Study on the tolerant function of soybean GmGST7 gene to acidic aluminum stress

Objective The GmGST7 gene was obtained from the gene expression profile of the GsMYB7 overexpressed lines of soybean ‘Huachun 6’ which was tolerant to acidic aluminum stress. GmGST7 lied downstream of the GsMYB7 gene, and was up-regulated by acidic aluminum stress. Its function of acidic aluminum resistance was further investigated to enhance the tolerance to aluminum stress in soybean.

Method The bioinformatics of the GmGST7 gene was analyzed using the base sequence, protein domain and phylogenetic tree. Subcellular localization of GmGST7 protein was accomplished by transient transformation in tobacco leaves. The tissue expression specificity of the GmGST7 gene was analyzed by RT-qPCR. Five AlCl₃ concentration gradients of 0, 25, 50, 75 and 100 µmol/L were designed to study the response of GmGST7 to aluminum stress. Under the treatment of 50 µmol/L AlCl₃, nine time gradients of 0, 4, 8, 12, 16, 24, 36, 48 and 72 h were designed to investigate the expression patterns of GmGST7. Arabidopsis (Col-0) was transformed by overexpression of GmGST7, positive plants were identified by molecular technology. The phenotype identification of Arabidopsis tolerant to acidic aluminum stress were performed with the oxidation level determination, the expression analysis of the genes response to aluminum stress and downstream genes of GmGST7.

Result The full-length sequence of GmGST7 located on chromosome 7 of soybean was 1 128 bp. The GmGST7 gene contained two exons and one intron which encodes a highly conserved N domain and a unconserved C domain of GST, respectively. GmGST7 encoded 226 amino acids. The GmGST7 protein was a tau member of the GST family in soybean, and localized in the nuclear and cytoplasm. GmGST7 was expressed in soybean root, stem, leaf, flower and young pod, and rich in root. The GmGST7 gene was up-regulated by AlCl₃ with the highest relative expression under 50 µmol/L AlCl₃ for 24 h. The relative root elongation of wild type was significantly lower than that of the transgenic lines, the oxidation level was higher, and the expression levels of acidic aluminum stress response genes and downstream genes were higher.

Conclusion The GmGST7 gene is a tau member of the GST family in soybean, locates in the nucleus and cytoplasm. The GmGST7 gene holds a constitutive expression pattern, and is rich in soybean root. GmGST7 is significantly up-regulated by acidic aluminum stress. Overexpression of GmGST7 enhances the tolerance to aluminum stress in Arabidopsis by activating the expression of the marker genes response to acidic aluminum stress and its downstream genes.