Polydnaviruses are a group of insect DNA viruses and are characterized in their segmented genome that is located in the chromosome（s） of host wasps. A polydnavirus, Cotesiaplutellae bracovirus （CpBV）, encodes a vi...Polydnaviruses are a group of insect DNA viruses and are characterized in their segmented genome that is located in the chromosome（s） of host wasps. A polydnavirus, Cotesiaplutellae bracovirus （CpBV）, encodes a viral ribonuclease （RNase） T2 in a specific segment #3 （CpBV-S3）. This study tested its effect on gene expression associated with host immune responses in the diamondback moth, Plutella xylostella. Micro-inj ection of CpBV- $3 into nonparasitized larvae induced expression of its two encoded genes, CpBV-ORF301 （= CpBV-RNase T2） and CpBV-ORF302. In response to a bacterial challenge, four antimi- crobial peptide genes （hemolin, gloverin, cecropin and lysozyme） and six phenoloxidase （PO）-associated genes （proPO-activating proteinase, PO, serine proteinase homolog and serpins 1-3） were up-regulated in their expressions. However, the transient expression of CpBV-S3 suppressed the expressions of cecropin, PO and serpin 1. Double-stranded RNA specific to the viral RNase T2 could specifically knockdown the viral gene expression and restored the three gene expressions suppressed in the larvae injected with CpBV-S3. The inhibitory activity of the viral RNase T2 on the target genes was further proven by the suppression of PO activation in response to bacterial challenge in the larvae injected with CpBV-S3. This immunosuppression by the expression of the viral RNase T2 resulted in significant increase of pathogen susceptibility ofP. xylostella against Bacillus thuringiensis or baculovirus infection.展开更多
Polydnaviruses （PDVs） are a group of insect DNA viruses, which exhibit a mutual symbiotic relationship with their specific host wasps. Moreover, most encapsidated genes identified so far in PDVs share homologies wit...Polydnaviruses （PDVs） are a group of insect DNA viruses, which exhibit a mutual symbiotic relationship with their specific host wasps. Moreover, most encapsidated genes identified so far in PDVs share homologies with insect-originated genes, but not with virus-originated genes. In the meantime, PDVs associated with 2 wasp genera Cotesia and Glytapanteles encode some genes presumably originated from other viruses. Cotesia plutellae bracovirus （CpBV） encodes 4 genes homologous to baculoviral p94： CpBV- E94k1, CpB V-E94k2, CpB V-E94k3, and CpB V-E94k4. This study was conducted to predict the origin of CpB V-E94ks by comparing their sequences with those ofbaculoviral orthologs and to determine the physiological functions by their transient expressions in nonparasitized larvae and subsequent specific RNA interference. Our phylogenetic analysis indicated that CpBV-E94ks were clustered with other E94ks originated from different PDVs and shared high similarity with betabaculoviral p94s. These 4 CpBV genes were expressed during most developmental stages of the larvae of Plutella xylostella parasitized by C. plutellae. Expression of these 4 E94ks was mainly detected in hemocytes and fat body. Subsequent functional analysis by in vivo transient expression showed that all 4 viral genes significantly inhibited both host immune and developmental processes. These results suggest that CpB 11- E94ks share an origin with betabaculoviral p94s and play parasitic roles in suppressing host immune and developmental processes.展开更多
文摘Polydnaviruses are a group of insect DNA viruses and are characterized in their segmented genome that is located in the chromosome（s） of host wasps. A polydnavirus, Cotesiaplutellae bracovirus （CpBV）, encodes a viral ribonuclease （RNase） T2 in a specific segment #3 （CpBV-S3）. This study tested its effect on gene expression associated with host immune responses in the diamondback moth, Plutella xylostella. Micro-inj ection of CpBV- $3 into nonparasitized larvae induced expression of its two encoded genes, CpBV-ORF301 （= CpBV-RNase T2） and CpBV-ORF302. In response to a bacterial challenge, four antimi- crobial peptide genes （hemolin, gloverin, cecropin and lysozyme） and six phenoloxidase （PO）-associated genes （proPO-activating proteinase, PO, serine proteinase homolog and serpins 1-3） were up-regulated in their expressions. However, the transient expression of CpBV-S3 suppressed the expressions of cecropin, PO and serpin 1. Double-stranded RNA specific to the viral RNase T2 could specifically knockdown the viral gene expression and restored the three gene expressions suppressed in the larvae injected with CpBV-S3. The inhibitory activity of the viral RNase T2 on the target genes was further proven by the suppression of PO activation in response to bacterial challenge in the larvae injected with CpBV-S3. This immunosuppression by the expression of the viral RNase T2 resulted in significant increase of pathogen susceptibility ofP. xylostella against Bacillus thuringiensis or baculovirus infection.
文摘Polydnaviruses （PDVs） are a group of insect DNA viruses, which exhibit a mutual symbiotic relationship with their specific host wasps. Moreover, most encapsidated genes identified so far in PDVs share homologies with insect-originated genes, but not with virus-originated genes. In the meantime, PDVs associated with 2 wasp genera Cotesia and Glytapanteles encode some genes presumably originated from other viruses. Cotesia plutellae bracovirus （CpBV） encodes 4 genes homologous to baculoviral p94： CpBV- E94k1, CpB V-E94k2, CpB V-E94k3, and CpB V-E94k4. This study was conducted to predict the origin of CpB V-E94ks by comparing their sequences with those ofbaculoviral orthologs and to determine the physiological functions by their transient expressions in nonparasitized larvae and subsequent specific RNA interference. Our phylogenetic analysis indicated that CpBV-E94ks were clustered with other E94ks originated from different PDVs and shared high similarity with betabaculoviral p94s. These 4 CpBV genes were expressed during most developmental stages of the larvae of Plutella xylostella parasitized by C. plutellae. Expression of these 4 E94ks was mainly detected in hemocytes and fat body. Subsequent functional analysis by in vivo transient expression showed that all 4 viral genes significantly inhibited both host immune and developmental processes. These results suggest that CpB 11- E94ks share an origin with betabaculoviral p94s and play parasitic roles in suppressing host immune and developmental processes.
