摘要: Sensory neuron membrane proteins (SNMPs), homologs of the human fatty acid transport protein CD36 family, are observed to play a significant role in chemoreception, especially in detecting sex pheromone in Drosophila and some lepidopteran species. In the current study, two full-length SNMP transcripts, MmedSNMP1 and MmedSNMP2, were identified in the parasitoid Microplitis mediator (Hymenoptera: Braconidae). Quantitative real-time polymerase chain reaction analysis showed that the expression of MmedSNMP1 was significantly higher in antennae than in other tissues of both sexes. In addition, the MmedSNMP1 transcript was increased dramatically in newly emerged adults and there were no significant differences between adults with or without mating and parasitic experiences. However, compared with MmedSNMP1, the expression of MmedSNMP2 was widely found in various tissues, significantly increased at half-pigmented pupae stage and remained at a relatively constant level during the following developmental stages. It was found that MmedSNMP1 contained eight exons and seven introns, which was highly conserved compared with other insect species. In situ hybridization assay demonstrated that MmedSNMP1 transcript was distributed widely in antennal flagella. Among selected chemosensory genes (odorant binding protein, odorant receptor, and ionotropic receptor genes), MmedSNMP1 only partially overlapped with MmedORco in olfactory sensory neurons of antennae. Subsequent immunolocalization results further indicated that MmedSNMP1 was mainly expressed in sensilla placodea of antennae and possibly involved in perceiving plant volatiles and sex pheromones. These findings lay a foundation for further investigating the roles of SNMPs in the chemosensation of parasitoids.

摘要: The tawny crazy ant (Nylanderia fulva) is a new invasive pest in the United States. At present, its management mainly relies on the use of synthetic insecticides, which are generally ineffective at producing lasting control of the pest, necessitating alternative environmentally friendly measures. In this study, we evaluated the feasibility of gene silencing to control this ant species. Six housekeeping genes encoding actin (NfActin), coatomer subunit beta (NfCOP beta), arginine kinase (NfArgK), and V-type proton ATPase subunits A (NfvATPaseA), B (NfvATPaseB) and E (NfvATPaseE) were cloned. Phylogenetic analysis revealed high sequence similarity to homologs from other ant species, particularly the Florida carpenter ant (Camponotus floridanus). To silence these genes, vector L4440 was used to generate six specific RNAi constructs for bacterial expression. Heat-inactivated, dsRNA-expressing Escherichia coli were incorporated into artificial diet. Worker ants exhibited reduced endogenous gene expression after feeding on such diet for 9 d. However, only ingestion of dsRNAs of NfCOP beta (a gene involved in protein trafficking) and NfArgK (a cellular energy reserve regulatory gene in invertebrates) caused modest but significantly higher ant mortality than the control. These results suggest that bacterially expressed dsRNA can be orally delivered to ant cells as a mean to target its vulnerabilities. Improved efficacy is necessary for the RNAi-based approach to be useful in tawny crazy ant management.

摘要: Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a major pathogen of the economic insect silkworm, Bombyx mori. Virus-encoded microRNAs (miRNAs) have been proven to play important roles in host-pathogen interactions. In this study we identified a BmCPV-derived miRNA-like 21 nt small RNA, BmCPV-miR-1, from the small RNA deep sequencing of BmCPV-infected silkworm larvae by stem-loop quantitative real-time PCR (qPCR) and investigated its functions with qPCR and lentiviral expression systems. Bombyx mori inhibitor of apoptosis protein (BmIAP) gene was predicted by both target prediction software miRanda and Targetscan to be one of its target genes with a binding site for BmCPV-miR-1 at the 5 ' untranslated region. It was found that the expression of BmCPV-miR-1 and its target gene BmIAP were both up-regulated in BmCPV-infected larvae. At the same time, it was confirmed that BmCPV-miR-1 could up-regulate the expression of BmIAP gene in HEK293T cells with lentiviral expression systems and in BmN cells by transfecting mimics. Furthermore, BmCPV-miR-1 mimics could up-regulate the expression level of BmIAP gene in midgut and fat body in the silkworm. In the midgut of BmCPV-infected larvae, BmCPV-miR-1 mimics could be further up-regulated and inhibitors could lower the virus-mediated expression of BmIAP gene. With the viral genomic RNA segments S1 and S10 as indicators, BmCPV-miR-1 mimics could up-regulate and inhibitors down-regulate their replication in the infected silkworm. These results implied that BmCPV-miR-1 could inhibit cell apoptosis in the infected silkworm through up-regulating BmIAP expression, providing the virus with a better cell circumstance for its replication.

摘要: Metamorphosis is one of the most important physiological processes in insects. It is regulated by a serial of ecdysone cascade genes. Recently, lots of microRNAs (miRNAs) were investigated in insects; however, their function in metamorphosis is largely unknown. In the present study, the dynamics of a small RNA population was investigated by RNA sequencing from the midgut of a lepidopteran pest Spodoptera litura during larval-pupal metamorphosis. A total of 101 miRNAs were identified, and 75 miRNAs were differentially expressed during the metamorphic process. The relationship between these differentially expressed miRNAs and 12 ecdysone cascade genes was analyzed by four classical software programs, and a multiple-to-multiple regulatory network was found to exist between these miRNAs and their targets. Among them, miR-14-3p and its two targets (EcR and E75) were chosen for further validation. MiR-14-3p had higher expression level in the 6th instar larvae as compared with either the prepupae or pupae, which was opposite to that of both EcR and E75, two ecdysone cascade genes. Luciferase reporter assay confirmed that both EcR and E75 were regulated by miR-14-3p. Interestingly, the 3 ' untranslated regions are nearly identical to each other among different transcript variants of the ecdysone cascade genes, including EcR, USP, E75, E74, E78, E93, Hr3, Hr4, Hr39, Krh1 and Ftzf1. Thus, different transcript variants of one ecdysone cascade gene could be regulated by the same miRNA. The above data suggest that the ecdysone signaling pathway is under the tight control of miRNA. These findings expand our understanding of the mechanism of insect metamorphosis and may also provide a novel possibility for the control of pest insects in the future.

摘要: During the last century, the coyote (Canis latrans) has increased its distribution in Central America. Before the 1980s, it had not been recorded in Panama. New records show that coyotes have crossed the Panama Canal, indicating that continues to expand; therefore, there is a possibility that it will reach northern South America. Our objectives were to identify potential coyote colonization routes to South America, and the variables that favor its expansion. We hypothesized that habitat fragmentation benefits coyote expansion. We applied 7 algorithms to model the potential distribution of the coyote, using 196 presence records and 12 variables. The models with better performance were used to generate a consensus model. Using our consensus model and the areas with highest probability of presence, a potential colonization route was generated between Central America and northern South America. This route lies through southern Costa Rica, along the Pacific coast of Panama to the south, to the Andean mountains in northern Colombia. The variables that explained potential coyote distribution were human population density, altitude, and percentage of crops with positive influence, and tropical broadleaf forests with negative influence. These results indicate that human activities and deforestation are related to coyote distribution expansion. Actions can be implemented within the identified route to improve environmental management, in order to avoid the presence of the coyote in the ecosystems of northern South America.