''Idaeovirus'' is a genus of

positive-sense ssRNA viruses Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a di ...

that contains two species: ''Raspberry bushy dwarf virus'' (RBDV) and ''Privet idaeovirus''. RBDV has two host-dependent

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s: one for

raspberries The raspberry is the edible fruit of a multitude of plant species in the genus ''Rubus'' of the rose family, most of which are in the subgenus '' Idaeobatus''. The name also applies to these plants themselves. Raspberries are perennial with w ...

; the other for

grapevines ''Vitis'' (grapevine) is a genus of 79 accepted species of vining plants in the flowering plant family Vitaceae. The genus is made up of species predominantly from the Northern Hemisphere. It is economically important as the source of grapes, b ...

. Infections are a significant agricultural burden, resulting in decreased yield and quality of crops. RBDV has a synergistic relation with ''

Raspberry leaf mottle virus The raspberry is the edible fruit of a multitude of plant species in the genus ''Rubus'' of the rose family, most of which are in the subgenus '' Idaeobatus''. The name also applies to these plants themselves. Raspberries are perennial with ...

'', with co-infection greatly amplifying the concentration of virions in infected plants. The virus is transmitted via

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...

with RBDV-infected pollen grains that first infect the stigma before causing systemic infection.

Virology

RBDV is

non-enveloped A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encase ...

with an isometric protein coat about 33 nanometres in diameter. Inside the protein coat is the viral genome, which is bipartite, with the

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

strands referred to as RNA-1 and RNA-2. RNA-1 is 5,449

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules wi ...

s in length and contains one

open reading frame In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible readin ...

(ORF) that encodes for a combined protein that has

methyltransferase Methyltransferases are a large group of enzymes that all methylate their substrates but can be split into several subclasses based on their structural features. The most common class of methyltransferases is class I, all of which contain a Rossm ...

helicase Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separatin ...

, and an

RNA-dependent RNA polymerase RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to t ...

domains. RNA-2 is 2,231 nucleotides in length and contains two ORFs, one at the 5' end and the other at the 3' end. The first ORF encodes for a cell-to-cell movement protein, while the second ORF is expressed as a subgenomic RNA strand. This strand, RNA-3, is 946 nucleotides in length and encodes for the coat protein. Infection has been shown to not occur if RNA-3 is either not present or is sufficiently damaged.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription is the method of transcription. The virus exits the host cell by tubule-guided viral movement. Plants serve as the natural host. Transmission routes are pollen associated.

Diagnosis

Single-step

reverse transcription polymerase chain reaction Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using polymerase cha ...

s has been developed to detect RBDV. Viruses are enriched by antibodies in the PCR microwells, followed by

lysis Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular bio ...

of the virus particles, then reverse transcription of the viral RNA. By including

reverse transcriptase A reverse transcriptase (RT) is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, ...

and

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create ...

in the whole process, the procedure can be conducted in a single step. These tests are sensitive enough to identify the specific strain of the virus.

Treatment

RBDV can be eradicated from infected plants by a procedure that first applies

thermotherapy Heat therapy, also called thermotherapy, is the use of heat in therapy, such as for pain relief and health. It can take the form of a hot cloth, hot water bottle, ultrasound, heating pad, hydrocollator packs, whirlpool baths, cordless FIR h ...

then

cryotherapy Cryotherapy, sometimes known as cold therapy, is the local or general use of low temperatures in medical therapy. Cryotherapy may be used to treat a variety of tissue lesions. The most prominent use of the term refers to the surgical treatment, s ...

to infected

shoot In botany, a plant shoot consists of any plant stem together with its appendages, leaves and lateral buds, flowering stems, and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the spri ...

s. Applying heat to infected plants causes

vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...

s in infected cells to enlarge, with these cells later being killed during cryotherapy. Adding either Fe-

ethylenediaminetetraacetic acid Ethylenediaminetetraacetic acid (EDTA) is an aminopolycarboxylic acid with the formula H2N(CH2CO2H)2sub>2. This white, water-soluble solid is widely used to bind to iron (Fe2+/Fe3+) and calcium ions (Ca2+), forming water-soluble complexes eve ...

or Fe-ethylenediaminedi(o)hydroxyphenylacetic acid after cryotherapy stimulates regrowth and prevents

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

from developing in plant shoots. Using this method, about 80% of shoots survive the initial heat therapy, with 33% surviving the cryotherapy and successfully regrowing.

References

External links

Viralzone: Idaeovirus

ICTV
{{Taxonbar, from=Q5987260 Positive-sense single-stranded RNA viruses Riboviria Virus genera