Expressions of human p53 and c-myc gene homologues during caryopsis development in maize.

Tumor suppressor gene p53 and proto-oncogene c-myc have been proved to be highly conserved and participate in many PCD processes in animals. In maize, proteins and RNAs related to p53 and c-myc have already been reported and the sequences homologous to these two genes have also been localized onto maize chromosomes by FISH. In this study, using immunohistochemistry we investigated the expression patterns of maize genes homologous to human p53 and c-myc during caryopsis development stages in maize. In a giving stage after pollination, p53 homologue showed high levels in the antipodal cells, integument, immature endosperm, ovary wall, tracheary elements, and aleurone layer, while c-myc homologue showed low levels in these tissues, only before pollination showed high expression in polar nucleus. The results of TUNEL assay demonstrated that TUNEL positive signals were detected where p53 homologue showed high expression levels. In animal cells, p53 shows reverse function with that of c-myc, so does it in maize basically. These results demonstrated that p53 and c-myc homologues might play some important roles in PCD during caryopsis development in maize. There may be conserved mechanisms for PCD in animals and in high plants.