The objective of the project is to understand the basis for maturation phase initiation during maize endosperm development when starch and protein accumulation occurs. The initiation of this process follows a marked change in the endosperm auxin/cytokinin ratio leading to endoreduplication of the central endosperm cells. Correct development of the endosperm and storage product accumulation is dependent on endoreduplication. We have recently isolated a maize kernel mutant (K10) characterised by smaller than normal seed size, reduced storage protein accumulation and failure of the endosperm cells to endoreduplicate. We intend to determine if this phenotype is linked to changes in auxin/cytokinin levels or their perception. We will also examine the levels of cell cycle markers in this mutant, some of which we will obtain by interaction cloning. Understanding the link between phytohormones, endoreduplication and storage product synthesis could provide the means to improve yield in maize and other cereals.