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

Abstract

SUMMARYPlant 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 Arabidopsis thaliana Alfin1-like PHD finger proteins (ALs) in terms of the responses to abiotic stresses. ALs localized to the nucleus and repressed transcription. Except AL6, all the ALs bound to G-rich elements. Mutations of the amino acids at positions 34 and 35 in AL6 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. AL5-over-expressing 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 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 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.

A Histone Code Reader and a Transcriptional Activator Interact to Regulate Genes for Salt Tolerance

“…Unlike other Alfin1-like proteins suppressing expression of negative factors during stress response (Wei et al, 2009(Wei et al, , 2015, the interaction of GmPHD6 with LHP1 activates transcription of its target genes ( Fig. 7A; Supplemental Fig.…”

“…proteins are transcriptional suppressors; they play biological roles through inhibition of their downstream genes (Wei et al, 2009(Wei et al, , 2015. However, GmPHD6 somehow loses its suppression activity (Fig.…”

“…Our previous study shows that the N-terminal domains of other GmPHD proteins play major roles in DNA binding (Wei et al, 2009), and mutation of two amino acids in the N-terminal domain caused the functional loss of G-rich element binding activity in Arabidopsis PHD protein AtAL6 (Wei et al, 2015). Thus, we performed an EMSA assay to test the DNA binding property of GmPHD6.…”

“…For instance, Alfin1 found in Medicago sativa was reported to bind to the promoter of MsPRP2 and enhance but not suppress the expression of MsPRP2 (Bastola et al, 1998;Winicov and Bastola, 1999). Besides, AtAL6 from Arabidopsis is unable to bind to the G-rich element, because the N-terminal has two crucial point mutations (Wei et al, 2015). In this study, we reported another special case of Alfin1-like protein, GmPHD6, in soybean, whose transcriptional regulatory ability is somehow missing.…”

“…GmPHD1 to GmPHD5 have transcriptional suppression activity but GmPHD6 does not have this activity (Wei et al, 2009). The Alfin1-like proteins are usually associated with abiotic stress responses (Wu et al, 2011;Song et al, 2013;Wei et al, 2015). They are also involved in elongation of root hairs during P starvation and the seed germination process (Chandrika et al, 2013;Molitor et al, 2014).…”