When light governs gene expression

Paris, May 7, 2002

CEA/CNRS/IRD Press release

Researchers from CEA, CNRS, and IRD have revealed, for the first time, the occurrence of a new type of phytochrome (protein acting as a light receptor) in photosynthetic bacteria. This new type of phytochrome is capable of regulating protein synthesis by means of appropriate illumination. This discovery has promising application possibilities and has been the subject of a patent application. It was published in the May 9, 2002, issue of Nature.

Initially characterized in plants about 40 years ago, phytochromes were discovered in bacteria only about five years ago. Phytochromes are present in two forms (active and inactive) that absorb either red light or near infrared light. Depending on how it is illuminated, the phytochrome goes from one form to the other, and then triggers a cascade of biochemical events which, in plants for example, cause germination or growth. The phytochrome thus acts as a genuine light switch whose function in bacteria had remained mysterious.
The results obtained by the two teams — a joint CEA-CNRS unit¹ and a team from IRD² — are original in two important ways. First, the researchers have identified for the first time the phenomenon activated by this new phytochrome and all of the various partner molecules involved in this regulation. Second, the results reveal a new type of phytochrome whose regulation mechanism is based on a simple protein-protein interaction (with a particular protein in charge of expressing certain genes), without any chemical modification, unlike the phytochromes scientists had studied prior to this, whose activation mechanism involves modifications in the state of phosphorylation of certain amino acids.

A patent application has been filed for the discovery of the action mechanism of this new type of phytochrome. Merely by means of illumination, it appears that it is now possible to activate or to inhibit the synthesis of specific genes. Most current systems, which are still at the experimental stage, use a chemical inducer, but they offer little flexibility and are difficult to reverse. The unusual nature of this new photoactivable regulation mechanism opens up numerous application possibilities, going from research into certain protein functions to gene therapy.

For further information, please see http://www.ird.fr/fr/inst/actualites/fiches/

Reference:
"Bacteriophytochrome controls photosystem synthesis in anoxygenic bacteria," Nature, May 9, 2002.

1 - "Biologie des échanges entre plantes et bactéries rhizosphériques" (Biology of exchanges between plants and rhizospheric bacteria, a joint CEA – CNRS research unit, Saint-Paul-les-Durance).
2 - "Laboratoire Symbiose tropicale et méditerranéenne" (Tropical and Mediterranean symbiosis laboratory, a joint IRD – CIRAD – INRA – ENSAM research unit, Montpellier).

Press contacts

CEA – Pascal Newton – Tel: +33 1 40 56 20 97 – pascal.newton@cea.fr
IRD – Hélène Deval or Marie-Lise Sabrié, - Tel: +33 1 48 03 75 19 - deval@paris.ird.fr
CNRS – Martine Hasler – Tel: +33 1 44 96 46 35 – martine.hasler@cnrs-dir.fr