Cloning And Gene Functional Study Of Apple BZIP Transcription Factor MdbZIP48

Apple?Malus domestia Borkh?is one of the fruits that people often eat which is widely grown all around the world.However,the yield and quality of apple were restricted by drought and high salt stress.It was reported that the basic leucine zipper?bZIP?protein has many important biological functions,such as signal transduction,response stress response,promotion growth and development,and plays an important role in plant resistance to abiotic stress.The b ZIP transcription factor family was analyzed and studied in the early stage of our study.112 bZIP genes were identified from the apple genome,and their functions in apple growth and stress resistance were revealed by gene expression and evolution analysis.On this basis,we cloned MdbZIP48 from Fuji apple and successfully transformed model plant Arabidopsis thaliana,and further studied the specific function and possible mechanism of bZIP gene.The results provided the basis for breeding and genetic improvement of resistant varieties of apple at molecular level.The following findings were obtained:1.The CDS sequence of MdbZIP48 gene was cloned from cDNA of Fuji apple as template.The accession number of MdbZIP48 gene is XM₀08367053.2.Sequence analysis shows that the open reading frame length of the gene is 900 bp,encoding 299 amino acids.The sequence contained a typical structure of bZIP domain and grouped into Class A in apple bZIP transcription factors subfamily.Construct over expression vector and transform vector into Arabidopsis thaliana by Agrobacterium.2.The results showed that,under drought and salt stress conditions,the seed germination rate and greening rate of cotyledons of the MdbZIP48 transgenic plants were significantly higher than that of the wild type strains,indicating that transgenes improved the plant's ability to resist drought and salt.After osmotic stress,relevant physiological indicators were measured and it was found that the chlorophyll content and proline content of the transgenic plants were significantly higher than that of the wild type strains,but the relative electrical conductivity and malondialdehyde content were lower than the wild type.Therefore,it can be surmised that the cell membrane structure of over-expressed plants is better in integrity and more resistant to osmotic stress than wild-type plants.After one week of drought and salt stress treatment,the growth status of the transgenic plants was significantly better than that of the wild type.The trypan blue staining experiments also showed that the wild-type leaves had more severe cell death compared to transgenic plants.The DAB and NBT staining of the treated leaves revealed that the wild type plants accumulated more active oxygen and their cell damage was more serious than the transgenic lines.Analyzing the expression levels of stress-related genes,it was found that MdbZIP48 may be involved in ABA biosynthesis and regulate downstream genes in the ABA signaling pathway.