Journal of Experimental Botany 52: 1753-1759 (2001)

Antisense-transformation reveals novel roles for class I ß-1,3-glucanase in tobacco seed after-ripening and photodormancy

Gerhard Leubner-Metzger and Frederick Meins, Jr.

Friedrich Miescher-Institut, P.O. Box 2543, CH-4002 Basel, Switzerland (G.L.-M., F.M.Jr.) and
Institut für Biologie II, Albert Ludwigs Universität, Schänzlestrasse 1, 79104 Freiburg, Germany (G.L.-M.)

Received: 27 September 2000 / Accepted: 17 May 2001

Abstract. Little is known about the molecular basis for seed dormancy, afterripening, and radicle emergence through the covering layers during germination. In tobacco, endosperm rupture occurs after testa rupture and is the limiting step in seed germination. Class I ß-1,3-glucanase (ßGLU I), which is induced in the micropylar endosperm just prior to its penetration by the radicle, is believed to help weaken the endosperm wall. Here we provide evidence for a second site of ßGLU I action during afterripening. Tobacco plants were transformed with antisense ßGLU I constructs with promoters thought to direct endosperm-specific expression. Unexpectedly, these transformants were unaffected in endosperm rupture and did not exhibit reduced ßGLU I expression during germination. Nevertheless antisense ßGLU I transformation delayed the onset of testa rupture in light-imbibed, afterripened seeds and inhibited the afterripening-mediated release of photodormancy. We propose that ßGLU I expression in the dry seed contributes to the afterripening-mediated release of seed dormancy.

Key words: Abscisic acid, After-ripening, Coat-enhanced seed dormancy, endosperm-limited germination, ß-1,3-Glucanase, Sense- and antisense transformation

Article in PDF format (160 KB) Abstract          Fig. 1          Fig. 2          Table 1          Table 2          Glucanase constructs
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