tailieunhanh - Insecticides Basic and Other Applications Part 8

Tham khảo tài liệu 'insecticides basic and other applications part 8', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Production of Insecticidal Baculoviruses in Insect Cell Cultures Potential and Limitations 129 can also infect lepidopteran insects but they produce granulosis. On the other hand the viruses classified into the genus Y-baculovirus can infect hymenopteran insects to produce nuclear polyhedrosis while the viruses of the genus 8-baculovirus are associated to the production of nuclear polyhedrosis in dipteran insects. As most baculoviruses used as insecticides so far belong to the genus a-baculovirus the subject henceforth will be focused on lepidopteran nucleopolyhedroviruses. Natural cycle and pathogenicity The main route of infection of lepidopteran larvae with nucleopolyhedrovirus is the ingestion of food contaminated with viral OBs Granados Williams 1986 . Once ingested OBs are transported to the larvae s midgut where they are dissolved to release the occluded virions due to the combined action of the alkaline environment and the presence of alkaline proteases. The released OVs pass through the midgut peritrophic matrix and find the brush border membrane of the columnar midgut epithelial cells which fuse with the viral envelope to enter the viral nucleocapsids within the cytoplasm. The ability of OVs to infect midgut epithelial cells is dependent on the expression of a set of genes whose products are denominated per os infectivity factors PIFs Rohrmann 2011 . Most nucleocapsids are then transported to the nucleus through a process that is dependent on actin polymerization. Once the nucleocapsid has been entered into the cell nucleus the viral DNA is naked and starts the transcriptional cascade that lead ultimately to the assembly of progeny nucleocapsids. A distinctive feature of the primary replication of nucleopolyhedroviruses in the midgut is that the nucleocapsids that were assembled in the nucleus are almost totally exported to the basal cytoplasmatic membrane from where they finally egress as BVs. The budding of BVs occurs at regions of the plasmatic .