Sulfur Dioxide Enhanced Cold Stress Adaptability Of Arabidopsis Thaliana

Sulfur dioxide(SO₂)is a common toxic air pollutant.High concentrations of SO₂ can exert adverse effects on plant photosynthesis,respiration,and nutrient metabolism,leading to inhibition of growth and development.Recently,it was found that exogenous SO₂ regulated plant responses to various environmental stresses.To date,the role of SO₂ in plants adaptation to cold stress is largely unknown.Nitric oxide(NO)is the first gas signal molecule to be identified,and it plays an important role in regulating the adversity stress process of plants.In the present research,we investigated the effects of exogenous SO₂ on the cold tolerance of Arabidopsis thaliana,as well as the regulatory roles and relevant mechanisms of NO in the improvement of the cold tolerance triggered by SO₂.The main results were as follows:(1)30 mg·m^-3 SO₂pre-exposure could enhance cold adaptability of Arabidopsis under low temperature conditions.The results showed that SO₂exposure resulted in the significant reduction of the stomatal aperture in the leaves of Arabidopsis under cold stress.Furthermore,SO₂ could enhance the activity of peroxidase(POD)to effectively reduce the reactive oxygen species(ROS)induced by low temperature,thereby alleviating the degree of oxidative damage.On the other hand,SO₂ could also increase P5CS activity and reduce PDH activity to promote proline accumulation in the leaves of Arabidopsis under cold stress.In addition,SO₂ could regulate the expression levels of CBF signaling pathway genes to enhance resistance to cold stress in Arabidopsis.(2)50?M SO₂ derivatives priming could effectively improve the cold resistance of Arabidopsis seedlings.Applying different concentrations of SO₂ derivatives(0,10,25,50,100?M),it was found that 50?M SO₂derivatives priming significantly effectively alleviated the growth inhibition of seedlings caused by cold stress.On the one hand,Exogenous SO₂derivatives could increase the activity of antioxidant enzymes(CAT,POD),thus reduced the content of hydrogen peroxide(H₂O₂)in Arabidopsis seedlings.Meanwhile,it could induce the upregulation of the expression of catalase gene At CAT and peroxidase gene At POD.On the one hand,SO₂derivative pretreatment exerted its positive effects on anthocyanin accumulation by increasing the expression level of genes involved in anthocyanin biosynthesis(At PAL,At CHS,At CHI,At F3H).Additionally,CBF pathway genes(At ICE1,At ICE2,At CBF1,At CBF2,At CBF3,At COR15a,At COR15b)were obviously upregulated with 50?M SO₂derivatives priming under cold stress.(3)Regulation of NO in the enhancement of cold resistance by SO₂derivatives in Arabidopsis thaliana.Studies have found that cold stress could induce a large accumulation of endogenous NO in Arabidopsis seedlings,and the application of 50?M SO₂ derivatives could inhibit the production of endogenous NO.SO₂ derivatives could increase the accumulation of anthocyanin by reducing the content of NO in seedlings,this change helped to alleviate the oxidative damage of seedlings.The purpose of this study is to illustrate the regulatory effects and related mechanisms of SO₂ on the adaptation of Arabidopsis seedlings under cold stress,and to provide a theoretical basis for improving cold tolerance of Arabidopsis thaliana plants.