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For information:
Robin B. Goldsmith
(619)5s4-8134
Embargoed by The Plant Journal:
November 30, 1993
Scripps ScientistsDiscoverNew Pathway to Inhibit Spread of Viral Plant Disease
La Jolla, CA. November30, 1993- A teamof scientists
led by RogerBeachy,Ph.D., head
of the Division of Plant Biology at The ScrippsResearchInstitute(TSRI), hasdeterminedthat
the spreadof a prevalentplant virus canbe effectivelyblockedby the use of genetic
engineeringtechniques.
The researchshowsthat the TobaccoMosaicVirus (TMV), which attacksnumerouscrops,
includingpotatoes,tomatoes,eggplant,bell peppersand orchids,can be substantiallyslowed
by manipulatinga key protein -- the movementprotein -- that enablesthe virus to spreadfrom
plant cell to plant cell.
Accordingto Beachy,"The significanceof this work lies in the mutantprotein's ability to
inhibit the spreadof TMV and other strainsof tobamoviruses.
By interferingwith a key
elementof the transmissionprocess,we've beenable to confer resistanceagainstall the
virusesin the group."
The scientists'findings were announcedin the November30 issueof The Plant Journal,an
internationalperiodicalbasedin England,by MosheLapidot, Ron Gafny, Biao Ding, Shmuel
Wolf, William J. Lucas,and RogerN. Beachyin an article entitled, "A Dysfunctional
MovementProteinof TobaccoMosaicVirus That Partially Modifies the Plasmodesmata
and
Limits Virus Spreadin TransgenicPlants." Wolf and Lucasare collaboratorsat the
University of California, Davies. The researchrepresents
anothermajor stepforward for the
world agriculturalsciencecommunity'sefforts in controllingand eradicatingplant viruses.
MORB
Page 2 -
Scripps ScientistsDiscoverNew pathway to Inhibit
Spread of Viral plant Disease
The ability of a plant virus to spreadfrom cell to cell is essentialfor
establishinga viral
infection' However, unlike animalcells, plant cells havea cell wall
barrier that virusesmust
crossto move from cell to cell. This movementoccursthroughplasmodesmata,
channelsthat
spanthe cell wall and provide continuitybetweenadjacentcells. These
intercellular
connectionsplay an importantrole in cell-to-cellcommunicationand provide
the route
through which water and other substances
passfrom cell to cell.
However, due to their relatively small sizeas well as the large size of plant
viruses,it is
assumedthat the structuremust be modified during viral infection. In fact,
the movement
protein of the tobaccomosaicvirus is known to modi$ the function
of plasmodesmata.
In this study, Beachy'sresearchteamintroduceda mutantor dysfunctional
TMV movement
protein *- createdby deletingthreeaminoacids-- into transgenic
tobaccoplants. By so
doing, they were able to reducethe spreadof TMV from the site of infection
to adjacentcells
and to upper leavespresumablyby preventingthe gatesof the plasmodesmata
from opening
as wide as is necessaryto allow virus passage.While the experimentalresultsprove
that a
mutantmovementprotein can confer a degreeof inhibition of viral spread,
the precisenature
of the interferenceis unknown.
Beachyexplainsthat the mutantattacksa fundamentalprocessin viral movement
that is used
by many plant viruses. "This is particularlyexcitingbecausethe work confronts
a
fundamentalaspectof cellular functionthat would makeit virnrally impossible
for the virus to
overcome"' he says. "It is clear that understanding
the cellular mechanisms
that underlie
reducedviral spreadmay lead to greaterunderstanding
of the structure,function and
developmentof plasmodesmata.At the sametime it may lead to novel ways
to engineer
plantsthat resista broad spectrumof virusesthroughthe expression
of a singlegene.,,
MORE
Page 3 -
Scripps ScientistsDiscoverNew Pathway to Inhibit
Spread of Viral Plant Disease
TheseresultscomplementBeachy'spreviouswork that led to the intemrptionof viral
replication.This was accomplished
by insertinga genethat createsthe outsidecoatingof a
virus into the geneticinformationof the cells of a plant. The geneprotectsby producinga
small amountof the protein coat insidethe cell. The presenceof the coat protein enhances
the cell's resistanceto the virus. Preciselyhow, researchers
are not sure,but the coatprotein
apparentlyinterfereswith the releaseof nucleicacid from the virus.
Beachystatesthat in plantswith coatproteinresistanceas well as a dysfunctionalmovement
protein, the resistancewill be additivebecausethey attackdifferent stagesin the infection
process.
In order to test how broad-based
the movementproteinresistancemay be, Beachyhasformed
a collaborationwith Dr. Alan Doddsat Universityof California, Riverside. They plan to test
the degreeof resistanceby inoculatingthe plantswith a variety of different viruses.
In additionto his appointmentat TSRI, Beachyalso is a foundingco-directorwith Dr. Claude
Fauquetof the InternationalLaboratoryfor Tropical Agricultural Biotechnology(ILTAB),
foundedin 1991as a collaborativeeffort of TSRI and the Institut Frangaisde Recherche
Scientifiquepour le Developpement
en Cooperation(ORSTOM). Its missionis to improve
the agriculturalresourcesof developingnationsthroughthe developmentof disease-resistant
crops. Also, ILTAB providespostgraduate
training to scientistsfrom developingnationsin
the techniquesof cell and tissueculture, virology and moleculargenetics.
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