growth of C. lividipennis. The reproductive stimulation might result from the up-regulation of ClVg or ClSPATA13. These findings may be useful in mediating populations of planthoppers. © 2017 Society of Chemical Industry.