Molecular regulation by H₂S of antioxidant and glucose metabolism in cold-sensitive Capsicum

Cold is an important environmental limiting factor affecting plant yield and quality. Capsicum (chili pepper), a tropical and subtropical vegetable crop, is extremely sensitive to cold. Although H₂S is an important signaling regulator in the responses of plant growth and development to abiotic stress, few studies have examined its effects on cold-sensitive capsicum varieties. Through biotechnology methods to enhance the cold resistance of peppers, to provide some reference for pepper breeding, investigated molecular regulation by H₂S of responses to cold stress in cold-sensitive capsicum plants, via physiological and transcriptomic analyses.

In capsicum seedlings, exogenous H₂S enhanced relative electrical conductivity (REC) and levels of malondialdehyde (MDA) under cold stress, maintained membrane integrity, increased the activity of enzymatic and non-enzymatic antioxidants, balanced reactive oxygen species levels (O₂^·- and H₂O₂), and improved photosynthesis, mitigating the damage caused by cold. In addition, 416 differentially expressed genes (DEGs) were involved in the response to cold stress after H₂S treatment. These DEGs were mainly enriched in the ascorbate-glutathione and starch-sucrose metabolic pathways and plant hormone signal-transduction pathways. Exogenous H₂S altered the expression of key enzyme-encoding genes such as GST, APX, and MDHAR in the ascorbate-glutathione metabolism pathway, as well as that of regulatory genes for stimulatory hormones (auxin, cytokinins, and gibberellins) and inhibitory hormones (including jasmonate and salicylic acid) in the plant hormone signal-transduction pathway, helping to maintain the energy supply and intracellular metabolic stability under cold stress.

These findings reveal that exogenous H₂S improves cold tolerance in cold-sensitive capsicum plants, elucidating the molecular mechanisms underlying its responses to cold stress. This study provides a theoretical basis for exploring and improving cold tolerance in capsicum plants.