ABA enhances drought tolerance in tomato seedlings partially dependent on SlDML2-directed DNA demethylation

Abstract Abscisic acid (ABA) is a kind of plant hormone that alleviates drought stress in many plant species. DNA methylation also plays an important role in plant drought stress tolerance. However, the relationship between ABA and DNA demethylase is unclear. Here, the action mechanism of tomato DEMETER-LIKE protein 2 (DML2) in ABA-mediated drought stress resistance was studied by mutating SlDML2. We found that the mutation of SlDML2 weakened plant growth conditions under drought stress. Additionally, the content of chlorophylls, the osmoregulatory substances (proline, soluble sugar, and soluble protein), and flavonoid were lower in sldml2-1 mutant under drought circumstances when compared with wild-type (WT) plants. However, these effects of the mutated SlDML2 couldn’t be reversed by the application of ABA. Furthermore, the expression levels of SlPYL1 and SlSnRK2.4 in ABA signaling pathway were downregulated in sldml2-1 mutants under drought stress compared with WT plants. Moreover, exogenous ABA reduced the DNA methylation level and the transcriptional abundances of its regulated genes by altering SlDML2-drived DNA demethylation under drought stress. The study here declared the important role of SlDML2 in ABA-improved plant drought tolerance, which may facilitate studies concerning ABA and DNA demethylation in the future.