Coordination of nuclear and plastid transcription for chloroplast biogenesis requires H4 acetylation by the NuA4 complex

Chloroplast biogenesis represents a crucial step in seedling development, and is essential for the transition to autotrophic growth in plants. This light-controlled process relies on the transcription of nuclear and plastid genomes that drives the effective assembly and regulation of the photosynthetic machinery. Here we reveal a novel regulation level for this process by showing the involvement of chromatin remodelling in the coordination of nuclear and plastid gene expression for proper chloroplast biogenesis and function. The two Arabidopsis homologs of the yeast EPL1 proteins, core components of the NuA4 histone acetyl-transferase complex, are essential for the correct assembly and performance of chloroplasts. EPL1 proteins are necessary for the coordinated expression of nuclear genes encoding most of the components of chloroplast transcriptional machinery, specifically promoting H4K5Ac deposition in these loci. These data unveil a key participation of epigenetic regulatory mechanisms in the coordinated expression of the nuclear and plastid genomes. Transcriptomic profiling through RNAseq of Arabidopsis plants grown on 1/2x Murashige & Skoog medium supplemented with 1% sucrose under long day photoperiod (16h light / 8h dark). Plants were grown at 22°C for 14 days, taking samples at Zeitgeber time (ZT) ZT8. Three libraries were generated using RNA from three independent experiments.