Development of beta-1,3-glucanase activity in germinated tomato seeds

Laminarin-hydrolysing activity developed in the endosperm of tomato (Lycope rsicon esculentum) seeds following germination. The enzyme was basic (pI>10 ) and the apparent molecular mass was estimated to be 35 kDa by SDS-PAGE. I t was specific for linear beta -1,3-glucan substrates. Laminarin was hydrol ysed by the enzyme to yield a mixture of oligoglucosides, indicating that t he enzyme had an endo-action pattern. Thus, the enzyme was identified as be ta -1,3-endoglucanase (EC 3.2.1.39). The activity of the enzyme developed i n the endosperm after radicle protrusion (germination) had occurred and the enzyme activity was localized exclusively in the micropylar region of the endosperm where the radicle had penetrated. When the lateral endosperm regi on, where no induction of the enzyme occurred, was wounded (cut or puncture d), there was a marked enhancement of beta -1,3-glucanase activity. Thus th e post-germinative beta -1,3-glucanase activity in the micropylar endosperm portion might be brought about by wounding resulting from endosperm ruptur e by radicle penetration.