|Morris, T. - UNIVERSITY OF NEBRASKA|
Submitted to: International Congress of Virology
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 1999
Publication Date: August 6, 1999
Citation: Stenger, D.C., Hall, J.S., Morris, T.J., French, R.C. 1999. Population structure of a plant virus implies linear rather than exponential growth. International Congress Of Virology. (Meeting-not published.) Technical Abstract: The quasispecies population structure and genotypic diversity resident with the Type and Sidney 81 isolates of wheat streak mosaic virus (WSMV) were examined. Single strand conformation polymorphism (SSCP) analysis of the P1 P3, NIa, and CP genes for 22 (Sidney 81 isolate) and 25 (Type isolate) limiting dilution sub-isolates (LDSIs) revealed genotypic differences among gLDSIs of the same isolate. Nucleotide sequencing indicated that each uniqu genotype identified by SSCP resulted from single nucleotide changes. Quasispecies variation within an isolate was low,estimated to be 0.38(Type) or 2.72 (Sidney 81) nts/genome. The low sequence diversity within both isolates implies a correspondingly low effective population size. Both the frequency patterns of all pairwise sequence differences and Tajima's D statistic values were consistent with the neutral infinite-site population model but were not consistent with a population history of a genetic bottleneck followed by exponential virus growth. A low effective populatio size seems inconsistent with the large number of virions produced during infection, but may be simply a consequence of plant tissue topology. Unlike lytic viruses, the vast majority of virions produced during infection by plant RNA viruses do not participate in further rounds of replication; instead they remain sequestered in the same cell in which they were assembled.Moreover, virus replication is further constrained by host growth rate after infection is fully systemic.At this point virus can only in- crease in newly developing cells and tissues.As a consequence,plant virus growth is predicted to be near-linear, rather than exponential. Notable, plant structure also causes virus populations to be highly subdivided,incre creasing chances that the most fit viral genomes dominate the population.