The Origins and Evolution of the RNA Virome in Land Flora

The colonization of land by plants was a major transition in the history of life, fundamentally reshaping the evolution of terrestrial organisms and Earth's ecosystems. Plants are hosts to an enormous diversity of viruses, but the origins and evolution of these viruses are not thoroughly understood. We mined the transcriptomes and genomes of 2,402 species sampled across the plant kingdom and discovered about 35,000 plant-associated RNA viruses, including several potential families not described previously, resulting in a 2.2-fold increase in the known plant-associated RNA virus diversity, greatly expanding the virus host ranges, and revealing many groups of atypical, apparently persistent viruses. Phylogenetic analysis shows that plant viruses emerged on numerous independent occasions, mostly, via horizontal virus transfer facilitated by close ecological associations of plants with other terrestrial organisms, such as invertebrates and fungi.