Article
Expression analysis of a GA 20-oxidase in embryos from two sorghum lines with contrasting dormancy: possible participation of this gene in the hormonal control of germination

Authors: Benech-Arnold R.L.^{4, 7}; Pérez-Flores L.^{1, 7}; Carrari F.^{2, 7}; Osuna-Fernández R.³; Rodríguez M.V.⁴; Enciso S.⁴; Stanelloni R.⁵; Sánchez R.A.⁴; Bottini R.^{6, 7}; Iusem N.D.²

Source: Journal of Experimental Botany, Volume 54, Number 390, 1 September 2003 , pp. 2071-2079(9)

Publisher: Oxford University Press

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Abstract:

The role of GAs in promoting seed germination is well known and experiments with seeds from different species have suggested the requirement of de novo synthesis of GAs upon imbibition for germination. There are also strong indications that the enhancement of GA synthesis is part of the mechanism through which environmental signals (i.e. light) induce germination. Since along the GA biosynthetic pathway, oxidation at C-20 carried out by GA 20-oxidases is thought to be a site of regulation, a cDNA clone encoding a GA 20-oxidase was isolated from embryos of sorghum (SbGA 20ox). Expression analysis of this gene in embryos within imbibed caryopses with low dormancy showed detectable amounts of the specific mRNA early upon incubation, increasing thereafter. In contrast, it remained barely detectable in embryos from dormant caryopses. Changes in endogenous GA₄ levels were in agreement with those of SbGA 20ox mRNA, suggesting that GA production might be regulated differentially at the level of transcription of this gene. The expression of SbGA 20ox was enhanced in incubated embryos isolated from either type of caryopses, illustrating a physiological control exerted by the surrounding seed tissues on gene expression. The results also show that ABA leads to a suppression of transcription of this gene.

Keywords: Key words: Dormancy; GA 20-oxidase; germination; gibberellins; Sorghum.

Document Type: Original article

Affiliations: 1: UAM-Iztapalapa, México 2: Laboratorio de Fisiología y Biología Molecular, FCEyN Universidad de Buenos Aires Argentina 3: Facultad de Ciencias, UNAM, México 4: IFEVA-Cátedra de Cerealicultura, Facultad de Agronomía, Universidad de Buenos Aires/CONICET,Av. San Martín 4453, 1417 Buenos Aires, Argentina 5: Instituto de Investigaciones Bioquímicas, Fundación Campomar, Argentina 6: Laboratorio de Fisiología Vegetal, Departamento de Ciencias Naturales, Universidad Nacional de Río Cuarto, Campus Universitario, 5800 Río Cuarto, Argentina 7: * These authors contributed equally to the work., † Present address: Cátedra de Química Orgánica y Biológica, Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo (Mendoza), Argentina., ‡ To whom correspondence should be addressed: Fax: +54 11 4524 8039. E-mail: benech@ifeva.edu.ar

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