Plant homeodomain (PHD) finger proteins affect processes of growth and development by changing transcription and reading epigenetic modifications of histones, but their functions in abiotic stress responses remain largely unclear. Here we characterized seven Arabidopsis thaliana Alfin1-like PHD finger proteins (ALs) in the response to abiotic stresses. ALs localized to the nucleus and repressed transcription. Except AL6, all the ALs bound to G-rich element. Natural alterations of the amino acids at positions 34 and 35 in AL6 caused loss of G-rich element binding ability. ALs expressions responded differentially to osmotic stress, salt, cold and abscisic acid treatments. AL5-overexpressing plants showed higher tolerance to salt, drought and freezing stress than Col-0. Consistently, al5 mutants showed reduced stress tolerance. We used ChIP-Seq assays to identify eight direct targets of AL5 and found that AL5 can bind to the promoter regions of these genes. Knock-out mutants of five of these target genes exhibited different tolerances to stresses. These results indicate that AL5 inhibits multiple signaling pathways to confer stress tolerance. Our study sheds light on mechanisms of AL5-mediated signaling in abiotic stress responses and provides tools for improvement of stress tolerance in crop plants.

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Keywords:Alfin1;Plant homeodomain;Arabidopsis;abiotic stress;ChIP-Seq