Global Functional Targets of the Histone Methyltransferase SDG8 Uncover a Role for Histone Modification in Energy Metabolism

Histone methylation modulates gene expression in response to external and internal cues. We uncovered a non-redundant role for the Arabidopsis histone methyltransferase, SDG8, which provides a unique opportunity to study the global function of a specific histone methyltransferase within in a multicellular organism. We previously used a promoter responsive to light and carbon in a positive genetic screen to identify an Arabidopsis carbon and light insensitive mutant cli186. In this study, we characterize the mutant cli186 as a complete deletion of a histone methyltransferase gene SDG8 (now renamed sdg8-5). To assess the global role of SDG8, we compared the global histone methylation patterns and the transcriptome of sdg8-5 to wild type (WT) in the context of a transient carbon and light treatment. We showed that the complete deletion of SDG8 in sdg8-5 is associated with a dramatic reduction of H3K36me3 towards the 3 of the gene body, which correlates with significant reduction in gene expression. We uncovered 1,084 high confidence functional targets of SDG8 affected in both H3K36me3 marks and gene expression that are associated with specific biological processes including defense, photosynthesis, nutrient metabolism and energy metabolism. Importantly, 71% of these functional targets are responsive to carbon and/or light. Our model suggests that SDG8 functions to mark specific sets of genes with H3K36me3 in the gene body for active transcription, to tune genes involved in primary metabolism that are responsive to the energy level in the environment.

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Li Y, Mukherjee I, Thum KE, Tanurdzic M, Katari MS, Obertello M, Edwards MB, McCombie WR, Martienssen RA, Coruzzi GM