Function Analysis Of Transcription Factor AtMYB44 And AtMYB15 During Defense Response In Arabidopsis

In response to biotic stresses and abiotic stresses, plants have developed complex signaling and defense mechanisms to protect themselves. Transcriptional regulation of related gene expression is critical for the plant responses to stresses. The MYB proteins comprise one of the largest families of transcription factors in plants. MYB family members are critical in many developmental processes and various defense responses. It is proved that AtMYB44 and AtMYB15 play important roles in response to abiotic stresses, but whether they involved in biotic stresses haven’t reported. Studies in this Ph.D thesis aim at determination of arabidopsis transcription factor AtMYB44 and AtMYB15 regulation function in plant responses to various biotic stresses through a series of biochemical, molecular biological and genetic methods.1. Function analyses of AtMYB44 in response to Erwinia carotovoraIn Arabidopsis, AtMYB44 can be induced by JA and Ecc. It is indicated that JA signaling is probably involved in resistance to Ecc. In order to analyze the function of AtMYB44, we generated transgenic Arabidopsis constitutively expressing AtMYB44 cDNA (35S-M-1) and ordered AtMYB44 T-DNA insertion mutants from TAIR (The Arabidopsis Information Resource). Ecc mainly infects in plant root. Compared with wild type (Col-0), the bacterial cells attached to root surfaces were significantly reduced on atmyb44 and increased on 35S-M-1 and were also same with leave. Moreover, several resistance-related genes were analyzed in Arabidopsis. Our results implied that AtMYB44 is a negative regulator in arabidopsis defense response against Ecc.2. AtMYB44 targets EIN2 to control the induction of GPA defenseHrpNEa is a harpin protein produced by the bacterial plant pathogen Erwinia amylovora. In Arabidopsis, HrpNEa can induce several signaling pathways and activate a lot of transcription factors. AtMYB44 is an ethylene-inducible transcription factor associated with defense responses in Arabidopsis. After treatment with HrpNEa, we studied 37 ethylene-inducible transcription factor genes in Arabidopsis. Ten genes increase transcription levels in response to HrpNEa, while AtMYB44 is most responsive. Further research implied that atmyb44 is more susceptible than WT to green peach aphid (GPA, Myzus persicae) infestation. EMS A show that AtMYB44 protein binds the EIN2 promoter. In conclusion, AtMYB44 targets EIN2 to control insect defense in the plant following HrpNEa application or under insect infestation.3. Mutant in Arabidopsis AtMYB15 transcription factor enhancing plant defense against Pseudomonas syringaeA common feature of plant defense responses is the transcriptional regulation of a large number of genes upon pathogen infection or treatment with pathogen elicitors. We analyzed the role of the AtMYB15 transcription factor from Arabidopsis in plant defense against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. AtMYB15 translational fusion with green fluorescent protein was localized to the nucleus. AtMYB15 is a R2R3-MYB and can be induced by JA and ABA. T-DNA insertion mutant for AtMYB15 reduced growth of Pst DC3000 and displayed reduced disease symptom severity as compared to wild-type plants. The atmybl5 mutant plants also displayed increased expression of the PR-1 and PDF1.2 genes after the pathogen infection. Based on analysis of T-DNA insertion mutants, AtMYB15 functions as a negative regulator of JA-mediated defense responses to Pst DC3000. In conclusion, AtMYB15 was a transcriptional activator and was able to activate the expression of genes involved in plant defense.Conclusive remarksIn Arabidopsis, we analyzed regulation function of arabidopsis transcription factor AtMYB44 and AtMYB15 in plant responses to various biotic stresses. We found:Firstly, AtMYB44 is a positve regulator in arabidopsis defense response against Ecc. Secondly, AtMYB44 targets EIN2 to control GPA defense in the plant following HrpNEa application or under insect infestation. Thirdly, we found that AtMYB 15 was a transcriptional activator and was able to activate the expression of genes involved in plant defense.