Functional Analysis Of Moso Bamboo BZR1 Gene

Bamboo is one of the most important non-timber forest resourse in the world and they flower at the end of very long vegetative growth phases.China,known as the "kingdom of bamboo",Phyllostachys edulis accounts is about 70%of the total area of bamboo cultivation.Bamboo unique fast-growing phenotype has been the research focus in the scientific research personnel.With the improvement of scientific technology,researchers find that the growth and development of bamboo are closely related with its complex plant hormones coordinate regulation,through research bamboo genome,transcriptome and hormone treatment to change its phenotype.Among them,Brassinosteroid[1]was reported to participate in the rapid growth of bamboo,however,the regulation mechanism of BR in bamboo was still not very clear.BR is a group of steroid phytohormones,which is widely found in plants.It participates in the regulation of lots of plant growth and developmental processes,such as photomorphogenesis,seed fertility,flowering time and so on.BZR1(Brassinazole resistance1)is the key transcription factor of BR signaling pathway.In order to explore the effect of BR on growth and development of bamboo,this research investigated the role of BZRs family in the bamboo growth.First,10 members of the BZRs family are found in the Moso bamboo genome database,and analyzed the similarity with BZR1 protein from Arabidopsis and Rice by alignment phylogenetic tree.RNAseq data shown the RNA expression level of each BZRs family member in root and shoot parts.Then we cloned PH01000086G0840 gene,which is the most close homologous with Rice OsBZR1(LOC Os07g39220)gene,with bamboo cDNA as template,and overexpressed it in Arabidopsis,named 35S::PeBZR1-YFP.We find that overexpression of PeBZR1 promoted seed germination,and curled down rosette leaf,late flowering,partial sterile and so on.In order to investigate the PeBZR1 function,we explore the response of PeBZR overexpression to BR and its synthetic inhibitor PPZ(propiconazole)treatment.The result showed that the seeds germination time of transgenic plants 35S::PeBZR1-YFP was earlier than wild type.Meanwhile,both seeds germination rate were decreased after PPZ treatment.35S::PeBZR1-YFP seeds were insensitive to the inhibition of seed germination by PPZ.It revealed that BL promote PeBZR1-YFP protein into the nucleus,while PPZ result in PeBZR1-YFP protein trapped outside the nucleus and eventually degraded.WB indicates the total amount of PeBZR1-YFP protein decreased after PPZ treatment,while BL treatment increased the dephosphorylated PeBZR1-YFP protein level.However,when inhibited endogenous BR and then treated with BL,the amount of phosphorylated PeBZR1-YFP protein was decreased,and the amount of dephosphorylated protein was increased.Finally,we study the co-regulation of BR and dark to the PeBZR1-YFP protein.The hypocotyl of 35S::PeBZR1-YFP transgenic plants is longer than Col-0 under both BL or PPZ treatment and control growing in darkness condition,it means transgenic plants are more resistant to PPZ.At the protein level,the total amount of PeBZR1 protein increase by BL treatment.Meanwhile,PPZ treatment significantly increased phosphorylated PeBZR1 protein amount.This study explore 35S::PeBZR1-YFP transgenic plants phenotype and the difference of pritein nuclear localization and phosphorylation level after hormone treatment,the result indicate PeBZR1 has similar function with AtBZR1(Arabidopsis thaliana BZR1),such as promot hypocotyl elongation,seed germination,and rescue the phenotype of PPZ inhibited BR synthesis.The phosphorylation level and function of PeBZR1 were also regulated by BR,and the mechanism was similar with Aabidopsis thaliana and rice.To sum up,this study provides a theoretical basis for exploring the role of PeBZR1 in the growth and development of bamboo and the study of BR signaling pathway.