Plant Physiology 109: 751-759 (1995)

Class I ß-1,3-glucanases in the endosperm of tobacco during germination

Gerhard Leubner-Metzger, Corinne Fründt, Regina Vögeli-Lange (1), Frederick Meins, Jr.

Friedrich Miescher Institute, Box 2543, CH-4002 Basel, Switzerland
(1) Present address: Botanical Institute, University of Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland

Received: 9 June 1995 / Accepted: 14 July 1995

Abstract. Rupture of the seed coat and rupture of the endosperm are separate events in the germination of Nicotiana tabacum L. cv. "Havana 425" seeds. Treatment with 10-5 M abscisic acid (ABA) did not appreciably affect seed-coat rupture but greatly delayed subsequent endosperm rupture by more than 100 h and resulted in the formation of a novel structure consisting of the enlarging radicle with a sheath of greatly elongated endosperm tissue. Therefore, ABA appears to act primarily by delaying endosperm rupture and radicle emergence. Measurements of ß-1,3-glucanase activity, antigen content, and mRNA accumulation together with reporter gene experiments showed that induction of class I ß-1,3-glucanase genes begins just prior to the onset of endosperm rupture but after the completion of seed-coat rupture. This induction was localized exclusively in the micropylar region of the endosperm where the radicle will penetrate. ABA treatment markedly inhibited the rate of ß-1,3-glucanase accumulation but did not delay the onset of induction. Independent of the ABA concentration used, onset of endosperm rupture was correlated with the same ß-1,3-glucanase content/seed. These results suggest that ABA-sensitive class I ß-1,3-glucanases promote radicle penetration of the endosperm, which is a key limiting step in tobacco seed germination.

Article in PDF format (2.5 MB) Abstract           Fig. 1          Fig. 2          Fig. 3          Fig. 4          Fig. 5          Table 1  

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