Localization of a centrin-like protein to higher plant plasmodesmata

Antibodies against centrin, the ubiquitous calcium-binding contractile prot ein, recognized a 17 kDa protein in extracts of onion root tips and caulifl ower florets, Using immunofluorescence microscopy, anti-centrin antibodies were localized to the developing cell plate of onion and cauliflower root t ip cells, In cauliflower florets, these antibodies localized to the walls i n a punctate manner, consistent with the distribution of plasmodesmata as s hown by colocalization with callose, Anti-centrin antibodies were localized to plasmodesmata of onion root tips and cauliflower florets with immunogol d electron microscopy, Furthermore, this label was concentrated around the necks of plasmodesmata. In contrast, an antibody against calmodulin, which is a closely related calcium-binding protein, did not label plasmodesmata. We propose that centrin is a component of calcium-sensitive contractile nan ofilaments in the neck region of plasmodesmata and facilitates the calcium- induced regulation of intercellular transport.