Expression pattern and deposition of three storage proteins, 11S globulin,2S albumin and 7S globulin in maturing sesame seeds

Seed storage proteins commonly comprise various groups of multiple isoforms encoded by gene families. I IS globulin and 2S albumin, conventionally ter med a-globulin and P-globulin, are the two major storage proteins and const itute 80-90 % of total seed proteins in sesame (Sesamum indicum L.). Two fu ll-length cDNA clones were sequenced and deduced to encode isoforms of sesa me 11S globulin and 2S albumin precursors, respectively. In addition, a ful l-length cDNA encoding a putative 7S globulin precursor was obtained. The e xistence of 7S globulin as a minor storage protein in sesame was confirmed by immunodetection. Southern hybridization indicates that all three storage protein genes are present in single or low copy number in the sesame genom e. Both northern and western analyses suggest that storage proteins are exp ressed and deposited into protein bodies later than the initiation of oil b ody formation in accord with the observation in electron microscopy. Immuno gold labeling reveals that all three storage proteins are co-existent in ea ch protein body of sesame seeds, and that 2S albumin and 7S globulin are pr eferentially located in the peripheral portion of protein bodies. (C) 2001 Editions scientifiques et medicales Elsevier SAS.