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Keywords:

  • after-ripening;
  • coat-imposed dormancy;
  • β-1,3-glucanase;
  • gene expression;
  • low-hydrated state;
  • seed germination;
  • testa rupture

Summary

An air-dry developmental state with low-hydrated tissues is a characteristic of most plant seeds. Seed dormancy is an intrinsic block of germination and can be released during after-ripening, that is air-dry storage of mature seeds. Both seed-covering layers, testa and endosperm, cause the coat-imposed dormancy of tobacco (Nicotiana tabacum). After-ripening and over-expression of class I β-1,3-glucanase (βGlu I) confer maternal effects on testa rupture and dormancy release. Very little is known about the molecular mechanisms of after-ripening and whether gene expression is possible in low-hydrated seeds. Transient, low-level βGlu I transcription and translation was detected during tobacco seed after-ripening. 1H NMR 2D micro-imaging showed uneven distribution of proton mobility in seeds. βGlu I gene expression is associated spatially with the inner testa and temporally with the promotion of testa rupture. Local elevation in moisture content seems to permit local, low-level βGlu I gene transcription and translation in the maternal tissues of air-dry, low-hydrated seeds. De novo gene expression is therefore proposed to be a novel molecular mechanism for the release of coat-imposed dormancy during oilseed after-ripening.