Physiological Function Of H₂S Signal In Response To Drought Stress In Arabidopsis Thaliana

Hydrogen sulfide?H₂S?plays an important physiological regulation function in plant as the third gasotransmitter after nitric oxide?NO?and carbon monoxide?CO?.With the study of H₂S signal in plant,the physiological and biochemical functions of H₂S in plant are gradually revealed: regulating growth and development processes including the seed germination,root organogenesis,photosynthesis,stomatal movement,flower organ development,leaf senescence and responsing to biotic and abiotic stresses.The research of H₂S as a new type of signal molecule has made great progress.However,there is still an urgent problem to describe its physiological function,mechanism and signal network relationship with other signal molecules systematically.Therefore,it is very important to explain the physiological function,mechanism of action and relationship with other signal molecules of endogenous H₂S in multi-angle and multi-level in plant.In this study,Arabidopsis thaliana wild-type WT?Col-0?,L-Cys desulfhydrase enzyme encoding gene LCD konckdown mutant?lcd?,WRKY18,WRKY40 and WRKY60 encoding gene knockout triple mutants?wrky18wrky40wrky60?,H₂S-producing enzyme encoding gene DES defective mutants?des?and DES over-expression plant?OE-DES?were used as experimental materials to investigate the physiological function and mechanism of H₂S signal in the root growth,stomatal movement,photosynthesis and leaf senescence of Arabidopsis thaliana.The main results are as follows:?1?The research about the relationship between H₂S signal and ABA in regulating root growth and stomatal movement showed that,the expression level of LCD and the content of endogenous H₂S in WT were increased after exogenous ABA treatment.H₂S signal could regulate the transcription level of WRKY18,WRKY40 and WRKY60.Due to endogenous H₂S deletion,the inhibition of ABA to WRKY18 and WRKY40 transcription disappeared in lcd mutant.So,H₂S participated inthe transcriptional regulation of ABA to WRKYs transcription factors;the root growth of lcd seedlings were weakly inhibited by exogenous ABA,the root growth of wrky18wrky40wrky60 were obviously promoted by exogenous H₂S.Above all,H₂S may take part in the regulation of ABA in root growth by regulating the genes expression of WRKY18,WRKY40 and WRKY60,while the regulation of H₂S to plant root growth partly depends on WRKYs,that is,the regulation of H₂S to plant root growth has other ways,which are not dependent on WRKY18 / 40 / 60 way.In addition,exogenous ABA promoted the stomatal closure of WT,but the feature of stomatal closure was significantly attenuated in lcd.Exogenous H₂S promoted the stomatal closure of wrky18wrky40wrky60 and WT,and there was no significant difference between them.All these results suggested that H₂S was involved in the process of ABA regulating the stomatal movement in a WRKY18,WRKY40 and WRKY60 independent way.?2?The research about H₂S signal on the photosynthesis of leaves showed that,under normal growth conditions,endogenous H₂S promoted the net photosynthesis rate,transpiration rate and chlorophyll content increased significantly in leaves.When the plant were subjected to drought stress,endogenous H₂S could protect the chloroplast structure intactly,promote the significant increase of net photosynthesis rate and intercellular CO2 concentration,induce stomatal closure and decrease of transpiration rate in leaves significantly.Therefore,H₂S may regulate the stomatal movement to achieve a balance between transpiration rate and photosynthetic efficiency,which promoted photosynthesis effectively and ensured the normal growth of plant in response to drought stress.?3?The study about the H₂S signal on energy metabolism and leaf senescence showed that,under normal growth conditions,endogenous H₂S mainly down-regulated leaf-age-dependent gene SAG12 to delay leaf premature senescence in OE-DES.While the genes expression level of ATP?-1,ATP?-2,ATP?-3 were up-regulated and the gene expressionlevel of ATPe was down-regulated in des.Under drought stress,the gene expression level of SAG13 was up-regulated significantly in des,which lead to premature senescence of its leaves.The genes expression level of ATP?-1,ATP?-2 and ATP?-3 were up-regulated and the gene expression level of ATPe was down-regulated in OE-DES.The activity of ATPase in OE-DES mitochondria was significantly higher than in des,and the content of ATP in des mitochondrial was significantly higher than in OE-DES.All these results implied that,endogenous H₂S regulated the expression pattern of ATP synthase-related genes,ATPase activity and ATP content,which played the role of energy metabolism regulator and maintained the dynamic balance of energy for plant growth and development.In addition,under drought stress,endogenous H₂S could reduce mitochondrial swelling damage and maintain the integrity of structure and function of mitochondrial,then improve mitochondrial energy production and delay leaves senescence.In conclusion,H₂S signal enhances the drought resistance by regulating the root growth,stomatal movement,photosynthesis and leaf senescence in Arabidopsis thaliana.