Expression of zma-miR169 miRNAs and their target ZmNF-YA genes in response to abiotic stress in maize leaves.

The miR169 miRNA family is highly conserved in plants. Its members regulate the expression of genes encoding the universal transcription factor subunit NUCLEAR FACTOR-Y subunit A (NF-YA) via transcript cleavage. NF-YA regulates gene expression by binding the CCAAT box sequence in target promoters. The miR169/NF-YA module plays a critical role during plant development and in plant responses to abiotic stress. We characterized the secondary structures of maize pre-miR169 miRNAs and predicted their potential gene targets. Coexpression of zma-miR169 and ZmNF-YA in Nicotiana benthamiana demonstrated that mutations in or deletion of target sites abolished regulation by zma-miR169. Maize seedlings were subjected to short-term (0-48h) and long-term (15days) drought, abscisic acid (ABA), or salt stress. Long-term exposure to PEG (drought stress) or NaCl (salt stress) repressed seedling growth. We investigated the expression patterns of zma-miR169s and their target ZmNF-YA genes in maize leaves and found diverse changes in expression in response to the three stress treatments. The expression of most zma-miR169 genes was downregulated by PEG and upregulated by ABA. In response to salt stress, zma-miR169 genes were upregulated initially and subsequently downregulated. Most ZmNF-YA genes were upregulated during the short term and downregulated by 15days in response to the three stress treatments.