Synergistic Effect of Methyl Jasmonate and Abscisic Acid Co-Treatment on Avenanthramide Production in Germinating Oats

Abstract

The oat (Avena sativa L.) is a grain of the Poaceae grass family and contains many powerful anti-oxidants, including avenanthramides as phenolic alkaloids with anti-inflammatory, anti-oxidant, anti-itch, anti-irritant, and anti-atherogenic activities. Here, the treatment of germinating oats with methyl jasmonate (MeJA) or abscisic acid (ABA) resulted in 2.5-fold (582.9 mg/kg FW) and 2.8-fold (642.9 mg/kg FW) increase in avenanthramide content, respectively, relative to untreated controls (232.6 mg/kg FW). Moreover, MeJA and ABA co-treatment synergistically increased avenanthramide production in germinating oats to 1505 mg/kg FW. Individual or combined MeJA and ABA treatment increased the expression of genes encoding key catalytic enzymes in the avenanthramide-biosynthesis pathway, including hydroxycinnamoyl-CoA:hydrocyanthranilate N-hydroxycinnamoyl transferase (HHT). Further analyses showed that six AsHHT genes were effectively upregulated by MeJA or ABA treatment, especially AsHHT4 for MeJA and AsHHT5 for ABA, thereby enhancing the production of all three avenanthramides in germinating oats. Specifically, AsHHT5 exhibited the highest expression following MeJA and ABA co-treatment, indicating that AsHHT5 played a more crucial role in avenanthramide biosynthesis in response to MeJA and ABA co-treatment of germinating oats. These findings suggest that elicitor-mediated metabolite farming using MeJA and ABA could be a valuable method for avenanthramide production in germinating oats.

Multiple Antioxidative and Bioactive Molecules of Oats (Avena sativa L.) in Human Health

“…The main polyphenolic compound found in oats includes protocatechuic, syringic, vanillic, p -hydroxybenzoic, gallic, p -coumaric, o -coumaric, and caffeic acids ( Figure 6 ) [ 91 , 92 , 93 ]. Among them, Avn biosynthesized from phenylalnine as an alkaloid ( Figure 7 ) [ 9 , 94 , 95 ] is a polyphenol with various physiological properties, including antioxidant, anti-inflammatory, anti-cancer, anti-thrombotic, anti-proliferative, and anti-itch activities [ 9 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 ]. Avn has 30 times higher antioxidant activity than other phenolic compounds [ 98 , 99 , 102 ].…”

“…Likewise, a similar phenomenon is observed in oats. The concentration of Avn in oats is significantly increased after germination compared to that before germination [ 9 , 131 , 132 ]. Furthermore, germination of grains can lead to saccharification effects, which can improve palatability such as by enhancing flavor [ 126 , 133 ].…”

“…Oats ( Avena sativa L.) are biennial herbaceous plants that belong to the Poaceae family. They are one of the representative crops that grow in cool and humid weather conditions [ 9 ]. Oats have a shape similar to barley and are available in different types, including black, red, yellow, and white oats.…”

“…Recently, unsaturated fatty acids were shown to lower blood cholesterol, leading to increased interest in oats as a functional food [ 20 , 21 , 22 ]. Oats also contain polyphenols including caffeic acids, coumaric acids, gallic acids, hydroxybenzoic acids, protocatechuic acids, syringic acids and vanillic acids as the bioactive compounds [ 2 , 9 , 10 ]. Alkaloids such as avenanthramides (Avns) are also found in oat [ 9 , 10 ].…”

“…Oats also contain polyphenols including caffeic acids, coumaric acids, gallic acids, hydroxybenzoic acids, protocatechuic acids, syringic acids and vanillic acids as the bioactive compounds [ 2 , 9 , 10 ]. Alkaloids such as avenanthramides (Avns) are also found in oat [ 9 , 10 ]. In addition, oat bran-derived by-products such as proteins, β-glucan, saponin, albumin, prolamins, and glutelins are also valuable for the nutritional components.…”