Spectrin-like protein has been found in a variety of plant cells. In this study, electron microscopic observation of immuno-gold labelled preparations from the leaf petiole of cucumber ( Cucumis sativus L.) shows that it also exists in the sieve element-companion cell (SE-CC) complex, being widely distributed in P-protein filaments and sieve element reticulum (SER), in the cytoplasm and mitochondrial membrane of companion cell (CC) and in the branched plasmodesmata between sieve element (SE) and CC as well. The results suggest that this protein could be synthesized in CC and transferred to SE through plasmodesmata. Western blotting showed that spectrin-like protein existed in the protein of phloem exudate of cucumber, and its molecular weight was about 260 kD.
