Deane, 25, is linking up with John for a third time, having previously played under him at his home-town Oldham Athletic, and arrives at Home Park from fellow Sky Bet League 2 side Oxford United.
He scored nine goals in 25 starts for the Us last season but will best (worst?) be remembered by the Green Army for notching twice against the Pilgrims to give Oxford a 2-1 win at the Kassam Stadium in August 2012.
Deane comes to the Pilgrims on a two-year deal, joining Lee Cox - like Luke McCormick, a former Oxford team-mate - as a summer recruit.
Welcome to Home Park, Deane.