The multiple effects of hydrogen sulfide on cadmium toxicity in tobacco may be interacted with CaM signal transduction.

Soilless culture experiments with tobacco were conducted to explore how the signal molecule HS (0.3, 0.6, 0.9, and 1.2 μM) alleviated the toxicity of Cd (50 mg/L). The results suggested that photosynthesis was enhanced as HS improved the tobacco ΦPSII, ETR, Photo, Cond, and Tr, and that by increasing the NPQ, it consumed considerable amount of energy to enhance plant resistances during Cd exposure. Furthermore, HS increased the gene transcription of NtSOD3, NtPOD1, and CAT1, to enhance antioxidant enzyme activity, which reduces the generation of the reactive oxygen protective membrane integrity. Additionally, HS increased the gene expression of the tobacco PC genes, Pr2 and Pr8 promoted the formation of the Cd complexes and transportation to the vacuole, resulting in improved Cd-ATPase gene expression, away from organelles, to alleviate the Cd poison. Furthermore, HS regulated the relative absorption of K and Ca, which antagonized the Cd, and reduced its transportation to the aboveground plant material. Finally, the expression level of CaM increased with the application of HS, and was highly correlated with the fitted results of a variety of resistance indicators, thereby indicating that HS regulatory resistance mechanisms might be associated with Ca signal transduction.