Regulation of metabolic gene clusters in Arabidopsis thaliana

Recent discoveries have revealed that the genes for the biosynthesis of a variety of plant specialized metabolites are organized in operon-like clusters within plant genomes. Here we identify a regulatory process that is required for normal expression of metabolic gene clusters in Arabidopsis thaliana. Comparative gene expression analysis of a representative clustered gene was performed in a set of chromatin mutant lines. Subsequently, metabolite levels were analysed by GC-MS and the local chromatin structure was investigated by chromatin immunoprecipitation and nucleosome positioning. We show that the transcript levels of genes within two metabolic clusters are coordinately reduced in an arp6 and h2a.z background. We demonstrate that H2A.Z enrichment in the clusters is positively correlated with active cluster expression. We further show that nucleosome stability within the cluster regions is higher in the arp6 background compared with the wild-type. These results implicate ARP6 and H2A.Z in the regulation of metabolic clusters in Arabidopsis thaliana through localized chromatin modifications that enable the coordinate expression of groups of contiguous genes. These findings shed light on the complex process of cluster regulation, an area that could in the future open up new opportunities for the discovery and manipulation of specialized metabolic pathways in plants.