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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]

The microvasculature is integral to nearly every tissue in the body, providing not only perfusion to and from the tissue, but also homing sites for immune cells, cellular niches for tissue dynamics, and cooperative interactions with other tissue elements. As a microtissue itself, the microvasculature is a composite of multiple cell types exquisitely organized into structures (individual vessel segments and extensive vessel networks) capable of considerable dynamics and plasticity. Consequently, it has been challenging to include a functional microvasculature in assembled or fabricated tissues. Isolated fragments of intact microvessels, which retain the cellular composition and structures of native microvessels, are proving effective in a variety of vascularization applications including tissue in vitro disease modeling, vascular biology, mechanistic discovery, and tissue prevascularization in regenerative therapeutics and grafting. In this review, we will discuss the importance of recapitulating native tissue biology and the successful vascularization applications of isolated microvessels. [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]

Tissue organoids hold enormous potential as tools for a variety of applications, including disease modeling and drug screening. To effectively mimic the native tissue environment, it is critical to integrate a microvasculature with the parenchyma and stroma. In addition to providing a means to physiologically perfuse the organoids, the microvasculature also contributes to the cellular dynamics of the tissue model via the cells of the perivascular niche, thereby further modulating tissue function. In this review, we discuss current and developing strategies for vascularizing organoids, consider tissue-specific vascularization approaches, discuss the importance of perfusion, and provide perspectives on the state of the field. [ABSTRACT FROM AUTHOR]

Summary: Anthocyanins are visual cues for pollination and seed dispersal. Fruit containing anthocyanins also appeals to consumers due to its appearance and health benefits. In kiwifruit (Actinidia spp.) studies have identified at least two MYB activators of anthocyanin, but their functions in fruit and the mechanisms by which they act are not fully understood.Here, transcriptome and small RNA high‐throughput sequencing were used to comprehensively identify contributors to anthocyanin accumulation in kiwifruit.Stable overexpression in vines showed that both 35S::MYB10 and MYB110 can upregulate anthocyanin biosynthesis in Actinidia chinensis fruit, and that MYB10 overexpression resulted in anthocyanin accumulation which was limited to the inner pericarp, suggesting that repressive mechanisms underlie anthocyanin biosynthesis in this species. Furthermore, motifs in the C‐terminal region of MYB10/110 were shown to be responsible for the strength of activation of the anthocyanic response. Transient assays showed that both MYB10 and MYB110 were not directly cleaved by miRNAs, but that miR828 and its phased small RNA AcTAS4‐D4(−) efficiently targeted MYB110. Other miRNAs were identified, which were differentially expressed between the inner and outer pericarp, and cleavage of SPL13, ARF16, SCL6 and F‐box1, all of which are repressors of MYB10, was observed.We conclude that it is the differential expression and subsequent repression of MYB activators that is responsible for variation in anthocyanin accumulation in kiwifruit species. [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.

Given the considerable research efforts in understanding and manipulating the vasculature in tissue health and function, making effective measurements of vascular density is critical for a variety of biomedical applications. However, because the vasculature is a heterogeneous collection of vessel segments, arranged in a complex three-dimensional architecture, which is dynamic in form and function, it is difficult to effectively measure. Here, we developed a semi-automated method that leverages machine learning to identify and quantify vascular metrics in an angiogenesis model imaged with different modalities. This software, BioSegment, is designed to make high throughput vascular density measurements of fluorescent or phase contrast images. Furthermore, the rapidity of assessments makes it an ideal tool for incorporation in tissue manufacturing workflows, where engineered tissue constructs may require frequent monitoring, to ensure that vascular growth benchmarks are met. [ABSTRACT FROM AUTHOR]

Abstract: Kiwifruit (Actinidia chinensis) has three FLOWERING LOCUS T (FT) genes, AcFT, AcFT1, and AcFT2, with differential expression and potentially divergent roles. AcFT was previously shown to be expressed in source leaves and induced in dormant buds by winter chilling. Here, we show that AcFT promotes flowering in A. chinensis, despite a short sequence insertion not present in other FT‐like genes. A 3.5‐kb AcFT promoter region contained all the regulatory elements required to mediate vascular expression in transgenic Arabidopsis thaliana (Arabidopsis). The promoter activation was initially confined to the veins in the distal end of the leaf, before extending to the veins in the base of the leaf, and was detected in inductive and noninductive photoperiods. The 3‐kb and 2.7‐kb promoter regions of AcFT1 and AcFT2, respectively, demonstrated different activation patterns in Arabidopsis, corresponding to differential expression in kiwifruit. Expression of AcFT cDNA from the AcFT promoter was capable to induce early flowering in transgenic Arabidopsis in noninductive photoperiods. Further, expression of AcFT cDNA fused to the green fluorescent protein was detected in the vasculature and was also capable to advance flowering in noninductive photoperiods. Taken together, these studies implicate AcFT in regulation of kiwifruit flowering time and as a candidate for kiwifruit florigen. [ABSTRACT FROM AUTHOR]

Anthocyanins are flavonoid compounds responsible for red/purple colors in the leaves, fruit, and flowers of many plant species. They are produced through a multistep pathway that is controlled by MYB transcription factors. VvMYBA1 and VvMYBA2 activate anthocyanin biosynthesis in grapevine (Vitis vinifera) and are nonfunctional in white grapevine cultivars. In this study, transgenic grapevines with altered VvMYBA gene expression were developed, and transcript analysis was carried out on berries using a microarray technique. The results showed that VvMYBA is a positive regulator of the later stages of anthocyanin synthesis, modification, and transport in cv Shiraz. One up-regulated gene, ANTHOCYANIN 3-O-GLUCOSIDE-699-O-ACYLTRANSFERASE (Vv3AT), encodes a BAHD acyltransferase protein (named after the first letter of the first four characterized proteins: BEAT [for acetyl CoA:benzylalcohol acetyltransferase], AHCT [for anthocyanin O-hydroxycinnamoyltransferase], HCBT [for anthranilate N-hydroxycinnamoyl/benzoyltransferase], and DAT [for deacetylvindoline 4-O-acetyltransferase]), belonging to a clade separate from most anthocyanin acyltransferases. Functional studies (in planta and in vitro) show that Vv3AT has a broad anthocyanin substrate specificity and can also utilize both aliphatic and aromatic acyl donors, a novel activity for this enzyme family found in nature. In cv Pinot Noir, a red-berried grapevine mutant lacking acylated anthocyanins, Vv3AT contains a nonsense mutation encoding a truncated protein that lacks two motifs required for BAHD protein activity. Promoter activation assays confirm that Vv3AT transcription is activated by VvMYBA1, which adds to the current understanding of the regulation of the BAHD gene family. The flexibility of Vv3AT to use both classes of acyl donors will be useful in the engineering of anthocyanins in planta or in vitro. [ABSTRACT FROM AUTHOR]

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]

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. [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., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2022 The Royal Society of New Zealand.)

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.)