Wolbachia wStri Blocks Zika Virus Growth at Two Independent Stages of Viral Replication.

Mosquito-transmitted viruses are spread globally and present a great risk to human health. Among the many approaches investigated to limit the diseases caused by these viruses are attempts to make mosquitos resistant to virus infection. Coinfection of mosquitos with the bacterium Wolbachia pipientis from supergroup A is a recent strategy employed to reduce the capacity for major vectors in the Aedes mosquito genus to transmit viruses, including dengue virus (DENV), Chikungunya virus (CHIKV), and Zika virus (ZIKV). Recently, a supergroup B Wolbachia wStri, isolated from Laodelphax striatellus, was shown to inhibit multiple lineages of ZIKV in Aedes albopictus cells. Here, we show that wStri blocks the growth of positive-sense RNA viruses DENV, CHIKV, ZIKV, and yellow fever virus by greater than 99.9%. wStri presence did not affect the growth of the negative-sense RNA viruses LaCrosse virus or vesicular stomatitis virus. Investigation of the stages of the ZIKV life cycle inhibited by wStri identified two distinct blocks in viral replication. We found a reduction of ZIKV entry into wStri-infected cells. This was partially rescued by the addition of a cholesterol-lipid supplement. Independent of entry, transfected viral genome was unable to replicate in Wolbachia-infected cells. RNA transfection and metabolic labeling studies suggested that this replication defect is at the level of RNA translation, where we saw a 66% reduction in mosquito protein synthesis in wStri-infected cells. This study's findings increase the potential for application of wStri to block additional arboviruses and also identify specific blocks in viral infection caused by Wolbachia coinfection.IMPORTANCE Dengue, Zika, and yellow fever viruses are mosquito-transmitted diseases that have spread throughout the world, causing millions of infections and thousands of deaths each year. Existing programs that seek to contain these diseases through elimination of the mosquito population have so far failed, making it crucial to explore new ways of limiting the spread of these viruses. Here, we show that introduction of an insect symbiont, Wolbachia wStri, into mosquito cells is highly effective at reducing yellow fever virus, dengue virus, Zika virus, and Chikungunya virus production. Reduction of virus replication was attributable to decreases in entry and a strong block of virus gene expression at the translational level. These findings expand the potential use of Wolbachia wStri to block viruses and identify two separate steps for limiting virus replication in mosquitos that could be targeted via microbes or other means as an antiviral strategy.

The receptor-like tyrosine phosphatase lar is required for epithelial planar polarity and for axis determination within drosophila ovarian follicles.

The follicle cell monolayer that encircles each developing Drosophila oocyte contributes actively to egg development and patterning, and also represents a model stem cell-derived epithelium. We have identified mutations in the receptor-like transmembrane tyrosine phosphatase Lar that disorganize follicle formation, block egg chamber elongation and disrupt Oskar localization, which is an indicator of oocyte anterior-posterior polarity. Alterations in actin filament organization correlate with these defects. Actin filaments in the basal follicle cell domain normally become polarized during stage 6 around the anterior-posterior axis defined by the polar cells, but mutations in Lar frequently disrupt polar cell differentiation and actin polarization. Lar function is only needed in somatic cells, and (for Oskar localization) its action is autonomous to posterior follicle cells. Polarity signals may be laid down by these cells within the extracellular matrix (ECM), possibly in the distribution of the candidate Lar ligand Laminin A, and read out at the time Oskar is localized in a Lar-dependent manner. Lar is not required autonomously to polarize somatic cell actin during stages 6. We show that Lar acts somatically early in oogenesis, during follicle formation, and postulate that it functions in germarium intercyst cells that are required for polar cell specification and differentiation. Our studies suggest that positional information can be stored transiently in the ECM. A major function of Lar may be to transduce such signals.

Molecular characterization of the DNA puff C-8 gene of Rhynchosciara americana.

We have mapped the only transcription unit known to be present in the C-8 DNA puff of Rhynchosciara americana and describe the isolation and sequence of a cDNA clone, pRa C-8-22, which contains a nearly complete copy of the mRNA transcribed from this DNA puff and part of the sequence of genomic clone BSC8-0.9, which contains the promotor region and the remainder of the transcription unit. The characteristics of the protein predicted from the ORF present in the cDNA indicate that it is unique and secreted.