Data_Sheet_1.docx

Aluminum (Al) toxicity in acidic soils affects crop production worldwide. C2H2-type zinc finger transcription factor STOP1/ART1-mediated expression of Al tolerance genes has been shown to be important for Al resistance in Arabidopsis, rice and other crop plants. Here, we identified and characterized four STOP1-like proteins (SbSTOP1a, SbSTOP1b, SbSTOP1c, and SbSTOP1d) in sweet sorghum, a variant of grain sorghum (Sorghum bicolor L.). Al induced the transcription of the four SbSTOP1 genes in both time- and Al concentration-dependent manners. All SbSTOP1 proteins localized to the cell nucleus, and they showed transcriptional activity in a yeast expression system. In the HEK 293 coexpression system, SbSTOP1d showed transcriptional regulation of SbSTAR2 and SbMATE, indicating the possible existence of another SbSTOP1 and SbSTAR2-dependent Al tolerance mechanism in sorghum apart from the reported SbMATE-mediated Al exclusion mechanism. A transgenic complementation assay showed that SbSTOP1d significantly rescued the Al-sensitivity characteristic of the Atstop1 mutant. Additionally, yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays showed that SbSTOP1d interacted with SbSTOP1b and SbSTOP1d itself, suggesting that SbSTOP1 may function as a homodimer and/or heterodimer. These results indicate that STOP1 plays an important role in Al tolerance in sweet sorghum and extend our understanding of the complex regulatory mechanisms of STOP1-like proteins in response to Al toxicity.

酸性土壤中铝（Al）的毒性对全球作物产量产生影响。研究表明，C2H2型锌指转录因子STOP1/ART1介导的耐铝基因表达在拟南芥、水稻及其他作物植物的抗铝性中至关重要。在本研究中，我们鉴定并表征了在甜高粱（一种高粱变种，Sorghum bicolor L.）中存在的四种STOP1样蛋白（SbSTOP1a、SbSTOP1b、SbSTOP1c和SbSTOP1d）。铝处理可诱导四种SbSTOP1基因在时间和铝浓度依赖性方式下的转录。所有SbSTOP1蛋白定位于细胞核内，并在酵母表达系统中表现出转录活性。在HEK 293共表达系统中，SbSTOP1d表现出对SbSTAR2和SbMATE的转录调控，这表明在已报道的SbMATE介导的铝排除机制之外，可能存在另一种由SbSTOP1和SbSTAR2依赖的铝耐受机制。转基因互补实验表明，SbSTOP1d显著挽救了Atstop1突变体的铝敏感性特征。此外，酵母双杂交和双分子荧光互补（BiFC）实验显示，SbSTOP1d与SbSTOP1b以及自身相互作用，表明SbSTOP1可能作为同源二聚体和/或异源二聚体发挥作用。这些结果揭示了STOP1在甜高粱耐铝性中的重要作用，并拓展了我们对于STOP1样蛋白在铝毒性响应中的复杂调控机制的理解。