The Alfin-like homeodomain finger protein AL5 suppresses multiple negative factors to confer abiotic stress tolerance in Arabidopsis

Summary Plant homeodomain ( PHD ) finger proteins affect processes of growth and development by changing transcription and reading epigenetic histone modifications, but their functions in abiotic stress responses remain largely unclear. Here we characterized seven A rabidopsis thaliana Alfin1‐like PHD finger proteins ( AL s) in terms of the responses to abiotic stresses. AL s localized to the nucleus and repressed transcription. Except AL 6, all the AL s bound to G ‐rich elements. Mutations of the amino acids at positions 34 and 35 in AL 6 caused loss of ability to bind to G‐rich elements. Expression of the AL genes responded differentially to osmotic stress, salt, cold and abscisic acid treatments. AL 5 ‐over‐expressing plants showed higher tolerance to salt, drought and freezing stress than Col‐0. Consistently, al5 mutants showed reduced stress tolerance. We used Ch IP ‐Seq assays to identify eight direct targets of AL 5, and found that AL 5 binds to the promoter regions of these genes. Knockout mutants of five of these target genes exhibited varying tolerances to stresses. These results indicate that AL 5 inhibits multiple signaling pathways to confer stress tolerance. Our study sheds light on mechanisms of AL 5‐mediated signaling in abiotic stress responses, and provides tools for improvement of stress tolerance in crop plants.