OsACA6, a P-type 2B Ca2+ ATPase functions in cadmium stress tolerance in tobacco by reducing the oxidative stress load

Abstract

The present study demonstrates the first direct evidence of the novel role of OsACA6 in providing Cd (2+) stress tolerance in transgenic tobacco by maintaining cellular ion homeostasis and modulating ROS-scavenging pathway. Cadmium, a non-essential toxic heavy metal, interferes with the plant growth and development. It reaches the leaves through xylem and may become part of the food chain, thus causing detrimental effects to human health. Therefore, there is an urgent need to develop strategies for engineering plants for Cd(2+) tolerance and less accumulation. The members of P-type ATPases family transport metal ions including Cd(2+), and thus play important role an ion homeostasis. The present study elucidates the role of P-type 2B Ca(2+) ATPase (OsACA6) in Cd(2+) stress tolerance. The transcript levels of OsACA6 were up-regulated upon Cd(2+), Zn(2+) and Mn(2+) exposure. Transgenic tobacco expressing OsACA6 showed tolerance towards Cd(2+) stress as demonstrated by several physiological indices including root length, biomass, chlorophyll, malondialdehyde and hydrogen peroxide content. The roots of the transgenic lines accumulated more Cd(2+) as compared to shoot. Further, confocal laser scanning microscopy showed that Cd(2+) exposure altered Ca(2+) uptake in OsACA6 transgenic plants. OsACA6 expression in tobacco also protected the transgenic plants from oxidative stress by enhancing the activity of enzymatic (SOD, CAT, APX, GR) and non-enzymatic (GSH and AsA) antioxidant machinery. Transgenic lines also tolerated Zn(2+) and Mn(2+) stress; however, tolerance for these ions was not as significant as observed for Cd(2+) exposure. Thus, overexpression of OsACA6 confers Cd(2+) stress tolerance in transgenic lines by maintaining cellular ion homeostasis and modulating reactive oxygen species (ROS)-scavenging pathway. The results of the present study will help to develop strategies for engineering Cd(2+) stress tolerance in economically important crop plants.

Research progressing of present contamination of Cd in soil and restoration method

“…Some researches found out that a kind of OsACA6, a P-type 2B Ca 2+ ATPase contained in transgene tobacco, may increase plants' antioxidation enzyme (SOD and CAT) activity and non-enzyme antioxidation activity. OsACA6 protects plant from Cd toxicity by adjusting and maintaining balance between ions and non-enzyme reactive oxygen species (ROS) inside cells [96] . 6) Selection of low-Cd-accumulation varieties Cd accumulation varies in different plants and varieties so that selection of low-Cd-accumulation varieties is considerable for reducing Cd absorption and accumulation in plants.…”

Calcium acetate‐induced reduction of cadmium accumulation in Oryza sativa: Expression of auto‐inhibited calcium‐ATPase and cadmium transporters

“…Although the role of ACA in up‐regulating ROS detoxification enzymes has been well described (Shukla et al . ), few studies have presented the response of Cd transporters under regulation of ACA . In 2014, OsACA6 ‐overexpressing tobacco growing in Cd‐contaminated medium had lower Cd concentrations and Cd translocation in the plant.…”

“…For example, transgenic tobacco with ACA6 had improved tolerance to Cd stress, by increasing activity of ROS detoxification enzymes and increasing the non‐enzymatic antioxidant content (glutathione and ascorbate; Shukla et al . ). Although the role of ACA in up‐regulating ROS detoxification enzymes has been well described (Shukla et al .…”

“…This result suggested that signal transduction from ACA not only effects ROS detoxification but can also affect Cd uptake and translocation in plants (Shukla et al . ). Therefore, the current study focused on the role of ACA in regulating Cd uptake and translocation.…”

“…In an experiment in 2014, transgenic tobacco with ACA6 seem to reduce the Cd concentration in the plant by reducing Cd translocation (Shukla et al . ). In this case, ACA6 might play a role in regulating the Cd transporter, resulting in a decrease in the Cd concentration in the plant.…”