JXB Advance Access originally published online on September 25, 2003
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Journal of Experimental Botany, Vol. 54, No. 392, pp. 2503-2510,
November 1, 2003
© 2003 Oxford University Press
The relationship between ß-mannosidase and endo-ß-mannanase activities in tomato seeds during and following germination: a comparison of seed populations and individual seeds
Received 27 February 2003; Accepted 13 July 2003
Department of Botany, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
* Present address: Department of Biology, The Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region, China. To whom correspondence should be addressed: Fax: +1 519 767 1991. E-mail: dbewley{at}uoguelph.ca
ß-Mannosidase and endo-ß-mannanase are involved in the mobilization of the mannan-containing cell walls of the tomato seed endosperm. The activities of both enzymes increase in a similar temporal manner in the micropylar and lateral endosperm during and following germination. This increase in enzyme activities in the micropylar endosperm is not markedly reduced in seeds imbibed in abscisic acid although, in the lateral endosperm, endo-ß-mannanase activity is more suppressed by this inhibitor than is the activity of ß-mannosidase. Gibberellin-deficient (gib-1) mutants of tomato do not germinate unless imbibed in gibberellin; low ß-mannosidase activity, and no endo-ß-mannanase activity is present in seeds imbibed in water, but both enzymes increase strongly in activity in the seeds imbibed in the growth regulator. For production of full activity of both ß-mannosidase and endo-ß-mannanase in the endosperm, this tissue must be in contact with the embryo for at least the first 6 h of imbibition, which is indicative of a stimulus diffusing from the embryo to the endosperm during this time. These results suggest some correlation between the activities of ß-mannosidase and endo-ß-mannanase, particularly in the micropylar endosperm, in populations of tomato seeds imbibed in water, abscisic acid and gibberellin. However, when individual micropylar endosperm parts are used to examine the effect of the growth regulators and of imbibition in water on the production of the two enzymes, it is apparent that within these individual seed parts there may be large differences in the amount of enzyme activity present. Micropylar endosperms with high endo-ß-mannanase activity do not necessarily have high ß-mannosidase activity, and vice versa, which is indicative of a lack of co-ordination of the activities of these two enzymes within individuals of a population.
Key words: Abscisic acid, ß-mannosidase, endo-ß-mannanase, endosperm, gib-1 mutant, tomato seed germination.
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