Functional Analysis Of GSNOR1 In The Regulation Of H₂O₂-induced SA Signaling Pathway In Arabidopsis Thaliana

It has been traditionally recogonized that oxidative stress induced by reactive oxygen species?ROS?has toxic effects on plant growth and development.However,a large body of evidence shows that ROS acts as an important signalling molecule in response to external stresses?such as drought,pathogen,etc?.Particularly,while hydrogen peroxide?H₂O₂?is the the most stable form of ROS and moderately reactive,it is involved in salicylic acid?SA?-associated plant immune response.Similar to H₂O₂,S-nitrosylated glutathione?GSNO?is also considered to be a signalling molecule in SA-dependent signalling pathway as well.However,it is still unclear if and how GSNO could interact with H₂O₂ in the regulating SA-associated pathway.To the end,catalase deficient mutant cat2 and S-nitrosylated glutathione reductase mutant gsnor1-3 were exploited to study the effects of interaction of H₂O₂ with GSNO in the regulation of SA-dependent pathways.The results shows that enhanced H₂O₂ availability due to CAT2 mutation could not only induced SA synthesis but also activated the expression of SA-related defense genes?PR1?and leaf programmed cell death.Nevertheless,mutation in GSNOR1 blocked H₂O₂-triggered SA accumulation and signaling pathway.Further analysis of transcriptome found that double mutant cat2 gsnor1-3 compeletely supressed H₂O₂-triggered SA accumulation and the expression of defense genes.These data demonstrates that GSNO negatively regulated the H₂O₂-induced SA signaling pathway.In order to further analyze the regulatory mechanism of GSNO in regulation of H₂O₂signaling pathway,I utilized laser scanning confocal microscope to determine ROS level in both leaf and root,and aslo measured glutathione content and GOX activity.It were found that there was not significant reduction of H₂O₂ production and level as well as its-triggered oxidative stress in cat2 gsnor1-3 compared with cat2.I also found that exogenously applied ROS inducer?paraquat?did not significantly enhance the expression of ROS response genes in gsnor1-3 mutant.In summary,my work suggests that GSNO negatively modulates H₂O₂-induced SA signaling pathway via regulating H₂O₂ downstrem signaling rather than inhibiting H₂O₂ level.