Endo-beta-mannanase is present in an inactive form in ripening tomato fruits of the cultivar Walter

Fruits of the tomato cultivar Waiter undergo normal development to the red- ripe stage but, unlike those of the cultivar Trust, they do not produce act ive endo-beta -mannanase, Reasons for this failure to produce the enzyme we re sought. The cv, Walter contains genes for endo-beta -mannanase, as shown by Southern blot analysis, and transcripts for the enzyme are present in r ipening fruits, as revealed using Northern hybridization, Moreover, the enz yme protein is detectable by Western blots using an endo-beta -mannanase-sp ecific antibody from tomato. In addition, the inactive enzyme is localized appropriately in the wall regions of the outer layers of the fruit (skin an d outer pericarp), Mixing inactive fruit extracts of cv. Walter, in excess, with extracts; from cv. Trust fruits, which contain active enzyme, leads t o an increase rather than a reduction in enzyme activity, showing that ther e are no inhibitors of endo-beta -mannanase in cv. Waiter fruits. Similar r esults were obtained with fruits of the tomato cv. Heinz 1439. In contrast to the situation in fruits, the seeds of both cvs Walter and Heinz 1439 pro duce active enzyme, especially following germination.