Population Validation Of Drought Tolerance Allelic Variations Of SNAC Gene In Maize And Its Regulation Of Gene Expression

Maize(Zea Mays L.)is one of the most important crops in China,and can be used as feed,industrial materials,food and other purposes.Drought is the most common water stress,which can cause crop yield loss.The genetic variation of drought tolerance genes in maize regulates the expression or function.It is helpful for breeding drought tolerant varieties to explore the excellent genetic variation of drought tolerance genes.NAC family is a class of plant specific transcription factors,which has important biological functions in plant growth and development,stress response and hormone regulation.SNAC subfamily belongs to a group of NAC genes related to stress response.In this study,three drought responsive SNAC genes,ZmSNAC13,Zm NAC111 and ZmSNAC1,were used to analyze the response of different haplotypes to drought stress,their expression characteristics in roots,stems and leaves of maize,and the promoter activity of ZmSNAC13 was analyzed.The main results are as follows:(1)Through amino acid sequence alignment analysis,it was found that the N-terminal of ZmSNAC13,Zm NAC111 and ZmSNAC1 had a conserved NAC domain,which is composed of about 160 amino acid residues.It can be divided into five subdomains: A,B,C,D and E.The C-terminal protein has a highly variable amino acid sequence.Two haplotypes were divided by allelic variation in three regulatory regions of SNAC gene in response to drought.Traits of two haplotypes under drought stress and normal irrigation were analyzed in Chinese inbred lines population,American inbred line population and Tropical inbred line population.The results showed that in American inbred lines population,the yield of ZmSNAC13 haplotype 2was significantly higher than that of haplotype 1,and the anthesis silking interval of ZmSNAC13 haplotype 2 was significantly shorter than that of haplotype 1 under drought condition in Hainan.The anthesis silking interval of ZmSNAC13 haplotype 2was also significantly shorter than that of haplotype 1 under drought condition in Tropical inbred line population,which indicated that ZmSNAC13 haplotype 2 could reduce the yield loss and improve the adaptability to drought by shortening the anthesis silking interval;In the Chinese inbred lines population and American inbred lines populations,the plant height of Zm NAC111 haplotype 1 was significantly higher than that of haplotype 2 under normal irrigation in Hainan;In American inbred lines population,the plant height of ZmSNAC1 haplotype 1 was significantly higher than haplotype 2 in Hainan under drought condition.(2)The temporal and spatial expression characteristics of ZmSNAC13 under drought stress were analyzed by q RT-PCR.The results showed that the expression of ZmSNAC13 was down-regulated in roots of B73 and Qi319,up-regulated in stem of B73 and Qi319 and up-regulated in leaf of Qi319 at 12 days after drought treatment,indicating that ZmSNAC13 responded to drought stress.The drought tolerant genes ZmSNAC1 and Zm NAC111 were similar in response to drought stress in the roots,stems and leaves of maize.They were down-regulated in B73 roots at 5 days after drought treatment,up-regulated in B73 stems at 12 days after drought treatment,up-regulated in B73 leaves at 12 days after drought treatment(3)In order to study how drought tolerance allele of ZmSNAC13 regulates gene expression,ZmSNAC13 haplotype 1(B73)and haplotype 2(Qi319)were used to analyze the promoter activity of ZmSNAC13 under ABA treatment by dual luciferase reporter system.The results showed that the promoter activity of ZmSNAC13 in Qi319 under ABA treatment was significantly higher than that in B73,furthermore,nine highly linked variants in 5’-UTR region of ZmSNAC13 in Qi319 could improve the promoter activity.It is speculated that the drought tolerance allele of ZmSNAC13 may regulate the gene expression by affecting the promoter activity.