MATERNAL-SPECIFIC DEMETHYLATION AND EXPRESSION OF SPECIFIC ALLELES OFZEIN GENES IN THE ENDOSPERM OF ZEA-MAYS L

Zeins constitute 60-70% of maize endosperm protein. Zein genes are spe cifically transcribed in the endosperm, and a correlation has been est ablished between tissue-specific expression and demethylation. Three i nbred lines and their reciprocal crosses were analysed to assess for a llele-specific differences in methylation, transcription and translati on. DNAs from endosperm, embryo and seedling tissues analysed by cleav age with methylation sensitive restriction enzymes and Southern blot h ybridization with zein cDNA and genomic sequences show that specific d emethylation of zein sequences occurs only in endosperm and is restric ted to the maternal complements. Steady-state transcript accumulation of zein mRNA assessed by RNase protection assay reveals qualitative an d quantitative differences among endosperm RNAs of the inbreds and of their reciprocal hybrids. Moreover, two dimensional gel electrophoresi s of zein proteins identified polypeptides that are maternally imprint ed in reciprocal crosses. These results indicate that endosperm-specif ic expression of specific zein alleles may occur via parental imprinti ng and disclose a possible role of methylation in regulating the expre ssion of genes differently contributed in the endosperm by the materna l and paternal genomes.