Arch Virol (2002) 147: 1371–1384
Isolate-speciﬁc synergy in disease symptoms
between cauliﬂower mosaic and turnip vein-clearing viruses
, R. Pennington
, S. Hartson, C. D. Taylor
, R. Lartey
, A. Williams,
D. Lewis, and U. Melcher
Department of Biochemistry and Molecular Biology,
Oklahoma State University, Stillwater, Oklahoma, U.S.A.
Received October 26, 2001; accepted February 15, 2002
Published online May 8, 2002
Summary. Simultaneous infection ofa plant by two viruses can cause more severe
disease than is caused by infection with either virus alone. Such synergy may be
due to effects on the replication of one virus by the second virus or to other
causes. The tobamovirus turnip vein-clearing virus (TVCV), itself causing almost
imperceptible symptoms in infected turnips, exacerbated symptoms of infection
of turnip by the Cabbage S isolate of the caulimovirus cauliﬂower mosaic virus
(CaMV). The synergy in symptom production was most evident in a reduced
size of leaves, providing an objective measure of synergy. In contrast, synergy
did not occur when the CM4-184 isolate of CaMV was used in combination
with TVCV. Both isolates of CaMV increased the level of TVCV accumulated
in leaves. TVCV did not increase the level of the Cabbage S CaMV isolate. The
use of Cabbage S–CM4-184 chimeras revealed that a region critical for isolate
synergy in stunting was within the coat protein gene and/or the 5
one third of the
reversetranscriptasegene.Weconcludethat the disease symptomsynergybetween
TVCV and Cabbage S CaMV is not caused by altered levels of accumulation
of the viruses, but instead reﬂects subtle genetic interactions mapping to the
ORF IV-ORF V region of CaMV DNA.
Children’s Hospital of Philadelphia, Abrahamson Pediatric Center, Philadelphia,
Roche Diagnostics Corporation, Roche Molecular Biochemicals, Indianapolis, U.S.A.
Department of Obstetrics, Gynecology and Women’s Health, St. Louis University School
of Medicine, St. Louis, Missouri, U.S.A.
USDA/ARS/Northern Plains Ag. Research Lab, Sidney, Montana, U.S.A.