The overexpression of ATPS1 gene, a homodimeric enzyme involved in sulfur assimilation, confers Fe-deficient tolerance in Malus halliana

Abstract

Iron (Fe) deficiency is one of the most common micronutrient deficiencies limiting crop production globally, especially in arid regions because of decreased availability of iron in alkaline soils. S supply increases Fe availability to plants, ATP sulphatase plays an important role in the synthesis of organic sulfur in plants, which is considered to be an important rate-limiting enzyme in sulphur uptake. However, the mechanism of whether it responds to Fe deficiency in plants remains unclear. Here, we identified a ATP sulphatase gene MhATPS1 from Malus hallinan based on qRT-PCR and then genetically transformed it into tobacco and apple calli, which showed that transgenic tobacco and overexpressed apple calli secreted more H+ content compared to the wild type (WT), resulting in increased inter-root acidification. In addition, the transgenic tobacco and apple calli showed better growth under Fe deficiency conditions. Furthermore, increased Fe2+ content and ferric chelate reductase (FCR) activity in the transgenic tobacco and overexpressed calli indicated improved Fe uptake, which is also confirmed by up-regulation of Fe uptake genes, e.g. FRO2, IRT1, FER and FIT. Under Fe deficiency stress, having more strengthened antioxidant capacity in transgenic tobacco, and the same results were shown in overexpressed apple calli. At last, the NBT and DAB staining results also verified the greater scavenging capacity of reactive oxygen species in transgenic tobacco. In summary, the MhATPS1 gene may play a positive role in Fe deficiency stress both tobacco and apple calli.