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

Abstract

SummarỳCoat-enhanced' seed dormancy of many dicotyledonous species, including tobacco, is released during after-ripening. Rupture of the endosperm, which is the limiting step in tobacco seed germination, is preceded by induction of class I b-1,3-glucanase (bGLU I) in the micropylar endosperm where the radicle will penetrate. Treating after-ripened tobacco seeds with abscisic acid (ABA) delays endosperm rupture and inhibits bGLU I induction. Sense transformation with a chimeric ABA-inducible bGLU I transgene resulted in over-expression of bGLU 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 bGLU I contributes to endosperm rupture. Over-expression of bGLU I during germination also replaced the effects of after-ripening on endosperm rupture. This suggests that regulation of bGLU I by ABA signalling pathways might have a key role in after-ripening.

Class I β-1,3-Glucanase and Chitinase Are Expressed in the Micropylar Endosperm of Tomato Seeds Prior to Radicle Emergence

“…6 and 7) and tobacco (Leubner-Metzger et al, 1995). Furthermore, sense transformation of tobacco with a chimeric ABAinducible class I ␤-1,3-glucanase transgene resulted in the promotion of endosperm rupture upon ABA treatment, providing evidence that class I ␤-1,3-glucanase contributes to endosperm rupture of tobacco seeds (Leubner-Metzger and Meins, 2000). However, in tomato seeds endosperm weakening was unaffected by ABA (Fig.…”

“…A close correlation between class I ␤-1,3-glucanase induction and endosperm rupture in response to plant hormones and environmental factors affecting tobacco seed germination constituted strong, but indirect, evidence that class I ␤-1,3-glucanase may promote radicle protrusion (for review, see Leubner-Metzger and Meins, 1999). More direct evidence of a causal role for class I ␤-1,3-glucanase during endosperm rupture of tobacco seeds was obtained by sense transformation with a chimeric ABA-inducible class I ␤-1,3-glucanase transgene, which promoted endosperm rupture upon ABA treatment (Leubner-Metzger and Meins, 2000). Although ␤-1,3-glucanase expression is often accompanied by expression of chitinase [1, 4-(N-acetyl-␤-dglucosaminide) glycanohydrolase, EC 3.2.1.14] in pathogenesis-related (PR) responses (see below), only very low chitinase activity was detected in germinating tobacco seeds.…”

Qualidade de sementes de tabaco durante o processo de pelotização e armazenamento

“…Além disso, as sementes de tabaco são fotoblásticas positivas (LEUBNER-METZGER & MEINS, 2000), de forma que o revestimento pode induzir a uma fotoinibição, afetando negativamente a germinação das sementes, portanto, a pelota utilizada no revestimento das sementes deve se desintegrar ou abrir com facilidade, para não constituir resistência à germinação (BONOME, 2003).…”

Dormancy of Nicotiana benthamiana seeds can be broken by different compounds

“…1A), compare to species such as Descurainia sophia (one year) (Li et al 2005). Our result suggests that after-ripening could be common among Nicotiana species because it was observed in case of many tobacco (Nicotiana tabaccum) cultivars where it is also fast (Leubner-Metzger & Meins 2000). Mentioned process runs on molecular level, though seeds are a relatively dry system, changes in gene expression were observed (Finch-Savage & LeubnerMetzger 2007;Finkelstein et al 2008).…”