Mulberry EIL3 confers salt and drought tolerances and modulates ethylene biosynthetic gene expression

Ethylene regulates plant abiotic stress responses and tolerances, and ethylene-insensitive3 (EIN3)/EIN3-like (EIL) proteins are the key components of ethylene signal transduction. Although the functions of EIN3/EIL proteins in response to abiotic stresses have been investigated in model plants, little is known in non-model plants, including mulberry (Morus L.), which is an economically important perennial woody plant. We functionally characterized a gene encoding an EIN3-like protein from mulberry, designated as MnEIL3. A quantitative real-time PCR analysis demonstrated that the expression of MnEIL3 could be induced in roots and shoot by salt and drought stresses. Arabidopsis overexpressing MnEIL3 exhibited an enhanced tolerance to salt and drought stresses. MnEIL3 overexpression in Arabidopsis significantly upregulated the transcript abundances of ethylene biosynthetic genes. Furthermore, MnEIL3 enhanced the activities of the MnACO1 and MnACS1 promoters, which respond to salt and drought stresses. Thus, MnEIL3 may play important roles in tolerance to abiotic stresses and the expression of ethylene biosynthetic genes.