Abstract
Actinorhizal plants are non legumes that are able to form root nitrogen-fixing nodules in association with the soil actnomycete Frankia. The aim of this work is to continue the characterization of Cg12, a gene coding for a subtilase isolated from the actinorhizal tree C. glauca. Using transgenic Casuarinaceae containing Cg12 promoter-reporter gene fusions we have shown that the expression of Cg12 starts very early during the symbiotic process and is specifically induced in cells infected by Frankia. Using antibodies, CG12 was detected in protein extracts from C. glauca and by immunolocalisation, CG12 was detected in cell walls and in the polysacharidic material surrounding Frankia. Cg12-reporter gene fusions were also introduced in the model plants A. thaliana and M. Truncatula. No expression was detected in A. thaliana. In M. truncatula, the conservation of the expression profile suggests that a signalling pathway independent from Nod factors, conserved between the two systems, is activated specifically in cells infected by symbiotic bacteria