Dynamic Transcriptome Analysis Of CM1 Maize Inbred Line At Seedling Stage In Response To High Temperature Stress

Maize(Zea mays L.)is the largest grain crop,as well as an important feed and energy crop in China.The high and stable yield of maize is an important basic factor to ensure food security.Anhui is located in the northern and southern climate transition zone.Extreme weather(such as high temperature,drought,rainy sparse sunlight,etc.)occurs frequently,which has a serious impact on maize agricultural production.Maize can lead to serious consequences of reducing or even cutting production after being subjected to high temperature stress.Therefore,in order to cope with the adverse effects of high-temperature stress on maize,it is urgent to excavate heat-resistant genes in the maize genome and cultivate new heat-resisting maize varieties.At present,a number of thermal stress-related genes have been excavated in model plants(such as Arabidopsis and rice),and signal transduction pathways have been constructed in detail.There are relatively few heat-resistant genes excavated in maize,especially the scientific problems such as the dynamic changes of maize at the transcription level under high temperature stress remain unclear.In this study,maize inbred line CM1 was selected as the research object.Through high-throughput transcriptome sequencing under high temperature treatments,the transcriptome dynamic changes of maize inbred line CM1 subjected to high temperature stress were preliminarily analyzed,which laid a foundation for the exploration of key genes in response to high temperature stress.The main experimental results are as follows:1.We treated maize inbred line CM1 seedlings at 45 ℃ for 24 hours.To reduce the influence of photoperiod on the expression of samples,samples were taken every 4 hours before and after high temperature treatment in this study.A total of 3 biological replicates were taken at each time point,and 39 experimental samples were finally obtained.Through sample correlation analysis and principal component analysis,it was found that the 39 experimental samples were clustered into three clusters,the samples before the high temperature treatment were clustered together,the samples after the high temperature treatment for 4-8 h were clustered together closely,and the samples after the high temperature treatment for 12-24 h had a high correlation.2.After calculating the gene expression data of all samples by FPKM method,a total of 23844 expressed genes were identified,of which 1414 genes encoded transcription factors.Time series analysis of expressed genes show that all expressed genes are clustered into 12 gene clusters(Clusters),and different Clusters have different numbers of expressed genes and different expression patterns.Among them,the expression of genes in Cluster4 increased significantly in 4-8 hours of high temperature stress,the expression of genes in Cluster5 increased significantly at 12-24 hours of high temperature stress,and the expression of genes in Cluster8 was significantly up-regulated at all time points of high temperature stress.3.Through Mapman analysis,further GO function enrichment analysis of all Clusters found that in the early stage of high temperature stress(Cluster4,4-8 h),vesicle transport related genes were significantly enriched(Wilcoxon Rank Sum Test,Benjamini Hochberg corrected,P-value = 0.00172);while in the middle and late stages of high temperature stress(Cluster5,12-24 h),protein homeostasis related genes were significantly enriched(P-value= 1.20 × 10-4).This indicates that maize may respond through a variety of different physiological processes at different stages of high temperature stress.4.In this study,we found that the proportion pf transcription factor in different Clusters is not consistent after high temperature stress.In the early stage of high temperature stress(Cluster4,4-8 h),the expression levels of 188 transcription factors were up-regulated,accounting for 7.75%;while in the middle and late stages of high temperature stress(Cluster5,12-24 h),only 116 transcription factors were included accounting for 3.90%.This indicates that in the early stage of high temperature stress,a large number of transcription factors will be expressed differently,while in the late stage of high temperature stress,it is mainly responded by other function proteins.In addition,in this study we found that the expression of some HSFs(Heat Shock transcription factors)was significantly up-regulated,which implies that these HSFs genes are key candidate genes in response to high temperature stress.5.Through co-expression network analysis,a total of 10 expression modules were identified,and some core regulatory genes were further screened to lay the foundation for the subsequent construction of a maize regulatory network that responds to high temperature stress,and also to provide theoretical basis for discovering key genes that respond to high temperature stress.