H₂S Signal Can Improve Cucumber Resistance To Gray Mold Through Regulate Expression Of The PR Genes

Cucumber gray mold is caused by Botrytis cinerea infection,and the annual yield loss caused by this is about 20%.Therefore,it is extremely important for the prevention and control of gray mold disease and other fungal infections.PR proteins（Pathogenesis-Pelated Protein）is a series of proteins that are encoded by host plant genes to respond to external stresses when plants are subject to pathogen invasion or stimulation by non-biological factors.Previous studies have found that it is effective in plant resistance to powdery mildew,gray mold,downy mildew and etc.WRKY family transcription factors play an important role in the signal transmission process of plants in response to biological stress,which can regulate the transcriptional expression of a variety of PR proteins.H₂S signal molecules regulate stomata and participate in plant response to a variety of abiotic stresses,such as salt stress,heavy metal stress,drought stress and etc.However,there are no in-depth research reports on biological stress.This subject used cucumber as the material to explore the function of H₂S in plant biological stress for the first time.It provides new ideas and theoretical basis for the prevention and control of cucumber gray mold and fungal diseases.The exploration has supplemented the research of hydrogen sulfide in the related fields of plant disease resistance,and laid the foundation for further research on the molecular mechanism of H₂S in the process of disease resistance.The results show as follow.（1）Plants treated with H₂S are more resistant to Botrytis cinerea than wild-type plants.（2）The 9 PR genes of Arabidopsis were used as query sequences to blast and screen out 6 PR genes in the cucumber genome database.Among them,the PR1 and PR4 genes of cucumber have obvious responses to exogenous hydrogen sulfide.Transcriptome analysis shows that H2S have no obvious regulatory of expression for genes upstream of the PR protein in the salicylic acid pathway.（3）Cucumber PR1 and PR4 recombinant proteins expressed in p ET-28a prokaryotic vector can inhibit the growth of Botrytis cinerea.（4）The promoter regions of cucumber PR1 and PR4 proteins contain binding sites for WRKY family transcription factors.WRKY46 and WRKY51recombinant proteins can be sulfhydrylated by hydrogen sulfide in vitro.Based on these experimental results,it is speculated that H₂S can sulfhydrylate WRKY46 and WRKY51 transcription factors to enhance their binding efficiency with the promoter of PR1 genes,thereby active the expression of PR1 and PR4 genes which enhances cucumber resistance to gray mold.The pathway of H₂S enhanced disease resistance is different from the pathway of salicylic acid or jasmonic acid,and is very likely a new signal transduction pathway.