The E3 Ubiquitin Ligase Gene Sl1 Is Critical for Cadmium Tolerance in Solanum lycopersicum L.

Abstract

Heavy metal cadmium (Cd) at high concentrations severely disturbs plant growth and development. The E3 ubiquitin ligase involved in protein degradation is critical for plant tolerance to abiotic stress, but the role of E3 ubiquitin ligases in Cd tolerance is largely unknown in tomato. Here, we characterized an E3 ubiquitin ligase gene Sl1, which was highly expressed in roots under Cd stress in our previous study. The subcellular localization of Sl1 revealed that it was located in plasma membranes. In vitro ubiquitination assays confirmed that Sl1 had E3 ubiquitin ligase activity. Knockout of the Sl1 gene by CRISPR/Cas9 genome editing technology reduced while its overexpression increased Cd tolerance as reflected by the changes in the actual quantum efficiency of PSII photochemistry (ΦPSII) and hydrogen peroxide (H2O2) accumulation. Cd-induced increased activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were compromised in sl1 mutants but were enhanced in Sl1 overexpressing lines. Furthermore, the content of Cd in both shoots and roots increased in sl1 mutants while reduced in Sl1 overexpressing plants. Gene expression assays revealed that Sl1 regulated the transcript levels of heavy metal transport-related genes to inhibit Cd accumulation. These findings demonstrate that Sl1 plays a critical role in regulating Cd tolerance by relieving oxidative stress and resisting heavy metal transportation in tomato. The study provides a new understanding of the mechanism of plant tolerance to heavy metal stress.

The Potential of CRISPR/Cas Technology to Enhance Crop Performance on Adverse Soil Conditions

“…Similarly, KO of the rice Low Cadmium (OsLCD) gene also diminished Cd accumulation in the shoot, but maintained yield under high Cd concentrations in comparison to the wild genotype [242]. Another Cd-related gene, Sl1, was knocked out in tomatoes, and edited plants displayed increased Cd accumulation in plant tissues, as well as increased ROS activity in comparison to the wild-type and overexpression lines [243].…”

Transcriptome Analysis Reveals Changes in Whole Gene Expression, Biological Process, and Molecular Functions Induced by Nickel in Jack Pine (Pinus banksiana)

“…The UPS can aid in the modulation of stress signaling by regulating the numbers of proteins and transcription factors involved in the stress response [76]. In other plants, increased expression of E3 ubiquitin ligases counteracted heavy metal stress by elevating the expression of antioxidant enzymes, reducing ROS and repressing the transportation of heavy metals via chelation [77,78]. Under high salinity and drought stress, the RING-H2 finger protein can also regulate the synthesis of ABA, which is a hormone involved in stress mitigation and stress-associated signaling [79,80].…”

A Systematic Review on the Improvement of Cd Stress Tolerance in Ramie Crop, Limitations and Future Prospective

“…CRISPR/Cas9 has been employed in many crops for the development of Cd tolerance. A successful example was presented by Liu et al [185], in which they edited the Sl1 gene in tomatoes using CRISPR/Cas9, which enhanced Cd tolerance by increasing the efficiency of antioxidant enzymes and increased photosynthesis. Gene expression analysis showed that Sl1 regulated the transcript levels of heavy metals transporter genes to prevent Cd accumulation [185].…”

“…A successful example was presented by Liu et al [185], in which they edited the Sl1 gene in tomatoes using CRISPR/Cas9, which enhanced Cd tolerance by increasing the efficiency of antioxidant enzymes and increased photosynthesis. Gene expression analysis showed that Sl1 regulated the transcript levels of heavy metals transporter genes to prevent Cd accumulation [185]. Many heavy metal transporters have been knocked out using CRISPR/Cas9 to enhance abiotic tolerance in many crops.…”