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Keywords:

  • Arabidopsis thaliana ;
  • chromatin;
  • FLOWERING LOCUS C (FLC);
  • FLOWERING LOCUS T (FT);
  • histone demethylase;
  • histone methyltransferase

Summary

  • Previous studies in Arabidopsis thaliana have identified several histone methylation enzymes, including ARABIDOPSIS TRITHORAX1 (ATX1)/SET DOMAIN GROUP 27 (SDG27), ATX2/SDG30, LSD1-LIKE1 (LDL1), LDL2, SDG8, SDG25, and CURLY LEAF (CLF)/SDG1, as regulators of the key flowering repressor FLOWERING LOCUS C (FLC) and the florigen FLOWERING LOCUS T (FT). However, the combinatorial functions of these enzymes remain largely uninvestigated.
  • Here, we investigated functional interplays of different histone methylation enzymes by studying higher order combinations of their corresponding gene mutants.
  • We showed that H3K4me2/me3 and H3K36me3 depositions occur largely independently and that SDG8-mediated H3K36me3 overrides ATX1/ATX2-mediated H3K4me2/me3 or LDL1/LDL2-mediated H3K4 demethylation in regulating FLC expression and flowering time. By contrast, a reciprocal inhibition was observed between deposition of the active mark H3K4me2/me3 and/or H3K36me3 and deposition of the repressive mark H3K27me3 at both FLC and FT chromatin; and the double mutants sdg8 clf and sdg25 clf displayed enhanced early-flowering phenotypes of the respective single mutants.
  • Collectively, our results provide important insights into the interactions of different types of histone methylation and enzymes in the regulation of FLC and FT expression in flowering time control.