Biosynthesis of plant‐derived flavor compounds

Abstract

SummaryPlants have the capacity to synthesize, accumulate and emit volatiles that may act as aroma and flavor molecules due to interactions with human receptors. These low-molecular-weight substances derived from the fatty acid, amino acid and carbohydrate pools constitute a heterogenous group of molecules with saturated and unsaturated, straight-chain, branched-chain and cyclic structures bearing various functional groups (e.g. alcohols, aldehydes, ketones, esters and ethers) and also nitrogen and sulfur. They are commercially important for the food, pharmaceutical, agricultural and chemical industries as flavorants, drugs, pesticides and industrial feedstocks. Due to the low abundance of the volatiles in their plant sources, many of the natural products had been replaced by their synthetic analogues by the end of the last century. However, the foreseeable shortage of the crude oil that is the source for many of the artifical flavors and fragrances has prompted recent interest in understanding the formation of these compounds and engineering their biosynthesis. Although many of the volatile constituents of flavors and aromas have been identified, many of the enzymes and genes involved in their biosynthesis are still not known. However, modification of flavor by genetic engineering is dependent on the knowledge and availability of genes that encode enzymes of key reactions that influence or divert the biosynthetic pathways of plant-derived volatiles. Major progress has resulted from the use of molecular and biochemical techniques, and a large number of genes encoding enzymes of volatile biosynthesis have recently been reported.

The Tomato FRUITFULL Homologs TDR4/FUL1 and MBP7/FUL2 Regulate Ethylene-Independent Aspects of Fruit Ripening

“…We found several genes related to cutin and fatty acid synthesis to be downregulated in FUL1/2 silenced fruits, among which were a glycerol-3-Pacyltransferase (log 2 = 21.2) and a cytochrome P450 hydroperoxide lyase (HPL) (log 2 = 21.8). The latter has also been implemented in lipid-derived volatile production (Schwab et al, 2008). In addition, the suberin pathway was found to be significantly changed in the transgenic fruits by upregulation of the genes encoding for cinnamic acid 4-hydroxylase (log 2 = 2.3) and caffeoyl-CoA 3-O-methyltransferase (log 2 = 3.7) (Plant MetGenMAP; see Supplemental Table 2 online).…”

A Role for Differential Glycoconjugation in the Emission of Phenylpropanoid Volatiles from Tomato Fruit Discovered Using a Metabolic Data Fusion Approach

“…It could have appeared as a by-product of extensive tomato breeding activities and now can be considered as a potentially beneficial trait. On the other hand, considering that fruit flavor is an important characteristic for natural seed-dispersing organisms (Goff and Klee, 2006;Schwab et al, 2008), one can assume that this mechanism could have already evolved in wild tomato (Solanum spp.) germplasm.…”

“…They also act as direct repellents of herbivorous pests or as attractants of the predators of these pests as part of the "cry for help" response Kappers et al, 2005;Baldwin et al, 2006). In addition, flower volatiles are important for the attraction of pollinators , while fruit volatiles may have a role in attracting seed dispersers (Goff and Klee, 2006;Schwab et al, 2008). Besides their physiological and ecological functions, plant volatiles are also important determinants of consumer quality traits in flowers, fruits, and vegetables as well as the processed products derived from them.…”

Optimization and scaling up of a biotechnological synthesis of natural green leaf volatiles using Beta vulgaris hydroperoxide lyase

“…Green note is one of the most attractive flavor in the aroma industry conferring freshness and authenticity to goods [1]. This odor is composed of different molecules collectively named green leaf volatiles (GLVs) suggesting that these compounds are usually synthesized in green organs of plants [2].…”