title: Seed after-ripening and over-expression of class I beta-1,3-glucanase confer maternal effects on tobacco testa rupture and dormancy release.
abstract: 'Coat-imposed' seed dormancy of many non-endospermic and endospermic species is released during after-ripening. After-ripening-mediated promotion of tobacco ( Nicotiana tabacum L.) seed germination is mainly due to a promotion of testa rupture and a similar promotion of subsequent endosperm rupture. Treatment of after-ripened or freshly harvested mature seeds with abscisic acid (ABA) delays endosperm rupture and inhibits the induction of class I beta-1,3-glucanase (betaGlu I) in the micropylar endosperm, but does not affect the kinetics of testa rupture. After-ripening-mediated release of photodormancy is correlated with a decreased gibberellin (GA) requirement for testa rupture during dark-imbibition. Reciprocal crosses between wild-type tobacco and sense-betaGlu I transformant lines showed that betaGlu I over-expression in the seed covering layers can replace the promoting effect of after-ripening on testa rupture in light, but only if the mother plant is a sense-betaGlu I line. This maternal effect supports the model of two sites for betaGlu I action: (i) betaGlu I contribution to the after-ripening-mediated release of dormancy in the dry seed state, which is manifested in the promotion and ABA-insensitivity of testa rupture during imbibition. (ii) ABA-sensitive expression of betaGlu I in the micropylar endosperm, which contributes to endosperm rupture. The importance of GA-signaling and testa characteristics appear to be a common feature during the after-ripening-mediated release of coat-imposed dormancy in endospermic and non-endospermic seeds.
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D016375:Antisense Elements (Genetics) / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D018525:Germination / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D005875:Gibberellins / Q000494:pharmacology; D043326:Glucan 1,3-beta-Glucosidase; D007150:Immunohistochemistry; D008027:Light; D010937:Plant Growth Regulators / Q000494:pharmacology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D012639:Seeds / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics; D014170:Transformation, Genetic; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D016375:Antisense Elements (Genetics); D005875:Gibberellins; D010937:Plant Growth Regulators; D000040:Abscisic Acid; D001617:beta-Glucosidase; D043326:Glucan 1,3-beta-Glucosidase