The Germplasm Evaluation And Folate Synthetic Metabolism During Kernel Development Of Waxy Maize

Fresh eating waxy maize?Zea mays L.var.ceratina?is an important crop in the fruit,vegetable and grain industry.It can be a good way to biofortify folate and improve folate intake.In this paper,we evaluated the folate contents of waxy maize germplasm under different planting environment,and study the changes of folate contents and relative quantity expression of genes during kernel development.Further,through the digital gene expression profile and transcriptome analysis,the differentially expressed genes related to folate pathways during kernel development of waxy maize were compared to explore the candidate genes and their molecular mechanisms involved in folate regulation.The main results are as follows:?1?Folate contents of 224 waxy maize germplasm resources were different,ranging from 24.71?g/100 g DW to 783.92?g/100 g DW in Guangzhou and from 33.54?g/100 g DW to 339.25?g/100 g DW in Handan.Folate contents of waxy maize germplasm were greatly influenced by the planting environment.Five waxy maize resources with high folate content in different planting environment were screened.?2?Six waxy maize resources were selected from germplasm of high,medium and low folate levels respectively.Contents of folate and vitamin C were found to be decreased during kernel development of waxy maize.At around the 20^th to 25^th day after pollination,fresh-eating waxy maize with high folate content could be harvested.The expression profiles of genes related to folate biosynthesis pathway were different among waxy maize with different kernel colors,which were also influenced by weather conditions.?3?Transcriptome analysis indicated that differentially expressed genes involved in folate pathways were different in different kernel colors of waxy maize.DHNA was supposed to be a key gene involved in folate synthesis,FBT1 and YMR166 were key genes involved in folate transport and SHMT was the key gene related to folate interconversion.The genes involved in folate synthesis were down-regulated and those related to folate transport and interconversion was up-regulated in white and yellow waxy maize,while purple waxy maize had the opposite variation trend.Folate contents of mature kernels were supposed to be decided by the coordination of gene expression patterns involved in folate synthesis,transport and interconversion processes.?4?The digital gene expression profiles of selected purple waxy maize in this study indicated that there were differences in folate-related differentially expressed genes enriched at different periods of kernel development.But the overall expression of genes involved in folate synthesis,transport and interconversion processes was up-regulated to affect the changes of folate levels possibly.5FCL was highly expressed in the whole process of kernel development to maintain the active folate metabolism,which could be the reason for the continuous folate interconversion.The up-regulation of MTHFR in the early period of kernel development was speculated to have indirect influence on the accumulation of folate involved in one-carbon metabolism.The expression pattern of GTPCH and DHFS was supposed to be the reason for the low content of folate and vitamin C in the end of kernel development.