Effect of Amino Acids on Folates Accumulation in Wheat Seedlings during Germination under Red Light Radiation.

Deficiency of folates can cause various health problems, and germination is a potential way to enrich folates in grain-based food materials. In the present study, the effects of six amino acids (phenylalanine, tyrosine, tryptophan, glutamate, γ-aminobutyric acid, and p-aminobenzoic acid) on folate accumulation during wheat germination under red light radiation were investigated, and an optimized combination of amino acids for promoting folate enrichment was established. The results showed that applying phenylalanine, tyrosine, tryptophan, glutamate, or p-aminobenzoic acid to wheat seedlings during germination can significantly increase the content of total folates through activating the synthesis of the precursors for folate synthesis (pterin and p-aminobenzoic acid) or condensation of these two moieties. Meanwhile, up-regulation of corresponding genes was observed by measuring their expressions to investigate the mechanism for promoting the accumulation of folates. The highest content of folates (ca. 417 µg/100 g DW) was observed when the germinated wheat was cultured with a mixture of 1.5 mM phenylalanine, 0.5 mM tyrosine, 0.5 mM tryptophan, 0.75 mM p-aminobenzoic acid, and 0.5 mM glutamic acid, which was 50% higher than the control seedlings. This study established a promising and practical approach to enhance the accumulation of folates in wheat seedlings.

Red light enhances folate accumulation in wheat seedlings.

Red, white, blue, green, and yellow lights were applied to investigate their effects on folate accumulation in wheat seedlings. The different lights, especially red light, significantly increased the total folate content. Total folate showed maximum accumulation under 30 µmol/(m2·s) of red light, with an increase of 24% compared with the control (darkness). 5-Methyl-tetrahydrofolate (5-CH3-THF) was the dominant folate component, and was significantly increased by red light irradiation. In addition, under red light, the folate content of leaves was higher and more sensitive to light than that of endosperm or roots. Red light up-regulated the expression of guanosine triphosphate (GTP) cyclohydrolase 1 (GCH1) and aminodeoxychorismate synthase(ADCS), enhanced the activity of GCH1 and ADCS, and increased the content of precursors of folate synthesis, including pterin and p-aminobenzoic acid (pABA). Hence, the increased folate accumulation promoted by light could be attributed to the increased content of folate synthesis precursors, the activity of key enzymes, and related gene expression.