Elevation of Condensed Tannins in the Leaves of Ta-MYB14-1 White Clover (Trifolium repens L.) Outcrossed with High Anthocyanin Lines

Ethylene modulates the phenylpropanoid pathway by enhancing VvMYB14 expression via the ERF5-melatonin-ERF104 pathway in grape seeds

The interaction between ethylene and melatonin in the regulation of polyphenol metabolism and the underlying mechanism remain largely unclear. This work demonstrated that ethylene treatment increased melatonin biosynthesis by inducing the VvASMT expression in grape seeds. Ethylene-induced VvERF5 transactivated VvASMT via binding to the ethylene response element in its promoter. VvERF5 overexpression led to an increase in melatonin biosynthesis while its suppression generated the opposite results in grape seeds, calli, and/or Arabidopsis seeds. A melatonin-responsive element (MTRE) was identified, and melatonin-induced VvERF104 was found to bind to the MTRE of the VvMYB14 promoter and activate its expression. VvMYB14 overexpression widely modified the expression of genes in the phenylpropanoid pathway and phenolic compound content in grape seeds. DNA affinity purification sequencing revealed that the MEME-1 motif was the most likely binding sites of VvMYB14. VvPAL, VvC4H, and VvCHS were verified to be the target genes of VvMYB14. Additionally, the overexpression of VvERF5 or VvERF104 increased the expression of VvPAL, VvC4H, and VvCHS, as well as the levels of the corresponding metabolites. Moreover, the roles of VvERF5, VvASMT, and VvERF104 in mediating ethylene-induced changes in the phenylpropanoid pathway were elucidated using their suppressing seeds. Collectively, ethylene increased the VvMYB14 expression via the pathway of ERF5-melatonin-ERF104 and thereby modified the phenylpropanoid pathway.

Plant leaf proanthocyanidins: from agricultural production by-products to potential bioactive molecules

Proanthocyanidins (PAs) are a class of polymers composed of flavan-3-ol units that have a variety of bioactivities, and could be applied as natural biologics in food, pharmaceuticals, and cosmetics. PAs are widely found in fruit and vegetables (F&Vegs) and are generally extracted from their flesh and peel. To reduce the cost of extraction and increase the number of commercially viable sources of PAs, it is possible to exploit the by-products of plants. Leaves are major by-products of agricultural production of F&Vegs, and although their share has not been accurately quantified. They make up no less than 20% of the plant and leaves might be an interesting resource at different stages during production and processing. The specific structural PAs in the leaves of various plants are easily overlooked and are notably characterized by their stable content and degree of polymerization. This review examines the existing data on the effects of various factors (e.g. processing conditions, and environment, climate, species, and maturity) on the content and structure of leaf PAs, and highlights their bioactivity (e.g. antioxidant, anti-inflammatory, antibacterial, anticancer, and anti-obesity activity), as well as their interactions with gut microbiota and other biomolecules (e.g. polysaccharides and proteins). Future research is also needed to focus on their precise extraction, bioactivity of high-polymer native or modified PAs and better application type.

Nutritional enhancement of animal feed and forage crops via genetic modification

Introducing beneficial productivity and nutritional traits into food, feed and forage crops utilising the tools of biotechnology can lead to improvements via genetic modification that cannot be achieved by traditional plant breeding. The timelines and costs are significant, and the regulatory hurdles can lead to some promising traits failing to be commercialised. These challenges mean that large commodity crops are the primary beneficiaries of biotechnology. New Zealand being primarily a grazing pastoral agricultural market and small in international terms, faces greater challenges. The species used in pastoral agriculture have relatively small seed markets and therefore limited investment for genetic improvement. The nutritional quality of feed and forages both in composition and in energy density per ha has a major influence on animal productivity and the environmental impacts of agriculture. Through government and private industry support, AgResearch has developed novel approaches to improve plant photosynthesis, energy density, and nutritional quality that has applications in crops globally. This review discusses the different challenges and solutions to improving plant nutrient density and outlines the benefits of these novel biotechnology traits in animal forage and feed crops.

Condensed Tannins in White Clover (Trifolium repens) Foliar Tissues Expressing the Transcription Factor TaMYB14-1 Bind to Forage Protein and Reduce Ammonia and Methane Emissions in vitro

Grazing ruminants contribute to global climate change through enteric methane and nitrous oxide emissions. However, animal consumption of the plant polyphenolics, proanthocyanidins, or condensed tannins (CTs) can decrease both methane emissions and urine nitrogen levels, leading to reduced nitrous oxide emissions, and concomitantly increase animal health and production. CTs are largely absent in the foliage of important temperate pasture legumes, such as white clover (Trifolium repens), but found in flowers and seed coats. Attempts at enhancing levels of CT expression in white clover leaves by mutagenesis and breeding have not been successful. However, the transformation of white clover with the TaMYB14-1 transcription factor from Trifolium arvense has resulted in the production of CTs in leaves up to 1.2% of dry matter (DM). In this study, two generations of breeding elevated foliar CTs to >2% of DM. The CTs consisted predominantly of prodelphinidins (PD, 75-93%) and procyanidins (PC, 17-25%) and had a mean degree of polymerization (mDP) of approximately 10 flavan-3-ol subunits. In vitro studies showed that foliar CTs were bound to bovine serum albumin and white clover proteins at pH 6.5 and were released at pH 2.-2.5. Using rumen in vitro assays, white clover leaves containing soluble CTs of 1.6-2.4% of DM significantly reduced methane production by 19% (p ≤0.01) and ammonia production by 60% (p ≤ 0.01) relative to non-transformed wild type (WT) controls after 6 h of incubation. These results provide valuable information for further studies using CT expressing white clover leaves for bloat prevention and reduced greenhouse gas emissions in vivo.

Large Inter- and Intraspecies Variability of Polyphenols and Proanthocyanidins in Eight Temperate Forage Species Indicates Potential for Their Exploitation as Nutraceuticals

Substantial efforts have been made in incorporating tannin-rich forages into grassland-based livestock production systems. However, the structural and functional diversity of tannins in different species limits their potential use at the field scale. We conducted a greenhouse experiment with 17 cultivars from 8 forage species and their cultivars. Ultraperformance liquid chromatography tandem mass spectrometry was used to analyze their polyphenolic profile and proanthocyanidin (PA) structural features in leaves. Our results highlight large inter- and intraspecies variability of plants in terms of polyphenol and tannin concentrations in the leaves. A concomitant and significant variation was also registered in the structural features of PA-rich forages such as the mean degree of polymerization and prodelphinidin percentage. The concentration of PA also varied within plant organs; the highest concentration was in flowers, but leaves had the highest contribution to harvestable PA biomass. Our research highlights that identifying these variations helps in identifying the representativeness of bioactivity and provides the basis for targeted breeding programs.

Tunisian Pistachio Hull Extracts: Phytochemical Content, Antioxidant Activity, and Foodborne Pathogen Inhibition

The present study aimed to discriminate pistachio (Pistacia vera L.) hulls belonging to three different Tunisian geographical origins and extracted separately by hexane, acetone, acetonitrile, and water in terms of phytochemicals and antioxidant and antibacterial activities using multivariate analysis. Significant differences ( $P<0.05$ ) in the phytochemical content, antioxidant, and antifoodborne bacterial activities were detected among the pistachio hulls populations. Pearson correlation, principal component analysis (PCA), hierarchical cluster analysis (HCA), and heat map were used to distinguish the relationship between the different regions on the basis of the biological activities. It was found that the twelve (4 extracts × 3 geographical sources) pistachio hulls extracts could be classified geographically into four distinct groups. To explore the mode of action of the aqueous pistachio hull extract against L. monocytogenes and S. enterica, polymyxin acriflavine lithium chloride ceftazidime aesculin mannitol (PALCAM) and xylose lysine deoxycholate (XLD) broth media were artificially contaminated at 104 CFU/mL. Using linear and general linear models, aqueous pistachio hull extract was demonstrated to control the two dominant food-borne pathogens by suppressing the bacterial growth.

Examining the Variables Leading to Apparent Incongruity between Antimethanogenic Potential of Tannins and Their Observed Effects in Ruminants—A Review

In recent years, several secondary plant metabolites have been identified that possess antimethanogenic properties. Tannin-rich forages have the potential to reduce methane emissions in ruminants while also increasing their nutrient use efficiency and promoting overall animal health. However, results have been highly inconclusive to date, with their antimethanogenic potential and effects on both animal performance and nutrition being highly variable even within a plant species. This variability is attributed to the structural characteristics of the tannins, many of which have been linked to an increased antimethanogenic potential. However, these characteristics are seldom considered in ruminant nutrition studies—often because the analytical techniques are inadequate to identify tannin structure and the focus is mostly on total tannin concentrations. Hence, in this article, we (i) review previous research that illustrate the variability of the antimethanogenic potential of forages; (ii) identify the source of inconsistencies behind these results; and (iii) discuss how these could be optimized to generate comparable and repeatable results. By adhering to this roadmap, we propose that there are clear links between plant metabolome and physiology and their antimethanogenic potential that can be established with the ultimate goal of improving the sustainable intensification of livestock.

Phytochemical profile and pharmacological properties of Trifolium repens

Trifolium repens belongs to the family Leguminosae and has been used for therapeutic purposes as traditional medicine. The plant is widely used as fodder and leafy vegetables for human uses. However, there is a lack of a detailed review of its phytochemical profile and pharmacological properties. This review presents a comprehensive overview of the phytochemical profile and biological properties of T. repens. The plant is used as antioxidants and cholinesterase inhibitors and for anti-inflammatory, antiseptic, analgesic, antirheumatic ache, and antimicrobial purposes. This review has summarized the available updated useful information about the different bioactive compounds such as simple phenols, phenolic acids, flavones, flavonols, isoflavones, pterocarpans, cyanogenic glucosides, saponins, and condensed tannins present in T. repens. The pharmacological roles of these secondary metabolites present in T. repens have been presented. It has been revealed that T. repens contain important phytochemicals, which is the potential source of health-beneficial bioactive components for food and nutraceuticals industries.