PHYTO MEDIZIN Mitteilungen der Deutschen ... - Die DPG

twodimensional gel electrophoresis in combination with hybridization and
electron microscopy we have discovered that the recombinational flexibility
is reasoned by a recombination-dependent replication mode (RDR) that is
widespread at least among begomoviruses and curtoviruses but does also
occur for satellites, beta DNAs and artificial episomes. Compared to complementary
strand synthesis (CSR) and rolling circle replication (RCR),
which both were found together with RDR, the latter mechanism allows the
virus to repair every broken or unfinished DNA intermediate as far as homologous
templates are available. Using virus-specific two colour detection,
we found out the the frequency by which different geminiviruses enter the
same nucleus was surprisingly high in tomatoes and N. benthamiana, so that
the chance to recombine two viruses is extremely high. Moreover, weeds are
ideal cradles for new geminiviruses since they are reservoirs and collect several
virus species over years, as exemplified for Sida micrantha-associated
geminiviruses. Surveying different combinations of geminiviral and satellite
DNAs two strategies can be discriminated between Old World and New
World begomoviruses. The first were rather promicous to transreplicate other
DNAs, even without a cognate Rep-binding sequence, whereas the latter need
the interaction of Rep and Rep-binding sequences and consequently DNAs B
were acquired by shuffling of the regulatory region (common region CR) by
homologous recombination. The consequences of these findings for efficient
resistance breeding and epidemiology will be discussed.
BNYVV-like particles formed by coat protein expressed from a potexvirus-based
vector construct
R Koenig, S Loss and D-E Lesemann; c/o Biologische Bundesanstalt, Institut für
Pflanzenvirologie, Mikrobiologie und biologische Sicherheit, Braunschweig
We have recently determined the nucleotide (nt) sequences of the genomic
RNAs of three potexviruses which had been isolated long ago from different
species in the Cactaceae and were originally designated as different strains,
i.e. BS, CC10 and K11, of Cactus virus X. Because serological and molecular
studies revealed only rather distant relationships between these viruses, we
have proposed to change their taxonomic status and rename them to Zygocactus
virus X (ZVX), Opuntia virus X (OVX) and Schlumbergera virus X
(ScVX), respectively. The full length cDNA sequence of ZVX RNA was
cloned into the 35S promoter-containing vector p35Stupa kindly provided by
E. Maiß, Hannover. The cDNA clones obtained consistently produced symptomless
local and occasionally also systemic infections in C. quinoa. In order
to enable insertion and expression of foreign genes an AscI and a SpeI site
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