Modification of storage protein content and quality in legume seeds

Worldwide, legume seed proteins represent a major source of amino acids for human and animal nutrition. However, they are notoriously deficient in sulphur-containing amino acids. Therefore attempts to overcome this imbalance are nutritionally relevant, and the concept of legume seed protein quality has been extended to technological and health-oriented aspects. This review focuses on the state-of-the-art of the conventional and innovative methodologies for the improvement of legume seed storage protein content and quality and also the constraints encountered. Modifications of storage protein quality can be achieved by conventional breeding and processing, and by genetic engineering. Various examples concerning selection of new lines by conventional breeding for the improvement of functional properties and modification of the sulphur content of the genetically engineered seeds are reported. It is becoming increasingly apparent that these two approaches are not mutually exclusive, rather they appear to be highly complementary. Although the task of legume seed storage protein modification for seed quality improvement is still far from being completed, the intense breeding and research activities of the last decades have contributed to a better understanding of seed molecular biology and structure/function relationships of storage proteins and their genes. Both aspects are prerequisites for the future activities aimed at a more effective and targeted improvement of nutritional quality.