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Date: October 2007
Source: The American Phytopathological Society, Plant Disease
2007; 91(10), 1212-1220 [edited] <http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-91-10-1212>
[Reference: P. Rajakaruna and S. Khandekar: Identification and
host relations of Turnip ringspot virus, a novel comovirus from
Ohio.
Plant Dis 2007, 91(10); 1212-1220; DOI: 10.1094/PDIS-91-10-1212]
Identification and host relations of Turnip ringspot virus, a
novel comovirus from Ohio
Viruslike chlorotic ring spot symptoms and line patterns of
unknown origin were observed on a greenhouse-grown turnip plant.
The suspected virus was mechanically transmissible to plants in
the _Brassicaceae_. Electron microscopic analysis revealed
icosahedral particles approximately 28 nanometers in diameter.
Reverse transcriptase-polymerase chain reaction (RT-PCR)
analyses suggested that the pathogen is a comovirus, an
observation that was confirmed by analysis of portions of the
genomic sequence. This virus was provisionally named Turnip
ringspot virus (TuRSV). Based on the RNA 1 sequence, TuRSV is
most similar to _Radish mosaic virus_ [genus _Comovirus_],
another pathogen that infects members of the _Brassicaceae_.
_Arabidopsis thaliana_ [see comments below] is susceptible to
TuRSV, and 12 out of the 23 ecotypes studied showed symptoms
when inoculated with the virus. TuRSV induced a variety of
responses on ecotypes from death to no infection. Some ecotypes
showed one or 2 rounds of symptom display followed by recovery
when inoculated with TuRSV.
About half of the ecotypes (11/23) analyzed showed no symptoms
when inoculated with TuRSV. Col-0 [_A. thaliana_ line from the
University of Missouri-Columbia] plants showed no symptoms, and
infectious virus was not recovered from systemic leaves,
although it could be detected by RT-PCR. Col-0 plants harboring
mutations impairing the ethylene, jasmonic acid, or salicylic
acid signaling pathways did not show symptoms when inoculated
with TuRSV.
--
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[Plant viruses belonging to the genus _Comovirus_ (type species
_Cowpea mosaic virus_) are transmitted by insects, grafting, and
mechanical inoculation. Some of them are also seed-transmitted.
_Radish mosaic virus_, to which the new TuRSV appears to be
related, is transmitted by several beetle species but not by
seed, and affects cruciferous and a few other species. The
family of _Brassicaceae_ (previously _Cruciferae_) from which
TuRSV is being reported includes a number of important crop
species such as cabbage, radish, cauliflower, turnip, and
oilseed rape. The fact that _A. thaliana_ strains (ecotypes)
seem to vary dramatically in their response to TuRSV infection
suggests that resistant or tolerant germplasm may be available
in this host. Whether this applies also to affected cruciferous
crop species will need to be tested.
_Arabidopsis thaliana_ (thale cress or mouse-ear cress, family
_Brassicaceae_) is widely used in plant virology as an
experimental indicator species and is also used as a model
species in other areas of plant research. It is a small plant
suitable for large-scale propagation in a small space, has one
of the smallest genomes in the plant kingdom, genetic
modification is easy, and homozygous lines for research can
readily be obtained.
Maps
USA:
<http://healthmap.org/promed?v=40,-97.6,4>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>
Pictures
Electron micrograph of comovirus particles (_Cowpea mosaic
virus_):
<http://www.ncbi.nlm.nih.gov/ICTVdb/WIntkey/Images/d2.gif>
_A. thaliana_:
<http://www.missouriplants.com/Whitealt/Arabidopsis_thaliana_plant.jpg>
Links
Genus _Comovirus_ taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.018.0.01.htm>
Information on _Radish mosaic virus_:
<http://image.fs.uidaho.edu/vide/descr662.htm>
_Comoviridae_ taxonomy and species list:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.018.htm>
_A. thaliana_ taxonomy:
<http://www.missouriplants.com/Whitealt/Arabidopsis_thaliana_page.html>
_A. thaliana_ as a model species for research:
<http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Arabidopsis.html>
Information on _A. thaliana_ lines, including Col-0:
<http://www.springerlink.com/content/b03505113x853715/>.
- Mod.DHA]
