Physiological Effect Of Hydrogen Sulfide On Regulating Amylase In Response To Drought Stress In Germinating Rice Seeds

Starch is the main material stored in rice seeds. It is degraded into small molecules to provide energy and matter for plants by amylase at the beginning of germination. Drought is an important factor limiting the germination of seeds and the normal growth of plants.Hydrogen Sulfide (H2S) is the third gas signal molecule named after CO and NO. It has been proved that H2S can promote the germination and growth of plant with a proper concentration.In this study, the rice (Oryza sativa L.) cultivar 'Hongtaiyou589' seeds were chosen to study the effect of H2S on antioxidant metabolism under drought stress by means of biochemistry, molecular biology, microscopy and histochemistry. Futhermore, the physiological effect of H2S was investigated on regulating the amylase in germinating rice seed subject to drought stress. The results indicated that exogenous H2S at a concentration of 0.75mM not only enhanced the activities of antioxidant enzymes such as catalase(CAT),peroxidase(POD), superoxide dismutase(SOD) and ascorbate peroxidase(APX) in rice seeds, but also increased the antioxidant content of soluble protein and ascorbic acid. It effectively eliminated the generation of hydrogen peroxide, and inhibited plasma membrane permeability and reduced malondialdehyde (MDA) content. Moreover, H2S accelerated seeds sorption and promoted seed germination, therefore, it significantly increased the germination rate of seeds. Further investigations showed that H2S significantly up-regulated the expression of the two key genes (OsAmy 1A and OsAmy 3D)of a-amylase in rice seeds under drought stress, correspondingly, increased the activity of a-amylase. Meanwhile, H2S significantly induced (3-amylase activity and raised the activity of total amylase in the germinated rice seeds subjected to drought stress, which resulted in faster degradation of starch stored in the endosperm. In addition, the degradation direction of starch endosperm was from proximal embryo to distal embryo in the germinating rice seeds. However,the H2S inhibitors HA and PAG reversed the above effects of H2S.Therefore, exogenous H2S could improve the antioxidant capacity of rice seed germination under drought stress, and effectively alleviate the effects of drought stress on the activity of amylase and promote seed germination.