Drosophila Myc (dMyc), as a broad-spectrum transcription factor, can regulate the expression of a large number of genes to control diverse cellular processes, such as cell cycle progression, cell growth, proliferation and apoptosis. However, it remains largely unknown about whether dMyc can be involved in Drosophila innate immune response. Here, we have identified dMyc to be a negative regulator of Drosophila Imd pathway via the loss- and gain-of-function screening. We demonstrate that dMyc inhibits Drosophila Imd immune response via directly activating miR-277 transcription, which further inhibit the expression of imd and Tab2-Ra/b. Importantly, dMyc can improve the survival of flies upon infection, suggesting inhibiting Drosophila Imd pathway by dMyc is vital to restore immune homeostasis that is essential for survival. Taken together, our study not only reports a new dMyc-miR-277-imd/Tab2 axis involved in the negative regulation of Drosophila Imd pathway, and provides a new insight into the complex regulatory mechanism of Drosophila innate immune homeostasis maintenance. Innate immunity is the first line of defense against pathogenic microorganisms. Both overactivation and depression of immune response are detrimental to the organism. It is indispensable to regulate the duration and intensity of immune response. In this work, we find that Drosophila Myc (dMyc) as a transcription factor activates the transcription of miR-277 to negatively regulate the Imd pathway via inhibiting the expression of imd/Tab2 gene in the middle and later stage of Drosophila innate immune. dMyc is required to restore Drosophila immune homeostasis for the survival of flies upon infection. Since dMyc is well conserved in animals, our findings will be important in understanding the complex regulatory mechanisms of innate immune responses in animals.

Zinc finger protein (Zelda) ofTribolium castaneum(TcZelda) has been showed to play pivotal roles in embryonic development and metamorphosis. However, the regulatory mechanism ofTcZeldaassociated with these physiology processes is unclear. Herein, the developmental expression profile showed thatZeldaofT. castaneumwas highly expressed in early eggs. Tissue expression profiling revealed thatTcZeldawas mainly expressed in the larval head and adult ovary of late adults and late larvae.TcZeldaknockdown led to a 95% mortality rate in adults. These results suggested thatTcZeldais related to the activation of the zygote genome in early embryonic development. Furthermore, 592 differentially expressed genes were identified from the dsZeldatreated group. Compared with the control group,altered disjunction(ALD) andAGAP005368-PA(GAP) in the dsZeldagroup were significantly down-regulated, whileTGF-beta, propeptide(TGF) was significantly up-regulated, suggesting thatTcZeldamay be involved in insect embryonic development. In addition, the expression ofUbx ultrabithorax(UBX),Cx cephalothorax(CX),En engrailed(EN), and twoEndocuticle structural glycoprotein sgabd(ABD) genes were significantly down-regulated, suggesting that they may cooperate withTcZeldato regulate the development of insect wings. Additionally,Elongation(ELO),fatty acid synthase(FAS), andfatty acyl-CoA desaturase(FAD) expression was inhibited in dsZeldainsects, which could disturb the lipase signaling pathways, thus, disrupting the insect reproductive system and pheromone synthesis. These results may help reveal the function ofTcZeldain insects and the role of certain genes in the gene regulatory network and provide new ideas for the prevention and control ofT. castaneum.

Uridine diphosphate glucosyltransferases (UGTs), which are phase II detoxification enzymes, are found in various organisms. These enzymes play an important role in the detoxification mechanisms of plant allelopathy and in insects. Artemisia vulgaris L. (Asterales: Asteraceae: Artemisia) essential oil has strong contact toxicity to Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) larvae. However, the effect of A. vulgaris essential oil on UGTs is unclear. In this study, A. vulgaris essential oil was shown to significantly induce the expression of the TcUgt86Dg transcript. Furthermore, treatment of TcUgt86Dg-silenced individuals with A. vulgaris essential oil resulted in higher mortality than for the control individuals, indicating that TcUgt86Dg is involved in detoxification of A. vulgaris essential oil in T. castaneum. The developmental expression profile showed that the expression of TcUgt86Dg in late adults was higher than in other developmental stages. Furthermore, the expression profile in adult tissues revealed higher expression of TcUgt86Dg in the head, antenna, fat body, and accessory gland than in other tissues. These data show that TcUgt86Dg may be involved in the metabolism of exogenous toxins by T. castaneum; thus, our results have elucidated one possible mechanism of resistance to A. vulgaris essential oil and provide a theoretical basis for a control scheme for T. castaneum.

Innate immune response is the first line of host defense against pathogenic microorganisms, and its excessive or insufficient activation is detrimental to the organism. Many individual microRNAs (miRNAs) have emerged as crucial post-transcriptional regulators of immune homeostasis in Drosophila melanogaster. However, the synergistical regulation of miRNAs located within a cluster on the Imd-immune pathway remains obscured. In our study, a genetic screening with 52 transgenic UAS-miRNAs was performed to identify ten miRNAs or miRNA clusters, including the miR310~313 cluster, which may function on Imd-dependent immune responses. The miRNA RT-qPCR analysis showed that the expression of miR-310~313 cluster members exhibited an increase at 6–12 h post E. coli infection. Furthermore, the overexpression of the miR-310~313 cluster impaired the Drosophila survival. And the overexpression of miR-310/311/312 reduced Dpt expression, an indication of Imd pathway induced by Gram-negative bacteria. Conversely, the knockdown of miR-310/311/312 led to increases in Dpt expression. The Luciferase reporter expression assays and RT-qPCR analysis confirmed that miR-310~313 cluster members directly co-targeted and inhibited Imd transcription. These findings reveal that the members of the miR-310~313 cluster synergistically inhibit Imd-dependent immune responses by co-targeting the Imd gene in Drosophila.