Cytosine Methylation of Isoflavone Synthase Gene in the Genic Region Positively Regulates Its Expression and Isoflavone Biosynthesis in Soybean Seeds

Abstract

Plants, being sessile organisms, have evolved several dynamic mechanisms of gene regulation. Epigenetic modification especially cytosine methylation and demethylation actively regulates the expression of genes. To understand the role of cytosine methylation during isoflavonoid biosynthesis and accumulation, we performed cytosine methylation analysis in the coding region of two isoforms IFS1 and IFS2 gene, in two contrasting soybean genotypes differing in total isoflavone content (NRC37: high isoflavone; and NRC7: low isoflavone). The results indicated increased 5-mC in both the isoforms in NRC37 (*20.51% in IFS2 and *85% in IFS1) compared with NRC7 (*7.8% in IFS2 and *2.5% in IFS1) genotype, which signifies the positive role of 5-mC in the coding region of the gene leading to enhanced expression. In addition, temporal expression profiling [35 days after flowering (DAF), 45, 55, and 65 DAF] of both the isoforms showed increasing trend of accumulation in both the genotypes with maximum in NRC37 at 65 DAF. To further establish a correlation between methylation and expression of transcripts, we quantified the different isoforms of isoflavone in both the genotypes across all the stages. Therefore, the finding of this study would certainly increase our understanding of epigenetic regulation of isoflavone biosynthetic pathway mediated by the cytosine methylation that would assist molecular breeders to get high-performing soybean genotypes with better isoflavone yield.

Metabolic Profiling Provides Unique Insights to Accumulation and Biosynthesis of Key Secondary Metabolites in Annual Pasture Legumes of Mediterranean Origin

“…Legumes possess a unique enzyme, isoflavone synthase (IFS), which is a cytochrome P450 monooxygenase that catalyzes the 2, 3 migration of the B-ring of naringenin or liquiritigenin, resulting in the production of various biologically active isoflavonoids [ 27 ]. The genes encoding enzymes in this pathway are tissue specific and are regulated both spatially and temporally in legumes [ 28 ]. Such catalytic enzymes are induced by various stress factors influencing plant condition, including climate, temperature, soil moisture availability, nutrient deficiency, and herbivory [ 29 ].…”

Biosynthesis and metabolic engineering of isoflavonoids in model plants and crops: a review

“…Moreover, epigenetic regulation, including DNA methylation and histone modifications, has been implicated in the control of isoflavonoid accumulation ( Baulcombe and Dean, 2014 ; Chang et al., 2020 ). A comprehensive comparative analysis across various soybean genotypes exhibiting distinct isoflavone contents revealed a positive correlation between the expression of the IFS gene and the cytosine methylation level within its coding region ( Gupta et al., 2019a ). This finding underscores the potential positive regulatory impact of epigenetic modifications on the intricate process of isoflavonoid biosynthesis.…”

Epigenetic Modifications in Plants – Impact on Phospholipid Signaling and Secondary Metabolism

“…V štúdii vykonanej Guptom a spol. bola preukázaná nezanedbateľná úloha metylácie DNA pri regulácii biosyntézy a akumulácie izoflavonoidov 57 . Izoflavonoidy v sóji sa považujú za veľmi hodnotné molekuly s niekoľkými liečivými vlastnosťami, ich obsah v semenách je však zanedbateľný.…”

“…Štúdia naznačuje spôsob, akým by pestovatelia mohli v budúcnosti kultivovať sóju obohatenú o izoflavonoidy. Výsledky demonštrovali pozitívnu úlohu 5-mC v kódujúcej oblasti génu, čo viedlo k jeho zvýšenej expresii a následnej syntéze izoflavonoidov 57 . Výsledky tejto štúdie nepochybne zvyšujú pochopenie epigenetickej regulácie biosyntetickej dráhy izofavonoidov prostredníctvom metylácie cytozínu a môžu pomôcť získať genotypy sóje so zlepšeným výťažkom účinných metabolitov.…”