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Characterization of ubiquitous interactors of the plastid transcriptional complex during the transition from dark to light

par Turquand, Maud
Président du jury Dahdouh-Guebas, Farid
Promoteur Verbruggen, Nathalie
Co-Promoteur Blanvillain, Robert
Publication Non publié, 2022-06-24

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Résumé :

For more than 1.5 billion years, the “green lineage” has participated in the composition of aspecific oxygenic atmosphere on Earth by a process called photosynthesis. It takes place in a semiautonomousorganelle originating from an endosymbiotic cyanobacteria, which became achloroplast. However, evolution has given enough time to the nucleus to strongly control thedevelopment and function of the chloroplast, especially when precursor plastids found in earlydevelopmental stages differentiate into fully functional chloroplasts. The transition takes placeduring the passage from a skotomorphogenesis phase to a photomorphogenesis phase. This leadsto changes in the major regulator of photosynthesis: the Plastid-Encoded RNA Polymerase (PEP).Light induces the assembly of the PEP with nuclear-encoded proteins PAPs (PEP associatedproteins), which will increase its transcriptional activity on Photosynthesis Associated PlastidGenes (PhAPGs). This PEP/PAPs complex interacts during its activity with a multitude of proteinssuch as LIN2, TIG, EMB1144, CPN20 or M24. These proteins all have specific activities but have thecommon point of always interacting with the complex, in dark and light conditions. This reportprovides data to validate the interaction between these proteins and the complex. Moreover, itwas shown that the corresponding genes are strongly co-expressed with PAP8, we will try and testwhether the regulatory elements of LIN2 and PAP8 could be exchanged in promoter-swapexperiments. Finally, we will assess the expression pattern of promoters such as that of LIN2 tocompare it with PAP8, which is epidermis-specific in the dark and palisade-specific in the light.