1-Aminocyclopropane-1-carboxylic Acid Enhances Phytoestrogen Accumulation in Soy Plants (Glycine max L.) by Its Acceleration of the Isoflavone Biosynthetic Pathway

Abstract

The low levels of bioactive metabolitesin target plants presenta bottleneck for the functional food industry. The major disadvantageof soy leaves is their low phytoestrogen content despite the factthat these leaves are an enriched source of flavonols. Our study demonstratedthat simple foliar spraying with 1-aminocyclopropane-1-carboxylicacid (ACC) significantly enhanced the phytoestrogen contents of thewhole soy plant, including its leaves (27-fold), stalks (3-fold),and roots (4-fold). In particular, ACC continued to accelerate thebiosynthesis pathway of isoflavones in the leaves for up to 3 daysafter treatment, from 580 to 15,439 & mu;g/g. The detailed changesin the levels of this metabolite in soy leaves are disclosed by quantitativeand metabolomic analyses based on HPLC and UPLC-ESI-TOF/MS. The PLS-DAscore plot, S-plot, and heatmap provide comprehensive evidence toclearly distinguish the effect of ACC treatment. ACC was also provedto activate a series of structural genes (CHS, CHR, CHI, IFS, HID, IF7GT, and IF7MaT) along the isoflavone biosynthesis pathway time-dependently. Inparticular, ACC oxidase genes were turned on 12 h after ACC treatment,which was rationalized to start activating the synthetic pathway ofisoflavones.