BackgroundAnthocyanins are a class of brightly colored, glycosylated flavonoid pigments that imbue their flower and fruit host tissues with hues of predominantly red, orange, purple, and blue. Although all anthocyanins exhibit pH-responsive photochemical changes, distinct structural decorations on the core anthocyanin skeleton also cause dramatic color shifts, in addition to improved stabilities and unique pharmacological properties. In this work, we report for the first time the extension of the reconstituted plant anthocyanin pathway from (+)-catechin to O-methylated anthocyanins in a microbial production system, an effort which requires simultaneous co-option of the endogenous metabolites UDP-glucose and S-adenosyl-l-methionine (SAM or AdoMet).ResultsAnthocyanin O-methyltransferase (AOMT) orthologs from various plant sources were co-expressed in Escherichia coli with Petunia hybrida anthocyanidin synthase (PhANS) and Arabidopsis thaliana anthocyanidin 3-O-glucosyltransferase (At3GT). Vitis vinifera AOMT (VvAOMT1) and fragrant cyclamen ‘Kaori-no-mai’ AOMT (CkmOMT2) were found to be the most effective AOMTs for production of the 3′-O-methylated product peonidin 3-O-glucoside (P3G), attaining the highest titers at 2.4 and 2.7 mg/L, respectively. Following modulation of plasmid copy number and optimization of VvAOMT1 and CkmOMT2 expression conditions, production was further improved to 23 mg/L using VvAOMT1. Finally, CRISPRi was utilized to silence the transcriptional repressor MetJ in order to deregulate the methionine biosynthetic pathway and improve SAM availability for O-methylation of cyanidin 3-O-glucoside (C3G), the biosynthetic precursor to P3G. MetJ repression led to a final titer of 51 mg/L (56 mg/L upon scale-up to shake flask), representing a twofold improvement over the non-targeting CRISPRi control strain and 21-fold improvement overall.ConclusionsAn E. coli strain was engineered for production of the specialty anthocyanin P3G using the abundant and comparatively inexpensive flavonol precursor, (+)-catechin. Furthermore, dCas9-mediated transcriptional repression of metJ alleviated a limiting SAM pool size, enhancing titers of the methylated anthocyanin product. While microbial production of P3G and other O-methylated anthocyanin pigments will likely be valuable to the food industry as natural food and beverage colorants, we expect that the strain constructed here will also prove useful to the ornamental plant industry as a platform for evaluating putative anthocyanin O-methyltransferases in pursuit of bespoke flower pigment compositions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0623-3) contains supplementary material, which is available to authorized users.

There is growing concern about food safety, environmental impact, and efficient energy usage in agricultural production systems. Producing lettuce under artificial lighting could be a solution addressing these concerns. Light-emitting diodes (LEDs) offer the advantages of a narrow light spectrum, low power consumption, and little heat production. The objective of this study was to determine the effects of different light sources on the growth of miniature “Tom Thumb” butterhead lettuce in a non-circulating hydroponic system. Lettuce seedlings, started in Oasis Horticubes, were transferred to net pots in containers with a hydroponic nutrient solution. The lettuce was grown in a lab under three light treatments—blue LEDs, red LEDs, and fluorescent lights. At the end of the study, fluorescent lights resulted in greater root dry weight than blue LEDs and red LEDs. Total plant dry weight under fluorescent lights was greater than under red LEDs. There were no significant differences in shoot dry weight and plant height among the treatments. Percent partitioning of dry weight to shoots was greatest with red LEDs, followed by blue LEDS, and fluorescent lights. Percent partitioning of dry weight to roots was greatest with fluorescent lights, followed by blue LEDS, and red LEDs. Leaf chlorophyll content was greater under blue LEDs and fluorescent lights than red LEDs. The pH of the nutrient solution of the blue LED and the fluorescent light treatments were greater than the red LED treatment. Electrical conductivity of the nutrient solution of the fluorescent light treatment was greater than the blue LED treatment and the red LED treatment. In conclusion, LEDs could provide an alternative lighting source for miniature lettuce production.

Perianths of 34 Dendrobium Sw. species and hybrids were examined to elucidate the roles of pigment distribution and shape of upper epidermal cells in determining color intensity, perception, and visual texture. Color intensity was determined by the spatial localization of anthocyanin in tissue layers, i.e., in the epidermal, subepidermal, and mesophyll layers, as well as by distribution of pigmented cells within the tissue layer. Anthocyanins were confined to the epidermal layer or subepidermal layer in flowers with low color intensity, whereas they were also in several layers of mesophyll in more intensely colored flowers. Striped patterns on the perianth were due to the restriction of pigment to cells surrounding the vascular bundles. Color perception is influenced by the presence or absence of carotenoids, which when present, were distributed in all cell layers. Anthocyanins in combination with carotenoids resulted in a variety of flower colors ranging from red, maroon, bronze to brown, depending on the relative location of the two pigments. Four types of epidermal cell shapes were identified in Dendrobium flowers: flat, dome, elongated dome, and papillate. Epidermal cell shape and cell packing in the mesophyll affected the visual texture. Petals and sepals with flat cells and a tightly packed mesophyll had a glossy texture, whereas dome cells and loosely packed mesophyll contributed a velvety texture. The labella in the majority of flowers examined had a complex epidermis with more than one epidermal cell shape, predominantly papillate epidermal cells.

Anthurium amnicola Dressler possesses a number of desirable and novel ornamental traits such as a purple-colored upright spathe, profuse flowering, and floral scent, some of which have been introgressed into modern Anthurium cultivars. As a first step in identifying genes associated with these traits, the transcriptome from root, leaf, spathe, and spadix from an accession of A. amnicola was assembled, resulting in 28,019 putative transcripts representing 19,458 unigenes. Genes involved in pigmentation, including those for the metabolism of chlorophyll and the biosynthesis of carotenoids, phenylpropanoids, and flavonoids were identified. The expression levels of one MYB transcription factor was highly correlated with naringenin 3-dioxygenase (F3H) and dihydroflavonol-4-reductase (DFR) in leaves, whereas a bHLH transcription factor was highly correlated with flavonoid 3′-monooxygenase (F3′H) and a DFR in spathes, suggesting that these two transcription factors might regulate flavonoid and anthocyanin synthesis in A. amnicola. Gene sequence and expression data from four major organs of A. amnicola provide novel basal information for understanding the genetic bases of ornamental traits and the determinants and evolution of form and function in the Araceae.Anthurium is a major cut flower and potted plant with a long and important history of breeding, selection, and cultivation in Hawaii. Today, the largest production comes from the Netherlands, with significant production and research in Hawaii and other tropical and subtropical areas. A popular attraction is its colorful spathe, a modified leaf that is associated with the spadix, an organ often also found in varied colors housing numerous bisexual, protogynous flowers. The major spathe color classes red, pink, orange, coral, and purple are from variations in anthocyanin type and levels and white coloration represents loss of pigment. Further, green coloration is thought to occur from variations in chlorophyll production, while brown coloration is likely derived from variations in anthocyanin and chlorophyll content [1][2][3][4][5] .The genus Anthurium consists of as many as 1,500 species found between Southern Mexico and Northern Argentina and is the largest genus in the Araceae family 6 . A limited sampling revealed that Anthurium species possess medium-sized genomes ranging from between 2 to 10 Gbp per haploid genome 7 . A majority of the modern Anthurium cultivars in the market today descend from historical or recent hybrids between species 8 particularly with A. andraeanum, which is characterized by the commercially popular heart-shaped spathe. Spathe and

The global orchid production has been active in tropical, subtropical countries, many with automated and efficiently managed large greenhouses. The most important exported potted orchid in the trade is Phalaenopsis with tremendous breeding and micropropagation technology achievements in several countries, such as Belgium, the Netherlands, Taiwan, and Thailand. Another reason for its popularity is its easiness of controlled flower induction for scheduled and year-around production. Cut orchids such as Cymbidium, Dendrobium, Oncidium, and Vanda are important cut flowers worldwide. Now orchids are quite popular in the global market, partly due to their long shelf life, diverse colors, and other desirable traits pursued by consumers, depending on the location or culture. European Union (EU) and the United States are the most important countries or areas for marketing of assortments of orchid products. New markets for orchids are increasing annually. Since the beginning of 2020, due to the severe coronavirus pandemic and disruption of global economy, orchid marketing has been shifting to an increased share of digitalization or E-commerce, co-existing with the traditional flower stores and supermarkets. In the future, more orchid products or novel new orchid hybrids being developed by non-conventional technologies, such as biotech-oriented efficient breeding, may help offer new opportunities for orchid production.