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Journal of Virology, February 2000, p. 1140-1148, Vol. 74, No. 3
Station de Recherche "Grandes Cultures,"
INRA, Colmar 68021 Cedex,1 and Institut
de Biologie Moléculaire des Plantes du CNRS et de
l'Université Louis Pasteur, Strasbourg,2
France
Received 28 June 1999/Accepted 21 October 1999
Point mutations were introduced into or near five conserved
sequence motifs of the readthrough domain of the beet western yellows virus minor capsid protein P74. The mutant virus was tested for
its ability to accumulate efficiently in agroinfected plants and
to be transmitted by its aphid vector, Myzus persicae. The stability of the mutants in the agroinfected and aphid-infected plants
was followed by sequence analysis of the progeny virus. Only the
mutation Y201D was found to strongly inhibit virus accumulation in
planta following agroinfection, but high accumulation levels were
restored by reversion or pseudoreversion at this site. Four of the five
mutants were poorly aphid transmissible, but in three cases successful
transmission was restored by pseudoreversion or second-site
mutations. The same second-site mutations in the nonconserved motif
PVT(32-34) were shown to compensate for two distinct primary
mutations (R24A and E59A/D60A), one on each side of the PVT sequence.
In the latter case, a second-site mutation in the PVT motif restored
the ability of the virus to move from the hemocoel through the
accessory salivary gland following microinjection of mutant virus into
the aphid hemocoel but did not permit virus movement across the
epithelium separating the intestine from the hemocoel. Successful
movement of the mutant virus across both barriers was accompanied by
conversion of A59 to E or T, indicating that distinct features of the
readthrough domain in this region operate at different stages of
the transmission process.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Effects of Point Mutations in the Readthrough Domain of the
Beet Western Yellows Virus Minor Capsid Protein on Virus
Accumulation In Planta and on Transmission by Aphids
*
Corresponding author. Mailing address: Institut de
Biologie Moléculaire des Plantes du CNRS et de
l'Université Louis Pasteur, Strasbourg, France. Phone: (33) 388 417257. Fax: (33) 388 614442. E-mail:
veronique.ziegler-graff{at}ibmp-ulp.u-strasbg.fr.
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