The Function Of MPK1/2and H₂O₂in BR Signaling And BR-induced Stress Tolerance In Tomato And The Study Of H2A.Z Involved In DNA Demethylation In Arabidopsis

Nowadays, due to the increasing of human activities and greenhouse effect, the global climate changed dramatically. The worse climate results in crops are easily affected by various abiotic stresses. These greatly restrict the safty of horticulture production and supply of vegetables in our country. Therefore, analyzing the physiological and molecular mechanisms of BR induced stress tolerance has very significant sense in both science and realism to improve the vegetable production, quality and economic benefit, and to establish sustainable agriculture.In this dissertation, the roles of MPK1/2and H2O2in BR signaling and BR-induced stress tolerance pathway were well studied in tomato. By using virus induced gene silencing (VIGS), the functions of MPK1、MPK2and RBOH1in BR induced tomato stress tolerance were further investigated from genetic level. The regulation of BR biosynthesis genes, dwarf and CPD in pTRV-RBOH1and pTRV-MPK1/2plant were studied. The connection and crosstalk between BR signaling pathway and BR-induced stress tolerance pathway were further investigated and a probable model was presented.Addtionally, the mechanisms of histone variant H2A.Z in the DNA demethylation were studied in Arabidopsis. The histone modification, gene silencing and DNA methylation were deeply investigated in order to research the epigenetic regulation to stress response genes in the future. Combining all the data we have in this dissertation, the conclusions are summarized as below:1EBR can active the phosphorylation of MPK1/2in tomato. The activiation of MPKl/2and burst of H2O2was induced by EBR treatment.2The function of MPK1、MPK2and RBOH1in EBR-induced stress tolerance were discovered. Virus-induced gene silenc-ing of RBOH1, MPK1, MPK2and MPK1/2resulted in reduced stress tolerance. BR-induced tolerance and MPK1/2activation were compromised in RBOH1-, MPK2-and MPK1/2-silenced plants but not in MPK1-silenced plants. These results suggested that MPK2played a more critical role than MPK1in EBR-induced apoplastic H2O2accumulation. RBOH1and MPK2were involved in BR-induced stress tolerance and likely involved a positive feedback loop among RBOH1, H2O2and MPK2.3The function of BR receptors BRI1、BAK1and the down stream transcriptional factor BZR1in the development and stress response were well studied. By VIGS, it was confirmed that BRI1, BAK1and BZR1were involved in the development and stress response in tomato. The silencing plants showed very strong deficient phenotype of development and were more sensitive to stresses.4The relative expression of BR biosynthesis genes, dwarf and CPD, were tested in pTRV-RBOH1and pTRV-MPK1/2plants. On one hand, the relative expression of dwarf and CPD were repress in pTRV-RBOH1and pTRV-MPK1/2plants. On the other hand, by analyzing the stress tolerance, production of H2O2and activity of MPK1/2in pTRV-BRI1, pTRV-BAK1and pTRV-BZR1plants, a probable relationship between the BR signaling pathway and BR-induced stress tolerance pathway was discovered.5In the root length based screen system, three new anti-silencing genes were cloned. The genes are ARP4, ARP6and PIE1. The native promoter of each gene was used to make the complementation in mutants.6The whole genomic DNA methylation by bisulfate sequence was analyzed. The DNA methylation levels were increased in arp4, arp6-1and piel-1. Using IP-MS and split-Luc, we confirm that ARP4, APR6, PIE1and H2A.Z are in a complex and H2A.Z can interact with ARP4. Using CHIP technology, The H2A.Z deposition was decreased in35S promoter in arp4, arp6-1and pie1-1.