| Maize is one of the most important agricultural crops all over the world,and the kernels contain a variety of sugars,carotenoids and unsaturated fatty acids.Investigating the molecular regulation mechanism of the biosynthesis of the above three substances during maize kernel development can provide a theoretical basis for directional breeding and variety improvement of maize.In this study,the transcriptome sequencing was systematically performed on the kernels that collected from four maize varieties at different developmental stages,and the gene regulation mechanism of the biosynthesis of sugars,carotenoids and oils was analyzed.The absorption efficiencies of the carotenoids in processed maize kernels and the industrial value of corn oil were also further investigated.The kernels of yellow maize(Tianta5)and waxy maize(BN2)at 15,20 and 25 days after self-pollination(DAP)were selected to detect the contents of glucose,sucrose,fructose and trehalose.Through transcriptome sequencing analysis of a total of 19 samples in two maize varieties at the three growth stages,it was found that there were 35 genes differentially expressed in the carbohydrate metabolism pathway.The increasing expression of INVCW1(Cell wall invertase 1)and INVVR1(Invertase)genes at 25 DAP was correlated with the decomposition of sucrose,and the down-regulation of HEK2(Hexokinase 2)and HEK5(Hexokinase 5)genes caused the continuous increase of the fructose content.In addition,through the co-expression analysis between the transcription factors and DEGs,it was found that 45 transcription factors and 9DEGs showed the interaction relationship.Among them,MYB96 and HDT102(Histone deacetylase 102)transcription factors had regulatory effects on multiple differentially expressed genes,and ultimately positively or negatively regulated the biosynthesis of fructose,glucose and trehalose.Four maize varieties with significant differences in carotenoid content(Tianta5,BN2,1653 and 1652)were selected in this study.The contents of lutein,zeaxanthin andβ-carotene were detected in the kernels at three developmental stages.Through the transcriptome analysis of a total of 37 samples in four maize varieties at three developmental stages,26 differentially expressed genes were found in carotenoid biosynthesis pathway,in which the expression of PSY1(Phytoene synthase 1)gene was correlated with the carotenoid content in the kernels of different maize varieties.The biosynthesis of lutein,zeaxanthin and β-carotene was regulated by HYD7(Betacarotene 3-hydroxylase),LCYE1(Lycopene epsilon cyclase 1)and ZEP-L4(Zeaxanthin epoxidase-like4)gene,respectively.Additionally,the in vitro simulation experiments were carried out on three kinds of maize processed products.It was found that different heating treatment methods would have a significant impact on the absorption of different type carotenoids in human digestion,and xanthophylls showed a competing relationship with β-carotene during the absorption process.This study provided the foundation on using molecular approach to increase the carotenoid content in maize kernel,and improving the processing method to increase the absorption of carotenoids in the human digestion.In order to investigate the molecular mechanism of the linoleic acid biosynthesis in maize kernel,six FAD2(Fatty acid desaturase 2)gene family members were identified and annotated in the maize genome.Through the expression analysis of the transcriptome from BN2 and Tianta5,the expressions of FAD2 gene family were analyzed,and it was found that Zm FAD2-1A and Zm FAD2-1C continuingly highly expressed during the kernel development in two maize varieties.Additionally,the corn oil blended with low-carbon alcohol and co-solvent under the specific percentage could construct alternative fuel.This study provided the guidance for genetic engineering to improve the industrial application value of corn and to efficiently improve the fuel characteristics of corn oil through blending method.In summary,the gene regulation mechanism of the biosynthesis of sugars,carotenoids and oils in developmental maize kernels as well as the maize application value were analyzed through the systematic research and simulation experiments,which provided the guiding significance for maize breeding and application. |
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