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

Background: Accumulated evidence suggest that specific patterns of histone posttranslational modifications (PTMs) and their crosstalks may determine transcriptional outcomes. However, the regulatory mechanisms of these "histone codes" in plants remain largely unknown.

Results: 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.

Conclusion: 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.