Positional cues specify and maintain aleurone cell fate in maize endospermdevelopment

A genetic analysis of maize aleurone development was conducted. Cell lineag e was examined by simultaneously marking cells with C1 for anthocyanin pigm entation in the aleurone and wx1 for amylose synthesis in the starchy endos perm. The aleurone and starchy endosperm share a common lineage throughout development indicating that positional cues specify aleurone fate. Mutants in dek1 block aleurone formation at an early stage and cause peripheral end osperm cells to develop as starchy endosperm. Revertant sectors of a transp oson-induced dek1 allele showed that peripheral endosperm cells remain comp etent to differentiate as aleurone cells until late in development. Ds-indu ced chromosome breakage was used to generate Dek1 loss-of-function sectors. Events occurring until late development caused aleurone cells to switch fa te to starchy endosperm indicating that cell fate is not fixed. Thus, posit ional cues are required to specify and maintain aleurone fate and Dek1 func tion is required to respond to these cues. An analysis of additional mutant s that disrupt aleurone differentiation suggests a hierarchy of gene functi ons to specify aleurone cell fate and then control aleurone differentiation . These mutants disrupt aleurone differentiation in reproducible patterns s uggesting a relationship to endosperm pattern formation.