Chloride (Cl⁻) is considered a crucial nutrient for plant growth, but it can be a challenge under saline conditions. Excessive accumulation of Cl⁻ in leaves can cause toxicity. Chloride channels (CLCs) are expressed in the inner membranes of plant cells and function as essential Cl⁻ exchangers or channels. In response to salt stress in plants, CLCs play a crucial role, and CLC proteins assist in maintaining the intracellular Cl⁻ homeostasis by sequestering Cl⁻ into vacuoles. Sodium chloride (NaCl) is the primary substance responsible for causing salt-induced phytotoxicity. However, research on plant responses to Cl⁻ stress is comparatively rare, in contrast to that emphasizing Na⁺. This review provides a comprehensive overview of the plant response and tolerance to Cl⁻ stress, specifically focusing on comparative analysis of CLC protein structures in different species. Additionally, to further gain insights into the underlying mechanisms, the study summarizes the identified CLC genes that respond to salt stress. This review provides a comprehensive overview of the response of CLCs in terrestrial plants to salt stress and their biological functions, aiming to gain further insights into the mechanisms underlying the response of CLCs in plants to salt stress.

Salt stress represents a significant abiotic stressor for plants and poses a severe threat to agricultural productivity. Glutaredoxins (GRXs) are small disulfide reductases that can scavenge cellular reactive oxygen species and are crucial for plant growth and development, particularly under stressful circumstances. Although CGFS-type GRXs were found to be involved in various abiotic stresses, the intrinsic mechanism mediated by LeGRXS14, a tomato (Lycopersicon esculentum Mill.) CGFS-type GRX, is not yet fully understood. We discovered that LeGRXS14 is relatively conserved at the N-terminus and exhibits an increase in expression level under salt and osmotic stress conditions in tomatoes. The expression levels of LeGRXS14 in response to osmotic stress peaked relatively rapidly at 30 min, while the response to salt stress only peaked at 6 h. We constructed LeGRXS14 overexpression Arabidopsis thaliana (OE) lines and confirmed that LeGRXS14 is located on the plasma membrane, nucleus, and chloroplasts. In comparison to the wild-type Col-0 (WT), the OE lines displayed greater sensitivity to salt stress, resulting in a profound inhibition of root growth under the same conditions. Analysis of the mRNA levels of the WT and OE lines revealed that salt stress-related factors, such as ZAT12, SOS3, and NHX6, were downregulated. Based on our research, it can be concluded that LeGRXS14 plays a significant role in plant tolerance to salt. However, our findings also suggest that LeGRXS14 may act as a negative regulator in this process by exacerbating Na⁺ toxicity and the resulting oxidative stress.

The tomato (Solanum lycopersicum L.), a widely cultivated and economically important vegetable crop, is subject to a number of biotic and abiotic stresses in nature. Several abiotic and biotic stresses have been demonstrated to elevate the concentration of cytosolic free Ca²⁺ ([Ca²⁺]_i) in Arabidopsis due to the influx of calcium ions. In this study, recombinant aequorin was introduced into the tomato in order to investigate the change in [Ca²⁺]_i when treated with exogenous Ca²⁺. This resulted in strong luminescence signals, which were mainly observed in the roots. Luminescence signals were also detected in the whole plant, including the leaves, when a surfactant (Silwet L-77) was added to coelenterazine. The concentration of [Ca²⁺]_i increased with the dosage of NaCl/elf18. The luminescence signals also showed a lower increase in intensity with elf18 treatment compared to NaCl treatment. Furthermore, the [Ca²⁺]_i responses to other abiotic or biotic stresses, such as H₂O₂ and Pep1, were also evaluated. It was found that this transgenic tomato expressing aequorin can effectively detect changes in [Ca²⁺]_i levels. The transgenic tomato expressing aequorin represents an effective tool for detecting changes in [Ca²⁺]_i and provides a solid basis for investigating the adaptation mechanisms of tomatoes to various abiotic and biotic stresses. Moreover, the aequorin-based system would be a highly valuable tool for studying the specificity and crosstalk of plant signalling networks under abiotic and biotic stresses in tomatoes.

The authors wish to correct the following error in the original paper