No Phenylketonuria in the Moss Physcomitrella patens
Phenylketonuria is the most common metabolic disease in humans. It occurs when the so-called PAH gene is defective, thus preventing the amino acid phenylalanine from being metabolized to the amino acid tyrosine. This leads to an accumulation of phenylalanine and to severe developmental disorders.
In the current issue of the journal Plant Cell, an international research team at the University of Florida, the CNRS Institute in Grenoble, the Noble Foundation, and the University of Freiburg 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 in Freiburg, led by 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 increased concentration of amino acids had no negative effect on the development of the moss. „Evidently, Physcomitrella has a previously unknown detoxification mechanism which has been lost in humans,“ explains Reski with regard to this surprising discovery.
The editors of the journal Plant Cell found these findings so important that they also drew attention to them in an editorial. The title of the original publication is Pribat et al. (2010): Nonflowering plants possess a unique folate-dependent phenylalanine hydroxylase that is localized in chloroplasts. Plant Cell 22, 3410-3422. The title of the editorial is Introducing aromatic amino acid hydroxylases from plants, by Kathleen L. Farquharson.