The Pilgrims have allowed the 22-year-old Benin international defender to travel north for talks with the Hillsborough outfit.
Argyle, who are desperately looking to raise funds in order to pay a tax bill to HM Revenue and Customs, have already sold Craig Noone to league leaders Brighton for £300,000 in the January transfer window.
Now Marseille-born Johnson, who moved to Home Park in 2009 from Amiens, looks set to be the next player to leave the troubled Devon club.
The division's top scorer Bradley Wright-Phillips is also said to be close to leaving Argyle, with Bristol City a possible destination.
Zimbabwe left-back / midfielder Onismor Bhasera is another Pilgrim who has been linked with a transfer, although Crystal Palace - who were also said to be tracking Johnson - may have cooled their interest following the dismissal of manager George Burley on Saturday.