Molecular cloning and expression analysis of a WRKY transcription factor in sugarcane

Abstract

The WRKY proteins comprise a superfamily of transcription factors which are unique in plants. In the present study, a WRKY gene of sugarcane was isolated. This gene is 1 003 bp in full length, which includes 93 bp 5’ untranslated region (UTR) and 172 bp 3’ UTR. The open reading frame (ORF) of this gene is 738 bp which encodes 245 amino acids, with a typical WRKY DNA-binding domain at the 127 ~ 186 aa of the deduced amino acid sequences. The cysteine and histidine are also rich at the 153 ~ 184 aa, which is a C2H2 zinc finger domain of Class II and located at the C-terminal end of this deduced amino acid sequence; thus, this gene belongs to WRKYII. Furthermore, the prokaryotic expression vector of Sc-WRKY gene was successfully constructed and expressed in Escherichia coli (BL21 strain), and the molecular weight of the targeted product was about 25.7 kD. Real-time quantitative PCR analysis demonstrated that the Sc-WRKY gene was strongly induced by Ustilago scitaminea, salicylic acid (SA), NaCl and PEG, which suggests that this gene might play an important role in smut-resistant, drought-tolerant and salt-tolerant mechanism. Key words: Sugarcane (Saccharum officinarum), WRKY transcription factors, prokaryotic expression, real-time quantitative PCR.