MYB transcription factors play vital role in various biotic and abiotic defense responses. A differentially expressed, stress-responsive, R2-R3-type, MYB-like transcription factor-associated EST (MYB18) from drought and salt SSH libraries was identified. A full-length DNA sequence of a MYB gene, namely SoMYB18, was isolated from sugarcane var. Co740. SoMYB18 encodes for an ORF of 1284 bp having 427 amino acids with 47.43 kDa theoretical protein size MYB protein. The phylogenetic characterization of the deduced amino acid sequence showed similarity with monocot MYB proteins. SoMYB18 is a member of the R2R3-MYB subfamily, containing two MYB DNA-binding domains (R2, R3) and a SANT/MYB DNA-binding domain. The SoMYB18 gene was transferred into tobacco, and stable transgenic plants expressing SoMYB18 were evaluated for salt, drought and cold tolerance. Compared to un-transformed tobacco plants, SoMYB18-expressing plants exhibited notably improved tolerances to salt and drought stress. The SOD and CAT activities were considerably elevated in transgenic plants, as well as proline accumulation and chlorophyll content were considerably high and lipid peroxidation was reduced relative to un-transformed plants during salt stress. These results indicated that this sugarcane R2R3-MYB transcription factor plays key role in regulating stress responses and may be implicated in the activation of salt-related genes, being useful in improving the salt stress tolerance in crops.
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