Every interaction is an opportunity to build your market. Lecture 2 also addresses the issue of on-farm events. If you do a good job of engaging your community through social media and when you are out and about, then it’s likely your community will be interested in seeing your farm and learning about what you do. You might find that visitors drop by for an impromptu farm tour. This can be difficult to manage, especially if there are very few workers on your farm. Hosting an on-farm event is a popular way of sharing all that is beautiful and interesting about your farm while creating a sense of community amongst all the different people who may be interested in coming out to learn more about how their food is grown. On-farm events can be a lot of fun, and regardless of whether they make money, they may generate good will in the community. But as discussed in Lecture 2, it’s important to be aware of the potential downside: events take a great deal of time and effort, aren’t always profitable, and you can open yourself up to new liabilities when you open your farm to the public.Phenylpropanoids are specialized metabolites involved in several aspects of plant growth and development and in the responses of plants to environmental stimuli. These compounds are synthesized from key intermediates of the shikimate pathway, which are structurally modified by the combined activities of lyases, transferases, ligases, reductases and oxygenases, flower bucket resulting in the organ- and developmental-specific synthesis and accumulation of diverse metabolites . The phenylpropanoid pathway provides the building blocks for lignin, suberin, and condensed tannins that play a role in structural support and mechanical strength.

Lignin is a major contributor to feedstock recalcitrance and negatively affects the conversion of plant biomass into downstream products in bio-refineries . Further, this pathway is key for the production of anthocyanins for organ pigmentation, flavonols and flavones for UV protection, various flavonoids and isoflavonoids for plant-microbe interactions, and antimicrobial phytoalexins for protection against pathogens . In addition to their biological functions in planta, phenylpropanoids are economically important metabolites. They constitute important components in the human diet, acting as nutraceutical compounds with antioxidant, chemopreventive, antimitotic, neuroprotective, cardioprotective, and anti-inflammatory activities. Several phenylpropanoids are considered high-value biochemicals employed in the production of fragrances, pharmaceuticals and biopolymers . Systems biology approaches have enabled the characterization of numerous aspects of the phenylpropanoid metabolism in different plant species, including genes, enzymes and metabolites involved in the different branches of the pathway and how these branches are regulated. However, there is still much to be explored and determined in terms of regulation, de novo biosynthesis, transport, compartmentation, and polymerization of phenylpropanoids. In addition to their complex biosynthetic machinery and extensive chemical diversity, the synthesis and accumulation of metabolites is also largely dependent on the tissue type, developmental stage, plant species, or might be triggered in response to specific environmental conditions . Advances in “omics” technologies provide a timely opportunity to further characterize even subtle changes in the levels of transcripts, enzymes and metabolites, and thus to provide a comprehensive systems view of phenylpropanoid metabolism throughout plant development and during stress responses.

Furthermore, phenylpropanoid bioengineering holds promise to generate more resilient and nutritious crops, to maximize our arsenal of useful biomolecules, and to re-design high-yield and sustainable bioenergy feedstocks by means of biotechnology. This Research Topic aimed to gather recent findings in all aspects of phenylpropanoid metabolism gained by means of systems biology approaches and the utilization of biotechnologyto exploit the economic, medicinal and nutraceutical potential of phenylpropanoids. The topic is organized into four sections: structural, molecular and computational approaches toward unraveling the biosynthetic pathways involved in synthesis of diverse phenylpropanoid-derived metabolites; discovery of genes and/or gene networks involved in distinct aspects of phenylpropanoid metabolism via omics technology; functional characterization of genes involved in the phenylpropanoid metabolism and its coordination with physiological processes; and biotechnological approaches to exploit the economic, medicinal, and nutraceutical potential of phenylpropanoids.The chemical diversity of phenylpropanoids results from the modification and amplification of a set of core structures derived from the shikimate pathway. A vast array of regulatory proteins, biosynthetic enzymes, oxidases and other genes are recruited to produce the various classes of phenolic metabolites. Additionally, many phenylpropanoids are specific to just one or a few plant species, underscoring the complexity of phenylpropanoid biosynthesis and the need for comprehensive characterization studies in diverse species that expand our knowledge base beyond traditional model plant and crop species. Structural, molecular and computational approaches have been applied to identify genes, enzymes and metabolites involved in the biosynthesis of phenylpropanoids in different plants. Delli-Ponti et al. have reviewed how gene expression and co-expression networks can be used as tools to uncover specialized metabolism biosynthetic pathways.

Also using a computational approach, Elder et al. have applied density functional theory calculations to evaluate the thermodynamics of coupling modes and subsequent rearomatization reactions between coniferyl alcohol and hydroxystilbene glucosides, which has been detected as a natural monomer in the bark lignin of Norway spruce. To this end, the effect of chilling treatment on the accumulation of phenylpropanoids and on antioxidant activity in seedlings of two rice varieties was studied by Du et al. . Lignin is a phenolic polymer important for plant growth and development but it is also considered a major bottleneck to the efficient conversion of plant biomass into downstream products. Rosado et al. have reported an indepth characterization of the structural characteristics of lignins present in rice husks and straw, which are agricultural byproducts that can be used to produce chemicals and materials in biorefineries. To identify the timing and key parameters of cell wall recalcitrance across different switchgrass genotypes, Saha et al. measured cell wall composition and phenylpropanoid/lignin biosynthesis gene expression in three switchgrass genotypes representing lowland and upland ecotypes. Yao et al. reviewed recent progress in defining the lignin biosynthetic pathway in lycophytes, monilophytes, gymnosperms, and angiosperms, and integrated new insights on major transcriptional regulators. In another study with evolutionary implications, Rencoret et al. structurally characterized the lignin-like fractions isolated from several ancestral plants, including those from moss, lycophyte, horsetail, fern, cycad, and gnetophyte species. Blaschek and Pesquet provided an overview of the differences and similarities in the structures, reaction mechanisms, substrate specificities, and functional roles between phenoloxidases. Because grasses are able to synthesize phenylpropanoids from either phenylalanine or tyrosine , Simpson et al. employed 13C isotopic-labeled precursors and mass spectrometry-based metabolomics to determine the downstream metabolites derived exclusively from Phe and Tyr in sorghum. Several phenylpropanoids show bioactivity that might influence plant growth and development or might be beneficial for human health. El Houari et al. reviewed reports describing altered accumulation of bioactive phenylpropanoids as the causal factor for observed phenotypes of lignin mutants in Arabidopsis. Cappellini et al. reviewed the recent progress in understanding the anthocyanin biosynthetic pathway in plants, with special emphasis on the differences in molecular mechanisms between monocot and dicot plants, and discuss the biological activities of anthocyanins as beneficial components of the human diet. Similar to anthocyanins, tannins form another group of phenolic compounds with beneficial effects on human health. Wang et al. performed a genome-wide analysis of the tannase gene family to identify candidate genes responsible for tannin metabolism in three nut tree species in the Juglandaceae family: walnut, pecan, and Chinese hickory.The identification of genes and transcriptional networks responsible for specific accumulation patterns of phenylpropanoids during a physiological development process or a stress response is essential to elucidate and harness the fine regulatory mechanisms involved in these patterns. Recent advancements in omics technologies enable integrated approaches to unravel these mechanisms at the transcriptomic, proteomic, plastic flower bucket and metabolomic levels. These studies provide platforms to guide future research on improving crops for human health and wellness. Tang et al. leveraged single-molecule real-time sequencing technology to elucidate flavonoid synthetic pathways in blueberries. Their transcriptome analyses led to the discovery of a R2R3 MYB transcription factor that can positively regulate anthocyanin synthesis in fruits. 5-aminolevulinic acid is a plant growth regulator that induces fruit coloration and thereby finds potential applications in modern fruit production. A transcriptome study by Zheng et al. identified the differentially expressed genes associated with ALA-induced anthocyanin accumulation in apple, including two R2R3-MYB transcription factors involved in flavonoid accumulation. A study by Aniciˇ c et al. ´ investigated flavonoid metabolism during fruit development in rockrose, a traditional medicinal plant rich in bioactive phenylpropanoids, using comparative metabolomic and transcriptomic approaches. This work highlights correlations between expression patterns of biosynthetic genes and the content of proanthocyanidins.

Phenolic compounds are modulated by biotic and abiotic stresses, and a study by Laoué et al. used quantitative trait locus mapping and RNA-Seq to explore the complex polygenic network underlying the constitutive production of specific stilbenoids, flavonoids, and lignans in white spruce. Understanding the formation of secondary cell walls and their lignification has important agro-industrial applications. Hixson et al. , by undertaking an integrated analysis of the metabolome, transcriptome, and proteome of Arabidopsis lines mutated in arogenate dehydratase genes, exposed the involvement of novel proteins and additional post-transcriptional and translational processes that govern phenylpropanoid/lignin biosynthesis. As a proxy to study SCW formation in the bioenergy crop sugarcane, Simões et al. established a lignifying cell culture system that they probed with transcriptomic and metabolomic analyses to illuminate the molecular mechanisms involved in this differentiation process, leading to the discovery of regulatory modules that control SCW deposition.The phenylpropanoid pathway in plants plays a major role in the synthesis of a wide variety of secondary metabolites. Metabolites originating from this pathway are frequently involved in plant structure or chemical signaling and defense, including flavonoids, lignins, hydroxycinnamic esters, flavonoids, anthocyanins and tannins. Dietary flavonoids, anthocyanins, proanthocyanidins, hydroxycinnamoyl acid amides and lignans are bioactive compounds that have been shown to exhibit multiple health promoting and antioxidant activities. Lignans are plant secondary metabolites composed of a core scaffold that is formed by two or more phenylpropanoid units that can adopt a spectrum of different structural forms. Chen et al. identified two non-selective uridine diphosphate glycosyltransferases from Isatis indigotica Fort. that catalyze the addition of a sugar molecule onto several structurally diverse lignin acceptor substrates. Shi et al. sought to explore the transcriptional regulatory mechanisms of anthocyanin and proanthocyanidin biosynthesis in Chinese bayberry, of which the fruit is considered an important dietary source of natural antioxidants. They identified a MrMYB6 gene that is highly upregulated during the latter stages of fruit development and determined it is a negative regulator of anthocyanin and proanthocyanidins through formation of a complex with two transcription factors, bHLH and WD40. Busche et al. carried out a study five 2-oxoglutaratedependent dioxygenases involved in the formation of the flavonoid aglycon in banana : flavanone 3-hydroxylase, flavonol synthase and anthocyanidin synthase. Biochemical analysis of several recombinant candidate proteins showed that MusaF3H1 and MusaF3H2 act as flavanone 3-hydroxylases, MusaFLS1 and MusaFLS3 both function as flavonol synthases, and MusaANS has anthocyanidin synthase activity. Elucidating the activity of these genes will facilitate the development of bananas with higher nutritional value. Hydroxycinnamoyl acid amides, such as clovamide, are phenylpropanoid metabolites that play roles in protecting plants from biotic and abiotic stresses. Sullivan and Knollenberg identified, cloned and biochemically characterized a hydroxycinnamoyl-CoA:L-DOPA hydroxycinnamoyl transferase from red clover that is capable of synthesizing clovamide and related hydroxycinnamoyl amides in vitro. Characterization of this enzyme activity expands our knowledge of the poorly characterized family of BAHD hydroxycinnamoyl-CoA transferase enzymes and will aid in future studies aimed at understanding the molecular basis of substrate specificity within this important family. Lignin is a heterogeneous phenolic polymer that is highly abundant in the secondary cell walls of all land plants and is composed of three major monolignol subunits: 4- hydroxyphenyl , guaiacyl , and syringyl . The monolignol building blocks of lignin are synthesized by enzymes acting in concert that catalyze sequential reactions. Lin et al. provide direct evidence that two key enzymes involved in monolignol biosynthesis, 4-Coumaric acid:CoA ligase and 4-hydroxycinnamoylCoA:shikimic acid hydroxycinnamoyl transferase, form a Ptr4CL-PtrHCT complex in Populus trichocarpa and its formation is a potential mechanism to modulate metabolic flux during secondary cell wall synthesis. The brown midrib phenotype found across several C4 grasses has been critical for identifying mutants compromised in lignin synthesis. Tetreault et al. used a combined bulk segregant analysis and nextgeneration sequencing approach to show that bmr30 encodes a chalcone isomerase and is involved in synthesis of the flavonoid tricin and not a monolignol.