2009. Regulation of aleurone cell fate determinants in Zea mays

2009. Regulation of aleurone cell fate determinants in Zea mays

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INTRODUCTION

 
Human nutrition is provided by a limited number of plant species. About 90% of mankind’s food supply is derived from approximately 17 species, of which cereal grains supply the greatest percentage. Wheat, maize and rice together comprise at least 75% of the world’s grain production (Cordain 1999) The primary nutritious part of the cereal grain is the seed endosperm. Despite detailed knowledge of events that occur in angiosperm fertilization and endosperm formation, very little is known about the regulatory networks controlling the complex developmental and metabolic processes of cereal grain formation.

In cereal plants, double fertilization initiates the process of seed formation, in which one sperm nucleus fertilizes the egg cell in the embryo sac resulting in a diploid zygote, a second sperm nucleus fuses with two polar nuclei of the central cell to initiate the development of the triploid endosperm (Dumas and Mogensen 1993). The diploid zygote and the primary triploid nucleus enter separate developmental patterns to give rise to the embryo and the nutritive endosperm. The pathway leading to the formation of the endosperm from the triploid nucleus is a four stage process. (1) syncytial stage, where the primary triploid nucleus in the central cell undergoes a period of mitotic nuclear divisions without cytokinesis resulting in a large syncytium; (2) cellularization, a period during which cytokinesis separates the nuclei into discrete cells involving both anticlinal and periclinal divisions; (3) growth and differentiation, which results in distinct tissues namely starchy endosperm, basal transfer layer and aleurone and (4) maturation, an important process characterized by accumulation of storage reserves and the development of desiccation tolerance and dormancy (Becraft 2001, Olsen 2001)  .