The Study Of Mechanisms Of Sulfide In The Regulation Of Leaf Senescence In Arabidopsis

Hydrogen sulfide (H2S) has recently been shown to be an endogenous gaseous molecule with physiologicalfunctions in plants as well as carbon monoxide (CO) and nitric oxide (NO). Previous studies have shown that exogenous H2S can significantly improve the antioxidant capacity of agricultural products such as strawberries and broccoli, and delay the preservation of these postharvest agricultural products. Emerging date suggest that in plant model Arabidopsis, a lost function mutant of DES1 (L-cysteine desulfhydrase 1) gene which is important to synthesis H2S, desl, negatively regulates autophagyin cytosol. The results revealed that H2S can regulate the senescence associated processes in plants. However, the molecular mechanism how H2S regulates plant senescence remains unclear. In this study, three genes LCD, DCD and DES1, that are associated with the synthesis ofH2S, were cloned from Arabidopsis thaliana and positive transgenic lines were obtained. These overexpressed lines served as unique materials for determine the potential roles of endogenous H2S on the regulation of senescence. Molecular biology, genetics and biochemistry methods are applied to investigate the effects of H2S on leaf senescence via these materials.Light is an important exogenous factors that affect plant senescence, and dark-induced senescence is considered to be the best model to research the plant senescence. We found that DES1 overexpressing transgenic lines significantly alleviated the chlorophyll degradation of detached leaf in dark. At the same time, the treatment of H2S from different exogenous donor also significantly inhibited the degradation of chlorophyll and pheophorbidea in detached leaf of Arabidopsis, but significantly increased the expression of senescence marker gene SAG12, SEN4 and SAG20. Furthermore the treatment of H2S can also accelerate senescence process and leaf cell death in detached leaves and living plants. Because there was a close link between antioxidant and leaf senescence, we determined the redox state of H2S-treated Arabidopsis leaves. We found H2S did not enhance the antioxidant capacity of leaves, but also significantly increased the level of plant leaves H2O2. However, the solution of H2S which induced the expression of leaf senescence signature gene such as SAG12 in dark, did not cause significant growth inhibition and leaf death under the light condition. It suggesting that H2S-controlled leaf senescence is not caused by toxicity and antioxidant. Furthermore, the study on the mutant gsnor1-3 which contains a higher content of NO than Col-0 found that the inhibitory effect of H2S on the chlorophyll degradation of Arabidopsis thaliana leaves could be alleviated by increasing the NO content. It suggests a possible cross-talk between NO and H2S during leaf senescence in Arabidopsis thaliana. Altogether, our data revealed that gaseous molecule H2S can enhance leaf senescence in Arabidopsis thaliana.