THE PLANT CELL, Vol 3, Issue 4 407-417, Copyright © 1991 by American Society of Plant Biologists
Maize Mesocotyl Plasmodesmata Proteins Cross-React with Connexin Gap Junction Protein Antibodies
A. Yahalom, R. D. Warmbrodt, D. W. Laird, O. Traub, J. P. Revel, K. Willecke and B. L. Epel
Botany Department, George S. Wise Faculty of Life Science, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
Polypeptides present in various cell fractions obtained from homogenized
maize mesocotyls were separated by sodium dodecyl sulfate-polyacrylamide
gel electrophoresis, immunoblotted, and screened for cross-reactivity with
antibodies against three synthetic polypeptides spanning different regions
of the rat heart gap junctional protein connexin43 and the whole mouse
liver gap junctional protein connexin32. An antibody raised against a
cytoplasmic loop region of connexin43 cross-reacted strongly with a cell
wall-associated polypeptide (possibly a doublet) of 26 kilodaltons.
Indirect immunogold labeling of thin sections of mesocotyl tissue with this
antibody labeled the plasmodesmata of cortical cells along the entire
length of the plasmodesmata, including the neck region and the cytoplasmic
annulus. Sections labeled with control preimmune serum were essentially
free of colloidal gold. An antibody against connexin32 cross-reacted with a
27-kilodalton polypeptide that was present in the cell wall and membrane
fractions. Indirect immunogold labeling of thin sections with this antibody
labeled the plasmodesmata mainly in the neck region. It is suggested that
maize mesocotyl plasmodesmata contain at least two different proteins that
have homologous domains with connexin proteins.