Overexpression of tomato RING E3 ubiquitin ligase gene SlRING1 confers cadmium tolerance by attenuating cadmium accumulation and oxidative stress

Abstract

Heavy metal pollution not only decreases crop yield and quality, but also affects human health via the food chain. Ubiquitination‐dependent protein degradation is involved in plant growth, development, and environmental interaction, but the functions of ubiquitin‐ligase (E3) genes are largely unknown in tomato (Solanum lycopersicum L.). Here, we functionally characterized a RING E3 ligase gene, SlRING1, which positively regulates cadmium (Cd) tolerance in tomato plants. An in vitro ubiquitination experiment shows that SlRING1 has E3 ubiquitin ligase activity. The determination of the subcellular localization reveals that SlRING1 is localized at both the plasma membrane and the nucleus. Overexpression of SlRING1 in tomato increased the chlorophyll content, the net photosynthetic rate, and the maximal photochemical efficiency of photosystem II (Fv/Fm), but reduced the levels of reactive oxygen species and relative electrolyte leakage under Cd stress. Moreover, SlRING1 overexpression increased the transcript levels of CATALASE (CAT), DEHYDROASCORBATE REDUCTASE (DHAR), MONODEHYDROASCORBATE REDUCTASE (MDHAR), GLUTATHIONE (GSH1), and PHYTOCHELATIN SYNTHASE (PCS), which contribute to the antioxidant and detoxification system. Crucially, SlRING1 overexpression also reduced the concentrations of Cd in both shoots and roots. Thus, SlRING1‐overexpression‐induced enhanced tolerance to Cd is ascribed to reduced Cd accumulation and alleviated oxidative stress. Our findings suggest that SlRING1 is a positive regulator of Cd tolerance, which can be a potential breeding target for improving heavy metal tolerance in horticultural crops.

Plant E3 Ligases and Their Role in Abiotic Stress Response

“…In tomato the REALLY INTERESTING NEW GENE 1 (SlRING1) protein is also critical for Cd 2+ tolerance [ 157 ]. Tomato transgenic lines that overexpress SlRING1 displayed higher photosynthetic rates and higher chlorophyll levels, compared to wildtype, when treated with Cd 2+ [ 157 ]. The transgenic lines also showed a reduction in ROS level and overall membrane damage [ 157 ].…”

Increase in Phytoextraction Potential by Genome Editing and Transformation: A Review

“…Thus, enhanced tolerance to Cd due to induced SlRING1-overexpression is attributed to reduced Cd accumulation and the alleviation of oxidative stress. These findings suggest that SlRING1 is a positive regulator of Cd tolerance, which could be a potential breeding target for improving HM tolerance in plants [ 93 ].…”

Praseodymium enhanced the tolerance of maize seedlings subjected to cadmium stress by up-regulating the enzymes in the regeneration and biosynthetic pathways of ascorbate and glutathione

“…Other studies showed that hormones KT and SA could enhance the Cd tolerance of plants by regulating the metabolism of ascorbate and glutathione, which further maintained redox balance in plant cells (Yan et al 2016, Bashri et al 2021. Ahammed et al (2021) found that tomato RING E3 ubiquitin ligase gene SlRING1 played an important role in fighting against Cd toxicity by regulating the metabolism of ascorbate and glutathione. However, under Cd stress, whether Pr can regulate the metabolism of ascorbate and glutathione through the above hormones and RING E3 ubiquitin ligase gene SlRING1 is still unclear.…”