f Competition between Isolates and Variants of Cauliflower Mosaic Virus in Infected Turnip Plants
- Authors: Xu Shao Zhang†, Ulrich Melcher
- J. Gen. Virol., December 1989 70: 3427-3437, doi: 10.1099/0022-1317-70-12-3427
- Subject: Plant
- Published Online:
The Cabb S isolate of cauliflower mosaic virus (CaMV) is the only isolate that can be recovered from turnip plants mixedly infected with Cabb S and an infectious variant of Cabb S. Analysis of the progeny resulting from mixed infections of turnip plants was done for a better understanding of this dominance. Cabb S DNA was the dominant DNA recovered from plants after a mixed infection with Cabb S and D/H or W isolates of CaMV, whereas UM130 (derived from Cabb S by the insertion of a short oligonucleotide in open reading frame III) coexisted in turnip plants with D/H, NY8153, CM4-184 and W isolates. To determine whether there are additional sequences responsible for the ability of Cabb S to dominate over UM130, coinoculation experiments were done using chimeric DNAs, obtained by in vivo recombination (IC141, IC143 and VR246) and by in vitro construction (W/CS and CS/W). Chimeras IC141, IC143 and VR246 coexisted in turnip plants with UM130. Chimera CS/W dominated over UM130, whereas UM130 dominated over W/CS. The location of Cabb S sequences in these chimeras suggests that more than one region is responsible for the competitive advantage of Cabb S DNA. A different modification of Cabb S DNA in open reading frame III also destroyed the ability of the DNA to dominate over the W isolate. In DNA from virions obtained after co-infection with UM130 and CS/W, more molecules were recovered with UM130-specific sequences at position 1364 than with those at position 2040. This and similar results with progeny from W/CS and UM130 co-infection suggest that genetic exchanges had occurred. However, exchanges were not detected in progeny from other mixed infections. Thus the dominance of the Cabb S isolate in mixed infections was due primarily to a better competitive ability of the Cabb S DNA. Plants inoculated first with UM130 and 2 to 8 days later with Cabb S contained only UM130 CaMV DNA, indicating that dominance was unable to overcome cross-protection.
Present address: University of Texas Cancer Research Center, P.O. Box 389, Smithville, Texas 78953, U.S.A.
© Society for General Microbiology 1989 | Published by the Microbiology Society
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