Enhancing Arabidopsis Salt and Drought Stress Tolerance by Chemical Priming for Its Abscisic Acid Responses

Drought and salt stress tolerance of Arabidopsis (<i>Arabidopsis thaliana</i>) plants increased following treatment with the nonprotein amino acid -aminobutyric acid (BABA), known as an inducer of resistance against infection of plants by numerous pathogens. BABA-pretreated plants showed earlier and higher expression of the salicylic acid-dependent <i>PR-1</i> and <i>PR-5</i> and the abscisic acid (ABA)-dependent <i>RAB-18</i> and <i>RD-29A</i> genes following salt and drought stress. However, <i>non-expressor of pathogenesis-related genes 1</i> and <i>constitutive expressor of pathogenesis-related genes 1</i> mutants as well as transgenic NahG plants, all affected in the salicylic acid signal transduction pathway, still showed increased salt and drought tolerance after BABA treatment. On the contrary, the <i>ABA deficient 1</i> and <i>ABA insensitive 4</i> mutants, both impaired in the ABA-signaling pathway, could not be protected by BABA application. Our data demonstrate that BABA-induced water stress tolerance is based on enhanced ABA accumulation resulting in accelerated stress gene expression and stomatal closure. Here, we show a possibility to increase plant tolerance for these abiotic stresses through effective priming of the preexisting defense pathways without resorting to genetic alterations.