Immunodetection of spectrin antigens in plant cells

AbstractThe occurrence of spectrin in plant cells was studied by immunoblotting of extracts, and its localization by immunolabelling of cells, using two polyclonal antibodies raised against spectrin from human and chicken erythrocytes. A variety of plant cells were studied. The two antibodies gave the same results on blots as well as on cells. Western blots of extracts showed weak immunolabelling at 220 kD, where spectrin can be expected, but bands at 85 kD stained more heavily. Because the latter bands were also seen on blots with commercially purified spectrin, we conclude that they were breakdown products of spectrin. Native plant extracts on blots from IEF gels showed a band at pI 4.8, where the purified animal spectrin is also found. Immunolocalizations done on whole cells, PEG‐, BMM‐, or cryo‐sections gave similar data. In most cells the labelling was localized predominantly at the plasma membrane, especially of thin‐walled cells. Labelling was also seen in the periphery of a particular class of organelles, probably plastids. This labelling was tissue specific in maize somatic embryos. During carrot somatic embryogenesis cytoplasmic labelling was observed depending on the developmental stage. Many cells with cytoplasmic labelling also had stained nuclei. Labelled nuclei had more condensed chromatin than non‐labelled nuclei.