Arch Virol (1998) 143: 1349–1363
Serological characterization of the 3
-proximal encoded proteins
of beet yellows closterovirus
, K. Harper
, G. Grantham
,and R. Creamer
Department of Plant Pathology, University of California, Riverside, California, U.S.A.
Department of Soil and Enviromental Science, University of California,
Riverside, California, U.S.A.
Accepted February 3, 1998
Summary. The 3
-proximal open reading frames (ORFs) of beet yellows clos-
terovirus, California isolate (BYV-CA), were sequenced and the expression of
the corresponding proteins analyzed. The nucleotide sequence of ORF 5 (coding
for p24) was most conserved compared with ORF 7 (coding for p20) and ORF 8
(coding for p21) among the isolates analyzed. Polyclonal antisera were produced
to GST fusion proteins of p24, p20, and p21. Accumulation of p24, CP, p20 and
p21 was studied in infected Tetragonia expansa plants and Chenopodium quinoa
protoplasts. All four proteins were expressed in all tissues (old leaves, young
leaves and stems), and most abundantly in young leaves. The subcellular local-
ization of each protein in different tissues showed that compared with p24, CP
and p21, p20 accumulated less in transfected protoplasts. Immunogold labeling in
sugarbeet with p24 and CP antisera demonstrated co-localization of p24 and CP
in vascular petiole tissues. In infectivity neutralization tests, antisera against p24
and CP greatly reduced transmission of BYV by viruliferous aphids compared
with viruliferous aphids fed on preimmune serum or antiserum to p21.
Closteroviruses are a diverse and poorly characterized group of plant viruses.
Beet yellows virus (BYV), the type member, is characterized by long ﬂexuous
rodmorphologyandinduction ofﬁbrous inclusionsin infectedplants [7,19]. BYV
has a single positive-sense RNA of 15, 480 nucleotides encoding nine putative
ORFs (for a review see ), and is transmitted semipersistently by aphids. The
Present address: Botany and Plant Pathology Department, Purdue University, West
Lafayette, Indiana, U.S.A.