The Ethylene Response factor SmERF1 Improves Salinity Tolerance and Impacts Seed Size in Tobacco

Abstract

Background Ethylene response factor (ERF) proteins play vital roles in plant resistance and plant development. However, little is known about the ERF transcription factors of Salvia miltiorrhiza, which is a famous Chinese herb with good resistance to stress. Result Screened from our previous transcriptome data, SmERF1, an ERF transcript factor, was isolated from S. miltiorrhiza. SmERF1 had a single AP domain and was classified in the ERF E3 subfamily. SmERF1-expressing tobacco plants showed slower growth, less biomass and a decrease in chlorophyll only at the seedling stage, and there was no significant difference in other growth stages. In addition, seeds of tobacco plants with SmERF1 expression were smaller and lighter than those of wild plants, similar to some AP2 TFs. Under NaCl treatment, transgenic tobacco lines showed better tolerance to salinity, and the proline content, SOD and POD activities of transgenic lines were higher than those of wild-type plants, while MDA content was lower than that of wild-type plants. Furthermore, we determined the phytohormones related to plant resistance and showed that transgenic tobacco plants had higher ABA levels and lower GA levels than wild tobacco. The expression of SmERF1 regulated the expression of key enzyme genes related to plant hormone biosynthesis, such as NtSDR, NtGA20ox, NtACO and NtACS. Conclusions The SmERF1-expression in tobacco affect plant growth at seedling stage, and increase plant tolerance to salt. And the expression of SmERF1 cause tobacco seeds smaller and lighter. Our study suggested that SmERF1 enhanced tobacco tolerance to salt and impacted seed size through an ABA-dependent pathway.