Immunolocalization indicates plasmodesmal trafficking of storage proteins during cambial reactivation in Populus nigra.
OBJECTIVE
Cambium reactivation after dormancy and budbreak in deciduous trees requires a supply of mobilized reserve materials. The pathway and mode of transfer of these materials are poorly understood.


METHODS
Transport of reserve materials during cambium reactivation in Populus nigra was investigated by conventional and immunocytochemical TEM analyses, SDS-PAGE, western blotting and intracellular microinjection of fluorescent dyes.


RESULTS
Proteinaceous compounds stored in vacuoles and protein bodies of vascular cells and ray cells disappeared within 3 weeks after cambial reactivation and budbreak. Some of these proteins (32 kDa, 30 kDa and 15 kDa) were labelled by lectin antibodies in SDS-PAGE. The same antibodies were localized to plasmodesmata (PDs) between phloem parenchyma, ray cells and fusiform cambial cells. In addition, proteinaceous particles were localized inside the cytoplasmic sleeves of these PDs during budbreak. During this period, the functional diameter of PDs was about 2.2 nm which corresponds approximately to the Stokes' radius of the detected 15-kDa protein.


CONCLUSIONS
Lectin-like reserve proteins or their degradation products seem to be transferred through PDs of phloem parenchyma and rays during cambial reactivation and budbreak. PD transfer of storage proteins is a novelty which supports the concept of symplasmic nutrient supply to the cambial region.
Fuchs
Maike
M
Institute of General Botany, Justus-Liebig-University, Senckenbergstrasse 17, Giessen, Germany.
Ehlers
Katrin
K
Will
Torsten
T
van Bel
Aart J E
AJ
D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D005456:Fluorescent Dyes; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D032107:Populus / Q000502:physiology*; D021381:Protein Transport; D055314:Seed Storage Proteins / Q000378:metabolism*
D005456:Fluorescent Dyes; D055314:Seed Storage Proteins