PubMed · 2026-04-21
Researchers compared the genetic blueprints of plant umbraviruses and related umbra-like viruses, discovering that the protective protein shells (capsids) found in some of these viruses most likely evolved from proteins that originally served a completely different job: helping the virus move between plant cells.
Umbraviruses encode two distinct movement proteins but no capsid protein, making them dependent on helper viruses for insect-mediated transmission to new host plants.
Group 2 umbra-like viruses evolved functional capsid-like proteins that free them from helper-virus dependency, likely enabling independent vector acquisition.
Structural and phylogenetic analyses indicate these capsid-like proteins descended from 30K-type movement proteins, representing a repurposing of cell-to-cell movement machinery into an encapsidation role.
