BpbZIP1调控白桦耐盐机制研究

To analyze the function and regulatory pathway of BpbZIP1 transcription factor in regulating the salt stress response of Betula platyphylla and provide a theoretical basis for studying the salt tolerance regulation mechanism of bZIP transcription factor family and the salt-tolerant breeding of birch.RT-qPCR was used to analyze the expression pattern of BpbZIP1 under salt and ABA treatment,and then the GUS gene expression and histochemical analysis were performed to verify the response of BpbZIP1 to salt stress by stable transformation of birch with pBI121-BpbZIP1-GUS vector.Using the leaf disc transformation method,BpbZIP1 was overexpressed and suppressed in birch plants,and the growth phenotypes were observed under 200mM NaCl stress treatment,and the tissues were stained with histochemical methods and physiological indicators were measured to identify the gene function.The downstream target genes of BpbZIP1 were screened by RNA-Seq analysis,combined with RT-qPCR and cis-element analysis,and validated by yeast one-hybrid(YIH),chromatin immunoprecipitation(ChIP)and dual-LUC assays.Yeast two-hybrid(Y2H)and bimolecular fluorescence complementation(BiFC)assays were used to identify BpbZIP1 interacting proteins.BpbZIP1 responds to salt stress and ABA treatment.pBI121-BpbZIP1-GUS transgenic birch was deeply stained and GUS gene was significantly induced under salt stress treatment.Transgenic plants with overexpression of BpbZIP1 showed better growth and higher superoxide dismutase(SOD),peroxide dismutase(POD)activity,chlorophyll content and proline(Pro)content,and lower hydrogen peroxide(H2O2)and malondialdehyde(MDA)content compared with wild type(WT)after salt stress treatment.The reverse phenotype was observed in BpbZIP1-RNAi plants.In the transcriptome of BpbZIP1 overexpression lines and WT lines,440 differentially expressed genes were identified,among which 153 genes were up-regulated and 287 genes were down-regulated.GO annotation showed that these differentially expressed genes were related to metabolic processes,growth and development,and abiotic stress responses,among which BpFLZ gene expression was significantly up-regulated.BpbZIP1 binds ABRE element and BpFLZ promoter fragment containing ABRE element to activate its expression.BpbZIP60 and BpZFP interact with BpbZIP1 and activate the expression of BpFLZ gene,respectively.BpbZIP1 is significantly induced by salt stress,which can interact with BpbZIP60 and BpZFP,regulate its expression by binding the BpFLZ promoter,and improve the salt tolerance of BpbZIP1 transgenic plants by scavenging ROS,reducing the degree of membrane peroxidation and cell death.