Involvement Of H₂S In SO₂-Induced Stomatal Movement And Guard Cell Death In Vicia Faba Leaves

Sulfur dioxide (SO2) is a major air pollutant. The lower concentration of SO2can affect plant stomatal movement, cause stomatal opening decreases and affect the normal physiology activity of plants; The higher levels of SO2can cause plant leaves green losting or necrosis, restrain cells division, induce micronucleus formation and leading cell death. When the concentration of SO2in environment is high, SO32-the metabolites of SO2, can be reductde into H2S in the action of the sulfite reductase. And then H2S is released out away the plant body. The plant can adjust their sulfur element balance through the release of H2S. H2S is confirmed the third kind of endogenous gas signal molecules after NO and CO, plays an important role in biology various response signal transduction pathways. So, whether H2S is Involved in the stress signal transduction process of SO2? It is not been reported.The stomatic guard cells, which in the model experiment system to study of the signal transduction of plant, can makes ingenious and accurate response to the changed of the external environment and the stimulates of internal development signal. In this study, the role of H2S were investigated in SO2stress signal transduction process in Vicia faba leaves. The expermential results indicated that H2S participate in the stress signal transduction process of SO2, and play a role mainly through influencing intracellular Ca2+level. The experimental results are as follows:Lower concentration of SO2can induce stomatal closure in Vicia faba, when the concentration of SO2is higher, it can induce cell death and nuclear abnormalities through affecting guard cell activityand the normal physiology function of guard cells.Stomatal aperture decreased after epidermal strips exposed to1~200umol·L-1SO2derivatives or exposed to10~100μmol·L-1H2S derivatives for2h. In the present study, Antioxidants HT can partly relieve stomatal aperture decrease caused by SO2derivatives and fully relieve stomatal aperture decrease caused by H2S. HT can significantly inhibits the rise of Ca2+level induced by SO2in guard cells, but not obvious effect to the rise of the levels of ROS and NO caused by SO2.100μmol·L-1H2S can cause the rise of Ca2+level in the guard cells.Epidermal strips can make the reducing of cell activity, partly the death after epidermal strips exposed to2-6mmol·L-1SO2derivatives or exposed to1~5mmol·L-1H2S derivatives for3h. In the present study, antioxidants HT can partly relieve the rate of cell death caused by SO2derivatives and H2S. HT can significantly inhibits the rise of Ca2+level, but not obvious effect to the rise of the levels of ROS and NO caused by200μmol·L-1SO2.1mmol·L-1H2S can cause the rise of Ca2+level in the guard cells.SO2can induced guard cell nuclear abnormalities in detached epidermis of Vicia faba leaves at concentrations of0.2mmol·L-1and higher(3-6h exposure). Antioxidants HT can partly relieve guard cell nuclear abnormalities caused by SO2. The exogenous H2S also can induced guard cell nuclear abnormalities.The results of the study show that:There were less SO2enters into plant through the stomatal closure. HT played important roles in SO2induced stomatal movement. SO2can induces ROS levels rising and NO synthetic increasing, and then the content of H2S is increased. Further, intracellular Ca2+level is rising mainly from Ca2+influx and Ca2+releasing from intracellular calcium library, then mediated a series of signal responses to regulate stomatal movement.SO2can induced guard cell death in Vicia faba. HT played important roles in SO2induced guard cell death. SO2can induces ROS levels rising sharply and NO synthetic massive increasing, and then the content of H2S is increased. Further, intracellular Ca2+level is greatly increased mainly from Ca2+influx and Ca2+releasing from intracellular calcium library, then mediated a series of signal responses to regulate stomatal movement.SO2can induced guard cell nuclear abnormalities, may be association with the reducing of the cell activity, and H2S participate in the process of guard cell nuclear abnormalities.