On the evolution of genome segmentation in plant RNA viruses

Genome segmentation, the division of the hereditary material into multiple physical units, is widespread across all domains of life. Although many viruses also have segmented genomes, some viruses go a step further and package each segment into a different virus particle. The separate packaging of each genome segment imposes a massive cost, because all virus genome segments must enter the same host to cause infection. The benefits of so-called multipartition are poorly understood, and it is therefore a mystery how multipartite viruses can thrive. Recent work has shown that frequency of the different types of viral particles can change over time, and that it converges on an equilibrium. The virus particles containing different genome segments are then present at different frequencies, and some observations suggest these changes might be adaptive. Moreover, this equilibrium is different for alternative host species, suggesting that multipartition might also have evolved to regulate gene expression in different environments. Here, we will test the hypothesis that multipartition has evolved to regulate gene expression in a robust yet flexible manner, using a interdisciplinary approach including mathematical modeling, laboratory experiments and ecological fieldwork. Models will be used to predict the robustness and the existence of multiple genome segment frequency equilibria. Experimental evolution will be used to test whether the genome segment frequency equilibrium changes under different environmental conditions. Finally, fieldwork will be performed to measure genome segment frequencies in the natural virus populations.