[1]

Dyer AG, Jentsch A, Burd M, Garcia JE, Giejsztowt J, et al. 2021. Fragmentary blue: resolving the rarity paradox in flower colors. Frontiers in Plant Science 11:618203

doi: 10.3389/fpls.2020.618203
[2]

van der Kooi CJ, Dyer AG, Kevan PG, Lunau K. 2019. Functional significance of the optical properties of flowers for visual signalling. Annals of Botany 123:263−276

doi: 10.1093/aob/mcy119
[3]

Streinzer M, Neumayer J, Spaethe J. 2021. Flower color as predictor for nectar reward quantity in an Alpine flower community. Frontiers in Ecology and Evolution 9:721241

doi: 10.3389/fevo.2021.721241
[4]

Husain A, Chanana H, Khan SA, Dhanalekshmi UM, Ali M, et al. 2022. Chemistry and pharmacological actions of delphinidin, a dietary purple pigment in anthocyanidin and anthocyanin forms. Frontiers in Nutrition 9:746881

doi: 10.3389/fnut.2022.746881
[5]

Takeda K, Osakabe A, Saito S, Furuyama D, Tomita A, et al. 2005. Components of protocyanin, a blue pigment from the blue flowers of Centaurea cyanus. Phytochemistry 66:1607−1613

doi: 10.1016/j.phytochem.2005.04.002
[6]

Trouillas P, Sancho-García JC, De Freitas V, Gierschner J, Otyepka M, et al. 2016. Stabilizing and modulating color by copigmentation: insights from theory and experiment. Chemical Reviews 116:4937−4982

doi: 10.1021/acs.chemrev.5b00507
[7]

Cui Y, Ren J, Fan J, Li H, Li Y, et al. 2025. Polyacylated delphinidin biosynthesis catalysed by PhF3'5' H-PhBGLU12-PhSCPL2 determines the blue pigmentation in Cineraria (Pericallis hybrida). Plant Biotechnology Journal 23:5585−5599

doi: 10.1111/pbi.70330
[8]

Wang J, Zhao Y, Sun B, Yang Y, Wang S, et al. 2024. The structure of anthocyanins and the copigmentation by common micromolecular copigments: a review. Food Research International 176:113837

doi: 10.1016/j.foodres.2023.113837
[9]

Yoshida K. 2024. Tracing the genealogy of research on the mechanism of blue flower coloration by anthocyanin based on Keita Shibata's work. Proceedings of the Japan Academy, Series B 100:446−464

doi: 10.2183/pjab.100.028
[10]

Tindal RA, Jeffery DW, Muhlack RA. 2024. Nonlinearity and anthocyanin colour expression: a mathematical analysis of anthocyanin association kinetics and equilibria. Food Research International 183:114195

doi: 10.1016/j.foodres.2024.114195
[11]

Tasaki K, Watanabe A, Nemoto K, Takahashi S, Goto F, et al. 2022. Identification of candidate genes responsible for flower colour intensity in Gentiana triflora. Frontiers in Plant Science 13:906879

doi: 10.3389/fpls.2022.906879
[12]

Yoshida K, Teppabut Y, Sugita C, Oyama KI. 2022. Blue flower coloration of Salvia macrophylla by the metalloanthocyanin, protodelphin. Bioscience, Biotechnology, and Biochemistry 86:1349−1352

doi: 10.1093/bbb/zbac135
[13]

Tanikawa N, Seto H, Suzuki S, Omori A, Tatsuzawa F. 2024. Identification of novel flower anthocyanins of Delphinium grandiflorum cultivars. Dyes and Pigments 228:112250

doi: 10.1016/j.dyepig.2024.112250
[14]

Noda N. 2018. Recent advances in the research and development of blue flowers. Breeding Science 68:79−87

doi: 10.1270/jsbbs.17132
[15]

Mekapogu M, Song HY, Lim SH, Jung JA. 2023. Genetic engineering and genome editing advances to enhance floral attributes in ornamental plants: an update. Plants 12:3983

doi: 10.3390/plants12233983
[16]

Murayama K, Kato-Murayama M, Sato T, Hosaka T, Ishiguro K, et al. 2021. Anthocyanin 5,3'-aromatic acyltransferase from Gentiana triflora, a structural insight into biosynthesis of a blue anthocyanin. Phytochemistry 186:112727

doi: 10.1016/j.phytochem.2021.112727
[17]

Sasaki N, Watanabe A, Asakawa T, Sasaki M, Hoshi N, et al. 2018. Biological effects of ion beam irradiation on perennial gentian and apple. Plant Biotechnology 35:249−257

doi: 10.5511/plantbiotechnology.18.0612a
[18]

Tasaki K, Higuchi A, Watanabe A, Sasaki N, Nishihara M. 2019. Effects of knocking out three anthocyanin modification genes on the blue pigmentation of gentian flowers. Scientific Reports 9:15831

doi: 10.1038/s41598-019-51808-3
[19]

Nakatsuka T, Sato K, Takahashi H, Yamamura S, Nishihara M. 2008. Cloning and characterization of the UDP-glucose: anthocyanin 5-O-glucosyltransferase gene from blue-flowered gentian. Journal of Experimental Botany 59:1241−1252

doi: 10.1093/jxb/ern031
[20]

Venter A, Fisher H, Stafford GI, Duodu KG. 2022. Pigmented flower extracts of plant species from the Geraniaceae and Lamiaceae families as natural food colourants: anthocyanin composition, thermal and oxidative stability. International Journal of Food Science & Technology 57:4347−4355

doi: 10.1111/ijfs.15761
[21]

Ramos da Silva LR, Ferreira OO, Cruz JN, de Jesus Pereira Franco C, Oliveira dos Anjos T, et al. 2021. Lamiaceae essential oils, phytochemical profile, antioxidant, and biological activities. Evidence-Based Complementary and Alternative Medicine 2021:6748052

doi: 10.1155/2021/6748052
[22]

Mori M, Kondo T, Yoshida K. 2008. Cyanosalvianin, a supramolecular blue metalloanthocyanin, from petals of Salvia uliginosa. Phytochemistry 69:3151−3158

doi: 10.1016/j.phytochem.2008.03.015
[23]

Mizuno T, Sugimura K, Iwashina T, Ishikawa-Takano Y, Nakane T, et al. 2025. Identification of phenolic compounds from the aerial parts of Holy basil (Ocimum tenuiflorum) cultivar 'Himalayan Sunset Blue', their anti-oxidant activity, and anthocyanin contribution to colour stability. Natural Product Research 00:1−7

doi: 10.1080/14786419.2025.2565812
[24]

Terahara N, Callebaut A, Ohba R, Nagata T, Ohnishi-Kameyama M, et al. 2001. Acylated anthocyanidin 3-sophoroside-5-glucosides from Ajuga reptans flowers and the corresponding cell cultures. Phytochemistry 58:493−500

doi: 10.1016/S0031-9422(01)00172-8
[25]

Inomata Y, Terahara N, Kitajima J, Kokubugata G, Iwashina T. 2013. Flavones and anthocyanins from the leaves and flowers of Japanese Ajuga species (Lamiaceae). Biochemical systematics and ecology 51:123−129

doi: 10.1016/j.bse.2013.08.004
[26]

Mizuno T, Seto H, Nakane T, Murai Y, Tatsuzawa F, et al. 2023. Anthocyanin and flavones from the flowers of Tripora divaricata (Lamiaceae) and their contribution to blue violet color. Bulletin of the National Museum of Nature and Science. Series B, Botany 49:57−64

doi: 10.50826/bnmnsbot.49.2_57
[27]

Sharma B, Pandher MK, Alcaraz Echeveste AQ, Romo RK, Bravo M. 2024. Delphinium as a model for development and evolution of complex zygomorphic flowers. Frontiers in Plant Science 15:1453951

doi: 10.3389/fpls.2024.1453951
[28]

Nishizaki Y, Sasaki N, Yasunaga M, Miyahara T, Okamoto E, et al. 2014. Identification of the glucosyltransferase gene that supplies the p-hydroxybenzoyl-glucose for 7-polyacylation of anthocyanin in Delphinium. Journal of Experimental Botany 65:2495−2506

doi: 10.1093/jxb/eru134
[29]

Buhrman K, Aravena-Calvo J, Ross Zaulich C, Hinz K, Laursen T. 2022. Anthocyanic vacuolar inclusions: from biosynthesis to storage and possible applications. Frontiers in Chemistry 10:913324

doi: 10.3389/fchem.2022.913324
[30]

Nishizaki Y, Yasunaga M, Okamoto E, Okamoto M, Hirose Y, et al. 2013. p-Hydroxybenzoyl-glucose is a zwitter donor for the biosynthesis of 7-polyacylated anthocyanin in Delphinium. The Plant Cell 25:4150−4165

doi: 10.1105/tpc.113.113167
[31]

Miyahara T, Sakiyama R, Ozeki Y, Sasaki N. 2013. Acyl-glucose-dependent glucosyltransferase catalyzes the final step of anthocyanin formation in Arabidopsis. Journal of Plant Physiology 170:619−624

doi: 10.1016/j.jplph.2012.12.001
[32]

Miyagawa N, Nishizaki Y, Miyahara T, Okamoto M, Hirose Y, et al. 2014. Sequence variations in the flavonoid 3′,5′-hydroxylase gene associated with reddish flower phenotypes in three Delphinium varieties. Plant Biotechnology 31:83−87

doi: 10.5511/plantbiotechnology.13.1203c
[33]

Sakaguchi K, Isobe C, Fujita K, Ozeki Y, Miyahara T. 2019. Production of novel red-purple Delphinium flowers containing cyanidin-based anthocyanin using hybridization breeding. The Horticulture Journal 88:514−520

doi: 10.2503/hortj.UTD-100
[34]

Takeda K. 2006. Blue metal complex pigments involved in blue flower color. Proceedings of the Japan Academy, Series B, Physical and Biological Sciences 82:142−154

doi: 10.2183/pjab.82.142
[35]

Tanaka Y, Tsuda S, Kusumi T. 1998. Metabolic engineering to modify flower color. Plant and Cell Physiology 39:1119−1126

doi: 10.1093/oxfordjournals.pcp.a029312
[36]

Katsumoto Y, Fukuchi-Mizutani M, Fukui Y, Brugliera F, Holton TA, et al. 2007. Engineering of the rose flavonoid biosynthetic pathway successfully generated blue-hued flowers accumulating delphinidin. Plant and Cell Physiology 48:1589−1600

doi: 10.1093/pcp/pcm131
[37]

Shunji Y, Satoshi A, Takanori S. 2013. Flavonoid-3′,5′-hydroxylase gene of Commelina communis. Google Patents. CA2681301. Canada

[38]

Huang H, Hu K, Han K, Xiang Q, Dai S. 2013. Flower colour modification of chrysanthemum by suppression of F3'H and overexpression of the exogenous Senecio cruentus F3'5'H gene. PLoS One 8:e74395

doi: 10.1371/journal.pone.0074395
[39]

Noda N, Aida R, Kishimoto S, Ishiguro K, Fukuchi-Mizutani M, et al. 2013. Genetic engineering of novel bluer-colored chrysanthemums produced by accumulation of delphinidin-based anthocyanins. Plant and Cell Physiology 54:1684−1695

doi: 10.1093/pcp/pct111
[40]

Noda N, Yoshioka S, Kishimoto S, Nakayama M, Douzono M, et al. 2017. Generation of blue chrysanthemums by anthocyanin B-ring hydroxylation and glucosylation and its coloration mechanism. Science Advances 3:e1602785

doi: 10.1126/sciadv.1602785
[41]

Han X, Luo Y, Lin J, Wu H, Sun H, et al. 2021. Generation of purple-violet chrysanthemums via anthocyanin B-ring hydroxylation and glucosylation introduced from Osteospermum hybrid F3'5'H and Clitoria ternatea A3'5'GT. Ornamental Plant Research 1:4

doi: 10.48130/opr-2021-0004
[42]

Faraco M, Spelt C, Bliek M, Verweij W, Hoshino A, et al. 2014. Hyperacidification of vacuoles by the combined action of two different P-ATPases in the tonoplast determines flower color. Cell Reports 6:32−43

doi: 10.1016/j.celrep.2013.12.009
[43]

Amato A, Cavallini E, Zenoni S, Finezzo L, Begheldo M, et al. 2017. A grapevine TTG2-like WRKY transcription factor is involved in regulating vacuolar transport and flavonoid biosynthesis. Frontiers in Plant Science 7:1979

doi: 10.3389/fpls.2016.01979
[44]

Yuan J, Yang W, Zhao Z, Cao J, Yang W, et al. 2026. A new small subunit of the mitochondrial F-ATPase, PhDC, determines flower color by acidifying vacuoles. New Phytologist 249:232−251

doi: 10.1111/nph.70676
[45]

Sasaki N, Nakayama T. 2015. Achievements and perspectives in biochemistry concerning anthocyanin modification for blue flower coloration. Plant and Cell Physiology 56:28−40

doi: 10.1093/pcp/pcu097