Pollen as the next viral frontier: Unrecognized threat to food security and native biodiversity

Abstract

Plant viral pathogens represent serious threats to food security and native biodiversity. The globalization of flora and co-invasion of pathogens and hosts amplifies the potential for emergence of novel viruses and host switching. Tradition wisdom maintains that viruses are transferred by plant-eating insects, but some viruses can exploit the plant’s own reproductive process for transmission, i.e., they hijack the pollen grains and are transported from one plant to another by pollinators. Yet our knowledge of pollenassociated viral taxa is limited to a handful of known viruses infecting a small set of symptomatic agricultural plants, leaving us entirely blind to potential diversity that exists within asymptomatic hosts, wild native or naturalized alien plant species, and hidden amongst world of undescribed viruses. Thus, we propose innovative curiosity-driven collaborative research that will use deep genome sequencing to broadly characterize viruses associated with pollen from the perspective of both micro-physical structure of pollen and the ecological and evolutionary context of the host plants. In doing so we will transform our understanding of how viral hijacking of pollen occurs, and determine whether pollen’s viral diversity is related to its novel pollinator-mediated mode of transmission or its host’s nativity or defense of the pollen. We suggest that greater consideration of this mode of transmission can resolve patterns of pathogen spread that defy explanation by entirely canonical vectors, forecast emergent plant diseases, and provide fundamental insight into viruses that occupy specialized niches. The proposed research will thus open exciting new research opportunities in pathogenesis and biodiversity research.

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