Study On The Role Of Brassica Napus WRKY75 In Response To Phosphate Starvation

Phosphorus is one of the essential nutrients for plant growth and development.Although abundant P is present in soils,very little of it is present in phosphate(Pi),the forms available for plants.So the plant evolves a complex mechanism to adapt to this long-term phosphate deficiency state.Some genes related to low phosphate stress,such as phosphate transporter,phosphatase and transcription factors,have been identified in Arabidopsis thaliana,but the low-phosphate response genes of Brassica napus,one of the important economic crops,are rarely studied.In this study,BnWRKY75 was cloned from Brassica napus and the results of the study were displayed as follows.1.Isolation and characterization of Bn WRKY75From Pi-response genes of B.napus,Bn WRKY75 was identified.Its ORF is 444 bp,and encodes 144 amino acids.The protein sequence of BnWRKY75 shares 87%similarity with AtWRKY75,and they are highly homologous which are in the the same branch of evolutionary tree.2.The transcription activity analysis of BnWRKY75In plants,the members of WRKY family are a kind of transcription factors.To test BnWRKY75 is a transcription activator or repressor,the transcriptional self-activation analysis was carried out in yeast cells.The results indicated that BnWRKY75 is a transcriptional activator.3.The expression pattern analysis of BnWRKY75The expression of BnWRKY75 in roots,stems,leaves and flowers of wild type B.napus was detected.The results showed that the expression level of BnWRKY75 in root was higher.By promoter activity analysis in transgenic Arabidopsis,BnWRKY75 promoter is inactive at transgenic Arabidopsis seedlings before 4th day after the seed germination,and then the promoter activity was detectable in elongated region of the roots.4.The phenotypic and PSI genes expressing analysis in BnWRKY75 overexpressing transgenic ArabidopsisOverexpression of BnWRKY75 in Arabidopsis had higher Pi content and lower anthocyanin content than wild type,and it prominently enhanced the expression of the low-phosphorus response genes,such as AtPT2,IP51 and PT1.5.The function analysis of BnWRKY75 in B.napusThe 35S promoter-driven BnWRKY75 was transformed into B.napus,and the supernatant of T1 was detected.The highest expression of L15 was found.The low-phosphorus response genes have no differences,however the expression of SAG12 and SAG101 were significantly up-regulated in L15.Further experimental analysis is in progress.