When some virus- and disease-free Musa spp. (banana and plantain) are propagated by tissue culture, the resulting plants develop infections with banana streak badnavirus (BSV), a pararetrovirus. In sharp contrast to the virion DNA recovered from natural infections, the virion DNA from tissue culture-associated infections of different Musa spp. was highly similar if not identical. Although BSV does not employ integration during the infection cycle, BSV DNA was found to be integrated into the Musa genome. While one integration consisted of a partial BSV genome, a second contained more than one complete genome that was almost identical to BSV recovered from tissue culture-derived plants. The arrangement of this integrated BSV DNA suggests that it can yield an infectious episomal genome via homologous recombination. This report documents the first instance of integrated DNA of a nonintegrating virus giving rise to an episomal viral infection and identifies tissue culture as a possible trigger for the infection, raising the question of whether similar activatable viral sequences exist in the genomes of other plants and animals.
Bibliographical noteFunding Information:
This work was supported in part by a grant from the International Network for Improvement of Banana and Plantain (INIBAP) to B.L. and by USAID program in Science and Technology Cooperation Grant 5600-G-00-2017-0 to N.E.O. and B.L. We thank the INIBAP Musa Transit Centre, Leuven, Belgium, and the International Institute of Tropical Agriculture, Ibadan, Nigeria, for supplying tissue culture plantlets and leaf samples used in this study.