Deltex positively regulates Toll signaling in a JNK independent manner in Drosophila

E3 ubiquitin ligase Deltex facilitates the expansion of Wingless gradient and antagonizes Wingless signaling through a conserved mechanism of transcriptional effector Armadillo/β-catenin degradation

The Wnt/Wg pathway controls myriads of biological phenomena throughout the development and adult life of all organisms across the phyla. Thus, an aberrant Wnt signaling is associated with a wide range of pathologies in humans. Tight regulation of Wnt/Wg signaling is required to maintain proper cellular homeostasis. Here, we report a novel role of E3 ubiquitin ligase Deltex in Wg signaling regulation. Drosophila dx genetically interacts with wg and its pathway components. Furthermore, Dx LOF results in a reduced spreading of Wg while its over-expression expands the diffusion gradient of the morphogen. We attribute this change in Wg gradient to the endocytosis of Wg through Dx which directly affects the short- and long-range Wg targets. We also demonstrate the role of Dx in regulating Wg effector Armadillo where Dx down-regulates Arm through proteasomal degradation. We also showed the conservation of Dx function in the mammalian system where DTX1 is shown to bind with β-catenin and facilitates its proteolytic degradation, spotlighting a novel step that potentially modulates Wnt/Wg signaling cascade.

The NF-κB/Relish Activates miR-308 to Negatively Regulate Imd Pathway Immune Signaling in Drosophila

The strength and duration of the NF-κB signaling response must be tightly modulated to avoid an inadequate or excessive immune response. Relish, a core NF-κB transcription factor of the Drosophila Imd pathway, can control the expression of antimicrobial peptides, including Dpt and AttA, to defend against Gram-negative bacterial infections, but whether Relish may regulate miRNA expression to participate in the immune response remains unclear. In this study, taking advantage of Drosophila S2 cells and different overexpression/knockout/knockdown flies, we first found that Relish could directly activate the expression of miR-308 to negatively regulate the immune response and promote the survival of Drosophila during Enterobacter cloacae infection. Second, our results demonstrated that Relish-mediated expression of miR-308 could suppress target gene Tab2 to attenuate the Drosophila Imd pathway signal during the middle and late stages of the immune response. Third, we detected the dynamic expression patterns of Dpt, AttA, Relish, miR-308, and Tab2 in wild-type flies after E. coli infection, which further revealed that the feedback regulatory loop of Relish-miR-308-Tab2 plays a crucial role in the immune response and homeostasis maintenance of the Drosophila Imd pathway. Overall, our present study not only illustrates an important mechanism by which this Relish-miR-308-Tab2 regulatory axis can negatively control the Drosophila immune response and participate in homeostasis maintenance but also provides new insights into the dynamic regulation of the NF-κB/miRNA expression network of animal innate immunity.

Drosophila as a Model Organism to Study Basic Mechanisms of Longevity

The spatio-temporal regulation of gene expression determines the fate and function of various cells and tissues and, as a consequence, the correct development and functioning of complex organisms. Certain mechanisms of gene activity regulation provide adequate cell responses to changes in environmental factors. Aside from gene expression disorders that lead to various pathologies, alterations of expression of particular genes were shown to significantly decrease or increase the lifespan in a wide range of organisms from yeast to human. Drosophila fruit fly is an ideal model system to explore mechanisms of longevity and aging due to low cost, easy handling and maintenance, large number of progeny per adult, short life cycle and lifespan, relatively low number of paralogous genes, high evolutionary conservation of epigenetic mechanisms and signalling pathways, and availability of a wide range of tools to modulate gene expression in vivo. Here, we focus on the organization of the evolutionarily conserved signaling pathways whose components significantly influence the aging process and on the interconnections of these pathways with gene expression regulation.

Identification of three novel Spätzle genes in Eriocheir sinensis and their roles during white spot syndrome virus infection

Proteins of Spätzle family play an essential role in innate immunity in invertebrates by activating the Toll pathway to induce the expression of antimicrobial peptides. However, little is known about the function of Spätzle in in the immune response of the Chinese mitten crab. In the present study, three novel Spätzle genes (named as EsSpz1, EsSpz2, and EsSpz3) were identified from Eriocheir sinensis. The genome structure of EsSpz1 contains two exons and an intron. Three Spätzle proteins all contain a Pfam Spaetzle domain. In the evolution, EsSpz1-3 cluster with other Spätzle proteins from crustaceans. EsSpz1-3 were widely distributed in multiple immune tissues. The expression levels of EsSpz1-3 in the intestine were remarkably upregulated after white spot syndrome virus (WSSV) challenge. The knockdown of EsSpz1-3 remarkably decreased the expressions of crustins and anti-lipopolysaccharide factors during WSSV infection. Moreover, EsSpz1-3 silencing remarkably increased the expression of WSSV envelope protein VP28. These findings suggest that new-found EsSpz1-3 in E. sinensis could promote the synthesis of antimicrobial peptides and inhibit the expression of VP28 during WSSV infection. Our study indicates that EsSpz1-3 in E. sinensis may participate in the innate immune defenses against WSSV by inducing the expression of antimicrobial peptides. This study provides new knowledge for the function of Spätzle in the antiviral immune defense in crustacean.

Deltex modulates Dpp morphogen gradient formation and affects the Dpp signaling in Drosophila

Deltex (Dx) is a context-dependent regulator of Notch signaling and regulates Notch signaling in a non-canonical fashion by facilitating the endocytosis of its receptor. In an RNAi- based modifier screen of kinases and phosphatases Thickveins (Tkv), the receptor of Decapentaplegic (Dpp), was identified as one of the interactors of Dx. Dpp, a Drosophila TGF-β/Bone Morphogenetic Protein homolog acts as a morphogen to specify cell fate along the anterior-posterior axis of the wing. Tight regulation of Dpp signaling is thus indispensable for its proper functioning. Here we present Dx as a novel modulator of Dpp signaling. We show evidence for the very first time that dx genetically interacts with dpp and its pathway components. Immunocytochemical analysis shows that Dx co-localizes with Dpp and its receptor Tkv in the Drosophila third instar larval tissues. Further, Dx is also seen to modulate the expression of dpp and its target genes. Here, we attribute this modulation to the endocytosis and trafficking of Dpp through Dx. This study thus presents a whole new avenue of Dpp signaling regulation via the cytoplasmic protein Dx.