Biomedical subjects

Soledad Sacristán

Publications and source records attributed to Soledad Sacristán.

3 recordsLinked to original sources

PubMed2006

Association and host selectivity in multi-host pathogens.

The distribution of multi-host pathogens over their host range conditions their population dynamics and structure. Also, host co-infection by different pathogens may have important consequences for the evolution of hosts and pathogens, and host-pathogen co-evolution. Hence it is of interest to know if the distribution of pathogens over their host range is random, or if there are associations between hosts and pathogens, or between pathogens sharing a host. To analyse these issues we propose indices for the observed patterns of host infection by pathogens, and for the observed patterns of co-infection, and tests to analyse if these patterns conform to randomness or reflect associations. Applying these tests to the prevalence of five plant viruses on 21 wild plant species evidenced host-virus associations: most hosts and viruses were selective for viruses and hosts, respectively. Interestingly, the more host-selective viruses were the more prevalent ones, suggesting that host specialisation is a successful strategy for multi-host pathogens. Analyses also showed that viruses tended to associate positively in co-infected hosts. The developed indices and tests provide the tools to analyse how strong and common are these associations among different groups of pathogens, which will help to understand and model the population biology of multi-host pathogens.

Ecosystem↗

PubMed2005

Role of recombination in the evolution of natural populations of Cucumber mosaic virus, a tripartite RNA plant virus.

The role of recombination in the evolution of Cucumber mosaic virus (CMV) was analyzed in a collection of Spanish isolates from 1989 to 2002. Isolates were characterized by ribonuclease protection assay using six RNA probes, two for each of the three genomic RNAs, which allowed the identification of the analyzed regions as belonging to CMV isolates in subgroups IA, IB, and II. Most isolates belonged to subgroups IA (64%) and IB (12%), 5% were reassortants among subgroups IA, IB, or II, and 17% were recombinants between these groups. Recombinants at RNA3 were significantly more frequent than recombinants at RNAs 1 and 2. One IB-IA recombinant RNA3 was as frequent in central Spain as the IA RNA3. The genetic structure of the virus population suggested that reassortants and most recombinant genotypes were selected against and was consistent with a higher biological cost of reassortment than recombination. Data also suggest that recombinants that encode hybrid proteins are at a higher disadvantage than recombinants that exchange whole ORFs.

Cucumovirus↗

PubMed2003

Estimation of population bottlenecks during systemic movement of tobacco mosaic virus in tobacco plants.

More often than not, analyses of virus evolution have considered that virus populations are so large that evolution can be explained by purely deterministic models. However, virus populations could have much smaller effective numbers than the huge reported census numbers, and random genetic drift could be important in virus evolution. A reason for this would be population bottlenecks during the virus life cycle. Here we report a quantitative estimate of population bottlenecks during the systemic colonization of tobacco leaves by Tobacco mosaic virus (TMV). Our analysis is based on the experimental estimation of the frequency of different genotypes of TMV in the inoculated leaf, and in systemically infected leaves, of tobacco plants coinoculated with two TMV genotypes. A simple model, based on the probability that a leaf in coinoculated plants is infected by just one genotype and on the frequency of each genotype in the source, was used to estimate the effective number of founders for the populations in each leaf. Results from the analysis of three leaves per plant in plants inoculated with different combinations of three TMV genotypes yielded highly consistent estimates. Founder numbers for each leaf were small, in the order of units. This would result in effective population numbers much smaller than the census numbers and indicates that random effects due to genetic drift should be considered for understanding virus evolution within an infected plant.

Genotype↗