KNOCK-OUT OF THE MG PROTOPORPHYRIN IX METHYLTRANSFERASE GENE IN ARABIDOPSIS: EFFECTS ON CHLOROPLAST DEVELOPMENT AND ON CHLOROPLAST-TO- NUCLEUS SIGNALING.

Protoporphyrin IX is the last common intermediate between the haem and chlorophyll biosynthesis pathways. The addition of Mg directs this molecule toward chlorophyll biosynthesis. The first step downstream from the branchpoint is catalyzed by the Mg chelatase and is a highly regulated process. The corresponding product, Mg protoporphyrin IX, has been proposed to play an important role as a signaling molecule implicated in plastid-to-nucleus communication. In order to get more information on the chlorophyll biosynthesis pathway and on M