Viruses from Within: The Risk of Viral Emergence in Zingiberales

Banana Streak Virus (BSV) is an emerging virus that has devastated banana (Musa, Musaceae: Zingiberales) crop production on a global scale. It has been shown to come from within the Musa genome itself as an endogenized viral element. Interspecific hybridization followed by tissue culture stress triggers this endogenous pararetroviral element (EPRV) to become an infectious virus that can in turn be transmitted to other hosts. EPRVs are not specific to bananas, and some lead to viral emergence in other crops such as tobacco, yams, and pineapples. Assessing the risk that an EPRV will become pathogenic is critical to prevention and control of these devastating viral outbreaks. To study the risk of emergence, banana and its wild relatives will be used as a test case to identify genomic, epigenomic, and biogeographical patterns of emergence using a phylogenetic framework.

First, EPRV sequences will be acquired via exon-capture, and a phylogenetic hypothesis of these EPRVs will be generated to determine the relationships between EPRVs and exogenous viral infections. With the incorporation of biogeographical data, this will provide evidence of which EPRVs have a history of emerging, and provide evidence for the extent of their potential host and geographic range. Finally, genomic patterns of small RNA-directed gene silencing will be correlated with viral emergence through the comparison of small RNA libraries (siRNA-Seq) from species with and without emergent EPRVs. In this way, the Zingiberales will serve as a model for the risk assessment of endogenous viral emergence and spread among wild and cultivated populations.