GmPHD5 acts as an important regulator for crosstalk between histone H3K4 di-methylation and H3K14 acetylation in response to salinity stress in soybean

In this study, we demonstrate for the first time that a salinity stress inducible PHD (plant homeodomain) finger domain containing protein GmPHD5 can read the "histone code" underlying the methylated H3K4. GmPHD5 interacts with other DNA binding proteins, including GmGNAT1 (an acetyl transferase), GmElongin A (a transcription elongation factor) and GmISWI (a chromatin remodeling protein). Our results suggest that GmPHD5 can recognize specific histone methylated H3K4, with preference to di-methylated H3K4. Here, we illustrate that the interaction between GmPHD5 and GmGNAT1 is regulated by the self-acetylation of GmGNAT1, which can also acetylate histone H3. GmGNAT1 exhibits a preference toward acetylated histone H3K14. These results suggest a histone crosstalk between methylated H3K4 and acetylated H3K14. Consistent to its putative roles in gene regulation under salinity stress, we showed that GmPHD5 can bind to the promoters of some confirmed salinity inducible genes in soybean.Here, we propose a model suggesting that the nuclear protein GmPHD5 is capable of regulating the crosstalk between histone methylation and histone acetylation of different lysine residues. Nevertheless, GmPHD5 could also recruit chromatin remodeling factors and transcription factors of salt stress inducible genes to regulate their expression in response to salinity stress.Previous studies demonstrated that histone modifications such as H3 and H4 acetylation and H3S10 phosphorylation are involved in plant salinity stress [1]. Chromatin immuno-precipitation (ChIP) studies indicated that the levels of H3K4me3, H3K9ac, H3K14ac, H3K23ac and H3K27ac are altered in the coding regions of drought stress-responsive genes, including RD29A (Responsive-to-Dessication protein 29A), RD29B (Responsive-to-Dessication protein 29A), and RD20 (Responsive-to-Dessication protein 20), when they were activated under drought stress conditions [2]. Besides, the protein profile analysis of salt-responsive proteins sugg