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Study of cg12, a subtilase encoding gene
involved in Casurina glauca infection by Frankia

Dr. Sergio Svistoonoff

    cg12 is an early Casuarina glauca nodulin gene that encodes a subtilisin-like protease. In situ hybridisation studies have shown an expression in the infection zone, and in prenodules, in cells being infected by Frankia (Laplaze et al., 2000).


    Using transgenic C. glauca and A. verticillata containing cg12-reporter gene fusions we have shown that the cg12 promoter is activated during the early steps of the actinorhizal symbiosis, i.e. when Frankia filaments infect a deformed root hair.We have also found that cg12 expression is specifically linked to plant cell infection by Frankia : the promoter activity shuts down as cells begin to differentiate and fix nitrogen. and it cannnot be induced by phytohormones, PR-hormones, rhizobial Nod factors or mycorhizal fungi (see Svistoonoff et al, 2003).

    In collaboration with Dr. Ana Ribeiro , cg12-reporter gene fusions were also introduced in the model legume legume Medicago truncatula. We found that the infection-related activation of the cg12 promoter is conserved between actinorhizal and legume-rhizobia symbioses (Svistoonoff et al., 2004).


    We produced antibodies against CG12 protein. Immunolocalization exsperiments showed that CG12 is present in infected cells in the matrix surrounding infecting Frankia hyphae.


GFP expression in transgenic A. verticillata nodules driven by the cg12 promoter

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Equipe Rhizogenèse 2006 - Institut de Recherche pour le Développement
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