Plant Journal 23: 215-221 (2000)

Sense transformation reveals a novel role for class I ß-1,3-glucanase in tobacco seed germination

Gerhard Leubner-Metzger and Frederick Meins, Jr.

Friedrich Miescher Institute, Maulbeerstr. 66, CH-4058 Basel, Switzerland

Received: 21 March 2000 / Accepted: 5 April 2000

Abstract. 'Coat-enhanced' seed dormancy of many dicotyledonous species, including tobacco, is released during afterripening. Rupture of the endosperm, which is the limiting step in tobacco seed germination, is preceded by induction of class I ß-1,3-glucanase (ßGLU I) in the micropylar endosperm where the radicle will penetrate. Treating after-ripened tobacco seeds with abscisic acid (ABA) delays endosperm rupture and inhibits ßGLU I induction. Sense transformation with a chimeric ABA-inducible ßGLU I transgene resulted in over-expression of ßGLU I in seeds and promoted endosperm rupture of mature seeds and of ABA-treated after-ripened seeds. Taken together, these results provide direct evidence that ßGLU I contributes to endosperm rupture. Over-expression of ßGLU I during germination also replaced the effects of after-ripening on endosperm rupture. This suggests that regulation of ßGLU I by ABA signaling pathways might have a key role in after-ripening.

Key words: Abscisic acid, After-ripening, Endosperm-limited seed germination, Gene function, ß-1,3-Glucanase, Sense transformation

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Figure 1 Figure 2 Table 1               Glucanase constructs
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