Understanding gene expression in the developing grain

Serial Analysis of Gene Expression (SAGE) has been used to understand more comprehensively the gene expression involved in the growth of a developing wheat grain. SAGE is a technique that allows rapid, detailed analysis of thousands of transcripts in a cell. The abundance of a particular tag relates directly to the expression level of the gene from which it is derived. The analysis of gene expression of different physiological states provides both qualitative and quantitative information. Seed development is a complex process involving both the up and down regulation of many genes. Samples of the developing grain were taken at 8, 14, 20, 30 and 40 days post anthesis. From these developmental stages five SAGE libraries were constructed totalling approximately 100 000 tags, of which 28 900 were unique. Differential expression profiles of abundant tags from each library reveal the coordinated expression of genes responsible for the cellular events constituting caryopsis development. Analysis has identified genes involved in activities of cellular proliferation, structure and differentiation, storage protein accumulation and starch biosynthesis. This SAGE platform has also provided a resource of novel sequence and expression information including promoter activities. Further investigations into the abundant, low expressing transcripts will hopefully provide greater insight into wheat caryopsis development and assist in wheat improvement programs.