The ORF 113 of Helicoverpa armigera single nucleopolyhedrovirus encodes a functional fibroblast growth factor

A Renewed Appreciation of Helicoverpa armigera Nucleopolyhedrovirus BJ (Formerly Helicoverpa assulta Nucleopolyhedrovirus) with Whole Genome Sequencing

Helicoverpa assulta is a pest that causes severe damage to tobacco, pepper and other cash crops. A local strain of HearNPV-BJ (formerly Helicoverpa assulta nucleopolyhedrovirus (HeasNPV-DJ0031)) was isolated from infected H. assulta larvae in Beijing, which had been regarded as a new kind of baculovirus in previous studies. Describing the biological characteristics of the strain, including its external morphology, internal structure and the pathological characteristics of the infection of various cell lines, can provide references for the identification and function of the virus. HearNPV-BJ virion was defined as a single-nucleocapsid nucleopolyhedrovirus by scanning electron microscopy. QB-Ha-E-5 (H. armigera) and BCIRL-Hz-AM1 (H. zea) cell lines were sensitive to HearNPV-BJ. Undoubtedly modern developed sequencing technology further facilitates the increasing understanding of various strains. The whole genome sequence of the HearNPV-BJ was sequenced and analyzed. The HearNPV-BJ isolate genome was 129, 800 bp nucleotides in length with a G + C content of 38.87% and contained 128 open reading frames (ORFs) encoding predicted proteins of 50 or over 50 amino acids, 67 ORFs in the forward orientation and 61 ORFs in the reverse orientation, respectively. The genome shared 99% sequence identity with Helicoverpa armigera nucleopolyhedrovirus C1 strain (HearNPV-C1), and 103 ORFs had very high homology with published HearNPV sequences. Two bro genes and three hrs were found to be dispersed along the HearNPV-BJ genome. Three of the highest homologs, ORFs with HearNPV, were smaller due to the earlier appearance of the stop codon with unknown functions. P6.9 of HearNPV-BJ, a structural protein, is distinctly different from that of Autographa californica nucleopolyhedrovirus (AcMNPV); its homology with the corresponding gene in HearNPV-C1 was 93.58%. HearNPV-BJ contains 38 core genes identified in other baculoviruses, and phylogenetic analysis indicates HearNPV-BJ belongs to Alphabaculovirus Group II, same as HearNPV-C1. The resulting data provide a better understanding of virion structure, gene function and character of infection. By supplementing the whole-genome sequencing data and Kimura-2 model index, there is more evidence to indicate that HearNPV-BJ may be a variant of Helicoverpa armigera nucleopolyhedrovirus, which also deepens our understanding of the virus species demarcation criteria.

Exploitation of receptor tyrosine kinases by viral-encoded growth factors

Receptor tyrosine kinases (RTKs) are essential components of cell communication pathways utilized from the embryonic to adult stages of life. These transmembrane receptors bind polypeptide ligands, such as growth factors, inducing signalling cascades that control cellular processes such as proliferation, survival, differentiation, motility and inflammation. Many viruses have acquired homologs of growth factors encoded by the hosts that they infect. Production of growth factors during infection allows viruses to exploit RTKs for entry and replication in cells, as well as for host and environmental dissemination. This review describes the genetic diversity amongst virus-derived growth factors and the mechanisms by which RTK exploitation enhances virus survival, then highlights how viral ligands can be used to further understanding of RTK signalling and function during embryogenesis, homeostasis and disease scenarios.

Comparative proteomics reveal fundamental structural and functional differences between the two progeny phenotypes of a baculovirus

The replication of lepidopteran baculoviruses is characterized by the production of two progeny phenotypes: the occlusion-derived virus (ODV), which establishes infection in midgut cells, and the budded virus (BV), which disseminates infection to different tissues within a susceptible host. To understand the structural, and hence functional, differences between BV and ODV, we employed multiple proteomic methods to reveal the protein compositions and posttranslational modifications of the two phenotypes of Helicoverpa armigera nucleopolyhedrovirus. In addition, Western blotting and quantitative mass spectrometry were used to identify the localization of proteins in the envelope or nucleocapsid fractions. Comparative protein portfolios of BV and ODV showing the distribution of 54 proteins, encompassing the 21 proteins shared by BV and ODV, the 12 BV-specific proteins, and the 21 ODV-specific proteins, were obtained. Among the 11 ODV-specific envelope proteins, 8 either are essential for or contribute to oral infection. Twenty-three phosphorylated and 6 N-glycosylated viral proteins were also identified. While the proteins that are shared by the two phenotypes appear to be important for nucleocapsid assembly and trafficking, the structural and functional differences between the two phenotypes are evidently characterized by the envelope proteins and posttranslational modifications. This comparative proteomics study provides new insight into how BV and ODV are formed and why they function differently.

Barriers to success: how baculoviruses establish efficient systemic infections

The mechanisms used by baculoviruses to exit the midgut and cause systemic infection of their insect hosts have been debated for decades. After being ingested, baculoviruses reach the midgut, where several host barriers need to be overcome in order to establish successful infection. One of these barriers is the basal lamina, a presumably virus-impermeable extracellular layer secreted by the epithelial cells lining the midgut and trachea. This review discusses new evidence that demonstrates how these viruses breach the basal lamina and establish efficient systemic infections. The biochemical mechanisms involved in dismantling basal lamina during baculovirus infection may also provide new insights into the process of basal lamina remodeling in invertebrate and vertebrate animals.