Immunosuppression induced by expression of a viral RNase enhances susceptibility of Plutella xylostella to microbial pesticides  

作　　者：Bokri Park Yonggyun Kim 

机构地区：[1]Department of Bioresource Sciences, Andong National University, Andong, South Korea

出　　处：《Insect Science》2012年第1期47-54,共8页昆虫科学（英文版）

摘　　要：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.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.

关 键 词：CpBV IMMUNE Plutella xylostella POLYDNAVIRUS RNase T2 RNA interference transient expression 

分 类 号：Q556[生物学—生物化学] Q965.8