Trehalose and NO work together to alleviate Cd toxicity in pepper (Capsicum annuum L.) plants by regulating cadmium sequestration and distribution within cells and the antioxidant defense system

The response of plants to trehalose (TR) and nitric oxide (NO) has been tested in different stressful conditions, but the contribution of endogenous TR to plant tolerance to cadmium stress (Cd-S) induced by NO is still unclear. Ten days after germination, among the pepper seedlings, half were immersed for 12 h in a solution containing 15.0 mM TR or 0.6 mM sodium citrate (SC), an inhibitor of trehalose-6-phosphate phosphatase (TPP). Then, the plants were exposed to control (no addition of Cd) or Cd-S (0.1 mM CdCl2) up to two additional weeks. Throughout the stress period, both treatments were combined with sodium nitroprusside (SNP; 0.1 mM), a NO donor, supplied through the nutrient solution. Plants exposed to Cd-S experienced a substantial reduction in plant growth, photosynthesis, and leaf water relation parameters, but an increase in oxidative stress parameters, free proline, phytochelatins (PCs), and the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), and ascorbate peroxidase (APX). The detrimental effects of Cd-S on the afore-mentioned traits were reversed by the supplementation of SNP, which in turn significantly increased the endogenous NO and TR levels, and leaf calcium (Ca2+) and potassium (K+), and reduced the leaf H2O2, MDA, and Cd contents as well as membrane leakage. SNP raised the amounts of GSH and PCs in Cd-S-plants, thereby modulating Cd sequestration to render it nontoxic. The treatment of SNP encouraged Cd build-up in the cell walls of root and leaf in order to prevent Cd from being transported to other vital cell organelles to safeguard them from metal toxicity. The supplementation of SC, a scavenger of TPP, eliminated TR content, thereby reversing the positive effect of SNP on Cd-S plants. Exogenous application of TR together with SNP+SC reversed the negative effect of SC. This suggests that TR is necessary for NO to be effective in improving the pepper plant Cd-S tolerance.

Automated summary

This study investigates the role of endogenous trehalose (TR) in plant tolerance to cadmium stress induced by nitric oxide (NO), and finds that TR plays an important role in NO's enhancement of pepper plant Cd-S tolerance.