Molecular Evolution And Marker Polymorphism Analysis Of Teosinte’s Specific Genes Containing Transposon

As the ancestor of modern cultivated maize,teosinte is an excellent basic material to broaden maize germplasm with its large number of excellent resistance genes.Transposons were once considered as "junk DNA",but more and more studies have shown their importance in organisms.With the development of sequencing technology,the genomes of teosinte and maize have been sequenced.However,it is unclear about the teosinte’s specific genes containing transposons.In this study,these teosinte’s specific genes were identified via comparative genomic methods of analyzing genomes of B73 and Zea mays ssp.Mexicana in the first place;secondly,their selective pressure were analyzed;thirdly,the effect of artificial selection loss of on transposons was evaluated and the DUF1644 gene family was analyzed;finally,their transposon polymorphism markers were developed and evaluated in the maize and teosinte.The main findings are as follows:1.Identification and selection pressure analysis of teosinte’s specific genes containing transposons: There are 1958 this kind of genes,containing 6662 transposons in total.Retrotransposons(54.53%)outnumbered DNA transposons(45.15%)teosinte’s specific genes.Selective pressure analysis indicated that the average value of dN/dS for orthologous genes of teosinte’s genes containing transposon between Teosinte and maize(0.3438)was greater than that for all orthologous genes between Teosinte and B73(0.3094)and that for all orthologous genes between Mo17 and B73(0.3290).It indicated that these teosinte’s specific genes as a whole have undergone relaxation of selective pressure during the process of domestication and modern genetic improvement.Inaddition,the proportion of genes undergoing positive selection in teosinte’s specific genes them(5.12%)was greater than that in all orthologous genes between Teosinte and B73(4.98%),indicating that the insertion of transposon is more likely to lead to the adaptive evolution of some genes.2.Effect of artificial selection on loss of transposon: Analyzing artificial selection orthologous genes of 35 maize materials that correspond to teosinte’s specific genes containing transposon,we found a large number of artificial selection’s orthologous genes have lost their transposons in different maize materials.The maize XTH family gene(Zm00001d014617)has no transposons in 36 maize materials(including maize B73)but its correspondant teosinte’s specific gene(ZMex03g012878)contains a PIF-Harbinger-like transposon.This gene responds to plant hormones and other environmental signals and plays an important role in plant growth and development,indicating that artificial selection has a significant effect on the evolution of transposons.containing the DUF1644 functional domain were identied in 20 plants.Analysis showed that there is no transposon in the DUF1644 gene in the lower plants such as moss and lycopodiophyta and such insertion happened more in monocotyledons than dicotyledons.4.Development and experimental evaluation of transposon molecular markers: 3470 transposon markers in teosinte’s specific genes were developed.Based on e-PCR’s results,40 pairs of randomly selected primers which can generate single band in teosinte genome and generate bands in B73 genome were evaluated in 4 maize materials.The experiment demonstrated that the 40 pairs of randomly selected primers obtained clear amplification in at least one maize and average value of PIC was 0.15,In addition,based on e-PCR’s results,30 pairs of randomly selected primers which can generate single band in teosinte genome and failed to produce bands in B73 genome were evaluated in 3 teosinte materials.The experiment demonstrated that the 28 pairs of randomly selected primers obtained clear amplification inat least one teosinte and average value of PIC was 0.2875.