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................................    Rhizogenesis Lab - Projects    ................................


Genetic transformation of tropical nitrogen-fixing trees

Dr. Claudine Franche
    

The transfer of foreign genes into tropical trees of the Casuarinaceae family was first achieved in Allocasuarina verticillata via Agrobacterium rhizogenes (Phelep et al, 1991) and then obtained in Casuarina glauca and A. verticillata by a disarmed strain of A. tumefaciens (Franche et al, 1997). The possibility to genetically engineer these forest trees has great promise with respect to the factors that limit classical genetic improvement in forestry, such as the large size of the mature plants and the long sexual generation time.

Understanding the regulation of gene expression is an essential requirement for the success of tree biotechnology. Therefore an important part of our work is devoted to the characterization of suitable constitutive or tissue-specific promoters for Casuarina.


Characterization of valuable genes in Casuarina

Dr. Claudine Franche

We have recently published a paper concerning the isolation of a metallothionein gene from Casuarina glauca (Laplaze et al, 2002). Metallothioneins (MTs) are defined as low molecular mass cystein-rich proteins that bind heavy metals. Animal MTs play a role in detoxification of heavy metals in homeostasis of intracellular metal ions. They may also participate in defence against intracellular oxidants and in the regulation of metal containing enzymes and transcription factors. Plant Mts have been isolated from a variety of plant species but their function is poorly understood.
The promoter region of cgMT1 was isolated and fused to the gus gene. Transgenic Casuarinaceae plants showed that the cgMT1 promoter was most active in roots and in the oldest region of the shoot. In situ hybridization indicated that in nodules cgMT1 transcripts are present in mature Frankia infected cells and in the pericycle (Laplaze et al, 2002).
Our current work deals with the role of cgMT1 in the functioning of symbiosis. Transgenic Casuarinaceae and Arabidopsis overexpressing cgMT1 will be tested for physiological alteration and resistance to heavy metal. CgMT1 protein will be purified and biochemical analysis will be carried out (affinity for heavy metals...).

An important function of our group is training and technology transfer to developing countries. Many students, postdoctoral researchers and senior scientists from developing countries benefit from training in our group.


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Equipe Rhizogenèse 2006 - Institut de Recherche pour le Développement
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