ABSTRACT Four Lupinus species (L. albus, L. luteus, L. angustifolius and L. mutabilis) are currently considered of great potential for modern and future agriculture. As grain legumes, they are recognized as important alternative sources of protein and vegetable oil. Intensive breeding programs and genetic engineering have and will overcome the two main constraints associated with this crop, namely the presence of high levels of alkaloids and the reduced amounts of sulphur containing amino acids in lupin protein, respectively. As with legumes in general, the main storage proteins in Lupinus seeds are globulins. During cotyledon developments, the reserve proteins are synthesized as precursors, processed and assembled into their native forms and stored inside the protein storage vacuoles for later use. Two major and two minor globulins have been characterized in lupin seeds: α-conglutin and β-conglutin, members of the widespread 11S or legumin-like and 7S or vicilin-like families of storage proteins, respectively; γ-conglutin, which belongs to a family of storage proteins with distinctly different properties; and δ-conglutin, more often reported as an albumin, a member of the 2S family of storage proteins. These proteins are subjected to differential proteolysis during germination and seedling growth. Particularly evident is the accumulation of a lectin-like, 20 kDa polypeptide which is part of a 210 kDa globulin and is a stable, intermediate breakdown product of β-conglutin catabolism. This polypeptide exhibits a number of biochemical and biological activities, including strong antifungal effects and toxicity to insects, which make it a versatile, multifunctional protein. This 20 kDa polypeptide may therefore play an important role in increasing the chance of plant survival, while functioning as a long lasting reserve in a situation where virtually all seed reserves have been mobilized.
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