Temporal and spatial pattern of the development of endo-β-mannanase activity in germinating and germinated lettuce seeds

The development of endo-β-mannanase activity and the changes in the enzyme content were followed during and after germination of lettuce seeds. Endo-β-mannanase activity was not detected before germination. It began to develop immediately after radicle protrusion. The development of the enzyme activity occurred specifically in the endosperm tissue and activity staining of native-PAGE gels revealed that three isoforms of the enzyme are present. SDS-denatured polypeptides of these isoforms were all recognized by anti-tomato-endo-β-mannanase antibodies. Molecular masses of these polypeptides seemed to be very close to each other and were estimated to be about 39 kDa. The pattern of changes in the activity of endo-β-mannanase in the endosperm during seedling growth was parallel to that of changes in the content of the enzyme protein, indicating that the increase in enzyme activity is due to the accumulation of the enzyme protein. Tissue prints showed that the activity initially developed in the endosperm region near the embryonic axis and then spread over the endosperm tissue. These results indicate that endo-β-mannanase production in lettuce endosperm is carried out in a spatially and temporally regulated manner.