Molecular Aspects of Storage Protein and Starch Synthesis in Wheat and Rice Seeds

Abstract

Seed formation in cereals is accompanied by the mobilization and transport of nitrogen from leaves and other source tissues to the developing cereal grain. Nitrogen enters the seed primarily as amino acids, of which glutamine appears to be the predominant constituent.1 It has been estimated that about 50% of the total nitrogen available in leaf and stem tissue of wheat is catabolized and transported to the developing grains2 where it is converted mainly into storage proteins. Storage proteins (defined here as any protein which serves as a nitrogen store and is packaged into protein bodies) are synthesized during the mid-stages of seed development and normally constitute about 80–90% of the total protein present in seeds. These proteins are subsequently utilized by the young developing seedling as a source of nitrogen and carbon and sometimes sulfur.