Phosphatase AtDBP1 negatively regulates drought and salt tolerance through altering leaf surface permeability in Arabidopsis

In our previous study, AtDBP1 encoding a DBP factor was identified as a putative abiotic stress candidate gene. DBP factors are important regulators that participate in both transcriptional regulation and post-translational regulation, but their roles in abiotic stress are still not well-understood. So we conducted a detailed study on the function of AtDBP1 in abiotic stress. It is found that expression of AtDBP1 could be induced by drought and salt, and the induction by salt was inhibited in ABA-deficient mutant aba2-3, indicating the expression of AtDBP1 was ABA-inducible. Overexpression of AtDBP1 resulted in a rapid stomatal closure, and elevated expression of drought/salt-responsive genes, which should help Arabidopsis to enhance the drought and salt tolerance. Unexpectedly, overexpression of AtDBP1 decreased the drought and salt tolerance of Arabidopsis. Further analysis suggested that AtDBP1 is involved in cuticle wax and cuticle membrane regulation. Overexpression of AtDBP1 showed increased cuticular conductance due to a decreased cuticle wax accumulation and cuticle membrane thickness. The cuticular wax provides an essential barrier for decreasing nonstomatal water loss during drought stress, so overexpression of AtDBP1 showed decreased drought tolerance possibly ascribed to the change of cuticle membrane structure. Our previous study elucidated that AtDBP1 was also involved in flowering time regulation. Taken together, the results above indicated that AtDBP1 was involved in both plant development and stress regulation. The mechanism of AtDBP1 in this study indicates that genes involved in both plant development and stress regulation might be not suitable for production application in breeding. Collectively, our results provide some new ideas on purposefully increasing the abiotic stress without influence on plant growth and development.