Pressure-Induced Release of Basic 7S Globulin from Cotyledon Dermal Tissue of Soybean Seeds

Abstract

Protein release by high-pressure treatment of soybean seeds was investigated. When soybean seeds were immersed in distilled water and pressurized at 100−700 MPa, a large amount of proteins, accounting for 0.5−2.5% of the total seed protein, were released from the seeds. By sodium dodecyl sulfate−polyacrylamide gel electrophoresis, immunoblot, and amino acid sequencing analyses, the major protein released was identified as basic 7S globulin (Bg), consisting of 16 and 27 kDa subunits. Bg was shown immunohistochemically to be localized in the dermal tissue of seed cotyledons, presumably in epidermal cells. There were almost no structural changes in seed inner cells, as determined by scanning electron microscopy, but considerably large changes in structures of cotyledon surface and epidermal cells were observed in the pressurized seeds. These results suggest that Bg localized in seed cotyledon dermal tissues is released from soybean seeds as a result of structural changes in cotyledon surface and epidermal cells that are caused by high-pressure treatment. Keywords: High pressure; basic 7S globulin; soybean seed