ZmWRKY30 modulates drought tolerance in maize by influencing myo-inositol and reactive oxygen species homeostasis.

Maize (Zea mays L.) is an important food crop with a wide range of uses in both industry and agriculture. Drought stress during its growth cycle can greatly reduce maize crop yield and quality. However, the molecular mechanisms underlying maize responses to drought stress remain unclear. In this work, a WRKY transcription factor-encoding gene, ZmWRKY30, from drought-treated maize leaves was screened out and characterized. ZmWRKY30 gene expression was induced by dehydration treatments. The ZmWRKY30 protein localized to the nucleus and displayed transactivation activity in yeast. Compared with wild-type (WT) plants, Arabidopsis lines overexpressing ZmWRKY30 exhibited a significantly enhanced drought stress tolerance, as evidenced by the improved survival rate, increased antioxidant enzyme activity by superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), elevated proline content, and reduced lipid peroxidation recorded after drought stress treatment. In contrast, the mutator (Mu)-interrupted ZmWRKY30 homozygous mutant (zmwrky30) was more sensitive to drought stress than its null segregant (NS), characterized by the decreased survival rate, reduced antioxidant enzyme activity (SOD, POD, and CAT) and proline content, as well as increased malondialdehyde accumulation. RNA-Seq analysis further revealed that, under drought conditions, the knockout of the ZmWRKY30 gene in maize affected the expression of genes involved in reactive oxygen species (ROS), proline, and myo-inositol metabolism. Meanwhile, the zmwrky30 mutant exhibited significant downregulation of myo-inositol content in leaves under drought stress. Combined, our results suggest that ZmWRKY30 positively regulates maize responses to water scarcity. This work provides potential target genes for the breeding of drought-tolerant maize.