Cloning of molecular chaperone ShDnaJ gene in sugarcane and its expression analysis under stress of sugarcane streak mosaic virus

【Objective】The purpose of the study was to clone the molecular chaperone gene ShDnaJ in sugarcane, and analyze its expression pattern under the stress of sugarcane streak mosaic virus(SCSMV), so as to provide a theoretical reference for exploring the function and mechanism of action of ShDnaJ gene in sugarcane in response to SCSMV infection.【Method】ShDnaJ gene complete open reading frame(ORF) sequence was cloned by homologous cloning technology and was analyzed by bioinformatics software. The subcellular localization of ShDnaJ protein was analyzed by fusion expression with green fluorescent protein(GFP). The expression levels of ShDnaJ gene in different tissues of sugarcane and under SCSMV stress were detected by real-time fluorescence quantitative PCR.【Result】The open reading frame(ORF) of ShDnaJ gene was 1260 bp in length, and encoded 419 amino acid residues. ShDnaJ protein, with molecular weight of 45682.47 Da and theoretical isoelectric point(pI) of 8.78, was a stable hydrophilic protein, which contained a DnaJ structural domain and belonged to the member of DnaJ superfamily. ShDnaJ protein was located in the endoplasmic reticulum. The secondary structure of ShDnaJ protein consisted of 113 α-helixes, 31 β-turns, 78 extended strands and 197random coils. The amino acid sequence of ShDnaJ protein had the highest amino acid sequence similarity with that of SbDnaJ in sorghum, which was 96.93%, indicating that the two proteins were most closely related. ShDnaJ gene was expressed in roots, stems and leaves of sugarcane, and the expression levels in roots and stems were significantly higher than that in leaves(P<0.05, the same below). However, the expression level of ShDnaJ gene in immature stems was higher than that in mature stems. The expression level of ShDnaJ gene in mature leaves was higher than that in immature leaves.With the pass of treatment time, the relative expression of ShDnaJ gene in the SCSMV stress group and the control group(treated with phosphate buffer) showed an overall downward trend, but the expression levels of ShDnaJ genes were significantly higher than those in the control group at different time points after SCSMV inoculation.【Conclusion】ShDnaJ gene has tissue expression specificity, and the maturity of the tissue affects its expression level. The expression of this gene is up-regulated under SCSMV stress, suggesting that this gene is involved in regulating sugarcane plant resistance to SCSMV.