Changes in Beneficial C-glycosylflavones and Policosanol Content in Wheat and Barley Sprouts Subjected to Differential LED Light Conditions

Abstract

The spectral quality and intensity of light, photoperiodism, and other environmental factors have profound impacts on the metabolic composition of light-dependent higher plants. Hence, we investigate the effects of fluorescent light (96 μmol m^-2s^-1) and white (100 μmol m^-2s^-1), blue (100 μmol m^-2s^-1), and red (93 μmol m^-2s^-1) light-emitting diode (LED) light irradiation on the C-glycosylflavone and policosanol contents in young seedlings of wheat and barley. Ultra-high-performance liquid chromatography (UHPLC) analyses of C-glycosylflavone contents in barley reveal that the saponarin content is significantly enhanced under blue LED light irradiation. Under similar conditions, isoorientin and isoschaftoside contents are improved in wheat seedlings. The contents of these C-glycosylflavones differed along with the light quality and growth period. The highest accumulation was observed in sprouts after three days under blue LED light irradiation. GC/MS analyses of policosanol contents showed that 1-hexacosanol (C26:o-OH) in barley and 1-octacosanol (C28:o-OH) in wheat seedlings were reduced under LED light irradiation, compared to seedlings under fluorescent light conditions. Nonetheless, the policosanol contents gradually improved with the extension of growth times and treatments, irrespective of the light quality. Additionally, a positive correlation was observed between the expression pattern of biosynthesis-related genes and the respective metabolite content in barley. This study demonstrates that blue LED light irradiation is useful in maximizing the C-glycosylflavone content in barley and wheat sprouts.

Keywords: fatty acyl-coenzyme A reductase (FAR); hexacosanol; isoorientin; octacosanol; saponarin.

Figure 1

C-glycosylflavone content in young barley and wheat seedlings subjected to differential light qualities. (A) represents the saponarin content of barley sprouts (mg/g dry weight (DW)) under different light and growth periods, while (B,C) represent the isoorientin and isoschaftoside contents (mg/g DW), respectively, of wheat sprouts. * (p < 0.05), ** (p < 0.001), and *** (p < 0.0001) indicate the statistical significance.

Figure 2

Policosanol content (μg/g DW) in barley and wheat seedlings during different growth periods and light conditions. (A) denotes hexacosanol (major policosanol) content in barley sprouts, whereas (B) denotes octacosanol content in wheat sprouts. * (p < 0.05), and *** (p < 0.0001) indicate the statistical significance.

Figure 3

Relative quantification of expression changes in flavonoid and policosanol biosynthesis-related genes in barley sprouts. (A–C) represent the relative expression levels of UDP-Glc: Isovitexin 7-O-glucosyltransferase 1 (OGT1), flavone synthase II (FNSII), and chalcone synthase 1 (CHS1), respectively. Likewise, (D–H) represent the expression patterns of different classes of fatty acyl-coenzyme A reductase (FAR) genes. The results represent the qRT-PCR-based relative quantification of genes in barley sprouts exposed to fluorescent and LED (white, blue, and red) light irradiations. The gene expression was normalized using the internal control HvActin. * (p < 0.05), ** (p < 0.001), and *** (p < 0.0001) indicate the statistical significance.

Figure 4

Leaf and root growth parameters of fluorescent and light-emitting diode (LED) light (white, blue, and red) irradiated barley and wheat seedlings at different growth periods. (A,C) represent barley growth parameters, while (B,D) represent the growth parameters of wheat sprouts. * (p < 0.05), ** (p < 0.001), and *** (p < 0.0001) indicate the statistical significance.

Figure 5

Schematic representation of experimental design used for LED treatment on barley and wheat seedlings. The diagram illustrates the germination method, growth period, and light quality and intensity.