Root-specific overexpression of OsERF48 causes regulation of OsCML16, a calmodulin-like protein gene that enhances root growth and drought tolerance

The AP2/ERF family is one of the plant-speci?c transcription factors (TFs) whose members have been associated with various developmental processes and stress tolerance. Here, we functionally characterized the drought-inducible OsERF48, a group Ib member of the rice ERF family that contains four conserved motifs, CMI-1, 2, 3 and 4. Transactivation assay in yeast revealed that the CMI-1 at the C-terminal end was essential for its transcriptional activity. When the OsERF48 was overexpressed in an either root-specific (ROXOsERF48) or whole-body (OXOsERF48) expression manner, both transgenic plants showed a longer and denser root phenotype than the nontransgenic (NT) controls. When plants were grown on a 40% PEG-infused medium, an in vitro drought condition, ROXOsERF48 plants showed a more vigorous root growth over OXOsERF48 and NT plants. In addition, the ROXOsERF48 plants exhibited higher grain yield under field-drought conditions than OXOsERF48 and NT plants. We constructed a putative regulatory network of OsERF48 by cross-referencing of RNA-seq data of ROXOsERF48 roots with a co-expression network database, revealing an involvement of 20 drought-related genes. These include genes for stress signaling, carbohydrate metabolism, cell-wall proteins, and drought-response. More importantly, OsCML16, a key gene for calcium signaling during abiotic stress, was identified to be the direct target of OsERF48 by the ChIP-qPCR and the protoplast transient assay. Thus, our results demonstrated that OsERF48 regulates OsCML16, a calmodulin-like protein gene that enhance root growth and drought tolerance. Overall design: RNA-Seq on roots of nontransgenic control (NT) and root-specific OsERF48 overexpression transgenic rice.

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Jung H, Chung PJ, Park SH, Redillas MCFR, Kim YS, Suh JW, Kim JK