B Vitamin Variations And Fine Mapping Of Folate QTLs In Maize

Maize(Zea mays L.)is a major cereal produced globally for food,feed and other uses as well as has large genetic diversity around the world.Utilizing these genetic resources on desirable traits for improvements is important among researchers.As a source of vitamin,maize is playing a vital role to mitigate human malnutrition and hidden hunger.Thiamine(B1),riboflavin(B2),niacinamide(B3),pantothenic acid(B5),pyridoxine(B6),and folate(B9)are essential micronutrients for human healthy possessing diverse physiological functions.Nowadays,vitamin biofortification is a major concern in molecular breeding and improvement of nutrition enriched cereal crops where B vitamins got a major interest.This study focuses on the research focus of B vitamins.In the first section of the study,156 maize inbred lines from all over the world were investigated for the natural variation of some B vitamins using high-performance liquid chromatography coupled with mass spectrometry method.B1,B2,B3,B5,and total vitamin B6 contents among maize germplasms ranged in samples of grains from 107.61 to 2654.54 μg/100 g,1.19 to 37.37 μg/100 g,19.6 to213.75μg/100 g,43.47 to 590.86 μg/100 g,and 138.59 to 1065.11μg/100 g,respectively,thus showing a remarked variation.Furthermore,By855,Si273,Gy386 B and CML114 are prospective inbred lines as they were stand out of their high values in most B vitamins observed in our principal component analysis.Positive synergistic relationships were also observed between B1 and B6,B1 and B5,PN and PM,PLP and PMP indicating the compatibility of B-vitamin metabolism,respectively.In the second section of the study,MeFox(pyrazino-s-triazine derivative of 4α-hydroxy-5-methyl THF)is one of the abundant folate derivatives found in maize kernels.Thus,identification of quantitative trait locus(QTL)and subsequently candidate genes for MeFox in folate metabolism can lead to understand the molecular mechanism of this vitamer in corn which led an intention to conduct this present study on the fine mapping of QTL responsible for MeFox production and accumulation in the kernel.A follow-up investigation was carried through fine mapping from a previously discovered QTL controlling kernel’s folate derivatives content,named QTL q5-F-THFa in chromosome 5(physical position of 1.532～2.672 Mb)which was responsible for 26.7% of the variation of this metabolite(GUO et al.,2019).Heterogeneous Inbred Family(HIF)population was constructed to conduct the fine mapping study for the above QTL using In Del markers.The Genotyping and phenotyping(MeFox content in grain)of F6 and F7 progenies(2017 and 2018,respectively)have been carried out to obtain see the phenotypic variation due to the locus effect in each member of HIF.This fine mapping has resulted in a candidate region within down-stream of 1.7Mb and up-stream of 2.4Mb.Later,annotations of genes within this region led to a study of EMS mutants to investigate the role of the gene on MeFox variations.In the EMS study,the present authors found that mutations in Zm00001d012917 for Carbohydrate-binding X8 domain superfamily protein,Zm00001d012932 for S-adenosyl-L-methionine-dependent methyltransferases superfamily protein,and Zm00001d012913 for Chaperone Dna J-domain superfamily protein had effects on the variation of MeFox and 5-MTHF in kernels.Taken together,the present studies on fine-mapping of QTL q5-F-THFa opens future direction for candidate gene confirmation and validation for MeFox regulation and vitamin B diversity in germplasm revealed potential resources of maize inbreds for future breeding programs in B vitamin improvement and biofortification in crops.