Immunohistochemical detection of the maize Ac protein in endosperm nuclei

--Manfred Heinlein

By using five antisera raised against different epitopes of the Ac-protein a signal has been obtained in endosperm nuclei of Ac-containing endosperm, which is absent in endosperm-nuclei devoid of Ac. The signal is not seen if various preimmune sera are taken as primary antibody. If an antibody is used which has been incubated with its specific antigen prior to its application the sensitivity of the detection is much reduced. The signal appears as large rod-like complexes, about 2�m long and 0.2�m wide. With decreasing Ac-dosage the complexes become less detectable. The visibility varies between endosperms containing different Ac-bearing alleles. In nuclei double-stained for DNA and Ac protein, the complexes in some cases appear to be perpendicularly oriented relative to DNA and thus support the assumption that the rod-like shape of the complexes might be due to binding of the protein to sites located side by side on different chromatids of endochromosomes within endopolyploid endosperm nuclei.

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