The Role of Histone Modifications in Plant Priming and Their Analysis by Chromatin Immunoprecipitation

Plants are frequently exposed to adverse conditions. Priming, also known as acclimation or hardening, induces stress memory and prepares plants for future challenges by activating defense and protective mechanisms. For this reason, priming is an effective means to maintain plant yield in the face of climate change. Memory behind the priming is mainly based on epigenetic modifications, for example, histone posttranslational modifications (PTMs) on the priming-related genes. While histone PTMs are the most diverse group of epigenetic modifications and regulate gene expression via addition of chemical groups to histone amino acids, their characterization is challenging. Chromatin immunoprecipitation (ChIP) is an essential method for the characterization of histone PTMs; however, subject to many challenges, especially in plant samples. This review discusses the current understanding of histone modifications in plant stress and priming and the ChIP methodology and troubleshooting. Yield losses resulting from climate change necessitate the use of priming as an agricultural practice. In order to apply priming, an in-depth analysis of stress- or priming-induced histone PTMs is essential. ChIP has been extensively used in plant stress studies and has undergone numerous improvements. Although there are more sophisticated methods, ChIP is still regarded as a standard method for the characterization of chromatin profiles. This review aims to support researchers in the utilization of ChIP, particularly, for plant stress and/or priming studies.