The structure and function of maize scutellum during early stages of germination

[eng] The embryo in grasses, at grain maturity, comprises the embryonic axis and the scutellum. The scutellum is supposed to be the single cotyledon in the monocotyledoneus embryos and is attached to the embryo axis in the scutelar node. The embryo has the highest concentration of lipid and lipid soluble vitamins in cereal grains. The embryo in grasses, at grain maturity, comprises the embryonic axis and the scutellum. The scutellum is supposed to be the single cotyledon in the monocotyledoneus embryos and is attached to the embryo axis in the scutelar node. The embryo has the highest concentration of lipid and lipid soluble vitamins in cereal grains. The embryonic axis originates the root, leaves and stem of the new plant. In the mature seed, the embryo axis is formed by the primary root, protected by the coleorhiza, and the stem tip with five or six short internodes and leaf primordia which, as a whole, form the plumule that is surrounded by the coleoptile. The name scutellum (small shield, in latin) derives from its shield-like shape and it liesbetween the embryonic axis and endosperm. Dissected scutellum constitutes 11% or the kernel mass, and about 90% of the embryo. During germination, scutellar epithelial cells suffer an elongation that increases the contact surface between the endosperm and the scutellum and facilitates the transport of the nutrients from the endosperm to the embryo. Scutellar cell elongation is inhibited by ABA and salicylic acid, basic and acid pH and high concentrations of sorbitol. Exogenous gibberellins stimulate elongation, but a reduction in gibberellin synthesis or perception does not inhibit it. Elongation is inhibited by sucrose, but not glucose. Transcription and translation inhibitors reduce scutellar cell elongation, indicating that transcription and translation are necessary for the elongation process. Scutellar epithelium cells play specific roles during germination different to parenchymal cells. So, we expect some differences in the gene expression pattern of this tissue. That’s why we construct a cDNA library using RNA extracted from scutellar epithelial cells 1 day after imbibition and selected them using array hybridization comparing the mRNA accumulated in epithelial cells with the mRNA accumulated in the other scutellar tissues. We identified 30 genes up-regulated in the epithelium. A high proportion of these genes are involved in metabolic processes, the production of energy or in the transport of peptides in