Cacao-swollen-shoot virus
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Cacao swollen-shoot virus (CSSV) is a former virus species from the family of Caulimoviridae , which is now the International Committee on Taxonomy of Viruses was divided (ICTV) in seven species. Together with about 23 other plant viruses, these form the genus Badnavirus . They infect the cocoa tree ( Theobroma cacao ) as the only host and are transmitted by mealybugs (Pseudococcidae) by sucking the sap. So far, this virus species has only been found in West African cocoa plantations, mainly in Ghana , Togo and Nigeria . Plant death due to CSSV infection and rapid spread within a plantation is a significant economic threat to cocoa cultivation .
In 1963, a CSSV was presented for the first time as a rod-shaped, non-enveloped virus and identified as the causative agent of the mosaic disease of the cocoa tree. A CSSV genome was first characterized in 1991; it consists of a circular, double-stranded DNA , some of which has single-stranded regions. The genome is by means of a reverse transcriptase of an RNA generated precursor why CSSV or Badnavirus the real retroviruses close stands.
Systematics
As of March 2019, the ICTV confirmed the following CSSV species:
- Genus Badnavirus
- Species Cacao swollen shoot CD virus (CSSCDV)
- Species Cacao swollen shoot CE virus (CSSCEV)
- Species Cacao swollen shoot Ghana M virus (CSSGMV)
- Species Cacao swollen shoot Ghana N virus (CSSGNV)
- Species Cacao swollen shoot Ghana Q virus (CSSGQV)
- Species Cacao swollen shoot Togo A virus (CSSTAV)
- Species Cacao swollen shoot Togo B virus (CSSTBV) with referendum strain Agou1-93
There are also other proposed, as yet unconfirmed species, such as:
- Species ' Cacao swollen shoot Ghana J virus ' (CSSGJV)
- Species ' Cacao swollen shoot Ghana K virus ' (CSSGKV)
- Species ' Cacao swollen shoot Ghana L virus ' (CSSGLV)
- Species ' Cacao swollen shoot Ghana P virus ' (CSSGPV)
- Species ' Cacao swollen shoot Ghana R virus ' (CSSGRV)
- Species ' Cacao swollen shoot Ghana S virus ' (CSSGSV)
- Species ' Cacao swollen shoot Ghana T virus ' (CSSGTV)
The proposed species S and T have so far (as of 2017) only incompletely decoded genomes.
morphology
The non-enveloped virus particles (virions) of the CSSV species are rod-shaped (“ bacilliform ”) and uniformly 30 nm wide; its length averages 130 nm, but varies between 60 and 900 nm. Based on an icosahedral symmetry of the capsid , the elongated shape is created by repeatedly inserted rings of hexamers , which create an elongated, non-isometric icosahedron.
Genome
The genome of the species CSSTBV has approximately 7161 bp (reference strain Agou1) and probably contains five open reading frames ( English open reading frames , ORFs) 1, 2, 3, X and Y, which are all located on the plus strand is of double-stranded DNA genome. The ORFs 1 and 2 code for proteins of unknown function, the ORF 2 being a DNA-binding protein. The gene product of ORF 3 (211 kDa ) can be divided into three different regions, with region 1 coding for a protein that is important for the direct spread of the virus between cells. The region 2 product is the viral capsid protein. Finally, region 3 has the structural properties of a DNA polymerase , reverse transcriptase and RNase H , as are typical for pararetroviruses. ORFs X and Y (13 and 14 kDa) overlap ORF 3 and are not present in any other described species of the genus Badnavirus . As with other Caulimoviridae , the CSSV has a similar genome organization to the enveloped Hepadnaviridae in animals.
illness
The CSSV species are only able to infect the cocoa plant experimentally. Like all viruses of the Badnavirus genus , the CSSV do not infect all cells of the host plant, but are restricted to cells of the vascular bundle . CSSV virions can mainly be observed in accompanying cells of the leaf phloem and less in those of the xylem . After an incubation period of 4 to 7 weeks, the symptoms of the infection appear on the plant, initially affecting the leaves. The later typical swelling of the trunk and young shoots ( shoot swelling ) is based on excessive, regenerative growth of the bark and the bundles of lines of the trunk and becomes visible after 8-11 weeks. A disease of plantation plants can be detected at an early stage (6 to 20 days after infection) using the polymerase chain reaction .
literature
- R. Hull et al .: Genus Badnavirus . In: CM Fauquet, MA Mayo et al .: Eighth Report of the International Committee on Taxonomy of Viruses . London / San Diego 2005, p. 392 f.
Web links
- EM image of the CSSV in a herbal preparation
- Species CSSV in the ICTV database
- Reference sequence of the CSSV
- CSSV taxonomy page. NCBI
Individual evidence
- ↑ a b c d ICTV: ICTV Taxonomy history: Commelina yellow mottle virus , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
- ^ AA Brunt, RH Kenten: The use of protein in the extraction of cocoa swollen-shoot virus from cocoa leaves . In: Virology , 1963, 19, pp. 388-392, PMID 14016365
- ↑ Hervé Lot, Edem Djiekpor, Mireille Jacquemond: Characterization of the genome of cacao swollen shoot virus . In: J. General Virology , 1991, 72, 7, pp. 1735-1739, PMID 1856700 ; microbiologyresearch.org (PDF; 6.1 MB) with an electron microscope image of the CSSV
- ↑ ICTV : Master Species List 2018b.v2 , MSL # 34 from March 2019
- ↑ Ervín Muller, Sammy Sackey: Molecular variability analysis of five new complete cacao swollen shoot virus genomic sequences , in: Archives of Virology 150 (1), pp. 53-66, February 2005, doi: 10.1007 / s00705-004-0394- 8th
- ↑ Emmanuelle Muller: Creation of 4 new species in the genus Badnavirus , ICTV Proposal 2015.026aP
- ↑ a b c d E. Muller, S. Ravel, C. Agret, F. Abrokwah, H. Dzahini-Obiatey, I. Galyuon, K. Kouakou, EC Jeyaseelan, J. Allainguillaume, A. Wetten: Next generation sequencing elucidates cacao badnavirus diversity and reveals the existence of more than ten viral species , in: Virus Research 2017, doi: 10.1016 / j.virusres.2017.11.019
- ↑ NCBI: Cacao swollen shoot Ghana J virus (species)
- ↑ NCBI: Cacao swollen shoot Ghana K virus (species)
- ↑ NCBI: Cacao swollen shoot Ghana L virus (species)
- ↑ NCBI: Cacao swollen shoot Ghana P virus (species)
- ↑ NCBI: Cacao swollen shoot Ghana R virus (species)
- ↑ NCBI: Cacao swollen shoot Ghana S virus (species)
- ↑ NCBI: Cacao swollen shoot Ghana T virus (species)
- ↑ E. Jacquot et al .: The open reading frame 2 product of cacao swollen shoot badnavirus is a nucleic acid-binding protein . In: Virology , 1996, 225, 1, pp. 191-195, PMID 8918546
- ↑ LS Hagen, M. Jacquemond et al .: Nucleotide sequence and genomic organization of cacao swollen shoot virus . In: Virology , 1993, 196.2, pp. 619-628, PMID 7690503
- ↑ E. Jacquot, LS Hagen et al. : In situ localization of cacao swollen shoot virus in agroinfected Theobroma cacao . In: Archives of Virology , 1999, 144.2, pp. 259-271, PMID 10470252
- ↑ E. Müller, E. Jacquot, P. Yot: Early detection of cocoa swollen shoot virus using the polymerase chain reaction . J. Virol. Methods. (2001) 93, 1-2: pp. 15-22 PMID 11311339