Change of thiamin-binding protein and thiamin levels during seed maturation and germination in sesame

Thiamin-binding proteins (TBPs) occur in many types of plant seeds. The biochemical and structural properties such as subunit structure and affinity for thiamin of the proteins have been characterized. However, the change of TBP and thiamin during seed maturation and germination is little known. Sesame (Sesamum indicum L.) seeds have unique albumin TBPs, because the other TBPs from plant seeds are generally globulins. In this study, we studied the change of the TBP and thiamin levels in sesame seeds. The protein content and thiamin-binding activity of the seeds increased with seed development after flowering. Immunological analysis using an antibody against the TBP of sesame seeds showed that the protein was accumulated in seeds during maturation. The thiamin content of the seeds increased with seed development after flowering. On the other hand, the thiamin-binding activity decreased during seed germination when TBP was degraded. The thiamin content of the seeds decreased during the germination. However, the amount of thiamin phosphate in the seeds during germination was little changed. These results suggested that thiamin was accumulated and stored as a complex with TBP in sesame seeds.