Abstract
BackgroundMaize is a major staple food crop globally and contains various concentrations of vitamins. Folates are essential water-soluble B-vitamins that play an important role as one-carbon (C1) donors and acceptors in organisms. To gain an understanding of folate metabolism in maize, we performed an intensive in silico analysis to screen for genes involved in folate metabolism using publicly available databases, followed by examination of the transcript expression patterns and profiling of the folate derivatives in the kernels of two maize inbred lines.ResultsA total of 36 candidate genes corresponding to 16 folate metabolism-related enzymes were identified. The maize genome contains all the enzymes required for folate and C1 metabolism, characterized by highly conserved functional domains across all the other species investigated. Phylogenetic analysis revealed that these enzymes in maize are conserved throughout evolution and have a high level of similarity with those in sorghum and millet. The LC-MS analyses of two maize inbred lines demonstrated that 5-methyltetrahydrofolate was the major form of folate derivative in young seeds, while 5-formyltetrahydrofolate in mature seeds. Most of the genes involved in folate and C1 metabolism exhibited similar transcriptional expression patterns between these two maize lines, with the highest transcript abundance detected on day after pollination (DAP) 6 and the decreased transcript abundance on DAP 12 and 18. Compared with the seeds on DAP 30, 5-methyltetrahydrofolate was decreased and 5-formyltetrahydrofolate was increased sharply in the mature dry seeds.ConclusionsThe enzymes involved in folate and C1 metabolism are conserved between maize and other plant species. Folate and C1 metabolism is active in young developing maize seeds at transcriptional levels.
Highlights
Maize is a major staple food crop globally and contains various concentrations of vitamins
Identification and phylogenetic analysis of putative folate metabolic genes in maize To understand the folate metabolism in maize, we first investigated the conservation of all folate-related genes between Arabidopsis and maize on a whole-genome scale as the folate metabolism pathway has been well characterised in Arabidopsis compared to other plant species
One ortholog was identified for Hydroxymethyldihydropterin pyrophosphokinase (HPPK)/ Dihydropteroate synthase (DHPS) and ADC synthase (ADCS), respectively, two for GTP cyclohydrolase (GTPCHI), Dihydroneopterin aldolase (DHNA), Dihydrofolate synthetase (DHFS), and Folylpolyglutamate synthetase (FPGS), respectively, three for ADC lyase (ADCL), and four for Dihydrofolate reductase (DHFR)
Summary
Maize is a major staple food crop globally and contains various concentrations of vitamins. Folates are essential water-soluble B-vitamins that play an important role as one-carbon (C1) donors and acceptors in organisms. Folates are essential water-soluble B-vitamins, including tetrahydrofolate (THF) and its derivatives. Folates play an important role as one-carbon (C1) donors and acceptors in all types of species. The C1 substituents attach to the N5 position of the pteridine and/or to the N10 position of p-ABA to form all types of folate derivatives. Dihydrofolate is converted by hydroxymethyldihydropterin pyrophosphokinase (EC:2.7.6.3, HPPK) and dihydropteroate synthase (EC:2.5.1.15, DHPS), which is a bifunctional enzyme in plants, and attached to the first glutamate through the action of dihydrofolate synthetase (EC:6.3.2.17, DHFS). 5,10-methylene-THF can be reduced to 5-methyl-THF (5-M-THF) by methylenetetrahydrofolate reductase (EC:1.5.1.20, MTHFR), and 5-methyl-THF can serve as a methyl donor for methionine synthesis (EC:2.1.1.14, MS) from homocysteine. 16 enzymes are involved in folate and C1 metabolism in plants (Fig. 1) [2, 3]
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