Arabidopsis Histone Variant H2A.X Functions in the DNA Damage-Coupling Abscisic Acid Signaling Pathway

Environmental variations initiate chromatin modifications, leading to the exchange of histone subunits or the repositioning of nucleosomes. The phosphorylated histone variant H2A.X (γH2A.X) is recognized for the formation of foci that serve as established markers of DNA double-strand breaks (DSBs). Nevertheless, the precise roles of H2A.X in the cellular response to genotoxic stress and the impact of the plant hormone abscisic acid (ABA) remain incompletely understood. In this investigation, we implemented CRISPR/Cas9 technology to produce loss-of-function mutants of <i>AtHTA3</i> and <i>AtHTA5</i> in <i>Arabidopsis</i>. The phenotypes of the <i>athta3</i> and <i>athta5</i> single mutants were nearly identical to those of the wild-type Col-0. Nevertheless, the <i>athta3 athta5</i> double mutants exhibited aberrant embryonic development, increased sensitivity to DNA damage, and higher sensitivity to ABA. The RT-qPCR analysis indicates that <i>AtHTA3</i> and <i>AtHTA5</i> negatively regulate the expression of <i>AtABI3</i>, a fundamental regulator in the ABA signaling pathway. Subsequent investigation demonstrated that <i>AtABI3</i> participates in the genotoxic stress response by influencing the expression of DNA damage response genes, such as <i>AtBRCA1</i>, <i>AtRAD51</i>, and <i>AtWEE1</i>. Our research offers new insights into the role of H2A.X in the genotoxic and ABA responses of <i>Arabidopsis</i>.