Modulation of an evolutionarily conserved epigenetic regulon controlling abscisic acid catabolism enhances drought tolerance in wheat.

Drought stress significantly reduces crop yield by triggering abscisic acid (ABA) accumulation in plants. It involves the suppression of CYP707A genes, which encode enzymes that catalyze ABA. However, little is known about epigenetic control in the CYP707A gene-mediated drought stress response in wheat. In this study, we reported that TaCYP707A-6A/6B/6D but not TaCYP707A-5A/5B/5D participates in drought response in common wheat. Disruption of TaCYP707A-6B showed enhanced drought tolerance but also decreased fertility. Expression of TaCYP707A-6B is negatively associated with H3K27me3 level. An evolutionarily conserved CTCTGYTY motif cluster (binding site for a Jumonji H3K27me3 demethylase) was found in the intron of TaCYP707A-6B as well as the intron of CYP707A homologs in other plant species. Blocking the CTCTGYTY motif by dead Cas9 (dCas9) maintained a high level of H3K27me3 on the CYP707A gene, while decreasing its expression level leading to enhanced drought tolerance in both wheat and Arabidopsis. In particular, the mutant in which the intron bound by H3K27me3 demethylase was cut out without change of splicing pattern showed enhanced drought tolerance. Therefore, our study provides a novel approach to improve plant drought tolerance by manipulating an evolutionarily conserved cis-element bound by histone demethylases in the intron of CYP707A genes.