Dynamic changes impact the plum pox virus population structure during leaf and bud development

Authors: TAMUKONG, YVETTE - University Of Maryland; Collum, Tamara - Tami; Stone, Andrew; KAPPAGANTU, MADHU - University Of Maryland; Sherman, Diana; Rogers, Elizabeth; Dardick, Christopher - Chris; CULVER, JAMES - University Of Maryland

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2020
Publication Date: 7/3/2020
Citation: Tamukong, Y.B., Collum, T.D., Stone, A.L., Kappagantu, M., Sherman, D.J., Rogers, E.E., Dardick, C.D., Culver, J.N. 2020. Dynamic changes impact the plum pox virus population structure during leaf and bud development. Virology. 548:192-199. https://doi.org/10.1016/j.virol.2020.06.014.
DOI: https://doi.org/10.1016/j.virol.2020.06.014

Interpretive Summary: Plum pox virus (PPV) infects a range of fruit trees including plum, peach, almonds, cherry and other stone fruits. The virus causes symptoms that include mottled misshapen leaves, low sugar content, increased acidity and premature fruit drop resulting in economic losses in the hundreds of millions of dollars. There are ten PPV strains that have been described that share 70 to 97 percent of their genetic material. New viral strains can emerge from combinations of existing strains or through an accumulation of small changes. This is an important but poorly understood aspect of viral evolution. In fact, virus strains exist as a population of closely related viral genomes that are continuously undergoing the process of genetic mutation, competition among the variants generated, and selection of the most fit variants for a particular environment. In fruit trees, viruses can persist and evolve over multiple growing seasons. This long time period provides an ideal environment for the mixing and development of new viral variants with potentially unique disease-causing abilities. In this study, a next generation sequencing approach was used to investigate how PPV populations change and genome variants arise over time and in different tissue types in plum trees. Results showed that more PPV genomic variants were found in buds and newly developing leaf tissues, where PPV levels were low. On the other hand, mature leaf tissue had high PPV levels but proportionately fewer genomic variants. This suggests that a large pool of PPV variants are maintained but only a few select variants become dominant in mature leaves. Results indicate PPV genomic variants are impacted by the tissue type and developmental stage of the fruit tree.

Technical Abstract: Plum pox virus (PPV) is a worldwide threat to stone fruit production. Its woody perennial hosts provide a dynamic environment for virus evolution over multiple growing seasons. To investigate the impact seasonal host development plays in PPV population structure, next generation sequencing of ribosome associated viral genomes, termed translatome, was used to assess PPV variants derived from phloem or whole leaf tissues over a range of plum leaf and bud developmental stages. Results show that translatome PPV variants occur at proportionately higher levels in bud and newly developing leaf tissues that have low infection levels while more mature tissues with high infection levels display proportionately lower numbers of viral variants. Additional variant analysis identified distinct groups based on population frequency as well as sets of phloem and whole tissue specific variants. Combined, these results indicate PPV population dynamics are impacted by the tissue type and developmental stage of their host.