Insect Science最新文献

Innate antibacterial defense in Drosophila relies on the IMD pathway to induce antimicrobial peptides (AMPs), but the auxiliary transcriptional networks that amplify or fine-tune this response remain poorly defined. Here, we identify the Fork head (Fkh) transcription factor, a FoxA-family protein classically linked to development and metabolism, as a critical amplifier of humoral immunity. Our results show that bacterial infection rapidly induces Fkh expression, and enhances host survival, as well as promotes robust induction of AMPs including Diptericin (Dpt), Attacin-A, and Cecropin-A1. Mechanistically, Fkh directly binds the Dpt promoter and synergizes with the NF-κB factor Relish, ensuring strong promoter activation. In parallel, Fkh activates miR-34 transcription to repress the negative regulator p38b, thereby relieving inhibitory pressure on IMD signaling. Disruption of either Fkh-binding motifs or the miR-34 seed site abolishes these effects. Together, our findings uncover a dual regulatory strategy in which Fkh simultaneously acts as a promoter-bound transcription factor and as an upstream activator of an immune-enhancing miRNA. This integrated Fkh-miR-34-p38b axis establishes a feed-forward mechanism that ensures rapid and high-amplitude antibacterial defense, providing a new paradigm for transcription factor-miRNA cooperation in innate immunity.

Gut microbiota play a key role in an insect's ability to overcome host tree defenses. Streltzoviella insularis (Lepidoptera: Cossidae) is a generalist wood-boring pest in China, and Fraxinus chinensis var. rhynchophylla is its preferred host in Xiong'an New Area. Previous mechanistic studies have demonstrated that S. insularis can tolerate and degrade host defense compounds via its gut microbes. However, whether hydroxytyrosol (a constitutive phenolic compound potentially involved in browning reactions) functions as a key defense of Fraxinus chinensis var. rhynchophylla against woodborers, and whether the gut microbiota of attacking S. insularis can degrade hydroxytyrosol, remains unclear. We determined the hydroxytyrosol content in S. insularis-infested and uninfested Fraxinus chinensis var. rhynchophylla. We further evaluated the effects of hydroxytyrosol on larval survival, tested the ability of larval gut bacteria to degrade hydroxytyrosol, and identified the resulting degradation products. Although hydroxytyrosol was toxic to S. insularis, its concentrations were lower in larval galleries than in uninfested trees, suggesting that S. insularis can degrade this compound. Gut bacteria from S. insularis degraded hydroxytyrosol both in vivo and in vitro, and Serratia sp. showed the strongest hydroxytyrosol degradation activity. Metabolomics further indicated that gut bacteria may degrade hydroxytyrosol via the tricarboxylic acid cycle pathway. Because this pathway yields ATP, the bacterial degradation products of hydroxytyrosol may provide an energy source for the insect hosts or their gut microorganisms.

Group-living insects like the pea aphid, Acythosiphon pisum, use population density as a key signal to regulate behavior, but the underlying mechanisms of individual responses remain unclear. This study employed a novel dual-color system to precisely track individual aphid behavior across a density gradient. We found that aphid behavioral responses are not linear but are triggered at critical density thresholds, which differ depending on the aphid's initial state (settled or active). As density increased, aphids exhibited significantly greater movement and reduced reproductive output, with a key behavioral shift toward dispersal occurring above 1.25 individuals/cm² (1: 11 group). To investigate the molecular basis for this shift, we analyzed the expression of genes related to three key monoamine neurotransmitters. The results showed a strong positive correlation between population density, locomotor activity, and the expression of the tyramine β-hydroxylase (TBH) gene, which is critical for octopamine synthesis. Conversely, the expression of the serotonin-related gene tryptophan hydroxylase (TPH) decreased, while the dopamine-related gene Tyrosine hydroxylase (TH) showed no clear trend. These findings suggest that aphids utilize a "threshold-triggered" model to rapidly shift from a settled to a dispersal state, a process primarily mediated by the monoamine neurotransmitters system. This provides a new perspective on the self-regulation mechanisms of insect populations.

The cotton aphid (Aphis gossypii) is a major pest of greenhouse peppers in southern Spain. Biological control using the parasitoid wasp Aphidius colemani is limited because the ant Tapinoma ibericum, engaged in a mutualistic relationship with aphids, protects them from parasitoid attack and thereby reduces parasitism success. To assess the impact of ants on pest biological control, an ant-exclusion experiment was conducted over two consecutive years in four experimental greenhouses. Pepper plants were infested with aphids and then treated with Aphidius colemani. The presence of natural enemies and fruit production were also evaluated. Excluding ants significantly increased the abundance of mummies by 22.2% and reduced the number of aphid colonies, while total aphid abundance showed variable, year-dependent effects and was not affected by ants. Ant presence negatively affected some natural enemies such as Chrysoperla carnea s.l., the mirid Nesidiocoris tenuis, and the ladybird Scymnus sp., had no effect on hoverflies and spiders, and increased the abundance of Aphidoletes aphidimyza, indicating contrasting responses among natural enemies. Fruit weight was not affected by ant presence. Overall, these findings confirm that T. ibericum reduces parasitism by A. colemani, and demonstrate that it modifies aphid spatial distribution, and reshapes the natural enemy community, but does not necessarily diminish crop production. These results suggest that combining A. aphidimyza with A. colemani could improve control of A. gossypii in ant-infested crops.

Baculoviruses, large double-stranded DNA viruses, are widely used in biological control and biotechnology; however, their success depends on complex interactions with host factors. Members of the AAA ATPase family are emerging as key regulators in these processes. Previous studies identified Bombyx mori ATAD3A (BmATAD3A) as a host factor hijacked by the viral protein LEF-11 to facilitate Bombyx mori nucleopolyhedrovirus (BmNPV) replication. However, the underlying mechanisms remain poorly understood. We generated transgenic silkworms overexpressing BmATAD3A and demonstrated that its overexpression enhances viral proliferation in vivo. Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis identified BmIGF2BP1 as an interacting protein of BmATAD3A. Further analysis showed that BmATAD3A negatively regulated the expression of BmIGF2BP1. Additionally, our results showed that BmIGF2BP1 suppresses BmNPV replication, while BmATAD3A-mediated downregulation of BmIGF2BP1 further promotes viral proliferation. This study solidifies the critical role of ATAD3A in BmNPV replication, identifies its interacting proteins, and elucidates the functional interplay between BmIGF2BP1 and BmATAD3A in viral propagation. These findings advance our understanding of the mechanisms by which AAA ATPase family members regulate viral replication, thereby enriching the baculovirus-host interaction network.

Monochamus alternatus Hope, commonly known as the pine sawyer beetle, is a devastating pest in coniferous forest ecosystems. While insect olfactory-related genes have been implicated in pathogen defense, the potential involvement of chemosensory protein (CSP) genes in M. alternatus immune responses to the entomopathogenic fungus, Beauveria bassiana remains largely unknown. In this study, we identified 15 CSP genes in M. alternatus based on transcriptome, seven of which exhibited altered expression following B. bassiana infection. Quantitative real-time PCR (RT-qPCR) analysis showed significant upregulation of MaCSP8 and MaCSP15 at 3 d post-infection. Tissue-specific profiling revealed predominant expression of MaCSP8 in larval heads and epidermis, whereas MaCSP15 expression was highest in the fat body. Crucially, RNA interference (RNAi)-mediated silencing of MaCSP8 and MaCSP15 significantly increased larval susceptibility to B. bassiana infection. Furthermore, knockdown of the two MaCSPs resulted in significant downregulation of key immune effectors such as Dorsal, Defense, Attacin, and Coleoptericin, suggesting modulation of the Toll pathway. Taken together, MaCSP8 and MaCSP15 were defined as critical components of the antifungal immune response in M. alternatus larvae, likely functioning through the regulation of antimicrobial peptide (AMP) production. This study provides novel insights into CSP-mediated innate immunity, establishing it as a promising target for developing next-generation bio-insecticides and enhancing fungal biocontrol strategies against forestry pests.

Dopa decarboxylase (DDC) is a crucial enzyme that regulates melanin synthesis and plays an essential role in cuticular pigmentation and insect development. However, the function of DDC in the fall armyworm, Spodoptera frugiperda, is not yet well understood. In this study, we knocked out the DDC gene and found that mosaic mutants displayed an albino phenotype across all life stages, including larval, pupal, and adult stages. Notably, homozygous DDC mutants showed complete larval albinism, exhibited developmental delays, and frequently failed to pupate, ultimately leading to death. Histological analyses revealed that tissue remodeling during metamorphosis was disrupted and became disorganized. A few individuals survived to adulthood, but they developed severely curled forewings. To clarify the molecular basis of these phenotypes, we performed a transcriptomic analysis and found that DDC influences pigmentation by regulating melanin-related and pteridine-related metabolic pathways. Additionally, DDC disruption altered the expression of genes involved in chitin metabolism and cuticular proteins, and affected the juvenile hormone and ecdysone signaling pathways. Overall, these results provide the first evidence that DDC is critical for pigmentation and development in S. frugiperda and shed new light on the molecular mechanisms underlying body color formation.

During insect oogenesis, follicular cells (FCs) typically undergo the endocycle to become polyploid, thereby supporting oocyte development. The brown planthopper (BPH, Nilaparvata lugens), one of the most destructive rice pests, exhibits remarkable fecundity. However, the polyploidization of FCs and its regulatory mechanisms remain poorly understood. Here, we demonstrate that 92.3% of FCs become binucleate via endomitosis at stage 4 of oogenesis, followed by a significant increase in DNA content through endoreplication at stage 5. Knockdown of fizzy-related protein (Fzr), a key regulator of the mitosis-to-endocycle transition, disrupted the expression of cell cycle-related genes and caused a marked reduction in both binucleate FC numbers and DNA content, resulting in ovarian malformation and impaired egg development. Gene expression analyses revealed that Fzr knockdown caused aberrant expression and alternative splicing of genes related to spliceosome function and energy metabolism. Furthermore, these alterations appear to be at least partially independent of the polyploidization process. Our findings reveal a two-step polyploidization mechanism in BPH reproduction, offering insights into the evolutionary adaptation of reproductive strategies in insect pests. Additionally, this work advances our understanding of the molecular mechanisms underlying cell cycle transitions and establishes a foundation for future studies on insect reproduction and pest management strategies.

Thrips are economically important pests in the global agriculture. Thrips cause direct damage to crops through feeding and also act as vectors for numerous plant viruses, particularly tomato spotted wilt virus (TSWV). TSWV, a member of the genus Orthotospovirus in the family Tospoviridae (order Elliovirales, class Bunyaviricetes), poses a threat to various crop plants in the world. This review summarizes the transmission mechanisms of TSWV by western flower thrip (WFT) and the effects of TSWV on WFT behavior and fitness. By synthesizing current literature, this review aims to offer novel insights into the complex relationships between thrips, viruses, and plants, and to establish a theoretical foundation for developing molecular-based strategies for virus prevention and control.

Parasitic wasps have evolved intricate strategies to manipulate host development for the benefit of their offspring. In the lepidopteran host Ostrinia furnacalis, parasitism by Macrocentrus cingulum leads to pupation failure; however, the molecular mechanisms remain unclear. Here, we demonstrate that miR-281a-5p, upregulated in the hemolymph of parasitized host larvae, inhibits pupation by directly targeting ecdysone-induced protein 93F (OfE93), a crucial transcription factor involved in metamorphosis. A dual-luciferase assay confirmed that miR-281a-5p binds to the 3' untranslated region of OfE93. Moreover, injection of agomiR-281a-5p significantly reduced both transcript and protein levels of OfE93 in O. furnacalis larvae. RNA interference-mediated knockdown of OfE93 partially replicated the effects of parasitism, causing pupation arrest in approximately 20% of O. furnacalis larvae. These findings reveal a microRNA-based mechanism by which M. cingulum disrupts the host's endocrine-driven metamorphosis, providing new insights into the molecular interactions between parasitoids and their hosts.