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cg12 Expression Is Specifically Linked to Infection of Root Hairs and Cortical Cells during Casuarina glauca and Allocasuarina verticillata Actinorhizal Nodule Development

July 2003 , Volume 16 , Number  7
Pages  600 - 607

Sergio Svistoonoff , 1 Laurent Laplaze , 1 Florence Auguy , 1 John Runions , 2 Robin Duponnois , 3 Jim Haseloff , 2 Claudine Franche , 1 and Didier Bogusz 1

1Equipe Rhizogenèse, UMR 1098, Institut de Recherche pour le Développement, BP 64501, 34394 Montpellier cedex 5, France; 2Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK; 3 Institut de Recherche pour le Développement, BP182, Ouagadougou, Burkina Faso


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Accepted 24 February 2003.

cg12 is an early actinorhizal nodulin gene from Casuarina glauca encoding a subtilisin-like serine protease. Using transgenic Casuarinaceae plants carrying cg12-gus and cg12-gfp fusions, we have studied the expression pattern conferred by the cg12 promoter region after inoculation with Frankia. cg12 was found to be expressed in root hairs and in root and nodule cortical cells containing Frankia infection threads. cg12 expression was also monitored after inoculation with ineffective Frankia strains, during my-corrhizae formation, and after diverse hormonal treatments. None of these treatments was able to induce its expression, therefore suggesting that cg12 expression is linked to plant cell infection by Frankia strains. Possible roles of cg12 in actinorhizal symbiosis are discussed.


Additional keywords: subtilase, Nod factors, genetic transformation.

© 2003 The American Phytopathological Society