Quantification Of Phytosterols In Maize(Zea Mays L.) Embryos And Study Of Association Analysis

Metabolites,the final productions of cell regulatory and metabolic progresses,could be regard as metabolic phenotype.Some metabolites,which were accumulating to low levels in the maize kernel,are of great importance in physiological and biochemical progress.Phytosterols,an important composition element of plant cell bilayer membrane,would participate in the process of plant photosynthesis,reproductive,immune,and be response to external stress.In addition,it is an important factor that could regulate plant senescence.However,the study comes from domestic and foreign researchers on phytosterols are major in the determination of phytosterol content and in its stability,physiological function and metabolic pathways,etc.,but there were less report about the key gene that regulate the biosynthesis of phytosterol and gene mapping,which resulted in the lack of understanding of the genetic basis of natural variation.Thus,revealing the genetic contribution to the natural variation of metabolite abundance will enhance efforts in breeding highly nutritious maize.In this study,the phytosterols of 244 maize inbred lines were extracted by the method of saponification,and its composition and content were identified by GC-MS,and these phenotype data were used for GWAS.As a result,we identified the maize strain of high phytosterol content and candidate genes which would control sterol content in maize kernel.These result will lay a solid foundation for the breeding of maize containing high phytosterol content.This research achieved these results:1.Phytosterols content of 244 maize inbred lines were identified as TMS derivatives by gas chromatography-mass spectrometry respectively.Their sterol composition showed little variation,mainly campesterol,stigmasterol,β-sitosterol and some other minor sterols.However,the content of sterols of each species has a big difference.The total phytosterol content in five embryos were ranged from 0.44 to 9.67 mg,and β-sitosterol,the predominant phytosterols,were accounted for the total phytosterols content ranged from 50.72 to 90.68%.2.Association mapping can dissect complex agriculture traits quickly and efficiently.In this study,a recently developed Illumina MaizeSNP50 BeadChip and related statistical analysis software,was used to analyse an association panel with 244 accessions.As a result,we identified nine SNPs which were significantly associated with phytosterols content,among which one were located on chromosome 5,three on chromosomes 1,three on chromosomes 2,two were on chromosomes 3,respectively.According to these SNPs and LD decay of the association panel,32 candidate genes that were associated with phytosterol content were identified.Gene Ontology(GO)term analysis revealed that the function ofmore than 1/3 of these genes were unknown,and the rest were related to different physiological and biochemical processes,such as plant stresses,redox reaction etc.3.The function of candidate genes ZmPS1 were preliminary verified by the experiment of transformation of saccharomyces cerevisiae(BY4741).This gene is a upstream regulatory factor of epoxy squalene,and its excessive expression would improve the yield of ergosterol in yeast.