Simple, but Not Branched, Plasmodesmata Allow the Nonspecific Trafficking of Proteins in Developing Tobacco Leaves

• Published in: Cell 1999-06, Vol.97 (6), p.743-754
• Main Authors: Oparka, Karl J, Roberts, Alison G, Boevink, Petra, Cruz, Simon Santa, Roberts, Ian, Pradel, Katja S, Imlau, Astrid, Kotlizky, Guy, Sauer, Norbert, Epel, Bernard
• Format: Article
• Language: English
• Subjects: Biological Transport; Carbon - metabolism; Genetic Vectors - genetics; Green Fluorescent Proteins; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Nicotiana - metabolism; Nicotiana tabacum; Plant Leaves - metabolism; Plant Proteins - metabolism; Plant Viral Movement Proteins; Plants, Toxic; Potexvirus - genetics; RNA, Messenger - metabolism; RNA, Viral - metabolism; Viral Proteins - metabolism
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/S0092-8674(00)80786-2

Leaves undergo a sink–source transition during which a physiological change occurs from carbon import to export. In sink leaves, biolistic bombardment of plasmids encoding GFP-fusion proteins demonstrated that proteins with an M r up to 50 kDa could move freely through plasmodesmata. During the sink–source transition, the capacity to traffic proteins decreased substantially and was accompanied by a developmental switch from simple to branched forms of plasmodesmata. Inoculation of sink leaves with a movement protein-defective virus showed that virally expressed GFP, but not viral RNA, was capable of trafficking between sink cells during infection. Contrary to dogma that plasmodesmata have a size exclusion limit below 1 kDa, the data demonstrate that nonspecific “macromolecular trafficking” is a general feature of simple plasmodesmata in sink leaves.