Hydrogen sulfide (H2S) has been shown to participate in various stress responses in plants, including drought, salinity, extreme temperatures, osmotic stress, and heavy metal stress. Manganese (Mn), as a necessary nutrient for plant growth, plays an important role in photosynthesis, growth, development, and enzymatic activation of plants. However, excessive Mn2+ in the soil can critically affect plant growth, particularly in acidic soil. In this study, the model plant Arabidopsis thaliana was used to explore the mechanism of H2S participation and alleviation of Mn stress. First, using wild-type Arabidopsis with excessive Mn2+ treatment, the following factors were increased: H2S content, the main H2S synthetase L-cysteine desulfhydrase enzyme (AtLCD) activity, and the expression level of the AtLCD gene. Further, using the wild-type, AtLCD deletion mutant (lcd) and overexpression lines (OE5 and OE32) as materials, the phenotype of Arabidopsis seedlings was observed by exogenous application of hydrogen sulfide donor sodium hydrosulfide (NaHS) and scavenger hypotaurine (HT) under excessive Mn2+ treatment. The results showed that NaHS can significantly alleviate the stress caused by Mn2+, whereas HT aggravates this stress. The lcd mutant is more sensitive to Mn stress than the wild type, and the overexpression lines are more resistant. Moreover, the mechanism of H2S alleviating Mn stress was determined. The Mn2+ content and the expression of the Mn transporter gene in the mutant were significantly higher than those of the wild-type and overexpression lines. The accumulation of reactive oxygen species was significantly reduced in NaHS-treated Arabidopsis seedlings and AtLCD overexpression lines, and the activities of various antioxidant enzymes (SOD, POD, CAT, APX) also significantly increased. In summary, H2S is involved in the response of Arabidopsis to Mn stress and may alleviate the inhibition of Mn stress on Arabidopsis seedling growth by reducing Mn2+ content, reducing reactive oxygen species content, and enhancing antioxidant enzyme activity. This study provides an important basis for further study of plant resistance to heavy metal stress.
Keywords: Arabidopsis; L-cysteine desulfhydrase; antioxidant enzyme; hydrogen sulfide; manganese stress.