Changes in a-and β-Amylase Activities during Germination of Seeds of Alfalfa (Medicago sativa L.)

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We examined the methods available for the assay of a-amylase in alfalfa (Medicago sativa) and found the Phadebas test most suitable. The Phadebas assay and activity staining on am-pholine gels after isoelectrofocusing revealed that an amylase is present in the dry seeds of alfalfa and that its activity decreases rapidly after the second day of seed germination. An amylase was purified by affinity chromatography and gel filtration. The kinds of sugar generated from soluble starch by the purified amylase resembled those generated by other a-amylases from plants, in particular those from mung bean (Vigna radiata). These results indicate that the amylase in alfalfa seeds belongs to the family of a-amylases. The molecular weight and isoelectric point of the a-amylase were determined to be 43 kDa and 4.92, respectively. The Pantrac assay and activity staining on immobiline gels after isoelectrofocusing revealed that the activities of β-amylases increased during the initial 4 to 5 days of germination. Further-more, treatment of whole seedlings with cycloheximide or actinomycin D inhibited the increase in activity of β-amylases but did not affect the reduction in activity of a-amylase. During germination of alfalfa seeds, a-amylase activity decreases while, in contrast, β-amylase activity increases (in the cotyledons of germinating seeds), changes that are specific to the germinating seeds of alfalfa.
日本植物生理学会の論文