The Role Of BZIP44 Gene In Plant Response To Iron Deficiency

Iron is an essential micronutrients for the human,animal and plant.It is noteworthy that aproximately one-third soil is alkalescent,which contains lower iron concentration.Plants are the main dietary sources of human and animal.Therefore,iron deficiency in plants has tremendously impacted on human health so that normal physiological activities cannot be completed,which easily leads to the decline of resistance and the increase of the incidence of iron-deficiency anemia.Therefore,it is a golabl threat urged to be solved for us.This paper mainly studies the role of the bZIP44 transcription factor in response to the iron deficiency stress in Arabidopsis thaliana,and will provide scientific basis for molecular genetic breeding to improve crop mineral nutrion content.The main results are as follows:(1)Pattern of bZIP44 tissue expression was analyzed.It was found that the transcript of bZIP44 was the highest in flowers of Arabidopsis thaliana.Expression of bZIP44 gene was induced by iron deficiency,suggesting that bZIP44 gene might be involved in the regulation of plant response to iron deficiency.(2)The bzip44 mutant homozygous plants were identified.The phenotype analysis showed that there was no significant difference between the bzip44 mutant and the wild type under normal condition.However,under iron deficiency,the bzip44 mutant was more sensitive than the wild type.This implyed that the bZIP44 gene positively regulates the iron deficiency stress response in plants.(3)Iron contents in roots and shoots were analyzed in wild-type and bzip44 mutant plants.It was found that under the normal condition,in roots,there was no significant difference in the iron content bewteen the wild type and bzip44-1 mutant,while in shoots,the iron content was significantly higher in the wild type than in bzip44-1 mutant.Under iron deficiency,the root iron contents in root and shoot were decreased in both the wild type and the bzip44-1 mutant,but the iron content in root of the bzip44-1 mutant was significantly lower than that of the wild type;however,in shoot,the wild-type iron content was higher than that in normal growth conditions,but the iron content in the bzip44-1 mutant shoot is similar to that under the normal condition.Under the iron deficiency stress,the ratios of root and shoot of iron content in the wild type and the bzip44-1 mutant were increased,but it was higher in the wild type than the bzip44-1 mutant,suggseting that bZIP44 gene might regulate the iron ion tansport from the root to shoot by regulating the expression of iron transport-related genes,thereby modulating the plant response to the iron deficiency stress.(4)Based on the analysis of gene expression related to iron deficiency,it was found that under iron deficiency,in bzip44 mutant,the transcription level of NAS2 and NAS4 genes encoding nicotinamide synthase and the MYB10 gene encoding transcription factor were significantly lower than those of the wild type,and there was no significant difference in the transcription levels of the FIT1,FRO2 and bHLH38 genes between the wild type and the bzip44-1 mutant,suggesting that the bZIP44 gene may regulate plant iron deficiency tolerance by regulating the expression of the NAS2,NAS4 and MYB10 genes.(5)Through the tobacco transient expression assays,it was found that bZIP44 activates the transcription of the NAS2 and MYB10 gene,suggesting that bZIP44 gene regulates the response to iron deficiency by regulating the expression of NAS2 and MYB10.(6)To further determine the role of bZIP44 in regulating plant iron deficiency response,a 35S:bZIP44 overexpression vector was constructed: the Arabidopsis thaliana bZIP44 gene was cloned,and the bZIP44 gene overexpression plants were obtained by gene recombination technology,and it was found that in the normal growth period,the bZIP44-overexpressing plants grew weaker than the wild type.(7)On the iron-deficient medium,the bZIP44-overexpressing plants showed a tolerant phenotype,and its the chlorophyll content is higher than that in the wild-type,indicating that bZIP44 gene played an important role in the regulation of iron deficiency tolerance in plants.In summary,bZIP44 gene regulates the response to iron deficiency stress in plants by activating NAS2 and MYB10 gene expression,and thereby improves the tolerance of plants to iron deficiency.