Failure of long-distance movement of southern bean mosaic virus in a resistant host is correlated with lack of normal virion formation.
Sunn-hemp mosaic tobamovirus (SHMV) facilitated the spread of the cowpea strain of southern bean sobemovirus (SBMV-C) only in inoculated leaves of common bean (Phaseolus vulgaris L. cv. Bountiful), a resistant host for SBMV-C. Tissue prints of bean primary leaves doubly inoculated with SHMV and SBMV-C, developed by Western blotting, showed the presence of the SBMV-C capsid antigen in the mesophyll and epidermis, but no antigen was detected in the conducting bundles. Typical SBMV-C virions were not seen in electron micrographs of immunogold-labelled mesophyll cells; instead, specifically labelled, amorphous protein clumps were found in the vacuole. Particles of smaller diameter than that of typical SBMV-C virions were specifically trapped by SBMV antibodies following immunosorbent electron microscopy of extracts from doubly infected leaves. SBMV-C coat protein from infected Vigna unguiculata L. (cowpea) and bean plants showed no difference in its mobility following electrophoresis in denaturing SDS-polyacrylamide gels. Lack of efficient assembly of SBMV-C virions does not impede cell-to-cell movement of the virus in doubly infected leaves of bean, yet it is probably an important factor in determining the inability of SBMV-C to move into and/or through the vascular system of this host.
Fuentes
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AL
Department of Plant Science, University of British Columbia, Vancouver, Canada.
Hamilton
R I
RI
D000956:Antigens, Viral / Q000032:analysis / Q000096:biosynthesis; D015153:Blotting, Western; D002213:Capsid / Q000032:analysis / Q000096:biosynthesis; D007887:Fabaceae / Q000382:microbiology*; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D009029:Mosaic Viruses / Q000502:physiology* / Q000648:ultrastructure; D010946:Plants, Medicinal; D014771:Virion / Q000502:physiology* / Q000648:ultrastructure
D000956:Antigens, Viral