GhCYS2 governs the tolerance against cadmium stress by regulating cell viability and photosynthesis in cotton.

Cysteine, an early sulfur-containing compound in plants, is of significant importance in sulfur metabolism. CYS encodes cysteine synthetase that further catalyzes cysteine synthesis. In this investigation, CYS genes, identified from genome-wide analysis of Gossypium hirsutum bioinformatically, led to the discovery of GhCYS2 as the pivotal gene responsible for Cd2+ response. The silencing of GhCYS2 through virus-induced gene silencing (VIGS) rendered plants highly susceptible to Cd2+ stress. Silencing GhCYS2 in plants resulted in diminished levels of cysteine and glutathione while leading to the accumulation of MDA and ROS within cells, thereby impeding the regular process of photosynthesis. Consequently, the stomatal aperture of leaves decreased, epidermal cells underwent distortion and deformation, intercellular connections are dramatically disrupted, and fissures manifested between cells. Ultimately, these detrimental effected culminating in plant wilting and a substantial reduction in biomass. The association established between Cd2+ and cysteine in this investigation offered a valuable reference point for further inquiry into the functional and regulatory mechanisms of cysteine synthesis genes.