RESUMEN
Vitellogenin receptors (VgRs) play critical roles in egg formation by transporting vitellogenin (Vg) into oocytes in insects. Although the function of VgR in insects is well studied, the transcriptional regulation of this gene is still unclear. Here, we cloned the promoter of the VgR gene from Bombyx mori (BmVgR), and predicted many POU cis-response elements (CREs) in its promoter. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that the POU transcription factor POU-M2 bound directly to the CREs of the promoter. Overexpression of POU-M2 in an ovarian cell line (BmNs) enhanced BmVgR transcription and promoter activity detected by quantitative reverse transcription PCR and luciferase reporter assays. Analyses of expression patterns indicated that POU-M2 was expressed in ovary at day two of wandering stage initially, followed by BmVgR. RNA interference of POU-M2 significantly reduced the transcription of BmVgR in ovary and egg-laying rate. Our results suggest a novel function for the POU factor in silkworm oogenesis by its involvement in BmVgR regulation and expands the understanding of POU factors in insect VgR expression.
Asunto(s)
Bombyx/genética , Proteínas del Huevo/genética , Factores del Dominio POU/genética , Receptores de Superficie Celular/genética , Transcripción Genética , Secuencia de Aminoácidos/genética , Animales , Femenino , Regulación de la Expresión Génica/genética , Oogénesis/genética , Regiones Promotoras Genéticas , Interferencia de ARN , Vitelogeninas/genética , Vitelogeninas/metabolismoRESUMEN
Vitellogenin receptors (VgRs) play crucial roles in oogenesis by mediating endocytosis of vitellogenin and other nutrients in ovipara. We conducted small RNA sequencing and screening with a luciferase reporter system, and found that bmo-miR-2739 and a novel miRNA (novel-miR-167) coordinately regulate the expression of VgR in Bombyx mori (BmVgR). Further analyses suggested that these two miRNAs direct target repression by binding directly to the BmVgR 3' untranslated region. Forced expression of either miRNA using the piggyBac system blocked vitellogenin (Vg) transport and retarded ovariole development. Antagomir silencing of bmo-miR-2739 or novel-miR-167 resulted in increased amounts of BmVgR protein in the ovaries and BmVgR mRNA in the fat body. This evidence, combined with spatiotemporal expression profiles, revealed that these two miRNAs function together to fine-tune the amount of BmVgR protein for ovarian development. Additionally, novel-miR-167 was mainly responsible for the post-transcriptional repression of BmVgR in non-ovarian tissues. The results of this study contribute to our understanding of the function of miRNAs during ovarian development of a lepidopteran and suggest a new strategy for controlling insect reproduction.
Asunto(s)
Bombyx/genética , Proteínas del Huevo/genética , Regulación del Desarrollo de la Expresión Génica , MicroARNs/genética , Oogénesis/genética , Receptores de Superficie Celular/genética , Regiones no Traducidas 3'/genética , Animales , Animales Modificados Genéticamente , Proteínas del Huevo/metabolismo , Genes Reporteros , Luciferasas/metabolismo , MicroARNs/metabolismo , Modelos Biológicos , Óvulo/metabolismo , Unión Proteica , Receptores de Superficie Celular/metabolismoRESUMEN
Microsporidia have attracted much attention because they infect a variety of species ranging from protists to mammals, including immunocompromised patients with AIDS or cancer. Aside from the study on Nosema ceranae, few works have focused on elucidating the mechanism in host response to microsporidia infection. Nosema bombycis is a pathogen of silkworm pébrine that causes great economic losses to the silkworm industry. Detailed understanding of the host (Bombyx mori) response to infection by N. bombycis is helpful for prevention of this disease. A genome-wide survey of the gene expression profile at 2, 4, 6 and 8 days post-infection by N. bombycis was performed and results showed that 64, 244, 1,328, 1,887 genes were induced, respectively. Up to 124 genes, which are involved in basal metabolism pathways, were modulated. Notably, B. mori genes that play a role in juvenile hormone synthesis and metabolism pathways were induced, suggesting that the host may accumulate JH as a response to infection. Interestingly, N. bombycis can inhibit the silkworm serine protease cascade melanization pathway in hemolymph, which may be due to the secretion of serpins in the microsporidia. N. bombycis also induced up-regulation of several cellular immune factors, in which CTL11 has been suggested to be involved in both spore recognition and immune signal transduction. Microarray and real-time PCR analysis indicated the activation of silkworm Toll and JAK/STAT pathways. The notable up-regulation of antimicrobial peptides, including gloverins, lebocins and moricins, strongly indicated that antimicrobial peptide defense mechanisms were triggered to resist the invasive microsporidia. An analysis of N. bombycis-specific response factors suggested their important roles in anti-microsporidia defense. Overall, this study primarily provides insight into the potential molecular mechanisms for the host-parasite interaction between B. mori and N. bombycis and may provide a foundation for further work on host-parasite interaction between insects and microsporidia.
