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Rubén González defends his thesis on experimental evolution of plant viruses

  • November 9th, 2021
Rubén González - Santiago F. Elena
Rubén González - Santiago F. Elena

This doctoral thesis, supervised by Santiago F. Elena, presents an experimental approach to the evolution and adaptation of plant pathogenic viruses under diverse biotic and abiotic conditions that modulate such evolution. The results of this research have been published in the journals Genome Biology and Evolution, Virus Evolution, Advances in Virus Research and Proceedings of the National Academy of Sciences. The thesis was defended on November 9, 2021.

Experimental evolution allows us to test theoretical postulates and make observations that increase our knowledge about evolution. This thesis aims to study the evolution of viruses using experimental approaches. Viruses show a high capacity for evolution and are therefore good models to address evolutionary questions rather quickly. The processes underlying the evolution and adaptation of pathogens are governed by many factors: from the intrinsic nature of the virus to environmental components affecting the host, the pathogen and the interaction between the two. In this thesis, a pathosystem consisting of a plant and a potyvirus is used to explore how different biotic and abiotic factors modulate virus evolution. First, the biological effects of mutations in a potyvirus protein, an essential component of the replication complex, was explored. The evolutionary constraints operating on this protein were revealed, a consequence of an evolutionary trade-off between accumulation within the host and symptom severity. Second, the effects of host population genetic structure on virus evolution were examined: viruses in genetically homogeneous populations of plants with different susceptibilities to infection and in a heterogeneous population were evolved. This work illustrated how host genetic diversity in an ecosystem affects virus adaptation, as viruses specialized faster in homogeneous populations but were more pathogenic in heterogeneous populations. Finally, the impact of the environment on virus-plant interaction was studied. For this purpose, the possible beneficial effects of virus infection in certain environments hostile to the plant were first reviewed. Subsequently, the effect of drought, an environmental condition with an increasing incidence and known to affect host physiology, was studied. Thus, a virus evolved in hosts under drought or heavily irrigated conditions. Viruses adapted under drought conditions conferred increased drought tolerance to the host plant through specific alterations in host gene expression and hormone signaling. In summary, this thesis contributes to the further understanding of the evolutionary biology of plant RNA viruses.

Rubén González’s thesis was carried out in the Evolutionary Systems Virology research group at I2SysBio under the supervision of Santiago F. Elena (CSIC Research Professor). During the development of his thesis Rubén González has enjoyed a contract within the FPI Program (Ministry of Science and Innovation, FEDER) and an EMBO short-term and FISABIO fellowships during his stay at Prof. Marie-Anne Félix lab (Institut de Biologie de l'École Normale Supérieure, Paris). The examining board was formed by Esteban Domingo (CBMSO, CSIC-UAM), Vicente Pallás (IBMCP, CSIC-UPV) and Anna-Liisa Laine (Zürich University), who graded the thesis as outstanding.