IDENTIFICATION OF 3 NOVEL UNIQUE PROTEINS IN SEED OIL BODIES OF SESAME

Plant seeds store triacylglycerols in discrete organelles called oil b odies. An oil body preserves a matrix of triacylglycerols surrounded b y a monolayer of phospholipids embedded with abundant structural prote ins termed oleosins and probably some uninvestigated minor proteins of higher molecular mass. Three polypeptides of 27, 37, and 39 kDa (temp orarily denominated as Sop1, Sop2, and Sop3) were regularly co-purifie d with seed oil bodies of sesame, Comparison of amino acid composition indicated that they were substantially less hydrophobic than the know n oleosins, and thus should not be aggregated multimers of oleosins, T he results of immune-recognition to sesame proteins extracted from sub cellular fractions of mature seeds, various tissues, and oil bodies pu rified from different stages of seed formation revealed that these thr ee polypeptides were unique proteins gathered in oh bodies, accompanyi ng oleosins and triacylglycerols, during the active assembly of the or ganelles in maturing seeds. Both in vivo and in intro, immunofluoresce nce labeling using secondary antibodies conjugated with FITC (fluoresc ein isothiocyanate) confirmed the localization of these three polypept ides in oil bodies.