Histone deacetylases regulating the diurnal transcriptome of maize

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Diurnal regulation of gene transcription is among the most basal regulatory processes in plants. The genes to be activated are packed with proteins in the cell nucleus in a condensed structure called chromatin. Research in recent years has highlighted the role of chromatin modifications in the regulation of these genes. Our model for studying gene regulation is C4 photosynthesis in maize, because the genes encoding the enzymes of this pathway are expressed at high levels and show a complex regulation by multiple stimuli. During three previous projects funded by the DFG, we established a model of chromatin as a signal integrator that allows plants to store information about the metabolic state of the cell, tissue identity, circadian control, and illumination. Particularly, we identified specific histone acetylation sites that are up-regulated upon illumination. Based on previous results, we hypothesize that this up-regulation is brought about by suppression of a histone deacetylase (HDAC). In this project, we aim at identifying the responsible HDAC by characterization of maize lines with suppressed expression of individual HDACs. The project will be extended to a whole transcriptome analysis in order to identify all target genes of the selected HDACs. We will analyse the promoter chromatin of these genes in wildtype and mutant plants by chromatin immunoprecipitation. Furthermore, we will generate transgenic maize plants that overexpress the selected HDACs fused to a protein tag. This will enable direct analysis of chromatin binding sites. These studies will allow new insights into the epigenetic control of gene expression in monocots and the regulation of C4 photosynthesis.