A transcriptional repressor of the ERF family confers drought tolerance to rice and regulates genes preferentially located on chromosome 11.

Plant-specific ethylene response factors (ERFs) play important roles in abiotic and biotic stress responses in plants. Using a transgenic approach, we identified two rice ERF genes, OsERF4a and OsERF10a, which conferred drought stress tolerance. In particular, OsERF4a contains a conserved ERF-associated amphiphilic repression (EAR) motif in its C-terminal region that has been shown to function as a transcriptional repression domain. Expression profiling of transgenic rice plants over-expressing OsERF4a using either a constitutively active or an ABA-inducible promoter identified 45 down-regulated and 79 up-regulated genes in common. The increased stress tolerance by over-expression of the EAR domain-containing protein OsERF4a could result from suppression of a repressor of the defense response. Expression of the putative silent information regulator 2 (Sir2) repressor protein was repressed, and expression of several stress-response genes were induced by OsERF4a over-expression. The Sir2 and 7 out of 9 genes that were down-regulated by OsERF4a over-expression were induced by high salinity and drought treatments in non-transgenic control plants. Genes that were down- and up-regulated by OsERF4a over-expression were highly biased toward chromosome 11. Rice chromosome 11 has several large clusters of disease-resistance and defense-response genes. Taken together, our results suggest that OsERF4a is a positive regulator of shoot growth and water-stress tolerance in rice during early growth stages. We propose that OsERF4a could work by suppressing a repressor of the defense responses and/or by controlling the expression of a large number of genes located on chromosome 11.