Ethylene response factors gene regulation and expression profiles under different stresses in rice

Stresses can cause large yield reductions in cultivated plants. The response to these stresses occurs via a plethora of signalling pathways, where a large number of genes is induced or repressed. Among the environmental stress responsive genes, there are the members of the ethylene response factors (ERF) gene family. The mRNA levels of different ERF are regulated by many hormones and molecules produced under different stress conditions. In this study, with the goal of identifying the response of rice ERF genes to environmental stress, it was analysed the transcriptional expression profile of 114 of these genes under stress by anoxia, salt and Magnaporthe grisea. Also, aiming to characterize how the regulation of ERF genes occurs, the amount of known cis regulatory elements in the promoter region of these genes and their association with the expression profiles under the tested conditions were also assessed. The results indicate that some ERF members present the same specific expression profiles under different environmental stresses, while others do not. Within the ERF family, the regulation of gene expression is complex for some genes which have many cis elements in their promoters, but simple for others, demonstrating high levels of divergence among them. The findings demonstrate the importance of the study of each ERF separately, since it is not possible to establish general rules for regulation and probably for the function of these genes. KeywoRDS: Oryza sativa, transcription, cis elements, environmental stresses. INTRoDUCTIoN Many biotic and abiotic agents can stress cultivated plants, negatively affecting their yield. However, during evolution, plants developped mechanisms capable of perceiving environmental changes regulating the induction or repression of many genes. The majority of these genes take part in metabolic response pathways, enabling the adaptation to adverse environmental conditions (Yamaguchi-Shinozaki and Shinozaki 2006). A complex regulatory network is involved in the induction of stress responsive genes (Yamaguchi-Shinozaki and Shinozaki 2006), and a large number of these genes was identified using differential expression analysis in many different species. In the majority of cases, these processes are coordinated by phytohormones, such as ethylene and abscisic acid (Fujimoto et al. 2000). One of the most important gene families that are related to environmental responses and tolerance is the ethylene response factors (ERF) gene family. Despite its name, these genes are not only regulated by ethylene, but also by other molecules such as abscisic, salicylic, jasmonic, giberellic acids and their interactions (Sakuma et al. 2002, Grennan 2008). ERF genes are defined by the domain AP2/ERF, which consists of aproximately 60 aminoacids involved in DNA binding. The cis element GCC-Box (AGCCGCC) is recognized by the majority of ERF members (Ohme-Takagi and Shinshi 1995); however, despite the high conservation on the aminoacid sequence in the ERF binding domain, these factors can also bind other motifs specifically (Nakano et al. 2006, Sasaki et al. 2007, Welsch et al. 2007, Maeo et al. 2009). ReSeARCH ARTICLe