Pandemic on the move: an emerging tobamovirus reveals a crossroad between viral movement and plant immunity

Abstract

Global pandemics severely threaten humanity: while human pandemics impact global health, crop pandemics pose a severe threat on food security. Determining the molecular mechanisms underlying pandemic emergence is critical for their prediction and mitigation. A new virus species of the Tobamovirus genus, tomato brown rugose fruit virus (ToBRFV) is currently causing a global pandemic detrimental to tomato crops worldwide. The key cause of this pandemic is that ToBRFV overcame the durable Tm-22 resistance gene, which had been effective against other viruses of the Tobamovirus genus for over 60 years. Tm-22 encodes a plant immune receptor that recognizes the tobamovirus movement protein (MP), a viral protein required for intercellular movement. We have recently found that ToBRFV MP enabled the virus to overcome Tm-22-mediated resistance. Yet, it was unknown how Tm-22 remained durable against other tobamoviruses (e.g. TMV and ToMV) for such a long period. We show that a single cysteine amino acid in the MP (C68) is both essential for intercellular movement of the virus and its recognition by the plant immune system to induce resistance. Cell-to-cell and systemic movement analysis combined with phylogenetic and structural prediction analysis revealed that C68 is conserved among all Solanaceae-infecting tobamoviruses, except ToBRFV, and required for viral movement by determining the MP subcellular localization. Currently, we are harnessing this system to uncover novel regulators of viral movement, and develop new ways to cope with this virus using directed evolution. Together, these results reveal how effective immunity against viruses targets processes essential for viral infection.

References

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