PHYTO MEDIZIN Mitteilungen der Deutschen ... - Die DPG

spread in various ornamental plant species belonging to the Scrophulariaceae
and Verbenaceae. Judged from its gene content, the folding properties of its
5’untranslated region and from in vitro translation experiments, NeRNV
RNA is a typical tymovirus RNA. Its 3’end, however, differs greatly from
those of the valine-specific tymoviral RNAs which have been analysed previously.
It can be folded into an upstream pseudoknot domain (UPD) and a
histidine-specific tRNA-like structure (TLS), a combination which so far has
been found only for tobamoviral RNAs. The identity elements found in
NeRNV RNA for the recognition by yeast histidyl-tRNA synthetase are more
similar to those of yeast tRNA His than the ones found in Tobacco mosaic
virus (TMV) RNA. As a result NeRNV RNA can be charged with histidine
even more efficiently than TMV RNA.
Identification and detection of a closterovirus from carrot in Germany
W Menzel, D-E Lesemann and HJ Vetten; Federal Research Center for Agriculture
and Forestry, Institute for Plant Virology, Microbiology and Biosafety, Braunschweig
Following dsRNA isolation from a stunted and chlorotic carrot plant growing
in a seed propagation plot near Bingenheim, Hessen, Germany, a complex
pattern of dsRNA bands was obtained. Since one of the dsRNAs had a notably
high molecular weight, it was used as starting material for random RT-
PCR, cloning and sequencing. Several clones were obtained which shared
sequence similarity with viruses of the genus Closterovirus. A stretch of
about 12,000 nucleotides comprising the complete 3’ half of the genome of
the carrot closterovirus (CCV) was sequenced and analysed. Based on the
hsp70h gene, which is commonly used for illustrating relationships in the
family Closteroviridae, CCV is most closely related to Beet yellow stunt
virus and Beet yellows virus, with which it shares hsp70h amino acid sequence
similarities of 49% und 48% respectively. Moreover, CCV has a
genomic organisation characteristic of the genus Closterovirus and, thus, can
be confidently assigned to the genus Closterovirus of the family Closteroviridae.
In attempts to develop a serological detection method for CCV, the
major coat protein (CP) gene of CCV was expressed in E. coli and the resulting
protein preparation was used for polyclonal antibody (PAb) production in
a rabbit. These PAbs allowed visualisation of numerous closterovirus-like
particles by immunosorbent electron microscopy. CCV particles had a normal
length of 1600 nm and a width of 12 nm. In Western-blot experiments,
the PAbs reacted with a protein band of about 25 kDa which was only present
in CCV-infected but not in non-infected carrot plants. PAbs also permitted
sensitive detection of CCV in field carrot samples by DAS-ELISA. A refer-
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