Baculoviridae
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The family Baculoviridae (baculovirus) includes double-stranded circular-filamentous DNA - viruses . They only infest invertebrates , their main host are moth larvae , but over 600 hosts have been described. Baculoviruses are used in genetic engineering to produce complex eukaryotic proteins in cell cultures and for vector cloning. They are also used in agriculture to control insect pests.
The name "Baculo" comes from the Latin baculum , stick, stick and refers to the morphology of the nucleocapsid . Within the family, two genera were previously distinguished: nucleopolyhedrovirus (NPV) and granulovirus (GV, now the genus Betabaculovirus ). With betabaculovirus there is only one nucleocapsid per envelope, with the genera alpha , gamma and deltabaculovirus newly subdivided from the genus nucleopolyhedrovirus , either single (SNPV) or several (MNPV) nucleocapsids per envelope occur. The virus particles ( virions , nucleocapsid and envelope) are now again embedded in a granulin (GV) or polyhedrin (NPV) matrix. The betabaculoviruses have only one virion per granulin matrix, with the other genera there are several virions in the polyhedrin matrix.
distribution
They are spread all over the world and were first described in the 16th century as a "wilt disease" in silkworms . In the 1940s, they were used as biopesticides in grain fields to decimate insect pests. In later studies, they were used in the 1990s for the production of eukaryotic proteins in insect cell cultures , since they can be easily reproduced there. The viruses are adapted to invertebrates with over 600 possible host species. They mainly attack moth larvae , but they have also been found on plant wasps , mosquitoes, and shrimp .
Life cycle
In its life cycle the virus occurs in two forms, the ODV ( English Occlusion Derived Virus ), with a protein envelope, and the BV ( English Budding Virus ). The ODV form is necessary for the initial infection; BV particles are then formed later.
The main route of infection is through contaminated leaves that are eaten by insects. The virus enters the digestive tract, where the protein envelope (ODV form) dissolves due to the alkaline environment. The free viruses now attach themselves to the intestinal epithelial cells and are absorbed into an endosome via endocytosis , from which they free themselves and are now transported into the cell nucleus as nucleocapsids, presumably by actin filaments . This is where the virus replicates. Non-enveloped viruses (BV) are now generated and the virus infects the surrounding (basolateral) epithelial cells. However, the BV particles are also loosely wrapped in cell membranes containing glycoproteins from the virus.
The infection can be divided into three phases: the early phase (0–6 hours), the late phase (6–24 hours) and the very late phase (18–24 to 72 hours after infection). Until the late phase, non-enveloped BV forms are released, but in the final phase only ODV forms that bud through the nuclear membrane and form virus-filled particles that are filled with OB (occlusion body) protein. These are now more resistant to environmental factors than the BV form and are used to spread the virus to the nearest host. Since the cell is lysed when the virus emerges, the entire insect liquefies, with only the chitin shell remaining intact. This later bursts open and spreads the virus over the entire leaf surface. This property was the disease caused by this virus also the English name "wilting disease" , Welkkrankheit ' .
Structure of the virion
The best-studied baculovirus is Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). It was first isolated from a gamma owl species ( Autographa californica ) that lives on alfalfa . The genome has 134 kbp (kilo base pairs) and has 154 Open reading frames ( English open reading frames , ORFs). The most important capsid protein is VP39, it forms the nucleocapsid (21 nm × 260 nm) with some smaller proteins, which envelops the DNA, which in turn is surrounded by the protein p6.9.
For infection, the BV particles require the glycoprotein gp64 (gene product 64), which occurs at the ends of the thread-like virion. This protein is not found in the ODV particles, there are some proteins that only occur in ODV. There are also differences in the composition of the lipids of the shell, in BV there is phosphatidylserine , ODV contains phosphatidylcholines and phosphatidylethanolamines .
Coat protein gp64
In the course of the evolution of the virus, the gp64 has changed. Ld139, (also baculovirus F-protein) of the gypsy moth Lymantria dispar (LdMNPV) is probably an original membrane fusion protein (to release the virus from the host cell ), which was replaced by gp64 as not "equivalent" protein because Ld139 and gp64 in Genome of many baculovirus species occur ( mulberry moth , gamma owl , Douglas fir brush moth (family of carrier moth )).
Gp64 itself is a homo trimeric protein that sits on the poles of the filamentous BV particles. It consists of 512 amino acids , with four glycolization sites on asparagine residues and an N-terminal signal sequence of 20 amino acids, as well as oligomerization and fusion domains, and a hydrophobic transmembrane domain at the C-terminal end of seven amino acids. It is formed in the early and late phases of the infection with a maximum of 24 to 26 hours after infection. The trimerization (assembly of 3 gp64 units each) via internal cystine bonds is important for the transport to the cell surface, since only 33% of the gp64 reach the surface and monomers are broken down within the cell.
This protein is essential for the budding of the virion from the cell, as well as for the infection of other cells in the infection cycle. Its main task is the fusion with the endosome, which is regulated by the pH value. Although gp64 is essential for virus replication, mutants which gp64 is missing, over substitution with LD130, or the G-protein of the "vesicular stomatitis virus" ( Vesicular stomatitis virus , VSV) be made functional again.
Systematics
Internal system
According to ICTV (Master Species List 2018b.v2, as of March 2019) the family consists of the following four genera (the type species are each indicated):
- Baculoviridae family
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- Genus Alphabaculovirus
- Species Autographa californica multiple nucleopolyhedrovirus (AcMNPV, type)
- Genus Betabaculovirus (outdated: Granulovirus , GV)
- Species Cydia pomonella granulovirus (CpGV, type)
- Species Phthorimaea operculella granulovirus (PhopGV)
- Genus Gammabaculovirus
- Species Neodiprion lecontei nucleopolyhedrovirus (NeleNPV, type)
- Genus Deltabaculovirus
- Species Culex nigripalpus nucleopolyhedrovirus (CuniNPV, type)
External system
The Baculoviridae apparently form an as yet unnamed family group with the Nimaviridae , Hytrosaviridae , Nudiviridae and the genus Bracovirus of the suspected polyphyletic Polydnaviridae , for which Koonin et al. (2015 and 2019) the following family tree was proposed:
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See also
swell
- ↑ SIB: Double Strand DNA Viruses , on: ViralZone
- ↑ ICTV database
- ↑ Viral Zone: Baculoviridae . ExPASy. Accessed July 31, 2019.
- ↑ SIB: Alphabaculovirus , on: ViralZone
- ^ ICTV: Autographa californica multiple nucleopolyhedrovirus , on: ICTV Taxonomy history
- ↑ NCBI: Autographa californica multiple nucleopolyhedrovirus (species)
- ↑ Zhaoyang Hu, Meijin Yuan, Wenbi Wu, Chao Liu, Kai Yang, Yi Pang: Autographa californica Multiple Nucleopolyhedrovirus ac76 Is Involved in Intranuclear Microvesicle Formation, in: J Virol. 84 (15), August 2010, pp. 7437-7447, onlin19. e May 2010, doi: 10.1128 / JVI.02103-09 , PMC 2897645 (free full text), PMID 20484514
- ↑ SIB: Betabaculovirus , on: ViralZone
- ↑ ICTV: Cydia pomonella granuloviruss , on: ICTV Taxonomy history
- ↑ NCBI: Cydia pomonella granulovirus (species)
- ↑ Anette Juliane Sauer: Novel types of resistance of codling moth to Cydia pomonella granulovirus , on: Technische Universität, Darmstadt, 2017, (dissertation)
- ↑ SIB: Gammabaculovirus , on: ViralZone
- ↑ ICTV: Neodiprion lecontei nucleopolyhedrovirus on: ICTV taxonomy history
- ↑ NCBI: Neodiprion lecontei nucleopolyhedrovirus (species)
- ↑ Hilary AM Lauzon, Alejandra Garcia-Maruniak, Paolo M. de A. Zanotto, José C. Clemente, Elisabeth A. Herniou, Christopher J. Lucarotti, Basil M. Arif, James E. Maruniak: Genomic comparison of Neodiprion sertifer and Neodiprion lecontei nucleopolyhedroviruses and identification of potential hymenopteran baculovirus-specific open reading frames , in: Journal of General Virology 87, 2006, pp. 1477-1489, doi: 10.1099 / vir.0.81727-0
- ↑ SIB: Deltabaculovirus , on: ViralZone
- ↑ ICTV: Culex nigripalpus nucleopolyhedrovirus on: ICTV taxonomy history
- ↑ NCBI: Culex nigripalpus nucleopolyhedrovirus (species)
- ↑ Becnel J1, White SE, Shapiro AM: Culex nigripalpus nucleopolyhedrovirus (CuniNPV) infections in adult mosquitoes and possible mechanisms for dispersal, in: J Invertebr Pathol. 83 (2), June 2003, pp. 181-183, PMID 12788288 , doi: 10.1016 / s0022-2011 (03) 00058-2
- ^ Dupuy C, Huguet E, Drezen JM: Unfolding the evolutionary story of polydnaviruses . In: Virus Res . 117, No. 1, 2006, pp. 81-89. doi : 10.1016 / j.virusres.2006.01.001 . PMID 16460826 .
- ↑ Eugene V. Koonin, Natalya Yutin: Evolution of the Large Nucleocytoplasmatic DNA Viruses of Eukaryotes and Convergent Origins of Viral Gigantism , in: Advances in Virus research, Volume 103, AP January 21, 2019, doi: 10.1016 / bs.aivir.2018.09 .002 , pp. 167-202
- ^ Eugene V. Koonin, Valerian V. Dolja, Mart Krupovic: Origins and evolution of viruses of eukaryotes: The ultimate modularity , in: Virology from May 2015; 479-480. 2-25, Epub March 12, 2015, PMC 5898234 (free full text), PMID 25771806 .