H3K36me3, catalyzed by ASHH proteins, serves as a positive histone mark associated with gene expression and plays a crucial role in plant development. In our study, we identified that sorghum SbASHH2 exhibits H3K36 methyltransferase activity. Immunoprecipitation analysis revealed that H3K36me3 rarely co-occurs with H3K27me3, and genome-wide profiling of these two marks indicates a non-overlapping distribution across the sorghum genome, underscoring the antagonistic relationship between H3K36me3 and H3K27me3. Furthermore, we observed that H2A.Z is deposited near the transcription start site (TSS) of genes enriched with H3K36me3, while genes with H2A.Z deposition in the gene body lack H3K36me3, suggesting an interplay between H3K36me3 and H2A.Z deposition. Our findings show that the high expression of photosynthesis genes in leaves is closely linked to H3K36me3 deposition, with only a small subset involving the removal of H3K27me3 or eviction of H2A.Z. This implies that H3K36me3 activates specific subsets of photosynthesis genes by antagonizing H3K27me3 or H2A.Z. Additionally, we found that the deposition of H3K36me3 on most photosynthesis genes is neither specific to mesophyll (M) nor bundle sheath (BS) cells and is independent of light induction. Our results emphasize the significance of H3K36me3 in the regulation of photosynthesis genes and lay the groundwork for further investigation into the mechanisms by which H3K36me3 contributes to gene regulation.