Molecular Mechanism Of N6-Methyladenine DNA Methylation Regulate The Heat Resistance Of Maize(Zea Mays L.)

Maize(Zea mays L.)is one of the three major food crops in the world.It is the fastest growing major food crop with a large sown area in recent years in China.N6methyladenosine(6mA)is one of the most abundant DNA modifications found in eukaryotes and prokaryotes,and is related to gene expression in plants.The potential functions of 6mA include transcriptional activation and silencing,cross-generation chromatin regulation and stress response.Compared with 5-methylcytosine(5mC),which has been extensively studied in maize,N6-methyladenosine(6mA)has not been studied much.6mA has reported in the model plant Arabidopsis and model crop rice,and the function of 6mA is still unclear in maize.Therefore,B73 and Mo 17 were used as experimental materials to analyze the changes of DNA 6mA methylation under high temperature stress,revealing the important role of DNA 6mA modification in maize heat tolerance.The main results obtained are as follows:1.42℃ temperature treatment of B73 and Mo 17 at the three-leaf stage.With the increase of time,B73 leaves showed obvious wilting until fully wilted after 24 hours,while Mo 17 showed only insignificant leaf bending at 24 hours.This shows that Mo 17 has better resistance to high temperature than B73.2.Dot-blot and LC-MS/MS was used to detect the difference of DNA 6mA content in B73 and Mo 17 after different treatments at 42℃,and showed that there was a significant difference in the content of 6mA between B73 and Mo 17.Compared with B73 with little change in content,the content of DNA 6mA modification in Mo 17 increased by about 2.5 times.3.The 6mA modification in maize was detected by high-throughput sequencing.After 18h heat treatment,the total peak number of B73 and the number of corresponding genes increased by 2319.0 and 1390.3,respectively,and Mo17 increased by 4668.7 and 2192.7,respectively.At the same time,the number of genes with increased and decreased methylation in B73 DNA was 2470 and 3133,and Mo17 was 2284 and 2713.The number of B73 6mA genes with high methylation and simultaneous up-regulation was 290,the number of genes with low methylation and down-regulation was 343,and Mo 17 was 712 and 236.4.The genome-wide methylation map showed that 6mA sites were widely distributed in 10 chromosomes of B73 and Mo 17.The distribution of 6mA loci on the gene was analyzed,and it was found that the 6mA loci were concentrated in the intergenic region.Conservative motif analysis 6mA is conserved in different subspecies of maize.5.By observing the agronomic traits such as plant height and 100-grain weight and measuring physiological indexes such as photosynthetic rate,the difference between B73,Mo 17 and F1 generation hybrids was compared.The results showed that there were differences in agronomic traits and physiological indexes between B73,Mo 17 and F1 generation hybrids.