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Summary: In the early 1900s, Erwin Baur established Antirrhinum majus as a model system, identifying and characterising numerous flower colour variants. This included Picturatum/Eluta, which restricts the accumulation of magenta anthocyanin pigments, forming bullseye markings on the flower face.We identified the gene underlying the Eluta locus by transposon‐tagging, using an Antirrhinum line that spontaneously lost the nonsuppressive el phenotype. A candidate MYB repressor gene at this locus contained a CACTA transposable element. We subsequently identified plants where this element excised, reverting to a suppressive Eluta phenotype. El alleles inhibit expression of anthocyanin biosynthetic genes, confirming it to be a regulatory locus. The modes of action of Eluta were investigated by generating stable transgenic tobacco lines, biolistic transformation of Antirrhinum petals and promoter activation/repression assays.Eluta competes with MYB activators for promoter cis‐elements, and also by titrating essential cofactors (bHLH proteins) to reduce transcription of target genes. Eluta restricts the pigmentation established by the R2R3‐MYB factors, Rosea and Venosa, with the greatest repression on those parts of the petals where Eluta is most highly expressed.Baur questioned the origin of heredity units determining flower colour variation in cultivated A. majus. Our findings support introgression from wild species into cultivated varieties. [ABSTRACT FROM AUTHOR]

Flavonoids are plant-specific secondary metabolites that arose early during land-plant colonisation, most likely evolving for protection from UV-B and other abiotic stresses. As plants increased in complexity, so too did the diversity of flavonoid compounds produced and their physiological roles. The most conspicuous are the pigments, including yellow aurones and chalcones, and the red/purple/blue anthocyanins, which provide colours to flowers, fruits and foliage. Anthocyanins have been particularly well studied, prompted by the ease of identifying mutants of genes involved in biosynthesis or regulation, providing an important model system to study fundamental aspects of genetics, gene regulation and biochemistry. This has included identifying the first plant transcription factor, and later resolving how multiple classes of transcription factor coordinate in regulating the production of various flavonoid classes – each with different activities and produced at differing developmental stages. In addition, dietary flavonoids from fruits/vegetables and forage confer human- and animal-health benefits, respectively. This has prompted strong interest in generating new plant varieties with increased flavonoid content through both traditional breeding and plant biotechnology. Gene-editing technologies provide new opportunities to study how flavonoids are regulated and produced and to improve the flavonoid content of flowers, fruits, vegetables and forages. [ABSTRACT FROM AUTHOR]

Abstract Background Flower development in kiwifruit (Actinidia spp.) is initiated in the first growing season, when undifferentiated primordia are established in latent shoot buds. These primordia can differentiate into flowers in the second growing season, after the winter dormancy period and upon accumulation of adequate winter chilling. Kiwifruit is an important horticultural crop, yet little is known about the molecular regulation of flower development. Results To study kiwifruit flower development, nine MADS-box genes were identified and functionally characterized. Protein sequence alignment, phenotypes obtained upon overexpression in Arabidopsis and expression patterns suggest that the identified genes are required for floral meristem and floral organ specification. Their role during budbreak and flower development was studied. A spontaneous kiwifruit mutant was utilized to correlate the extended expression domains of these flowering genes with abnormal floral development. Conclusions This study provides a description of flower development in kiwifruit at the molecular level. It has identified markers for flower development, and candidates for manipulation of kiwifruit growth, phase change and time of flowering. The expression in normal and aberrant flowers provided a model for kiwifruit flower development.

FLOWERING LOCUS T ( FT) and CENTRORADIALIS ( CEN) homologs have been implicated in regulation of growth, determinacy and flowering., The roles of kiwifruit FT and CEN were explored using a combination of expression analysis, protein interactions, response to temperature in high-chill and low-chill kiwifruit cultivars and ectopic expression in Arabidopsis and Actinidia., The expression and activity of FT was opposite from that of CEN and incorporated an interaction with a FLOWERING LOCUS D ( FD)-like bZIP transcription factor. Accumulation of FT transcript was associated with plant maturity and particular stages of leaf, flower and fruit development, but could be detected irrespective of the flowering process and failed to induce precocious flowering in transgenic kiwifruit. Instead, transgenic plants demonstrated reduced growth and survival rate. Accumulation of FT transcript was detected in dormant buds and stem in response to winter chilling. In contrast, FD in buds was reduced by exposure to cold. CEN transcript accumulated in developing latent buds, but declined before the onset of dormancy and delayed flowering when ectopically expressed in kiwifruit., Our results suggest roles for FT, CEN and FD in integration of developmental and environmental cues that affect dormancy, budbreak and flowering in kiwifruit. [ABSTRACT FROM AUTHOR]

Floral pigmentation patterning is important for pollinator attraction as well as aesthetic appeal. Patterning of anthocyanin accumulation is frequently associated with variation in activity of the Myb, bHLH and WDR transcription factor complex (MBW) that regulates anthocyanin biosynthesis. Investigation of two classic mutants in Antirrhinum majus, mutabilis and incolorata I, showed they affect a gene encoding a bHLH protein belonging to subclade bHLH-2. The previously characterised gene, Delila, which encodes a bHLH-1 protein, has a bicoloured mutant phenotype, with residual lobe-specific pigmentation conferred by Incolorata I. Both Incolorata I and Delila induce expression of the anthocyanin biosynthetic gene DFR. Rosea 1 (Myb) and WDR1 proteins compete for interaction with Delila, but interact positively to promote Incolorata I activity. Delila positively regulates Incolorata I and WDR1 expression. Hierarchical regulation can explain the bicoloured patterning of delila mutants, through effects on both regulatory gene expression and the activity of promoters of biosynthetic genes like DFR that mediate MBW regulation. bHLH-1 and bHLH-2 proteins contribute to establishing patterns of pigment distribution in A. majus flowers in two ways: through functional redundancy in regulating anthocyanin biosynthetic gene expression, and through differences between the proteins in their ability to regulate genes encoding transcription factors., (©2020 The Authors New Phytologist ©2020 New Phytologist Foundation.)