Hairy Root Nodulation of Casuarina glauca:A System for the Study of Symbiotic Gene Expressionin an Actinorhizal Tree. Diaga Diouf . Laboratoire de Biotechnologie des Symbioses Forestieres Tropicales (ORSTOM-CIRAD/Foret), 45 bis avenue de la Belle Gabrielle, 94736 Nogent-sur-Marne cedex, France. Hassen Gherbi,Yves Prin, Claudine Franche, Emile Duhoux, and Didier Bogusz. Laboratoire de Biotechnologie des Symbioses Forestieres Tropicales (ORSTOM-CIRAD/Foret), 45 bis avenue de la Belle Gabrielle, 94736 Nogent-sur-Marne cedex, France. MPMI 8:532-537. Accepted 14 April 1995. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1995.

The purpose of this study was to establish a fast system for producing transgenic actinorhizal root nodules of Casuarina glauca. Agrobacterium rhizogenes strain A4RS carrying the p35S-gusA-int gene construct was used to induce hairy roots on hypocotyls of 3-week-old C. glauca seedlings. Three weeks after wounding, the original root system was excised, and composite plants consisting of transgenic roots on Untransformed shoots were transferred to test tubes to be inoculated with Frankia. The actinorhizal nodules formed on transformed roots had the nitrogenase activity and morphology of Untransformed nodules. (-Glucuronidase (GUS) activity was examined in transgenic roots and nodules by fluorometric and histo-chemical assays. The results indicate that transgenic nodules generated with this root transformation system could facilitate the molecular study of symbiotic nitrogen fixation in actinorhizal trees.