Cell fate specification in the cereal endosperm

While superficially simple, endosperm development is a complex, dynamic pro cess. Cereal endosperms contain three major cell types: starchy endosperm, transfer cells and aleurone. The localized accumulation of the END1 transcr ipt in the syncitial endosperm suggests that signals from the maternal plac ental tissue specify transfer cell type early. Aleurone fate is plastic and requires the continual input of positional cues to maintain cell identity. Starchy endosperm appears to be the default cell type. Mutant patterns sug gest that a regulatory hierarchy integrates endosperm development. requirem ents for gametic imprinting, maternal: paternal genome ratios and putative chromatin modeling factors indicate the importance of genomic control.