Molecular characterization of GmSTOP1 homologs in soybean under Al and proton stress

Background and aims The Sensitive to Proton Rhizotoxicity1 (STOP1) transcription factor has been implicated in the regulation of aluminium (Al) stress and proton toxicity for several plant species. This study aimed to characterize STOP1 homologs in soybean. Method Five GmSTOP1 homologs were studied by transcriptional expression, subcellular localization and overexpression experiments. Results Five GmSTOP1 homologs were nuclear-localized and exhibited transactivation activity. They constitutively expressed throughout the whole soybean plant. Their expressions were increased from 2 h, peaked at 4 h, returned to basal levels for the remaining duration of Al treatment but varied in aptitude and genotype. They were sensitive to pH conditions with various responses. Overexpression of GmSTOP1a in soybean hairy root increased the expression of the malate transporter gene GmALMT1, and decreased Al accumulation under Al stress. Its overexpression also regulated some pH-sensitive genes, including GmSTOP1c and GmCIPK23. Overexpression of GmSTOP1a in Arabidopsis slightly increase its Al resistance, and partially restored the root growth of the atstop1 mutant under Al stress. Conclusion GmSTOP1a contributes to both proton and Al resistance and plays a role similar to that of AtSTOP1. The functions of other four GmSTOP1 genes need further clarified.