Sequences of elongation factors-1 alpha and -1 gamma and stimulation by juvenile hormone in Locusta migratoria

Using Proteomic Approaches to Unravel the Response of Ctenocephalides felis felis to Blood Feeding and Infection With Bartonella henselae

Among the Ctenocephalides felis felis-borne pathogens, Bartonella henselae, the main aetiological agent of cat scratch disease (CSD), is of increasing comparative biomedical importance. Despite the importance of B. henselae as an emergent pathogen, prevention of the diseases caused by this agent in cats, dogs and humans mostly relies on the use of ectoparasiticides. A vaccine targeting both flea fitness and pathogen competence is an attractive choice requiring the identification of flea proteins/metabolites with a dual effect. Even though recent developments in vector and pathogen -omics have advanced the understanding of the genetic factors and molecular pathways involved at the tick-pathogen interface, leading to discovery of candidate protective antigens, only a few studies have focused on the interaction between fleas and flea-borne pathogens. Taking into account the period of time needed for B. henselae replication in flea digestive tract, the present study investigated flea-differentially abundant proteins (FDAP) in unfed fleas, fleas fed on uninfected cats, and fleas fed on B. henselae-infected cats at 24 hours and 9 days after the beginning of blood feeding. Proteomics approaches were designed and implemented to interrogate differentially expressed proteins, so as to gain a better understanding of proteomic changes associated with the initial B. henselae transmission period (24 hour timepoint) and a subsequent time point 9 days after blood ingestion and flea infection. As a result, serine proteases, ribosomal proteins, proteasome subunit α-type, juvenile hormone epoxide hydrolase 1, vitellogenin C, allantoinase, phosphoenolpyruvate carboxykinase, succinic semialdehyde dehydrogenase, glycinamide ribotide transformylase, secreted salivary acid phosphatase had high abundance in response of C. felis blood feeding and/or infection by B. henselae. In contrast, high abundance of serpin-1, arginine kinase, ribosomal proteins, peritrophin-like protein, and FS-H/FSI antigen family member 3 was strongly associated with unfed cat fleas. Findings from this study provide insights into proteomic response of cat fleas to B. henselae infected and uninfected blood meal, as well as C. felis response to invading B. henselae over an infection time course, thus helping understand the complex interactions between cat fleas and B. henselae at protein levels.

Molecular characterization, expression analysis and RNAi knock-down of elongation factor 1α and 1γ from Nilaparvata lugens and its yeast-like symbiont

In the present paper, four cDNAs encoding the alpha and gamma subunits of elongation factor 1 (EF-1) were cloned and sequenced from Nilaparvata lugens, named NlEF-1α, NlEF-1γ, and its yeast-like symbiont (YLS), named YsEF-1α and YsEF-1γ, respectively. Comparisons with sequences from other species indicated a greater conservation for EF-1α than for EF-1γ. NlEF-1α has two identical copies. The deduced amino acid sequence homology of NlEF-1α and NlEF-1γ is 96 and 64%, respectively, compared with Homalodisca vitripennis and Locusta migratoria. The deduced amino acid sequence homology of YsEF-1α and YsEF-1γ is 96 and 74%, respectively, compared with Metarhizium anisopliae and Ophiocordyceps sinensis. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis revealed that the expression level of NlEF-1α and NlEF-1γ mRNA in hemolymph, ovary, fat body and salivary glands were higher than the midgut and leg tissue. YsEF-1α and YsEF-1γ was highly expressed in fat body. The expression level of NlEF-1α was higher than that of NlEF-1γ. Through RNA interference (RNAi) of the two genes, the mortality of nymph reached 92.2% at the 11th day after treatment and the ovarian development was severely hindered. The RT-qPCR analysis verified the correlation between mortality, sterility and the down-regulation of the target genes. The expression and synthesis of vitellogenin (Vg) protein in insects injected with NlEF-1α and NlEF-1γ double-stranded RNA (dsRNA) was significantly lower than control groups. Attempts to knockdown the YsEF-1 genes in the YLS was unsuccessful. However, the phenotype of N. lugens injected with YsEF-1α dsRNA was the same as that injected with NlEF-1α dsRNA, possibly due to the high similarity (up to 71.9%) in the nucleotide sequences between NlEF-1α and YsEF-1α. We demonstrated that partial silencing of NlEF-1α and NlEF-1γ genes caused lethal and sterility effect on N. lugens. NlEF-1γ shares low identity with that of other insects and therefore it could be a potential target for RNAi-based pest management.

Juvenile Hormone Activates the Transcription of Cell-division-cycle 6 (Cdc6) for Polyploidy-dependent Insect Vitellogenesis and Oogenesis

Although juvenile hormone (JH) is known to prevent insect larval metamorphosis and stimulate adult reproduction, the molecular mechanisms of JH action in insect reproduction remain largely unknown. Earlier, we reported that the JH-receptor complex, composed of methoprene-tolerant and steroid receptor co-activator, acts on mini-chromosome maintenance (Mcm) genes Mcm4 and Mcm7 to promote DNA replication and polyploidy for the massive vitellogenin (Vg) synthesis required for egg production in the migratory locust (Guo, W., Wu, Z., Song, J., Jiang, F., Wang, Z., Deng, S., Walker, V. K., and Zhou, S. (2014) PLoS Genet. 10, e1004702). In this study we have investigated the involvement of cell-division-cycle 6 (Cdc6) in JH-dependent vitellogenesis and oogenesis, as Cdc6 is essential for the formation of prereplication complex. We demonstrate here that Cdc6 is expressed in response to JH and methoprene-tolerant, and Cdc6 transcription is directly regulated by the JH-receptor complex. Knockdown of Cdc6 inhibits polyploidization of fat body and follicle cells, resulting in the substantial reduction of Vg expression in the fat body as well as severely impaired oocyte maturation and ovarian growth. Our data indicate the involvement of Cdc6 in JH pathway and a pivotal role of Cdc6 in JH-mediated polyploidization, vitellogenesis, and oogenesis.

Argonaute 1 is indispensable for juvenile hormone mediated oogenesis in the migratory locust, Locusta migratoria

Juvenile hormone (JH) is the primary hormone controlling vitellogenesis and oocyte maturation in the migratory locust Locusta migratoria, an evolutionarily primitive insect species with panoistic ovaries. However, molecular mechanisms of locust oogenesis remain unclear and the role of microRNA (miRNA) in JH mediated locust vitellogenesis and oocyte maturation has not been explored. Using miRNA sequencing and quantification with small RNA libraries derived from fat bodies of JH-deprived versus JH analog-exposed female adult locusts, we have identified 83 JH up-regulated and 60 JH down-regulated miRNAs. QRT-PCR validation has confirmed that transcription of selected miRNAs responded to JH administration and correlated with changes in endogenous hemolymph JH titers. Depletion of Argonaute 1 (Ago1), a key regulator of miRNA biogenesis and function by RNAi in female adult locusts dramatically decreased the expression of vitellogenin (Vg) and severely impaired follicular epithelium development, terminal oocyte maturation and ovarian growth. Our data indicate that Ago1 and Ago1-dependent miRNAs play a crucial role in locust vitellogenesis and egg production.

Elongation factor 1Bgamma (eEF1Bgamma) expression during the molting cycle and cold acclimation in the crayfish Procambarus clarkii

Eukaryotic elongation factor 1Bgamma (eEF1Bgamma) is a subunit of elongation factor 1 (EF1), which regulates the recruitment of amino acyl-tRNAs to the ribosome during protein synthesis in eukaryotes. In addition to structural roles within eEF1, eEF1Bgamma has properties which suggest sensory or regulatory activities. We have cloned eEF1Bgamma from axial abdominal muscle of freshwater crayfish, Procambarus clarkii. The predicted amino acid sequence has 66% identity to Locusta migratoria eEF1Bgamma and 65% identity to Artemia salina eEF1Bgamma. We measured eEF1Bgamma expression by real-time PCR, using the relative quantification method with 18s ribosomal RNA as an internal calibrator. eEF1Bgamma expression was lowest in gill, axial abdominal muscle, and hepatopancreas, and was highest in the antennal gland (5.7-fold above hepatopancreas) and cardiac muscle (7.8-fold above hepatopancreas). In axial abdominal muscle, eEF1Bgamma expression was 4.4-fold higher in premolt and 11.9 higher in postmolt compared to intermolt. In contrast, eEF1Bgamma was decreased or unchanged in epithelial tissues during pre- and postmolt. eEF1Bgamma expression in the hepatopancreas was 3.5-fold higher during intermolt compared to premolt and was unchanged in gill and antennal gland. No significant differences in eEF1Bgamma were found after 1 week of acclimation to 4 degrees C. These results show that eEF1Bgamma is regulated at the mRNA level with tissue-specific differences in expression patterns.

TheLeptynia hispanicaspecies complex (Insecta Phasmida): polyploidy, parthenogenesis, hybridization and more

The Leptynia hispanica stick insect species complex includes bisexuals, triploid and tetraploid parthenogenetic populations, suggesting that polyploidy has played a central role in the evolution of this complex. An analysis of karyotype, mitochondrial DNA (cox2) and nuclear DNA (ef1-alpha) markers was carried out to clarify phylogenetic relationships and microevolutionary/phylogeographical patterns of the L. hispanica complex. Our analyses suggested a subdivision of bisexual populations into four groups, tentatively proposed as incipient species. Moreover, triploids and tetraploids showed two independent origins, the latter being more ancient than the former. From ef1-alpha analysis, triploids showed hybrid constitution, while the hybrid constitution of tetraploids is likely, but more data are needed. We suggest that L. hispanica is a case of 'geographical parthenogenesis' with parthenogenetic strains colonizing large peripheral ranges, and bisexuals confined to glacial refuge areas. Moreover, the age, wide distribution and competitive advantage of polyploids over diploids, demonstrate their significance in the evolution of the L. hispanica species complex.

Distribution of elongation factor-1alpha in larval tissues of the fall armyworm, Spodoptera frugiperda

Elongation factor-1alpha (EF-1alpha) promotes the delivery of aminoacyl-tRNA to the acceptor site of the ribosome during protein synthesis. The enzyme has a number of additional functions, including regulation of apoptosis and interaction with the cytoskeleton. We determined the distribution of EF-1alpha in larval tissues of the fall armyworm, Spodoptera frugiperda , with a monoclonal antibody generated to EF-1alpha from Sf21 cells, a cell line developed from ovarian tissue of S. frugiperda. Enzyme-linked immunosorbent assay showed that EF-1alpha comprised 1.9-9.9% of the total protein within the tissues that were examined, which included fat body, Malpighian tubules, midgut, muscle, salivary glands, trachea, and ventral nerve cord. To a certain extent, EF-1alpha concentrations reflected the expected metabolic activity level of each of the represented tissues. Closer examination by immunofluorescence microscopy revealed that EF-1alpha concentrations varied among different cell types within a given tissue, i.e. midgut columnar epithelial cells yielded strong signals, while goblet cells failed to react with the EF-1alpha-specific antibody.

Quantification of vitellogenin-mRNA during maturation and breeding of a burying beetle

Burying beetles (Nicrophorus orbicollis) are unusual in that to breed they require an unpredictable and valuable resource, a small carcass. Thus the timing of reproduction is unpredictable and beetles' physiological response must be fast. We hypothesized that their pattern of vitellogenin (Vg) synthesis might reflect these requirements. We examined the expression of two Vg genes (sequenced for this study) during sexual maturation and through a reproductive bout. Vg-mRNA, juvenile hormone (JH) titers, ovarian development, and hemolymph concentrations of Vg were quantified in the same individuals. All four variables gradually increased during maturation to peak 15-20 days after eclosion. Twelve hours after the discovery of a carcass, a few hours before oviposition, mRNA was high, hemolymph Vg had decreased, JH and ovarian weight had increased. After oviposition, mRNA was low, hemolymph Vg concentrations and JH were high. This is consistent with our hypothesis that beetles produce and store Vg in the hemolymph prior to the discovery of a breeding resource and replace it quickly. Partial regression of these variables (with the effect of time removed) indicated that JH was not correlated with mRNA, hemolymph Vg, or ovarian weight at any time. Thus the role of JH as a gonadotropin remains unclear.