CHAPTER 9 - Hormonal and Stress Regulation of Gene Expression in Cereal Aleurone Layers

Abstract

This chapter discusses hormonal and stress regulation of gene expression in cereal aleurone layers. The aleurone layers of barley and wheat seeds play a crucial role in the mobilization of endosperm nutrients to support the post-germination seedling growth. This tissue is usually one to three cell layers-thick and lies directly underneath the seed coat and forms the outermost layers of endosperm. Like the rest of endosperm, aleurone cells are triploid, with one set of chromosomes from the male parent and two sets from the female parent. After the onset of germination, the aleurone layers respond to the hormone gibberellins (GA) from the embryo by synthesizing and secreting several hydrolytic enzymes—including α-amylases, proteases, l,3; l,4-β-glucanase, xylanase, and nuclease —to the endosperm, where these enzymes hydrolyze the stored starch, proteins, cell wall polysaccharides, and remnant nucleic acids. Another hormone, abscisic acid (ABA), which induces seed dormancy, prevents all the known GA effects in this tissue.