biostudies-literatureLi XNational Key Research and Development Program of China303https://www.ebi.ac.uk/biostudies/studies/S-EPMC12461997biostudies-literatureUnknown26(1)<h4>Background</h4>Histone modifications are critical for transcriptional regulation. A notable genetic innovation in land plants is the emergence of histone lysine methyltransferases ATXR5/6, which specifically catalyze the repressive histone H3 lysine 27 monomethylation (H3K27me1). Current knowledge of ATXR5/6 function is largely based on Arabidopsis studies using a weak atxr5;atxr6 hypomorphic mutant, in which ATXR6 is still partially expressed and defects are primarily observed in heterochromatin. However, the significance for land plants to evolve these enzymes remains unclear.<h4>Results</h4>In this study, we generate strong atxr5;atxr6 mutants with further reduced ATXR6 expression in Arabidopsis to explore the broader roles of ATXR5/6. Our results show that ATXR5/6 are essential forGenome biologyLand plant-specific H3K27 methyltransferases ATXR5 and ATXR6 control plant development and stress responses.PMC124619972023YFD1200704Li XLi HPan JZhang HLiu QJiang DfalseLand plant-specific H3K27 methyltransferases ATXR5 and ATXR6 control plant development and stress responses.<h4>Background</h4>Histone modifications are critical for transcriptional regulation. A notable genetic innovation in land plants is the emergence of histone lysine methyltransferases ATXR5/6, which specifically catalyze the repressive histone H3 lysine 27 monomethylation (H3K27me1). Current knowledge of ATXR5/6 function is largely based on Arabidopsis studies using a weak atxr5;atxr6 hypomorphic mutant, in which ATXR6 is still partially expressed and defects are primarily observed in heterochromatin. However, the significance for land plants to evolve these enzymes remains unclear.<h4>Results</h4>In this study, we generate strong atxr5;atxr6 mutants with further reduced ATXR6 expression in Arabidopsis to explore the broader roles of ATXR5/6. Our results show that ATXR5/6 are essential for2025-01-01T00:00:00Z2025 Sep2026-06-03T20:32:44.811Z2026-05-01T03:11:02.902ZS-EPMC124619974099951810.1186/s13059-025-03801-5