On the hunt for 'metallo-genes’

It was during his post-doctoral studies in Germany at the Max Planck Institute of Molecular Plant Physiology (Dr. Ute Krämer's laboratory) that Marc Hanikenne, the principal authour of the study recently published in Nature, started to work on the 'Arabidopsis sisters'. If the major part of the present research was carried out in Germany, important results have also been obtained at the ULg’s Laboratory of Functional Genomics and Molecular Plant Imaging, directed by Professor Patrick Motte.

‘A.thaliana’s genome now having been completely decrypted, it represents an undeniable resource in order to carry out comparative analysis with that of A.halleri', explains Marc Hanikenne. What is the goal of such an operation? To discover the genes involved in metal homeostasis. Homeostasis is the ability of a living organism to maintain a balance within its internal structure. In the case of metal absorption the plant’s physiological limits have to be respected, otherwise these substances can become toxic for the organism.

The team at the Max-Planck Institute thus turned its attention to the expression of arabidopsis' genes. To do this it used the DNA microarray technique. This recent biotechnology allows for the genes’ level of expression in a cell to be quantified, for a given tissue, at a given moment and in a given state.

‘We thus realised that in A.halleri many genes were overexpressive in comparison with A.thaliana, and a good number of these genes code for metal transporters’, explains Marc Hanikenne.

Amongst around 30 gene candidates, HMA4 held the team’s particular attention. In fact, previous studies of Arabidopsis thaliana had already suspected HMA4's role in metal homeostasis. This genome fragment codes for a transporter (also called (HMA4) which is important in the translocation of zinc and cadmium from the roots to the leaves.