Genomic DNA Methylation Differences And Physiological Indexes In Diploid And Haploid Maize

With the continuous development of maize breeding technology,maize haploid breeding has become one of the important methods for maize breeding,and haploid breeding can effectively shorten the breeding time.DNA methylation is a conserved chromatin modification in plant evolution,which contributes to gene regulation and gene structure integrity.Therefore,the changes of physiological and biochemical indexes of maize haplotypes and the changes of methylation levels and patterns were explored in order to provide a theoretical basis for the analysis of the specific inheritance of corn haplotypes and the development of haploid breeding.Understanding the body characteristics,methylation levels,and patterns of changes in the chromosome number of maize diploids by half provides an epigenetic theory basis for the selection of elite inbred lines and the formation of superior hybrid combinations.In this study,the maize inbred lines B73 and H99 were used to test the physiological and biochemical indexes of their diploids and their haplotypes.The physiological and biochemical indexes of the haplotypes and diploids of the two inbred lines were analyzed together.The differences were significant,and methylation sensitive amplified polymorphism(MSAP)method was used to study the DNA methylation level and pattern changes of maize diploid and its haploid.The result is as follows:1.The haploid chromosome number was reduced by half compared with the diploid,and its plant height and leaf development were all affected.The plant height and leaf width were significantly lower than those of the diploid,and the stamens and stamens were all poorly developed.2.The leaf soluble sugar content and soluble protein content of H99 haploid seedlings were significantly lower than their diploids,decreasing by 10.85% and 7.29%,respectively.The leaf soluble sugar content and soluble protein content of B73 haploid seedlings were significantly lower than those of their diploids,which were decreased by 23.62% and 38.11%,respectively.The POD,CAT and SOD of H99 haplotype were significantly lower than those of diploid plants,which were decreased by 21.98%,24.08% and 4.26%,respectively.The CAT activity of B73 haplotype at the tasseling stage was significantly lower than that of its diploid,a decrease of 30.71%.However,the leaf POD activity and SOD activity of B73 haplotype were significantly higher than those of its diploid.The chlorophyll content of H99 haplotype and B73 haplotype in the tasselling period were also significantly lower than those of diploid,which was reduced by 64.89% and 40.52%,respectively.3.H99 diploid POD,SOD,soluble protein content was significantly higher than B73 diploid.The CAT activity,soluble sugar content and chlorophyll content of diploid B73 were significantly higher than those of H99 diploid.However,the activity of HIP haplotypes and the content of soluble protein in haplotypes were still significantly higher than those in B73 haplotypes.The POD activity,soluble sugar content,and chlorophyll content of the B73 haplotype were still significantly higher than those of the H99 haplotype.However,the activity of superoxide of B73 haplotype increased after ploidy change,and the change was significant.4.Haplotype methylation-sensitive amplified polymorphisms of H99 and B73 were 79.90% and 83.03%,respectively.Haplotype methylation-sensitive amplified monomorphisms of H99 and B73 were 20.10% and 17.97%,respectively.Compared with H99 diploid maize,the total methylation rate of H99 haplotype was decreased,the rate of permethylation was decreased,and the half-methylation rate was increased in H99 haploid maize genomic DNA.Compared with B73 diploid maize,the methylation rate of B73 haploid maize genomic DNA increased the total methylation rate of B73 haplotype,increased the rate of permethylation,and decreased the half-methylation rate.Maize haploid genomic DNA methylation patterns have also changed.The effect of ploidy on the cytosine methylation of maize genomic DNA was initially revealed.5.The total methylation level of H99 haplotype is the same as that of its diploid physiological indicators,which are all decreased after the haplotype of diploid.However,the total haplotype methylation level of B73 increased,and the SOD activity and POD activity in physiological indicators also increased with the decrease of ploidy.The two trends were the same.In addition,the index decreased.