ZmABA2, an interacting protein of ZmMPK5, is involved in abscisic acid biosynthesis and functions

Summary In maize ( Zea mays ), the mitogen‐activated protein kinase Zm MPK 5 has been shown to be involved in abscisic acid ( ABA )‐induced antioxidant defence and to enhance the tolerance of plants to drought, salt stress and oxidative stress. However, the underlying molecular mechanisms are poorly understood. Here, using Zm MPK 5 as bait in yeast two‐hybrid screening, a protein interacting with Zm MPK 5 named Zm ABA 2, which belongs to a member of the short‐chain dehydrogenase/reductase family, was identified. Pull‐down assay and bimolecular fluorescence complementation analysis and co‐immunoprecipitation test confirmed that Zm MPK 5 interacts with Zm ABA 2 in vitro and in vivo . Phosphorylation of Ser173 in Zm ABA 2 by Zm MPK 5 was shown to increase the activity of Zm ABA 2 and the protein stability. Various abiotic stimuli induced the expression of Zm ABA 2 in leaves of maize plants. Pharmacological, biochemical and molecular biology and genetic analyses showed that both Zm MPK 5 and Zm ABA 2 coordinately regulate the content of ABA . Overexpression of Zm ABA 2 in tobacco plants was found to elevate the content of ABA , regulate seed germination and root growth under drought and salt stress and enhance the tolerance of tobacco plants to drought and salt stress. These results suggest that Zm ABA 2 is a direct target of Zm MPK 5 and is involved in ABA biosynthesis and functions.