Decoding the Reproductive System of the Olive Fruit Fly, Bactrocera oleae

Seminal fluid proteins in the Queensland fruit fly: Tissue origins, effects of mating and comparative genomics

In many insect species, the ability of males to inhibit their mates from remating is an important component of fitness. This ability is also essential for the effective management of insect pests, including tephritid fruit flies, using the Sterile Insect Technique. Here we apply transcriptomics and proteomics to male reproductive tissues before and after mating to characterize components of semen that might mediate remating inhibition in Queensland fruit fly. We found 144 genes whose transcripts were enriched, or proteins expressed, in reproductive tissue and which also varied in amount after mating. Some were associated with testes, accessory glands and ejaculatory apodeme, but those from the ejaculatory apodeme were over-represented compared to those not enriched in reproductive tissue or mating responsive. These included 13 related genes clustered within one Mb on chromosome 5. Functional annotations implicated a broad range of biochemical processes in the genes/proteins enriched in reproductive tissue and mating responsive, with cuticle structure most commonly implicated among the subset of these that were apodeme-enriched and a kinase involved in vitellogenesis implicated for one of the 13 clustered genes. We did not find a homolog of the much studied Drosophila melanogaster Sex Peptide but comparative genomics indicated that some of the tissue-enriched, mating responsive genes/proteins were rapidly evolving in tephritids (including in the Queensland fruit fly lineage), suggesting recent adaptation to new functional niches. Our results provide a set of candidate mediators of remating inhibition for further functional testing.

Knockdown of the ZcVgR Gene Alters the Expression of Genes Related to Reproduction and Lifespan in Zeugodacus cucurbitae (Coquillett) Under Extreme Heat Conditions

Zeugodacus cucurbitae (Coquillett) is an important migratory vegetable pest. Previous research has demonstrated that short-term high temperatures induce differential expression of the vitellogenin receptor (ZcVgR) gene, reducing the number of eggs laid and the lifespan of female Z. cucurbitae. In this paper, we used Tandem Mass Tags (TMT) quantitative proteomics and Illumina high-throughput sequencing to determine the proteomic and transcriptomic information of female Z. cucurbitae after siRNA-mediated silencing of the target gene (ZcVgR) to gain a comprehensive understanding of the molecular mechanism of this gene in the regulation of reproduction and lifespan. The findings demonstrated that following the target gene's silencing, the ZcVgR gene's transcriptional expression was significantly downregulated, and there was no significant difference in protein level. The transcriptome and proteome had a low correlation; when the ZcVgR gene was silenced, vitellogenin-1 (ZcVg1), juvenile hormone epoxide hydrolase (JHEH), troponin C (TnC), heat shock protein 70 (HSP70), and other related genes were downregulated at the transcriptional level. By silencing the ZcVgR gene, transcriptionally level immune-related pathways were activated and energy metabolism-related pathways were inhibited; protein-level glycometabolism and phagosome pathways were activated, while phototransduction-fly and autophagy-animal pathways were inhibited. The findings of this study might offer a theoretical foundation for integrated management of Z. cucurbitae in the summertime.

RNAi-mediated pest control targeting the Troponin I (wupA) gene in sweet potato weevil, Cylas formicarius

The sweet potato weevil (Cylas formicarius) is a critical pest producing enormous global losses in sweet potato crops. Traditional pest management approaches for sweet potato weevil, primarily using chemical pesticides, causes pollution, food safety issues, and harming natural enemies. While RNA interference (RNAi) is a promising environmentally friendly approach to pest control, its efficacy in controlling the sweet potato weevil has not been extensively studied. In this study, we selected a potential target for controlling C. formicarius, the Troponin I gene (wupA), which is essential for musculature composition and crucial for fundamental life activities. We determined that wupA is abundantly expressed throughout all developmental stages of the sweet potato weevil. We evaluated the efficiency of double-stranded RNAs in silencing the wupA gene via microinjection and oral feeding of sweet potato weevil larvae at different ages. Our findings demonstrate that both approaches significantly reduced the expression of wupA and produced high mortality. Moreover, the 1st instar larvae administered dswupA exhibited significant growth inhibition. We assessed the toxicity of dswupA on the no-target insect silkworm and assessed its safety. Our study indicates that wupA knockdown can inhibit the growth and development of C. formicarius and offer a potential target gene for environmentally friendly control.

The Roles of Mating, Age, and Diet in Starvation Resistance in Bactrocera oleae (Olive Fruit Fly)

The olive fruit fly (Bactrocera oleae (Rossi) (Diptera: Tephritidae)), although a pest of major economic importance for the olive industry, has not been sufficiently studied with respect to the factors affecting its survival resistance to food deprivation. In the present study, we examined the effect of the interaction between mating status (virgin/mated), age class (11-20/21-30/31-40/41-50), and diet quality (protein plus sugar or only sugar) on starvation resistance in B. oleae under constant laboratory conditions. We conducted a total of 16 treatments (2 × 4 × 2 = 16) for each gender. Our results showed that starvation resistance in B. oleae did not differ significantly between females and males. The main conclusions of our study regarding mating status, age, and diet indicated that mated adults showed much less starvation resistance compared to virgins, younger adults endured longer, and the adults fed a restricted diet endured longer than those fed a full diet. A three-way interaction between mating status, diet, and age class was also identified and was the same for both genders. The interaction between mating status, age class, and diet also had a significant influence on starvation resistance in both sexes.

Postcopulatory Behavior of Tephritid Flies

Mating produces profound changes in the behavior of female flies, such as an increase in oviposition, reduction in sexual receptivity, increase in feeding, and even excretion. Many of these changes are produced by copulation, sperm, and accessory gland products that males transfer to females during mating. Our knowledge on the function of the male ejaculate and its effect on female insects is still incipient. In this article, we review peri- and postcopulatory behaviors in tephritid flies. We address the effects of male copulatory behavior; copula duration; and the male ejaculate, sperm, and accessory gland products on female remating behavior. Many species from these families are pests of economic importance; thus, understanding male mating effects on female behavior contributes to both developing more effective environmentally friendly control methods and furthering our understanding of evolutionary implications of intersexual competition and sexual conflict.

RNA interference (RNAi) applications to the management of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae): Its current trends and future prospects

The fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) is among the invasive insect pests that damages maize and sorghum, the high-priority crops in newly colonized agro-ecologies, including African contexts. Owing to the increasing infestation of the pest and the limitations of current conventional methods for its management, there is a call for discovering advanced pest management approaches. RNA interference (RNAi) is an emerging molecular tool showing flexible potential for the management of S. frugiperda. We conducted a search of the recent application of RNAi literature using Google Scholar and Mendeley to find advanced papers on S. frugiperda management using RNAi molecular tools that led to growth inhibition, developmental aberrations, reduced fecundity, and mortality, mainly by disruption of normal biological processes of the pest. Although efforts have been made to accelerate the utility of RNAi, many factors limit the efficiency of RNAi to achieve successful control over S. frugiperda. Owing to RNAi’s potential bioactivity and economic and ecological acceptability, continued research efforts should focus on improving its broad applicability, including field conditions. Screening and identification of key target genes should be a priority task to achieve effective and sustainable management of this insect via RNAi. In addition, a clear understanding of the present status of RNAi utilization in S. frugiperda management is of paramount importance to improve its efficiency. Therefore, in this review, we highlight the biology of S. frugiperda and the RNAi mechanism as a foundation for the molecular management of the pest. Then, we discuss the current knowledge of the RNAi approach in S. frugiperda management and the factors affecting the efficiency of RNAi application. Finally, the prospects for RNAi-based insect pest management are highlighted for future research to achieve effective management of S. frugiperda.

Characterization of reproductive proteins in the Mexican fruit fly points towards the evolution of novel functions

Seminal fluid proteins (Sfps) modify female phenotypes and have wide-ranging evolutionary implications on fitness in many insects. However, in the Mexican fruit fly, Anastrepha ludens, a highly destructive agricultural pest, the functions of Sfps are still largely unknown. To gain insights into female phenotypes regulated by Sfps, we used nano-liquid chromatography mass spectrometry to conduct a proteomic analysis of the soluble proteins from reproductive organs of A. ludens. The proteins predicted to be transferred from males to females during copulation were 100 proteins from the accessory glands, 69 from the testes and 20 from the ejaculatory bulb, resulting in 141 unique proteins after accounting for redundancies from multiple tissues. These 141 included orthologues to Drosophila melanogaster proteins involved mainly in oogenesis, spermatogenesis, immune response, lifespan and fecundity. In particular, we found one protein associated with female olfactory response to repellent stimuli (Scribble), and two related to memory formation (aPKC and Shibire). Together, these results raise the possibility that A. ludens Sfps could play a role in regulating female olfactory responses and memory formation and could be indicative of novel evolutionary functions in this important agricultural pest.