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Seed dormancy and ABA metabolism in Arabidopsis and barley: the role of ABA 8¢-hydroxylase

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Millar, AA and Jacobsen, JV and Ross, JJ and Helliwell, CA and Poole, AT and Scofield, G and Reid, JB and Gubler, F (2006) Seed dormancy and ABA metabolism in Arabidopsis and barley: the role of ABA 8¢-hydroxylase. The Plant Journal, 45. pp. 942-954. ISSN 0960-7412

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Abstract

We have investigated the relationship between seed dormancy and abscisic acid (ABA) metabolism in the monocot barley and the dicot Arabidopsis. Whether dormant (D) or non-dormant (ND), dry seed of Arabidopsis and embryos of dry barley grains all had similarly high levels of ABA. ABA levels decreased rapidly upon imbibition, although they fell further in ND than in D. Gene expression profiles were determined in Arabidopsis for key ABA biosynthetic [the 9-cis epoxycarotenoid dioxygenase gene family] and ABA catabolic [the ABA 8¢- hydroxylase gene family (CYP707A)] genes. Of these, only the AtCYP707A2 gene was differentially expressed between D and ND seeds, being expressed to a much higher level in ND seeds. Similarly, a barley CYP707 homologue, (HvABA8¢OH-1) was expressed to a much higher level in embryos from ND grains than from D grains. Consistent with this, in situ hybridization studies showed HvABA8¢OH-1 mRNA expression was stronger in embryos from ND grains. Surprisingly, the signal was confined in the coleorhiza, suggesting that this tissue plays a key role in dormancy release. Constitutive expression of a CYP707A gene in transgenic Arabidopsis resulted in decreased ABA content in mature dry seeds and a much shorter after-ripening period to overcome dormancy. Conversely, mutating the CYP707A2 gene resulted in seeds that required longer afterripening to break dormancy. Our results point to a pivotal role for the ABA 8¢-hydroxylase gene in controlling dormancy and that the action of this enzyme may be confined to a particular organ as in the coleorhiza of cereals.

Item Type: Article
Journal or Publication Title: The Plant Journal
Page Range: pp. 942-954
ISSN: 0960-7412
Identification Number - DOI: doi: 10.1111/j.1365-313X.2006.02659.x
Additional Information: The definitive published version is available online at: http://onlinelibrary.wiley.com/ Sherpa = author cannot archive publisher's version/PDF Publisher = http://olabout.wiley.com/WileyCDA/Section/id-406074.html Wiley-Blackwell restricts posting of the final published version in order to ensure the integrity of the version of record and as a result of our considerable investment in the journal and the article.
Date Deposited: 07 Jul 2011 23:37
Last Modified: 18 Nov 2014 04:20
URI: http://eprints.utas.edu.au/id/eprint/11374
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