Project : chloroplast biogenesis

Biochemical and structural studies of the plastid-encoded RNA-polymerase and its associated proteins involved in chloroplast biogenesis

Contact : David Cobessi

The health of our biosphere is maintained by the green linage’s ability to perform photosynthesis within its chloroplasts, which are essential for the cycles of carbon and oxygen. The assembly of the photosynthetic apparatus in plastids requires transcription of the photosynthesis associated plastid genes (PhAPGs) and of photosynthesis associated nuclear genes (PhANGs). Upon perception of the first rays of light, plastids differentiate into chloroplasts with strong coordination of PhAPGs and PhANGs transcription. The PhAPGs are transcribed by the plastidial RNA-polymerase (PEP), a machinery of unknown 3D structure of 1 MDa that contains 4 catalytic chloroplastic rpo subunits, and 12 PEP associated proteins (PAPs) essential for an in vitro activity encoded by the nuclear genome and transported into the plastid. Several PAPs are dually localized into the plastid and nucleus where they could regulate the transcription of PhANGs. In collaboration with LPCV, using a multi-scale integrated approach we investigate the nuclear and plastid transcription by chloroplast proteins and the 3D structure of the proteins and complexes involved.

Selected publications :

1. Three-dimensional envelope and subunit interactions of the plastid-encoded RNA polymerase from Sinapis alba. Ruedas, R, Muthukumar, SS, Kieffer-Jaquinod, S, Gillet, FX, Fenel, D, Effantin, G, Pfannschmidt, T, Couté, Y, Blanvillain, R & Cobessi, D. (2022) Int. J. Mol. Sci. , 23, 9922.

2. Nucleo-plastidic PAP8/pTAC6 couples chloroplast formation with photomorphogenesis. Liebers M, Gillet FX, Israel A, Pounot K, Chambon L, Chieb M, Chevalier F, Ruedas R, Favier A, Gans P, Boeri Erba E, Cobessi D, Pfannschmidt T, Blanvillain R (2020) EMBO J. 39:e104941.