Phenylketonuria is the most common metabolic disease in humans. The disease occurs when the so-called PAH gene is defective, thus preventing the amino acid phenylalanine from being metabolised into the amino acid tyrosine. This leads to the accumulation of phenylalanine and to severe developmental disorders.

In the current issue of the journal Plant Cell, an international team of researchers from the University of Freiburg (Germany), the University of Florida (USA), the CNRS Institute in Grenoble (France) and the Noble Foundation now reports that the PAH gene is not only present in animals and humans, but also in algae, mosses and coniferous trees. The scientists have not yet succeeded in discovering this gene in flowering plants. The biologists from Freiburg led by biotechnologist Prof. Dr. Ralf Reski switched off the PAH gene in the moss Physcomitrella patens through so-called gene targeting in order to study gene function in the moss. As expected, these knockout mosses accumulated phenylalanine. In contrast to humans with phenylketonuria, however, the elevated concentration of amino acids had no negative effect on the development of the moss. "It appears that Physcomitrella patens has a previously unknown detoxification mechanism that has been lost in humans," said Reski explaining this surprising discovery.

The editors of the journal Plant Cell considered these findings to be so important that they chose to draw attention to them in an editorial. The title of the original publication authored by Pribat et al. is ‘Nonflowering plants possess a unique folate-dependent phenylalaninehydroxylase that is localized in chloroplasts' (Plant Cell 22, 3410-3422 (2010)). The title of the editorial is ‘Introducing aromatic amino acid hydroxylases from plants' by Kathleen L. Farquharson.

Further information:
Prof. Dr. Ralf Reski
University of Freiburg,
Faculty of Biology
Department of Plant Biotechnology 
Tel.: +49 (0)761/203-6968
Fax: +49 (0)761/203-6967
E-mail: pbt(at)biologie.uni-freiburg.de