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DEVELOPMENT AND HORMONE ACTION

Evidence for a Role of Gibberellins in Salicylic Acid-Modulated Early Plant Responses to Abiotic Stress in Arabidopsis Seeds¹

Departamento de Fisiología Vegetal, Centro Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, Universidad de Salamanca, 37007 Salamanca, Spain (A.A.-R., D. Rodríguez, D. Reyes, J.A.J., G.N., C.N.); and Departamento de Ciencias Agrarias y del Medio Natural, Universidad Jaume I, Campus Riu Sec, 12071 Castellon, Spain (M.L.-C., A.G.-C.)

Exogenous application of gibberellic acid (GA₃) was able to reverse the inhibitory effect of salt, oxidative, and heat stresses in the germination and seedling establishment of Arabidopsis (Arabidopsis thaliana), this effect being accompanied by an increase in salicylic acid (SA) levels, a hormone that in recent years has been implicated in plant responses to abiotic stress. Furthermore, this treatment induced an increase in the expression levels of the isochorismate synthase1 and nonexpressor of PR1 genes, involved in SA biosynthesis and action, respectively. In addition, we proved that transgenic plants overexpressing a gibberellin (GA)-responsive gene from beechnut (Fagus sylvatica), coding for a member of the GA₃ stimulated in Arabidopsis (GASA) family (FsGASA4), showed a reduced GA dependence for growth and improved responses to salt, oxidative, and heat stress at the level of seed germination and seedling establishment. In 35S:FsGASA4 seeds, the improved behavior under abiotic stress was accompanied by an increase in SA endogenous levels. All these data taken together suggest that this GA-responsive gene and exogenous addition of GAs are able to counteract the inhibitory effects of these adverse environmental conditions in seed germination and seedling growth through modulation of SA biosynthesis. Furthermore, this hypothesis is supported by the fact that sid2 mutants, impaired in SA biosynthesis, are more sensitive to salt stress than wild type and are not affected by exogenous application of GA₃.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Carlos Nicolás (cnicolas{at}usal.es).

www.plantphysiol.org/cgi/doi/10.1104/pp.109.139352

^* Corresponding author; e-mail cnicolas{at}usal.es.

Received April 3, 2009; accepted May 7, 2009; published May 13, 2009.