Produzione di virus sintetici per lo studio dei meccanismi di interazione coinvolti nell'induzione di resistenza
Creators: name: Bianchi, Laura <1979>
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2008
Subjects: AGR/12 Patologia vegetale

description: Beet soil-borne mosaic virus (BSBMV) and Beet necrotic yellow vein virus
(BNYVV) are members of Benyvirus genus. BSBMV has been reported only in
the United States while BNYVV has a worldwide distribution. Both viruses are
vectored by Polymyxa betae, possess similar host ranges, particles number and
morphology. Both viruses are not serologically related but have similar genomic
organizations. Field isolates consist of four RNA species but some BNYVV
isolates contain a fifth RNA. RNAs 1 and 2 are essential for infection and
replication while RNAs 3 and 4 play important roles on plant and vector
interactions, respectively. Nucleotide and amino acid analyses revealed BSBMV
and BNYVV are different enough to be classified in two different species.
Additionally in BNYVV/BSBMV mixed infections, a competition was
previous described in sugar beet, where BNYVV infection reduces BSBMV
accumulation in both susceptible and resistant cultivars.
Considering all this observations we hypothesized that BNYVV and
BSBMV crossed study, exploiting their similarities and divergences, can improve
investigation of molecular interactions between sugar beets and Benyviruses.
The main achievement of our research is the production of a cDNA
biologically active clones collection of BNYVV and BSBMV RNAs, from which
synthetic copies of both Benyviruses can be transcribed.
Moreover, through recombination experiments we demonstrated, for the
first time, the BNYVV RNA 1 and 2 capability to trans-replicate and encapsidate
BSBMV RNA 3 and 4, either the BSBMV RNA 1 and 2 capability to replicate
BNYVV RNA2 in planta. We also demonstrated that BSBMV RNA3 support
long-distance movement of BNYVV RNA 1 and 2 in B. macrocarpa and that
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foreign sequence as p29HA, GFP and RFP, are successfully expressed, in C.
quinoa, by BSBMV RNA3 based replicon (RepIII) also produced by our
research. These results confirm the close correlation among the two viruses.
Interestingly, the symptoms induced by BSBMV RNA-3 on C. quinoa
leaves are more similar to necrotic local lesions caused by BNYVV RNA-5 p26
than to strongly chlorotic local lesions or yellow spot induced by BNYVV RNA-
3 encoded p25. As previous reported BSBMV p29 share 23% of amino acid
sequence identity with BNYVV p25 but identity increase to 43% when compared
with sequence of BNYVV RNA-5 p26.
Based on our results the essential sequence (Core region) for the longdistance
movement of BSBMV and BNYVV in B. macrocarpa, is not only
carried by RNA3s species but other regions, perhaps located on the RNA 1 and
2, could play a fundamental role in this matter.
Finally a chimeric RNA, composed by the 5’ region of RNA4 and 3’ region
of RNA3 of BSBMV, has been produced after 21 serial mechanically inoculation
of wild type BSBMV on C. quinoa plants. Chimera seems unable to express any
protein, but it is replicated and transcript in planta. It could represent an
important tool to study the interactions between Benyvirus and plant host.
In conclusion different tools, comprising a method to study synthetic
viruses under natural conditions of inoculum through P. Betae, have been
produced and new knowledge are been acquired that will allow to perform future
investigation of the molecular interactions between sugar beets and Benyviruses.