Brassica napus seed endosperm: Metabolism and signaling in a dead end tissue

Oilseeds are an important element of human nutrition and of increasing significance for the production of industrial materials. The development of the seeds is based on a coordinated interplay of the embryo and its surrounding tissue, the endosperm. This study aims to give insights into the physiological role of endosperm for seed development in the oilseed crop Brassica napus. Using protein separation by two-dimensional (2D) isoelectric focusing (IEF)/SDS polyacrylamide gel electrophoresis (PAGE) and protein identification by mass spectrometry three proteome projects were carried out: (i) establishment of an endosperm proteome reference map, (ii) proteomic characterization of endosperm development and (iii) comparison of endosperm and embryo proteomes. The endosperm proteome reference map comprises 930 distinct proteins, including enzymes involved in genetic information processing, carbohydrate metabolism, environmental information processing, energy metabolism, cellular processes and amino acid metabolism. To investigate dynamic changes in protein abundance during seed development, total soluble proteins were extracted from embryo and endosperm fractions at defined time points. Proteins involved in sugar converting and recycling processes, ascorbate metabolism, amino acid biosynthesis and redox balancing were found to be of special importance for seed development in B. napus. Implications for the seed filling process and the function of the endosperm for seed development are discussed.