Accumulation of Phenolic Compounds and Expression Profiles of Phenolic Acid Biosynthesis-Related Genes in Developing Grains of White, Purple, and Red Wheat

Abstract

Polyphenols in whole grain wheat have potential health benefits, but little is known about the expression patterns of phenolic acid biosynthesis genes and the accumulation of phenolic acid compounds in different-colored wheat grains. We found that purple wheat varieties had the highest total phenolic content (TPC) and antioxidant activity. Among phenolic acid compounds, bound ferulic acid, vanillic, and caffeic acid levels were significantly higher in purple wheat than in white and red wheat, while total soluble phenolic acid, soluble ferulic acid, and vanillic acid levels were significantly higher in purple and red wheat than in white wheat. Ferulic acid and syringic acid levels peaked at 14 days after anthesis (DAA), whereas p-coumaric acid and caffeic acid levels peaked at 7 DAA, and vanillic acid levels gradually increased during grain filling and peaked near ripeness (35 DAA). Nine phenolic acid biosynthesis pathway genes (TaPAL1, TaPAL2, TaC3H1, TaC3H2, TaC4H, Ta4CL1, Ta4CL2, TaCOMT1, and TaCOMT2) exhibited three distinct expression patterns during grain filling, which may be related to the different phenolic acids levels. White wheat had higher phenolic acid contents and relatively high gene expression at the early stage, while purple wheat had the highest phenolic acid contents and gene expression levels at later stages. These results suggest that the expression of phenolic acid biosynthesis genes may be closely related to phenolic acids accumulation.

Comparative Analysis of Phenolic Compound Characterization and Their Biosynthesis Genes between Two Diverse Bread Wheat (Triticum aestivum) Varieties Differing for Chapatti (Unleavened Flat Bread) Quality

“…Among them, only chalcone synthase showed high expression in the good chapatti variety and the remaining seven genes showed low expression in the good chapatti variety. Chalcone synthase is a key enzyme in flavonoid/isoflavonoids biosynthesis pathway and catalyses the conversion of p -coumaroyl CoA into naringenin chalcone (Dao et al, 2011; Ma et al, 2016). The seven genes are flavonol synthase, cinnamyl alcohol dehydrogenase, cinnamate 4-hydroxylase, benzoate 4-monoxygenase, caffeoyl- CoA O-methyl transferase, quercetin-3-O-glucoside L-rhamnosyl transferase, and flavone synthase.…”

Progress and Challenges in Improving Nutritional Quality in Wheat

“…However, TaC3H1 was the single gene that was expressed only during the later stage of grain development. Finally, ive genes (TaC4H, TaPAL1, TaPAL2, Ta4CL2 and TaCOMT1) showed higher expressions in both early and later grain developmental stages [39]. Hence, there is still a need to conduct studies to further characterize the process of phenolic acid accumulation in seeds.…”

“…Phenolic acids are mainly synthesized from phenylalanine, a major precursor molecule for the phenlypropanoid biosynthetic pathway [39,75,76]. The biosynthesis of phenolic acids is mainly governed by several genes, which encode enzymes to carry out biochemical reactions involved in the production of selected phenolic acids.…”

“…The major process requires a genotypic and phenotypic characterization of key biological processes or pathways that are involved in the assimilation, accumulation, biosynthesis, translocation and remobilization of desired nutritional quality components such as Fe, Zn, vitamins and phenolic acids in the wheat grain [12,15,[37][38][39]. The ultimate process involves the application of biofortiication, which is the most sustainable approach that can reach the nutritional requirements of the global community in a cost-efective manner.…”

“…Ma et al [39] reported ive key enzymes, namely phenylalanine ammonia lyase (PAL), coumaric acid 3-hydrolase (C 3 H), cinnamic acid 4-hydrolase (C 4 H), 4-coumarate CoA ligase (4CL) and caffeic acid/5-hydroxyferulic acid O-methlytransferase (COMT), which are essential for the biosynthesis of phenolic acids. Ma et al [39] also characterized gene expression paterns of nine candidate genes associated with phenolic acid biosynthesis during early and late grain illing stages, the most crucial growth stage in polyphenol accumulation [85,86]. The study revealed that seven genes (TaPAL1, TaPAL2, Ta4CL1, Ta4CL2, TaCOMT1, TaCOMT2 and TaC3H2) are highly expressed during the early stages of grain development among white, red and purple wheat.…”