Expression Pattern And Promoter Functional Analysis Of Apple MdbZIP26 Gene

Apple plays an important role in China’s fruit industry,but it is inevitably affected by adverse factors such as drought and salt stress during its development.It has been reported that bZIP family transcription factors are closely related to abiotic stress.Our team has conducted preliminary functional studies on apple MdbZIP26 gene,and the results indicate that MdbZIP26 may improve plant resistance to drought and salt stress via ABA-mediated signal transduction pathway.To further elucidate the function of the MdbZIP26 gene and its response mechanism to abiotic stress,we verified the subcellular localization and selfactivating activity of the MdbZIP26 and predicted the potential phosphorylation sites after transcription.Besides,the tissue expression pattern of MdbZIP26 was analyzed by real-time quantitative PCR.Meanwhile,the promoter of MdbZIP26 gene was isolated from Fuji apple leaves and genetically transformed into arabidopsis thaliana plants after connecting it with pcanbia1391Z-GUS vector,so as to further analyze the spatial and temporal expression patterns of MdbZIP26.The main results obtained are as follows:1.MdbZIP26 subcellular localization results showed that MdbZIP26 was localized in the nucleus.The results of yeast self-activation showed that MdbZIP26 had transcriptional selfactivation activity,but its self-activation activity was inhibited by 200ng/ml AbA.This indicates that MdbZIP26 has the characteristics of transcription factors.2.Analysis of the tissue expression pattern of MdbZIP26 gene in apple showed that MdbZIP26 gene was wildly expressed in stems,leaves,flowers,fruits and seeds.Among them,the expression of the gene was highest in seed and lowest in stem.3.The MdbZIP26 gene promoter was continuously expressed in Arabidopsis plants to study the spatial and temporal expression pattern of MdbZIP26 gene in more detail.The results showed that the expression of GUS driven by the MdbZIP26 promoter was different at different growth stages.Under normal growth conditions,transgenic Arabidopsis showed lower GUS tissue staining activity in radicle and hypocotyls at 2,5 and 7 days,respectively,but there were no GUS tissue staining activity in cotyledons.Weakly GUS tissue staining activity was observed in each tissue of the 14-day and 3-week seedling.In addition,both the floral organs except the stamens and the base of the silique exhibited higher GUS activity.When subjected to stress and ABA treatment,the GUS staining activity of the transgenic lines was enhanced at different growth stages,and GUS activity was mainly promoted in cotyledon,root,leaf vascular tissue and guard cells.4.The cis-acting element prediction and analysis of the MdbZIP26 promoter revealed that the promoter region of MdbZIP26 gene contains ABA response or stress response element ABRE/G-box,drought response element DRE and salt response element GT1GMSCAM4.Experiments on transient transformation of tobacco leaves with different deletion fragments of the MdbZIP26 promoter showed that ABRE and DRE elements in the-1314bp~-1061 bp region were likely played a key role in response to drought and ABA.In addition,the salt response element at-1061bp~-766 bp may be mainly involved in salt stress response.