CHARACTERIZATION OF 2S AND 7S STORAGE PROTEINS IN EMBRYOS OF OIL PALM

Storage proteins that accumulated during oil palm embryo development w ere extracted, purified and characterized. Only water- and low-salt-so luble proteins, with respective sedimentation coefficients of 2S and 7 S, were detected in mature embryos. After purification by gel filtrati on, the various protein classes identified were characterized by elect rophoresis and amino acid composition analysis. The 2S proteins compri se polypeptides of 22 kD and 19 kD, which are acidic (pI < 6) and basi c (pI > 9) respectively, The 7S proteins predominate and are heterogen eous oligomers (Mr of 156 and 201 kD), comprising a polypeptide triple r of Mr between 45 and 65 kD with no disulphide bonds. Their amino aci d composition is broadly similar to those of the 7S proteins of other monocotyledon embryos, but differs from those of the legume 7S vicilin s. Histological examinations and electrophoresis showed that the 2S an d 7S proteins appeared at the third month after fertilization, and no qualitative changes were detected up to the sixth month of embryo deve lopment. The characterization of the embryo storage proteins of oil pa lm is discussed with reference to legume, cereal and palm seed storage proteins. This study will enable further investigation of storage pro tein synthesis during somatic embryogenesis. (C) 1997 Elsevier Science Ireland Ltd.