SALT-RESPONSIVE ERF1 regulates reactive oxygen species–dependent signaling during the initial response to salt stress in rice

Early detection of salt stress is vital for plant survival and growth. Still, the molecular processes controlling early salt stress perception and signaling are not fully understood. Here, we identified SALT-RESPONSIVE ERF1 (SERF1), a rice (Oryza sativa) transcription factor (TF) gene that shows a root-specific induction upon salt and hydrogen peroxide (H2O2) treatment. Loss of SERF1 impairs the salt-inducible expression of genes encoding members of a mitogen-activated protein kinase (MAPK) cascade and salt tolerance–mediating TFs. Furthermore, we show that SERF1-dependent genes are H2O2 responsive and demonstrate that SERF1 binds to the promoters of MAPK KINASE KINASE6 (MAP3K6), MAPK5, DEHYDRATION-RESPONSIVE ELEMENT BINDING2A (DREB2A), and ZINC FINGER PROTEIN179 (ZFP179) in vitro and in vivo. SERF1 also directly induces its own gene expression. In addition, SERF1 is a phosphorylation target of MAPK5, resulting in enhanced transcriptional activity of SERF1 toward its direct target genes. In agreement, plants deficient for SERF1 are more sensitive to salt stress compared with the wild type, while constitutive overexpression of SERF1 improves salinity tolerance. We propose that SERF1 amplifies the reactive oxygen species–activated MAPK cascade signal during the initial phase of salt stress and translates the salt-induced signal into an appropriate expressional response resulting in salt tolerance.This work was in part conducted within the European Reseacrh Area Network Plant Genomics project ‘TRIESTER - Trilateral Initiative for Enhancing Salt Tolerance in Rice’ for which funding was provided by the Bundesministerium für Bildung und Forschung (BMBF) in Germany (Grant 0313993A), the Agence Nationale de la Recherche in France (Grant ANR-06-ERAPG-005-01), and Ministerio de Educación y Ciencia (Grant GEN2006-27794-C4-1-E) in Spain. Part of this work was conducted on the Rice Functional Genomics platform, Montpellier, France, funded by Agropolis Foundation. R.S. thanks the FAZIT Stiftung for providing a PhD fellowship.Peer reviewe