NuA4 and H2A.Z control environmental responses and autotrophic growth in Arabidopsis

The nucleosomal acetyltransferase of H4 (NuA4) is an essential transcriptional coactivator in eukaryotes, though it remains poorly characterized in plants. Here, we describe Arabidopsis homologues of the NuA4 scaffold proteins Enhancer of Polycomb-Like1 (EPL1) and Esa1-Associated Factor1 (EAF1). Loss of AtEAF1 results in inhibition of growth and chloroplast development. These effects are stronger in the Atepl1 mutant and are further enhanced by loss of Golden2-Like (GLK) transcription factors suggesting that NuA4 activates nuclear plastidic genes alongside GLK. We demonstrate that AtEPL1 is necessary for nucleosomal acetylation of histones H4 and H2A.Z by NuA4 in vitro. These chromatin marks are diminished in Atepl1 genome-wide while another active chromatin mark H3K9ac is locally enhanced. Many chloroplast-related genes depend on NuA4 as they are downregulated with loss of H4ac and H2A.Z alone. Finally, we demonstrate that NuA4 promotes deposition of H2A.Z and by doing so prevents spurious activation of stress response genes. Overall design: RNA-Seq transcriptome analysis of of A. thaliana wild type, Atepl1-2, Ateaf1-1, glk leaves, and ChIP-Seq profiling of wild type and Atepl1-2 for H3K9ac, H4K5ac, H2A.Zac and H2A.Z