58:	Cell-wall associated endo-b-mannanase in the skin and outer pericarp of ripening tomato fruits.

Authors:	Bewley, J. Derek(A)Banik, Mitali(A)Bourgault, Richard(A)Feurtado, Allan(A)Reid, Alexandra(A)
Affiliations:	(A): Dept. Botany, Univ. Guelph
Presenter:	Bewley, J. Derek , dbewley@uoguelph.ca

Activity of endo-b-mannanase increases during ripening of tomato fruit cv. Trust. Inrease in enzyme activity is greatest in the skin, with less in the outer pericarp region, and none in the inner pericarp, developing seed or locule. Mannanase is associated with the cell wall and can only be extracted by a high-salt buffer. b-Mannosidase also requires high-salt for extraction, but its activity declines during ripening. The enzyme protein, as detected by western blots, is present during early ripening, before enzyme activity is detectable. The mRNA for mannanase is also present at these stages, as shown by northern blots and in situ hybridization using a DIG-labelled probe, which is indicative that mannanase is transcribed and translated before apparently being sequestered temporarily in a mature-size inactive form. Non- or slow-ripening mutants exhibit lower mannanase activities than their equivalent wild-type although this is not always related to reduced softness of the fruits. One cultivar, Walter, exhibits no mannanase activity, but ripens and softens normally.