A Toll-dependent Bre1/Rad6-cact feedback loop in controlling host innate immune response

Autophagy enhances the antibacterial response in Macrobrachium rosenbergii by modulating cellular metabolism and immune pathways

Autophagy plays a crucial role in innate and adaptive immunity against invading microorganisms. However, the mechanism underlying autophagy in Macrobrachium rosenbergii remains largely unknown. Here, we demonstrate that Aeromonas hydrophila activates autophagy in M. rosenbergii, according to Western blot, qRT-PCR, and transmission electron microscopy observations. Rapamycin treatment to activate autophagy in M. rosenbergii followed by stimulation with A. hydrophila significantly decreased the A. hydrophila OmpA copy number in the gills of M. rosenbergii. Furthermore, high-throughput RNA-seq analysis of M. rosenbergii gills treated with rapamycin revealed 1684 upregulated and 1500 downregulated differentially expressed genes (DEGs), most of which regulate metabolic pathways. A comprehensive joint analysis of the two transcriptomic databases for A. hydrophila infection and rapamycin treatment identified 15 upregulated and 25 downregulated DEGs, respectively. These genes enhance the immune defense of M. rosenbergii by negatively regulating metabolic pathways and promoting immune pathways. Our results provide a theoretical basis for further exploration of the antibacterial mechanism of M. rosenbergii.

Cul2 Is Essential for the Drosophila IMD Signaling-Mediated Antimicrobial Immune Defense

Cullin 2 (Cul2), a core component of the Cullin-RING E3 ubiquitin ligase complex, is integral to regulating distinct biological processes. However, its role in innate immune defenses remains poorly understood. In this study, we investigated the functional significance of Cul2 in the immune deficiency (IMD) signaling-mediated antimicrobial immune reactions in Drosophila melanogaster (fruit fly). We demonstrated that loss-of-function of Cul2 led to a marked reduction in antimicrobial peptide induction following bacterial infection, which was associated with increased fly mortality and bacterial load. The proteomic analysis further revealed that loss-of-function of Cul2 reduced the expression of Effete (Eff), a key E2 ubiquitin-conjugating enzyme during IMD signaling. Intriguingly, ectopic expression of eff effectively rescued the immune defects caused by loss of Cul2. Taken together, the results of our study underscore the critical role of Cul2 in ensuring robust IMD signaling activation, highlighting its importance in the innate immune defense against microbial infection in Drosophila.

Combined intestinal microbiota and transcriptomic analysis to investigate the effect of different stocking densities on the ability of Pacific white shrimp (Litopenaeus vannamei) to utilize Chlorella sorokiniana

Aiming to investigate the impact of different stocking densities on the ability of Pacific white shrimp (Litopenaeus vannamei) to utilize Chlorella sorokiniana (CHL), a 3 × 2 factorial design stocking experiment was used in this study. Specifically, shrimp was fed with two dietary protein sources (fishmeal [FM] and CHL) at low (LSD; 100 per m3), medium (MSD; 200 per m3) and high (HSD; 300 per m3) stocking densities for 8 weeks. The growth performance and resistance to Vibrio parahaemolyticus (1.0 × 107 CFU/mL) of shrimp decreased with the increase of stocking density, but dietary CHL improved this result. Differences between the CHL and FM groups for V. parahaemolyticus resistance were significant only under high-density conditions (P < 0.05). Significant interactions between stocking density and protein source were found on the activities of catalase (CAT), superoxide dismutase (SOD) and phenol oxidase (PO), and the contents of malondialdehyde (MDA) in the hepatopancreas and the activities of intestinal amylase, most of which were significantly different between CHL and FM groups only at high stocking density (P < 0.05). Analysis of 16S rDNA sequencing showed that dietary CHL increased the alpha diversity of intestinal microbiota, inhibited the colonization of pathogenic bacteria and enhanced the abundance of beneficial bacteria. Transcriptomic results showed that at high stocking densities, differentially expressed genes (DEGs) in the FM vs CHL group were mostly upregulated and primarily enriched in immune and metabolic related pathways including Toll, immune deficiency (Imd) and glycolysis-gluconeogenesis pathways. Pearson correlation analysis revealed significant correlation between the top ten intestinal bacteria at the genus level and markedly enriched DEGs, also more were detected under high density situations. In conclusion, CHL has great potential as a novel protein source in the intensive farming of shrimp.

Drosophila eIF3f1 mediates host immune defense by targeting dTak1

Eukaryotic translation initiation factors have long been recognized for their critical roles in governing the translation of coding RNAs into peptides/proteins. However, whether they harbor functional activities at the post-translational level remains poorly understood. Here, we demonstrate that eIF3f1 (eukaryotic translation initiation factor 3 subunit f1), which encodes an archetypal deubiquitinase, is essential for the antimicrobial innate immune defense of Drosophila melanogaster. Our in vitro and in vivo evidence indicate that the immunological function of eIF3f1 is dependent on the N-terminal JAMM (JAB1/MPN/Mov34 metalloenzymes) domain. Mechanistically, eIF3f1 physically associates with dTak1 (Drosophila TGF-beta activating kinase 1), a key regulator of the IMD (immune deficiency) signaling pathway, and mediates the turnover of dTak1 by specifically restricting its K48-linked ubiquitination. Collectively, these results provide compelling insight into a noncanonical molecular function of a translation initiation factor that controls the post-translational modification of a target protein.

Toll-mediated airway homeostasis is essential for fly survival upon injection of RasV12-GFP oncogenic cells

Toll signaling is well known for its pivotal role in the host response against the invasion of external pathogens. Here, we investigate the potential involvement of Toll signaling in the intersection between the host and oncogenic cells. We show that loss of myeloid differentiation factor 88 (Myd88) leads to drastic fly death after the injection of RasV12-GFP oncogenic cells. Transcriptomic analyses show that challenging flies with oncogenic cells or bacteria leads to distinct inductions of Myd88-dependent genes. We note that downregulation of Myd88 in the tracheal system accounts for fly mortality, and ectopic tracheal complementation of Myd88 rescues the survival defect in Myd88 loss-of-function mutants following RasV12-GFP injection. Further, molecular and genetic evidence indicate that Toll signaling modulates fly resistance to RasV12-GFP cells through mediating airway function in a rolled-dependent manner. Collectively, our data indicate a critical role of Toll signaling in tracheal homeostasis and host survival after the injection of oncogenic cells.

Suppression of Drosophila antifungal immunity by a parasite effector via blocking GNBP3 and GNBP-like 3, the dual receptors for β-glucans

The tactics used by animal pathogens to combat host immunity are largely unclear. Here, we report the depiction of the virulence-required effector Tge1 deployed by the entomopathogen Metarhizium robertsii to suppress Drosophila antifungal immunity. Tge1 can target both GNBP3 and GNBP-like 3 (GL3), and the latter can bind to β-glucans like GNBP3, whereas the glucan binding by both receptors can be attenuated by Tge1. As opposed to the surveillance GNBP3, GL3 is inducible in Drosophila depending on the Toll pathway via a positive feedback loop mechanism. Losses of GNBP3 and GL3 genes result in the deregulations of protease cascade, Spätzle maturation, and antimicrobial gene expressions in Drosophila upon fungal challenges. Fly survival assays confirm that GL3 plays a more essential role than GNBP3 in combating fungal infections. In addition to evidencing the gene-for-gene interactions between fungi and insects, our data advance insights into Drosophila antifungal immunity.

Dietary Supplementation of Aspirin Promotes Drosophila Defense against Viral Infection

Aspirin, also known as acetylsalicylic acid, is widely consumed as a pain reliever and an anti-inflammatory as well as anti-platelet agent. Recently, our studies using the animal model of Drosophila demonstrated that the dietary supplementation of aspirin renovates age-onset intestinal dysfunction and delays organismal aging. Nevertheless, it remains probable that aspirin plays functional roles in other biological activities, for instance antiviral defense reactions. Intriguingly, we observed that the replications of several types of viruses were drastically antagonized in Drosophila macrophage-like S2 cells with the addition of aspirin. Further in vivo experimental approaches illustrate that adult flies consuming aspirin harbor higher resistances to viral infections with respect to flies without aspirin treatment. Mechanistically, aspirin positively contributes to the Drosophila antiviral defense largely through mediating the STING (stimulator of interferon genes) but not the IMD (immune deficiency) signaling pathway. Collectively, our studies uncover a novel biological function of aspirin in modulating Drosophila antiviral immunity and provide theoretical bases for exploring new antiviral treatments in clinical trials.