Intraplastidial trafficking of a phage-type RNA polymerase is mediated by a thylakoid RING-H2 protein.
The plastid genome of dicotyledonous plants is transcribed by three different RNA polymerases; an eubacterial-type enzyme, PEP; and two phage-type enzymes, RPOTp and RPOTmp. RPOTp plays an important role in chloroplast transcription, biogenesis, and mesophyll cell proliferation. RPOTmp fulfills a specific function in the transcription of the rrn operon in proplasts/amyloplasts during seed imbibition/germination and a more general function in chloroplasts during later developmental stages. In chloroplasts, RPOTmp is tightly associated with thylakoid membranes indicating that functional switching of RPOTmp is connected to thylakoid association. By using the yeast two-hybrid system, we have identified two proteins that interact with RPOTmp. The two proteins are very similar, both characterized by three N-terminal transmembrane domains and a C-terminal RING domain. We show that at least one of these proteins is an intrinsic thylakoid membrane protein that fixes RPOTmp on the stromal side of the thylakoid membrane, probably via the RING domain. A model is presented in which light by triggering the synthesis of the RING protein determines membrane association and functional switching of RPOTmp.
Laboratoire Plastes et Differénciation Cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, B.P. 53, F-38041 Grenoble Cedex 9, France.
Jacinthe
J
Azevedo
Florence
F
Courtois
Mohamed-Ali
MA
Hakimi
Emilie
E
Demarsy
Thierry
T
Lagrange
Jean-Pierre
JP
Alcaraz
Pankaj
P
Jaiswal
Laurence
L
Maréchal-Drouard
Silva
S
Lerbs-Mache
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D001435:Bacteriophages / Q000201:enzymology*; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D015723:Gene Library; D007425:Intracellular Membranes / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000528:radiation effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000528:radiation effects; D021381:Protein Transport / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D020524:Thylakoids / Q000201:enzymology* / Q000528:radiation effects; D014157:Transcription Factors / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C052130:GAL4 protein, S cerevisiae; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases