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

Abstract

Seed storage proteins commonly comprise various groups of multiple isoforms encoded by gene families. 11S globulin and 2S albumin, conventionally termed α-globulin and β-globulin, are the two major storage proteins and constitute 80–90 % of total seed proteins in sesame ( Sesamum indicum L.). Two full-length cDNA clones were sequenced and deduced to encode isoforms of sesame 11S globulin and 2S albumin precursors, respectively. In addition, a full-length cDNA encoding a putative 7S globulin precursor was obtained. The existence 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 genome. Both northern and western analyses suggest that storage proteins are expressed and deposited into protein bodies later than the initiation of oil body formation in accord with the observation in electron microscopy. Immunogold labeling reveals that all three storage proteins are co-existent in each protein body of sesame seeds, and that 2S albumin and 7S globulin are preferentially located in the peripheral portion of protein bodies.