Group leader: Fernando García-Arenal Rodríguez - Professor
fernando.garciaarenal@upm.es 
+34 91 336 4548 / +34 91 452 4900 ext.1812 (Labs 227,229)
Personnel:
- Ahangaran, Akbar - Visiting Scientist
- Donaire Segarra, Livia - Postdoctoral Fellow
- Fraile Pérez, Aurora - Associate Professor
- Hily, Jean Michel - Marie Curie fellow
- López Quirós, Antolín - Technician
- Montes Casado, Nuria - PhD Student
- Mora Plaza, Miguel Ángel - Technician
- Moreno Pérez, Manuel Guillermo - PhD Student
- Pagán Muñoz, Jesús Israel - Marie Curie fellow
- Poulicard, Nils - Postdoctoral Fellow
- Rodelo Urrego, Manuel Alfredo - PhD Student
| The long term research of the group focuses on understanding the emergence of new viral diseases. Plant viral diseases have a high socio-economic impact, as they affect crop and forest productivity as well as ecosystem composition and dynamics. The highest impact of diseases in host populations is often caused by emerging diseases, defined as those whose incidence in a host population is increasing as a result of long-term changes in their underlying epidemiology. Major factors favouring disease emergence are genetic change in pathogen and host populations, and changes in host ecology and environment. Hence, the research interests of the group are organised around plant virus evolution and plant-virus co-evolution. |
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| Our interest in plant virus evolution focuses on quantitative and population genetics, rather than on historical, aspects. Over the years we have made relevant contributions on the characterisation of the genetic variability of plant viruses, on the analysis of the genetic structure of their populations and of the factors that shape it, on the mechanisms that generate genetic variability in RNA viruses, and on the processes that constrain genetic variation. Our more recent interest is on the estimation of parameters required for modelling the within-host and between host dynamics and genetics of virus populations, such as population bottlenecks during cell-to-cell movement, systemic colonisation, or between-host transmission by different procedures. |
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Viruses may damage their hosts if they are virulent parasites, and another major interest of the group is on virulence evolution. Within this area our research aims to understand the relationship between virulence and factors of the virus life-cycle such as the within-host rates of multiplication, between-host rates of transmission, or survival during non-infectious stages. We are also interested in the relationship between virulence evolution and adaptation to different host species or genotypes, or between virulence evolution and host ecology, such as host population demography or genetic structure. Hosts respond to virulent parasites with different defence mechanisms. Although for plant parasites research has mostly focused on dominant monogenic resistance expressed as hypersensitivity, we are more interested in quantitative resistance and on tolerance, which our data suggest could be more relevant in plant-virus co-evolution. A major part of our future research efforts will be directed at understanding the mechanisms of tolerance to viruses associated to modification of the host life-history traits. The questions above are approached using different host-virus pathosystems, including both crops and wild plants in natural ecosystems. A major thrust is on developing Arabidopsis thaliana as a model plant for the study of plant-virus co-evolution, both in its ecological an in its mechanistic aspects, because of the obvious advantages of this species for populational and molecular studies in plant biology. Research on other areas of host-pathogen interactions are also being developed in the group. Thus, Dr. Soledad Sacristán is leading a project aimed at characterising the endophytic mycobiota of wild A. thaliana populations in Central Spain, and at understanding the similarities and differences between endophytic and pathogenic life-styles of plant-associated fungi. Dr. María-Ángeles Ayllón is also leading a new project aimed at studying mycoviruses and their impact on the pathogenicity of plant pathogenic fungi. Relevant resultsResearch on virus evolution has focussed on constraints to genetic variation. Genetic exchange by recombination or by re-assortment of genomic segments, is a major mechanisms generating genetic variation in viruses. However, our analyses of the genetic structure of populations of different viruses showed a low fraction of recombinant genotypes, suggesting constraints to genetic exchange. We analysed this subject experimentally co-inoculating different strains of Cucumber mosaic virus (CMV), a virus with a tripartite, ssRNA genome, into tobacco plants, and analysed the genetic composition of the resulting virus population at different stages of host colonisation. Results showed selection against recombinant and re-assortant genotypes and indicated epistatic interactions compatible with co-adaptation of co-evolved genes within a genome (Escriu et al. 2007). |
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| Another factor limiting genetic variation would be small population numbers. The census numbers of within-hosts virus population are huge, but effective numbers might be much smaller if severe population bottlenecks would occur within the virus life cycle. We estimated the size of the population bottleneck during aphid transmission of CMV, based on a model of allele segregation between generations, and found very small effective numbers for the founder population of a new infection, in the order of 1 to few units (Betancourt et al. 2008). These results show that selection may not be the major force in plant virus evolution and stress the relevance of considering random genetic drift. Last, we estimated the efficiency of complementation of deleterious mutants in populations of Tobacco mosaic virus (TMV) by quantifying the fraction of mutants lethal for cell-to-cell movement in wild-type plants and in transgenic plants complementing the function. Complementation was highly efficient (~30%) indicating, again, the relevance of forces that will counter selection in plant virus evolution (Fraile et al. 2008). |
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On the plant-virus co-evolution side the most relevant results pertain to the analysis of the interaction of viruses with A. thaliana. Filed surveys of six wild populations of A. thaliana in central Spain during four years showed that CMV was the most prevalent virus (unpublished). Thus, the interaction of 21 wild genotypes of this plant species with three CMV genotypes was analysed. Virulence depended on the host and pathogen genotypes involved, and on the time of infection relative to developmental stage. Virus fitness, estimated as multiplication rate, was uncorrelated with virulence, estimated as effect of infection on the production of viable seeds, contrary to theoretical predictions. This result was explained by genotype-specific tolerance to virus infection (Pagán et al., 2007). Tolerance was related to plant architecture, and analyses of resource allocation and of temporal developmental schedule showed that tolerant genotypes were able to modify their life-history traits upon infection, allocating a larger fraction of resources to reproduction than to vegetative growth, thus reducing its impact (Pagán et al. 2008). These results set the stage for the analysis f the genetic determinants of tolerance and the mechanisms involved in this defence reaction. |
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Recent PublicationsGibbs, A.J.; Fargette, D.; Garcia-Arenal, F.; Gibbs, M.J. 2010. "Time - the emerging dimension of plant virus studies". Journal of General Virology. 91:13-22 Pagan, I.; Betancourt, M.; de Miguel, J.; Pinero, D.; Fraile, A.; Garcia-Arenal, F. 2010. "Genomic and biological characterization of chiltepin yellow mosaic virus, a new tymovirus infecting Capsicum annuum var. aviculare in Mexico". Archives of Virology. 155(5):675-684 Pagan, I.; Fraile, A.; Fernandez-Fueyo, E.; Montes, N.; Alonso-Blanco, C.; Garcia-Arenal, F. 2010. "Arabidopsis thaliana as a model for the study of plant-virus co-evolution". Philosophical Transactions of the Royal Society B-Biological Sciences. 365(1548):1983-1995 Cubero, J.; Ayllon, M.A.; Gell, I.; Melgarejo, P.; de Cal, A.; Martin-Sanchez, P.M.; Perez-Jimenez, R.M.; Soria, C.; Segundo, E.; Larena, I. 2009. "Detection of strawberry pathogens by real-time PCR". Acta Horticulturae. 842:263-266 Gonzalez-Jara, P.; Fraile, A.; Canto, T.; Garcia-Arenal, F. 2009. "The Multiplicity of Infection of a Plant Virus Varies during Colonization of Its Eukaryotic Host". Journal of virology. 83:(15)7487-7494 Gonzalez-Vazquez, M.; Ayala, J.; Garcia-Arenal, F.; Fraile, A. 2009. "Occurrence of Beet black scorch virus Infecting Sugar Beet in Europe". Plant Disease. 93:(1)21-24 Pagan, I.; Alonso-Blanco, C.; Garcia-Arenal, F. 2009. "Differential tolerance to direct and indirect density-dependent costs of viral infection in Arabidopsis thaliana". PLoS pathogens. 5:(7)e1000531 Sacristan, S.; Vigouroux, M.; Pedersen, C.; Skamnioti, P.; Thordal-Christensen, H.; Micali, C.; Brown, J.K.M.; Ridout, C.J. 2009. "Coevolution between a Family of Parasite Virulence Effectors and a Class of LINE-1 Retrotransposons". Plos One. 4:(10)e7463 Betancourt, M.; Fereres, A.; Fraile, A.; Garcia-Arenal, F. 2008. "Estimation of the Effective Number of Founders That Initiate an Infection after Aphid Transmission of a Multipartite Plant Virus". Journal of virology. 82(24):12416-12421 Fraile, A.; Sacristan, S.; Garcia-Arenal, F. 2008. "A quantitative analysis of complementation of deleterious mutants in plant virus populations". Spanish Journal of Agricultural Research. 6:195-200 Pagan, I.; Alonso-Blanco, C.; Garcia-Arenal, F. 2008. "Host responses in life-history traits and tolerance to virus infection in Arabidopsis thaliana". Plos Pathogens. 4(8)e1000124 Sacristan, S.; Garcia-Arenal, F. 2008. "The evolution of virulence and pathogenicity in plant pathogen populations". Molecular Plant Pathology. 9(3):369-384 Escriu, F.; Fraile, A.; Garcia-Arenal, F. 2007. "Constraints to genetic exchange support gene coadaptation in a tripartite RNA virus". Plos Pathogens. 3(1):67-74 Pagan, I.; Alonso-Blanco, C.; Garcia-Arenal, F. 2007. "The Relationship of Within-Host Multiplication and Virulence in a Plant-Virus System". Plos One. 2(8)786 |
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Centro de Biotecnología y Genómica de Plantas U.P.M. – I.N.I.A. Parque Científico y Tecnológico de la U.P.M. Campus de Montegancedo
28223 Pozuelo de Alarcón (Madrid) Tel.: +34 91 4524900 ext. 1806 / +34 91 3364539 Fax: +34 91 7157721. Contacto