RsERF1 derived from wild radish ( Raphanus sativus ) confers salt stress tolerance in Arabidopsis

The change in environmental parameters affects normal growth of plants, eventually reduces agricultural production. Ethylene plays vital roles in plant stress responses, germination, fruit ripening, organ abscission, pathogen response, and senescence. Expression of an ethylene-responsive transcription factor ( ERF ) was induced in Korean halophyte, Raphanus sativus var. hortensis f. raphanistroides (wild radish) by 200-mM sodium chloride (NaCl). Raphanus sativus ethylene-responsive transcription factor 1 (RsERF1) is also localized to nucleus, similar to other transcription factors. In yeast, RsERF1 showed transcriptional activation property, by expressing the reporter gene. Being a TF, RsERF1 specifically bound to the cis -acting elements, GCC box and DRE/CRT in vitro, to initiate transcription. Homozygous T3 transgenic Arabidopsis, overexpressing RsERF1 , showed significant tolerance against salt stress in soil-grown conditions. The tolerance was also marked by an increased germination rate of RsERF1 transgenics in salt-containing media. In RsERF1 overexpression lines, abiotic stress-related genes such as ABF3 , ABF4 , ADH , Rab18 , and SUS1 were upregulated by 200-mM NaCl. ERF s have been studied and proven for their tolerance potential against various abiotic stresses, but RsERF1 belongs to an ERF subgroup called ethylene-responsive transcription factor related to AP2 ( ERF - RAP2 ). Thus, this is a first report for ERF - RAP2 from Korean halophyte cDNA library. We believe that extensive posttranslational modification studies will reveal the role and location of RsERF1 in stress tolerance pathway.