Heterologous expression of HsPstS gene reducing arsenic accumulation and improving As-tolerance in transgenic tobaccos by enhancing CAT activity

Abstract

Arsenic (As) is a toxic metalloid element that affects plant growth and development. Reducing the uptake of arsenic by plants via genetic engineering strategy can effectively improve the tolerance and safety of economic crops in As-contaminated soil. In this paper, the HsPstS gene coded ABC-type periplasmic phosphate-binding protein (PBP) of Halomonas strain GFAJ-1 was introduced into tobacco K326 by Agrobacterium-mediated genetic transformation to create transgenic tobaccos. Under As stress, NBT and DAB staining of tobacco leaves showed significant accumulation of H2O2 in wild-type and CK plants, and the further determination showed that the H2O2 content in CK plants was higher than that in transgenic plants except for L35S-2 and LREL-4 at 3 d after stress. Generally, the activity of antioxidant enzymes (CAT and POD) in tobaccos increased first and then decreased under As stress, and the CAT activity in most transgenic tobacco plants was significantly higher than that in wild-type and CK plants at 5 d after stress. By contrast, POD activity in CK and wild-type plants was significantly higher than that in transgenic tobaccos except for L35S-2. Additionally, As content determination showed that all transgenic tobacco plants except for CK showed the characteristic of low As-accumulation, especially in transgenic tobaccos L35S-2 and LREL-4, which suggested that the introduction of HsPstS could significantly reduce the As absorption in HsPstS-contained transgenic tobaccos, while there was no significant influence on agronomic traits and photosynthetic characteristics of transgenic tobaccos compared with wild-type ones. Interestingly, the introduction of HsPstS gene also reduced the content of nicotine and nornicotine in transgenic tobacco plants, while there was no significant difference on K content between transgenic and non-transgenic tobaccos. These results above provided ideal parental materials for cultivating tobacco germplasm with the characteristic of low As-accumulation.