45 kDa protein isolated from the nodal walls of Chara corallina is localised to plasmodesmata

The cellular anatomy of the green alga, Chara corallina, was exploited to isolate putative plasmodesmata-associated proteins. In C. corallina, large internodal cells are symplastically connected via intervening nodal complexes of smaller cells which have plasmodesmata in their cell walls. Comparison of proteins extracted from walls with plasmodesmata (nodal complexes) with those from walls without plasmodesmata (external internodal walls) identified four putative plasmodesmata-associated proteins. These putative plasmodesmata-associated proteins were approximately 95, 45, 44 and 33 kDa. A monoclonal antibody (MAB45/22) was raised against the 45 kDa putative plasmodesmata-associated protein (CPAP45). Using immunofluorescence, this antibody colocalised with aniline blue induced fluorescence of callose in the source cell walls. MAB45/22 was localised to the plasmodesmata of C. corallina and, in particular, to the central cavity using immunogold cytochemistry. In contrast, a monoclonal antibody to callose specifically labelled the mouth of C. corallina plasmodesmata. MAB45/22 also labelled higher plant plasmodesmata.