Abstract
Proanthocyanidins (PAs) are a group of oligomers or polymers composed of monomeric flavanols. They offer many benefits for human fitness, such as antioxidant, anticancer, and anti-inflammatory activities. To date, three types of PA have been observed in nature: procyanidins, propelargonidins, and prodelphinidins. These are synthesized as some of the end-products of the flavonoid pathway by different consecutive enzymatic activities, from the same precursor—naringenin. Although the general biosynthetic pathways of PAs have been reported in a few model plant species, little is known about the species-specific pathways in major crops containing different types of PA. In the present study, we identified the species-specific pathways in 10 major crops, based on the presence/absence of flavanol-based intermediates in the metabolic pathway, and found 202 orthologous genes in the reference genomic database of each species, which may encode for key enzymes involved in the biosynthetic pathways of PAs. Parallel enzymatic reactions in the pathway are responsible for the ratio between PAs and anthocyanins, as well as among the three types of PAs. Our study suggests a promising strategy for molecular breeding, to regulate the content of PAs and anthocyanins and improve the nutritional quality of food sources globally.
Highlights
Proanthocyanidins (PAs), or condensed tannins, are oligomeric or polymeric endproducts of flavonoid metabolism, starting from the central phenylpropanoid pathway [1]
These are found in all of our target crops (Table 1), except for catechin, which has not been identified in A. thaliana to date [58,59,97]. This is consistent with our results, which showed that orthologous genes of leucoanthocyanidin reductase (LAR) were not detected in A. thaliana, which catalyzed catechin from leucoanthocyanidins. Both catechin and epicatechin were detected in V. vinifera and P. dulcis [21,22,52,53,73], orthologous genes of anthocyanidin reductase (ANR) were not detected in V. vinifera, while flavanone 3 -hydroxylase (F3H) and flavonoid 3 -hydroxylase (F3 H) were not detected in P. dulcis
Different types of PAs are present in many cash crops, PAs have been relatively underinvestigated compared to other flavonoids, such as anthocyanins
Summary
Proanthocyanidins (PAs), or condensed tannins, are oligomeric or polymeric endproducts of flavonoid metabolism, starting from the central phenylpropanoid pathway [1]. PAs are brown-pigmented and present in the seed coats or seeds, fruits, bark, and leaves of a wide range of plant species, including important cash crops, such as apples, grapes, soybeans, common beans, cereals, and most berries [2]. Depending on the composition of the monomer precursor, the type of PA varies, including catechin, epicatechin, gallocatechin, epigallocatechin, afzelechin, and epiafzelechin, which are commonly found in the plant kingdom [2,20,21,22] Because of their beneficial properties, the accumulation of PAs has become a target of breeding and genetic engineering in a few model species; yet, the key genes involved in the pathway remain unclear in most cash crops [18].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
