SEED STORAGE PROTEINS IN DEVELOPING SOMATIC EMBRYOS OF ALFALFA - DEFECTS IN ACCUMULATION COMPARED TO ZYGOTIC EMBRYOS

Somatic embryos of alfalfa (Medicago sativa L.) synthesized all of the major storage proteins of zygotic embryos; an 11S globulin (medicagin), a 7S globulin (alfin), and a 2S albumin (LMW). In zygotic embryos (cotyledons and/or axis) these storage proteins accounted for 30%, 10%, and 20%, respectively, of the total extractable protein. In somatic embryos the 7S protein was predominant while the 11S(particularly subfamily I) and 2S proteins were present in lower amounts. Analysis of cultivars and selfed seed of the embryogenic clone (RL34) demonstrated that these differences were predominantly physiologically, rather than genetically, based. The accumulated 7S and 11S storage proteins of somatic embryos were processed normally, aggregated as oligomers, and were deposited in protein bodies. This was not the case for the 2S storage protein. In somatic embryos that protein was localized in the cytoplasm rather than in protein bodies, the site of deposition in zygotic embryos.