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Plant biologist Roger Innes and his team at Indiana University Bloomington wanted to understand how plant cells died. In the fall of 2012, they infected leaves of the model organism Arabidopsis thaliana with a bacterial pathogen. They then cut thin slices of infected leaves and put the sections under an electron microscope. The researchers were surprised when they repeatedly saw bunches of round structures in the space between the cell walls and interior plasma membranes. Unfamiliar with the tiny blobs, Innes showed images to colleagues, who pointed him to older studies, some going back to the 1960s, that described something similar in other plants: groups of small, membrane-wrapped spheres called vesicles encased in a larger membrane called a multivesicular body (MVB).1
Finding vesicles inside a plant cell wasn’t that unusual; plant and animal cells use vesicles for all sorts of things, such as ferrying molecules around ...
