Global epigenetic changes of histone modification under environmental stresses in rice root.

Abiotic stresses are non-living factors with negative morphological and physiological effects on living organisms. Substantial evidence exists that gene expression changes during plant cell growth are regulated by chromatin reconfiguration and histone modification. Several types of histone modifications are dramatically transformed in stress-responsive gene regions under drought stress conditions. Environmental stresses also cause the root apical meristem (RAM) region to decelerate root growth. In this study, we investigated how quantitative changes in epigenetic markers in this region influence rice morphology and physiology. Both iron and salinity treatments changed the epigenetic landscape from euchromatic to heterochromatic according to heterochromatin (H3K9me2) and euchromatin (H3K4me) markers, especially in the proximal meristem region. Moreover, supplementation with external abscisic acid (ABA) was able to mimic the effect of environmental stresses on global epigenetic changes. In contrast, the addition of external auxin (IAA) to rice under saline conditions affected heterochromatin formation without influencing euchromatin transformation. Chromatin dynamics is therefore believed to be directly connected to plant growth regulator signaling. We discuss insights into the role of plant growth regulators: ABA and IAA, peroxide signaling, and their effects on the global epigenetic change of histone modification under abiotic stresses.