Soybean GmVIT1 Gene Confers Plant Tolerance to Excess Fe/Mn Stress

Abstract

Iron (Fe) and (Mn) are essential for the plant but are toxic when in excess. Vacuolar iron transporters (VITs) are involved in plant metal storage and detoxication. In this study, we screened two soybean cultivars (HN51 and SN37) with different responses to iron stress. From HN51 and SN37, we identified a new gene GmVIT1, for which expression is closely related to iron stress response by transcriptomic and quantitative analysis. We obtained GmVIT1 and GmVIT1 promoter from the iron deficiency-tolerant soybean variety Heinong51. Sequence analysis showed that GmVIT1 contained a conserved 170-residue VIT domain and localized at the tonoplast. Moreover, GmVIT1 is expressed in soybean leaves, stems, and roots. The expression of GmVIT1 was significantly induced by excessive Fe/Mn in leaves and stems. GUS assay showed that excess Fe/Mn enhanced GmVIT1 promoter activity. Furthermore, overexpression of GmVIT1 in Arabidopsis seedlings showed reduced phytotoxic effects induced by excess Fe/Mn stress, including yellowing in leaves, decreased chlorophyll content, and accumulated MDA. GmVIT1 overexpression in Arabidopsis showed relatively higher soluble sugar content and SOD, POD, and CAT activity. In addition, the ferric reductase activity in GmVIT1 overexpression in Arabidopsis decreased under excess Fe, while it increased under excess Mn. By integrating all these results, we found that GmVIT1 plays a vital role in plant response to excess Fe/Mn. The results showed that GmVIT1 was worthy of metal homeostasis mechanism research in plants and could be applied in the metal toxic-tolerance improvement in crops.