The Relationship Between Sorghum Transcription Factor SbbHLH1 And Iron Nutrition Balance Of Plants

The lack of trace elements in soil will greatly limit the improvement of yield and quality of most crops,and the food lacking trace elements may further affect human health.Iron deficiency in soil is a common abiotic stress in agricultural production.In calcareous soil covering more than 30%of the earth's surface,iron deficiency occurs in varying degrees.Plants growing under this stress often show the symptom of"chlorosis",and the yield and quality of crops production decrease.Therefore,iron is one of the key determinants of crop yield and quality in the world.Sorghum is the fifth largest food crop in the world.In China,it is mainly used for brewing beer and liquor.It is also a high-quality feed crop.It not only has high nutritional value such as food and medicine,but also has potential value such as bioenergy for development.Because sorghum is widely planted in the north of China,Central Plains and Xinjiang,this part of alkaline calcareous soil is lack of iron.The response to iron stress is the key to improve its yield and quality.Previous studies have found that SbbHLHl can negatively regulate the synthesis of lignin,and the rice SbbHLH1 Homologous gene OsIR02 has been found that it may participate in the plant iron nutrition balance.In this paper,SbbHLHl gene of sorghum(Sorghum icolor L.Moench)was used as for these research.Wild type and SbbHLHl overexpression lines of Arabidopsis were used to study the preliminarily function of this geng and the relationship between the gene and plant iron balance.SbbHLH1 gene has been cloned from sorghum in our laboratory previously,SbbHLH1 protien,as a transcription factor,is located in the nucleus and cytoplasm(Dr,Yan Li,2011).Through bioinformatics analysis,the SbbHLHl gene has three exons and two introns,and its protein contains 244 amino acids,including a conservative bHLH domain,Org transcription regulators of Arabidopsis bHLH family such as AtbHLH38 and AtbHLH39 have some similarity to SbbHLHl.These two transcription factors,together with fit transcription factors,regulate the expression of downstream iron deficiency response genes.Through sequence alignment,SbbHLHl protein has some homology with AtbHLH38/39/100/101,and the promoter analysis of SbbHLHl gene shows that the gene may be related to jasmonate(JA)response,and jasmonate is the verified negative regulatory factor of iron deficiency related gene expression.Through the above biological analysis,it is found that SbbHLH1 transcription factor is quite likely to participate in plant iron deficiency stress response.Under the stress of iron deficiency and complete iron deficiency stress,the inhibition of root length,number of lateral roots and aboveground part of SbbHLHl over expression line to wild type(Col-0)was significantly lower,and its resistance to iron deficiency phenotype was very obvious,which proved that SbbHLHl gene participated in the response to iron deficiency stress.According to the way of SbbHLH1 participating in the response to iron deficiency,we found that under iron deficiency stress,the expression trend of AtbHLH104 was the same as that of AtZIFl,AtYSL3,AtEIL1 and AtEIN3,which were significantly up-regulated in SbbHLHl overexpression lines;under complete iron free stress,the expression trend of AtbHLH38 was the same as that of AtbHLH1019 AtAHA2 and AtAOXl,which were significantly up-regulated in SbbHLHl overexpression lines The expression level was significantly higher than that of wild type.Under oxidative stress,different extent of inhibition were observed in the growth of SbbHLHl overexpression lines and wild type control the root length became shorter,the number of lateral roots increased,the growth of Arabidopsis seedlings overexpresson lines wereless inhibited than that of wild type.It was also found that the average leaf number,root length and number of lateral roots of over expression lines were significantly higher than those of wild type under oxidative stress,especially the number and length of lateral roots.With the increase of H2O2 concentration,the average leaf number,root length and number of lateral roots of over expression lines were more significant than those of wild type.In order to further explore the response of SbbHLHl to oxidative stress,we found that in Arabidopsis seedlings in Mock,the H2O2 Content of over expression lines was significantly lower than that of wild type.After iron deficiency stress and treated with exogenous H2O2,the H2O2 Content of each line increased,but the H2O2 Content of each line under iron deficiency stress was lower than that under H2O2 treatment,with oxidation stress increase,the relative value of H2O2 Content in wild type increased significantly.The results of RT-PCR showed that the expression of maker gene related to ROS production and clearance in SbbHLH1 overexpression line was significantly lower than that in the wild type under iron deficiency and complete iron deficiency conditions.Based on the above results,it was found that SbbHLH1 gene responded to iron deficiency stress by up regulating the expression of genes related to iron acquisition and transportation.SbbHLHl may increase the resistance of transgenic Arabidopsis to oxidative stress by reducing the content of H2O2 in cells,and reduce the accumulation of ROS in plants under iron deficiency stress.