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Functional Analysis of the Metallothionein Gene cgMT1 Isolated from the Actinorhizal Tree Casuarina glauca

October 2007 , Volume 20 , Number  10
Pages  1,231 - 1,240

Mariana Obertello,1,2 Luis Wall,2 Laurent Laplaze,1 Michel Nicole,3 Florence Auguy,1 Hassen Gherbi,1 Didier Bogusz,1 and Claudine Franche1

1Groupe Rhizogénèse Symbiotique, UMR 1098, IRD (Institut de Recherche pour le Développement), 911 avenue Agropolis, BP 5045, 34394 Montpellier Cedex 5, France; 2Programa de Investigación en Interacciones Biológicas, Universidad Nacional de Quilmes (UNQ), Roque Sáenz Peña 352, (B1876BXD) Bernal, Argentina; 3Résistance des plantes aux bioagresseurs, UMR RPB, IRD, Montpellier, France

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Accepted 22 June 2007.

cgMT1 is a metallothionein (MT)-like gene that was isolated from a cDNA library of young nitrogen-fixing nodules resulting from the symbiotic interaction between Frankia spp. and the actinorhizal tree Casuarina glauca. cgMT1 is highly transcribed in the lateral roots and nitrogen-fixing cells of actinorhizal nodules; it encodes a class I type 1 MT. To obtain insight into the function of cgMT1, we studied factors regulating the expression of the MT promoter region (PcgMT1) using a β-glucuronidase (gus) fusion approach in transgenic plants of Arabidopsis thaliana. We found that copper, zinc, and cadmium ions had no significant effect on the regulation of PcgMT1-gus expression whereas wounding and H2O2 treatments led to an increase in reporter gene activity in transgenic leaves. Strong PcgMT1-gus expression also was observed when transgenic plants were inoculated with a virulent strain of the bacterial pathogen Xanthomonas campestris pv. campestris. Transgenic Arabidopsis plants expressing cgMT1 under the control of the constitutive 35S promoter were characterized by reduced accumulation of H2O2 when leaves were wounded and by increased susceptibility to the bacterial pathogen X. campestris. These results suggest that cgMT1 could play a role during the oxidative response linked to biotic and abiotic stresses.

© 2007 The American Phytopathological Society