Biological Functions Of Maize ZmNAC17 Transcription Factor In Response To Drought Stress

Maize(Zea Mays L.)is the world’s largest food crop,and it is also an important component of China’s food crops.Drought can have a serious impact on the growth and yield of maize,while the water resources in Northern China are not abundant.Therefore,how to improve the drought resistance of maize is an important issue in maize breeding.As one of the largest of transcription factors(TFs)families in plants,NAC transcription factors play critical roles in resisting stresses and regulating plant growth and development which have been studied in many species.Notably,overexpression of At NAC1 in Arabidopsis thaliana can lead to a phenotype of increased lateral roots in transgenic lines,while the number of lateral roots in the antisense expressed strain is significantly reduced.Developed root systems play a very important role in improving the drought resistance of plants.Therefore,we isolated four maize NAC transcription factors ZmNAC17,ZmNAC36,ZmNAC73 and ZmNAC144 with high homology to At NAC1.First,the NAC transcription factors of maize were analyzed using bioinformatics methods,and then heterologously expressed in Arabidopsis.It was found that phenotype of ZmNAC17 overexpression Arabidopsis lines was the most obvious,resulting in an increase in root length of transgenic lines.After that,we conducted experiments on subcellular localization,expression pattern analysis,and stress resistance analysis of ZmNAC17 overexpression Arabidopsis lines,and preliminarily determined the biological functions of ZmNAC17.The results are as follows:1.A total of 124 NAC transcription factors were identified in maize through the NAM conserved domain,which were divided into 11 subfamilies,and NAC members within the same subfamily have similar gene structures.Bioinformatics analysis showed that the NAC transcription factors in maize were more similar to those in rice,another monocot plant,and that the upstream promoter regions contained a large number of response elements related to abscisic acid and stress.2.Subcellular localization analysis showed that ZmNAC17 was located in the nucleus.Quantitative real-time PCR analysis demonstrated that ZmNAC17 was expressed throughout the whole maize plant,and expression levels were higher in roots,stems,leaves,and tassels.Meanwhile,expression of ZmNAC17 was continuously increased under drought treatment,and the expression peak was observed at 24 hours,indicating that ZmNAC17 was positively responded to drought.3.Compared with the control,transgenic Arabidopsis lines overexpressing ZmNAC17 enhanced the drought tolerance of transgenic lines.Under drought treatment,the growth inhibition of the transgenic lines was reduced,and the expression of stress-responsive genes was upregulated.In terms of growth and development,ZmNAC17 promoted root and fruit development and accelerated the time of bolting.The above experimental analysis results indicate that the transcription factor ZmNAC17 plays an important role in improving drought resistance in maize,and is also a positive regulatory factor in plant growth and development.