Ascovirus
Encyclopedia
Ascovirus is a family
of double strand DNA viruses that infect primarily invertebrates. Currently only a single genus in this family is recognised: Ascovirus.
Six species in this genus are currently known. The type species is Spodoptera frugiperda ascovirus 1a which infects the army worm (Spodoptera frugiperda). Other species include Spodoptera frugiperda ascovirus-1d.
. The genome has a guanine
+ cytosine
content of 42-60%.
The genome of Spodoptera frugiperda ascovirus 1a has been sequenced. It is 156,922 bases in length and encodes 123 putative open reading frames. The G+C ratio is 49.2%. Among the encoded proteins are a caspase
, a cathepsin B
, several kinase
s, E3 ubiquitin ligases, a fatty acid elongase, a sphingomyelinase, a phosphate acyltransferase
and a patatin
-like phospholipase
.
is enveloped
and measures 130 nm in diameter, and 200-240 nm in length. Virions are bacilliform, ovoid, and allantoid.
These viruses infect immature stages of the order Lepidoptera
, in which they cause a chronic, fatal disease. They are transmissed by endoparasitic wasps and the host develops a unique cytopathology that resembles apoptosis. Cell infection induces apoptosis and in some species is associated with synthesis of a virus-encoded executioner caspase
and several lipid-metabolizing enzymes. After infection the host cell DNA is degraded, the nucleus fragments and the cell then cleaves into large virion-containing vesicles. Synthesis of viral proteins results in the rescue of developing apoptotic bodies that are converted into large vesicle
s in which virions accumulate and continue to assemble. In infected larvae, millions of these virion-containing vesicles begin to disperse from infected tissues 48-72 hours after infection into the haemolymph, making it milky white, a characteristic of this disease. The circulation of virions and vesicles in the blood facilitates mechanical transmission by parasitic wasp
s.
) that also attack lepidopteran larvae and are likely the evolutionary source of ichnoviruses (family Polydnaviridae).
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of double strand DNA viruses that infect primarily invertebrates. Currently only a single genus in this family is recognised: Ascovirus.
Six species in this genus are currently known. The type species is Spodoptera frugiperda ascovirus 1a which infects the army worm (Spodoptera frugiperda). Other species include Spodoptera frugiperda ascovirus-1d.
Genome
The genome is not segmented and contains a single molecule of circular double-stranded DNADNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. The genome has a guanine
Guanine
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...
+ cytosine
Cytosine
Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine . It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached . The nucleoside of cytosine is cytidine...
content of 42-60%.
The genome of Spodoptera frugiperda ascovirus 1a has been sequenced. It is 156,922 bases in length and encodes 123 putative open reading frames. The G+C ratio is 49.2%. Among the encoded proteins are a caspase
Caspase
Caspases, or cysteine-aspartic proteases or cysteine-dependent aspartate-directed proteases are a family of cysteine proteases that play essential roles in apoptosis , necrosis, and inflammation....
, a cathepsin B
Cathepsin B
Cathepsin B is an enzymatic protein belonging to the peptidase families. In humans, it is coded by the CTSB gene.- Function :...
, several kinase
Kinase
In chemistry and biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates, a process referred to as phosphorylation. Kinases are part of the larger family of phosphotransferases...
s, E3 ubiquitin ligases, a fatty acid elongase, a sphingomyelinase, a phosphate acyltransferase
Acyltransferase
Acyltransferase is a type of transferase enzyme that acts upon acyl groups.Examples include:* Glyceronephosphate O-acyltransferase* Lecithin-cholesterol acyltransferase...
and a patatin
Patatin
Patatin is a glycoprotein found in potatoes . The main function of patatin is as a storage protein but it also has lipase activity and can cleave fatty acids from membrane lipids. The patatin protein makes up about 40% of the soluble protein in potato tubers. Members of this protein family have...
-like phospholipase
Phospholipase
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. There are four major classes, termed A, B, C and D, distinguished by the type of reaction which they catalyze:*Phospholipase A...
.
Virology
The virions consist of an envelope, a core, and an internal lipid membrane associated with the inner particle. The virus capsidCapsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
is enveloped
Viral envelope
Many viruses have viral envelopes covering their protein capsids. The envelopes typically are derived from portions of the host cell membranes , but include some viral glycoproteins. Functionally, viral envelopes are used to help viruses enter host cells...
and measures 130 nm in diameter, and 200-240 nm in length. Virions are bacilliform, ovoid, and allantoid.
These viruses infect immature stages of the order Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
, in which they cause a chronic, fatal disease. They are transmissed by endoparasitic wasps and the host develops a unique cytopathology that resembles apoptosis. Cell infection induces apoptosis and in some species is associated with synthesis of a virus-encoded executioner caspase
Caspase
Caspases, or cysteine-aspartic proteases or cysteine-dependent aspartate-directed proteases are a family of cysteine proteases that play essential roles in apoptosis , necrosis, and inflammation....
and several lipid-metabolizing enzymes. After infection the host cell DNA is degraded, the nucleus fragments and the cell then cleaves into large virion-containing vesicles. Synthesis of viral proteins results in the rescue of developing apoptotic bodies that are converted into large vesicle
Vesicle
Vesicle may refer to:In cellular biology or chemistry* Vesicle , a supramolecular assembly of lipid molecules, like a cell membrane* Synaptic vesicleIn human embryology* Auditory vesicle* Optic vesiclesIn human anatomy and morphology...
s in which virions accumulate and continue to assemble. In infected larvae, millions of these virion-containing vesicles begin to disperse from infected tissues 48-72 hours after infection into the haemolymph, making it milky white, a characteristic of this disease. The circulation of virions and vesicles in the blood facilitates mechanical transmission by parasitic wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
s.
Evolution
Ascoviruses evolved from iridoviruses (family IridoviridaeIridoviridae
Iridoviridae are a family of viruses with double stranded DNA genomes. The name is derived from Iris the Greek goddess of the rainbow. This name was chosen because of the "rainbow like" iridescence observed in heavily infected insects and pelleted samples of invertebrate iridoviruses.-Taxonomy:The...
) that also attack lepidopteran larvae and are likely the evolutionary source of ichnoviruses (family Polydnaviridae).