Correction: The bZIP transcription factor AREB3 mediates FT signalling and floral transition at the Arabidopsis shoot apical meristem.

[This corrects the article DOI: 10.1371/journal.pgen.1010766.].

The bZIP transcription factor AREB3 mediates FT signalling and floral transition at the Arabidopsis shoot apical meristem.

The floral transition occurs at the shoot apical meristem (SAM) in response to favourable external and internal signals. Among these signals, variations in daylength (photoperiod) act as robust seasonal cues to activate flowering. In Arabidopsis, long-day photoperiods stimulate production in the leaf vasculature of a systemic florigenic signal that is translocated to the SAM. According to the current model, FLOWERING LOCUS T (FT), the main Arabidopsis florigen, causes transcriptional reprogramming at the SAM, so that lateral primordia eventually acquire floral identity. FT functions as a transcriptional coregulator with the bZIP transcription factor FD, which binds DNA at specific promoters. FD can also interact with TERMINAL FLOWER 1 (TFL1), a protein related to FT that acts as a floral repressor. Thus, the balance between FT-TFL1 at the SAM influences the expression levels of floral genes targeted by FD. Here, we show that the FD-related bZIP transcription factor AREB3, which was previously studied in the context of phytohormone abscisic acid signalling, is expressed at the SAM in a spatio-temporal pattern that strongly overlaps with FD and contributes to FT signalling. Mutant analyses demonstrate that AREB3 relays FT signals redundantly with FD, and the presence of a conserved carboxy-terminal SAP motif is required for downstream signalling. AREB3 shows unique and common patterns of expression with FD, and AREB3 expression levels are negatively regulated by FD thus forming a compensatory feedback loop. Mutations in another bZIP, FDP, further aggravate the late flowering phenotypes of fd areb3 mutants. Therefore, multiple florigen-interacting bZIP transcription factors have redundant functions in flowering at the SAM.

GIGANTEA Is a Negative Regulator of Abscisic Acid Transcriptional Responses and Sensitivity in Arabidopsis.

Transcriptional reprogramming plays a key role in drought stress responses, preceding the onset of morphological and physiological acclimation. The best-characterized signal regulating gene expression in response to drought is the phytohormone abscisic acid (ABA). ABA-regulated gene expression, biosynthesis and signaling are highly organized in a diurnal cycle, so that ABA-regulated physiological traits occur at the appropriate time of day. The mechanisms that underpin such diel oscillations in ABA signals are poorly characterized. Here we uncover GIGANTEA (GI) as a key gatekeeper of ABA-regulated transcriptional and physiological responses. Time-resolved gene expression profiling by RNA sequencing under different irrigation scenarios indicates that gi mutants produce an exaggerated ABA response, despite accumulating wild-type levels of ABA. Comparisons with ABA-deficient mutants confirm the role of GI in controlling ABA-regulated genes, and the analysis of leaf temperature, a read-out for transpiration, supports a role for GI in the control of ABA-regulated physiological processes. Promoter regions of GI/ABA-regulated transcripts are directly targeted by different classes of transcription factors (TFs), especially PHYTOCHROME-INTERACTING FACTOR and -BINDING FACTOR, together with GI itself. We propose a model whereby diel changes in GI control oscillations in ABA responses. Peak GI accumulation at midday contributes to establishing a phase of reduced ABA sensitivity and related physiological responses, by gating DNA binding or function of different classes of TFs that cooperate or compete with GI at target regions.

Nutritional Regimes Enriched with Antioxidants as an Efficient Adjuvant for IBD Patients under Infliximab Administration, a Pilot Study.

Antioxidants are privileged candidates for the development of adjuvants able to improve the efficiency of pharmacological therapies, particularly for chronic inflammatory syndromes. During the last 20 years, anti-TNFα (tumor necrosis factor alpha) monoclonal antibodies infusion has been the biological therapy most frequently administered but there is still large space for improvement in disease remission rates and maintenance. In this context, nutritional bioactive compounds contained in dietary patterns or included as supplements, may act as adjuvants for the induction and maintenance of IBD (inflammatory bowel diseases) remission. To verify this possibility, a single-center preliminary study (SI-CURA, Soluzioni Innovative per la gestione del paziente e il follow up terapeutico della Colite UlceRosA) was designed and carried out to evaluate whether a daily administration of purple corn supplement could improve the response to Infliximab (IFX) infusion of IBD patients with both Crohn's disease (CD) and ulcerative colitis (UC). A cohort of 47 patients was enrolled in the study. Biological samples were collected before the first and the third IFX infusion. All patients received nutritional guidelines, 27 of them received commercial red fruit tea with low anthocyanins content, while 20 received a purple corn supplement with a high anthocyanin content. Results show that the administration of an antioxidant-enriched purple corn supplement could improve IFX-mediated disease remission in terms of circulating inflammatory markers. Comparison between CD and UC patients revealed that, at this anthocyanin dosage, the purple corn extract administration improved the IFX response in CD but not in UC patients. Our results may pave the way for a new metacentric study of CD patients, recruiting a wider cohort and followed-up over a longer observational time.

The AtMYB60 transcription factor regulates stomatal opening by modulating oxylipin synthesis in guard cells.

Stomata are epidermal pores formed by pairs of specialized guard cells, which regulate gas exchanges between the plant and the atmosphere. Modulation of transcription has emerged as an important level of regulation of stomatal activity. The AtMYB60 transcription factor was previously identified as a positive regulator of stomatal opening, although the details of its function remain unknown. Here, we propose a role for AtMYB60 as a negative modulator of oxylipins synthesis in stomata. The atmyb60-1 mutant shows reduced stomatal opening and accumulates increased levels of 12-oxo-phytodienoic acid (12-OPDA), jasmonic acid (JA) and jasmonoyl-L-isoleucine (JA-Ile) in guard cells. We provide evidence that 12-OPDA triggers stomatal closure independently of JA and cooperatively with abscisic acid (ABA) in atmyb60-1. Our study highlights the relevance of oxylipins metabolism in stomatal regulation and indicates AtMYB60 as transcriptional integrator of ABA and oxylipins responses in guard cells.

Dietary intake of cyanidin-3-glucoside induces a long-lasting cardioprotection from ischemia/reperfusion injury by altering the microbiota.

The anthocyanin class of flavonoids, including cyanidin-3-glucoside (C3G) present in berries, blood oranges and pigmented cereal crops, are food bioactives with antioxidant and anti-inflammatory action, capable to reduce myocardial ischemia/reperfusion (I/R) injury by unclear mechanism. Assessing the value of sporadic beneficial diet is critical for practical application. We aimed to determine whether and how the cardioptotective effect of dietary intake of anthocyanins persists. Gene expression, histology and resistance to I/R were investigated ex vivo in hearts from mice after a month beyond the cease of the C3G-enriched diet. Cardiac injury, oxidative stress and mitochondrial damage following I/R was effectively reduced in mice fed C3G-enriched diet, even after a month of wash out with standard diet. Cardioprotection was observed also in immune-deficient mice lacking mature B and T cells indicating the anti-inflammatory activity of C3G was not involved. Moreover, the transcription reprogramming induced by the C3G-enriched diets was rescued by the wash out treatment. Instead, we found C3G-enriched diet changed the microbiome and the transplantation of the fecal microbiota transferred the cardioprotection from mice fed C3G-enriched diet to mice fed standard diet. These findings established the effect of C3G dietary intake on gut microbiota determines long lasting cardioprotection.

Anthocyanins: From Mechanisms of Regulation in Plants to Health Benefits in Foods.

Anthocyanins represent the major red, purple, and blue pigments in many flowers, fruits, vegetables, and cereals. They are also recognized as important health-promoting components in the human diet with protective effects against many chronic diseases, including cardiovascular diseases, obesity, and cancer. Anthocyanin biosynthesis has been studied extensively, and both biosynthetic and key regulatory genes have been isolated in many plant species. Here, we will provide an overview of recent progress in understanding the anthocyanin biosynthetic pathway in plants, focusing on the transcription factors controlling activation or repression of anthocyanin accumulation in cereals and fruits of different plant species, with special emphasis on the differences in molecular mechanisms between monocot and dicot plants. Recently, new insight into the transcriptional regulation of the anthocyanin biosynthesis, including positive and negative feedback control as well as epigenetic and post-translational regulation of MYB-bHLH-WD40 complexes, has been gained. We will consider how knowledge of regulatory mechanisms has helped to produce anthocyanin-enriched foods through conventional breeding and metabolic engineering. Additionally, we will briefly discuss the biological activities of anthocyanins as components of the human diet and recent findings demonstrating the important health benefits of anthocyanin-rich foods against chronic diseases.

Comparative Analysis of Histone H3K4me3 Distribution in Mouse Liver in Different Diets Reveals the Epigenetic Efficacy of Cyanidin-3-O-glucoside Dietary Intake.

BACKGROUND: Different diets result in significantly different phenotypes through metabolic and genomic reprogramming. Epigenetic marks, identified in humans and mouse models through caloric restriction, a high-fat diet or the intake of specific bioactives, suggest that genomic reprogramming drives this metabolic reprogramming and mediates the effect of nutrition on health. Histone modifications encode the epigenetic signal, which adapts genome functions to environmental conditions, including diets, by tuning the structure and properties of chromatin. To date, the effect of different diets on the genome-wide distribution of critical histone marks has not been determined. METHODS: Using chromatin immunoprecipitation sequencing, we investigated the distribution of the trimethylation of lysine 4 of histone H3 in the liver of mice fed for one year with five different diets, including: chow containing yellow corn powder as an extra source of plant bioactives or specifically enriched with cyanidin-3-O-Glucoside, high-fat-enriched obesogenic diets, and caloric-restricted pro-longevity diets. CONCLUSIONS: Comparison of the resulting histone mark profiles revealed that functional food containing cyanidin determines a broad effect.

Skin toxicity following radiotherapy in patients with breast carcinoma: is anthocyanin supplementation beneficial?

BACKGROUND: The EU-supported ATHENA project stems from a previous study suggesting that moderate wine consumption reduced the side-effects of radiotherapy (RT) in breast cancer patients, an effect possibly due to non-alcoholic anthocyanin fractions of wine. OBJECTIVE: To evaluate the role of anthocyanins on RT skin side effects in breast cancer patients. METHODS: Randomized, controlled, double-blind clinical trial. Patients were assigned to an intensity modulated radiation therapy (IMRT) either for three or five weeks, then randomized to receive three times a day a water-soluble anthocyanin (125 mg)-rich extract of corn cob or a placebo. Supplementation started one week before till the end of RT. Skin characteristics were detected by a standardized, non-invasive Cutometer® dual-MPA580, providing quantitative indices of skin maximal distensibility (R0), elasticity (R2, R5, R7) and viscoelasticity (R6); a Mexameter® MX18 probe evaluated the skin erythema (Er) and melanin (M). Measures were performed before (T0), at the end of RT and of supplementation (T1), and 1, 6 and 12 months after RT (T2-T4). Acute and late skin toxicity were scored according to the RTOG/EORTG scale. Selected biomarkers were measured at T0 and T1. RESULTS: 193 patients previously assigned to 3- or 5-week RT schedules were randomized to either anthocyanin (97) or placebo (96) supplementation. RT induced changes in skin parameters: R0, R2, R5 and R7 decreased, while R6 increased; the changes in R0 and R6 continued in the same direction up to one year, while the others recovered towards basal values; Er and M peaked at T1 and T2, respectively, and returned to basal values at T4. Comparable skin changes were apparent in anthocyanin and placebo groups. A moderate RT-induced increase in total and HDL cholesterol and triglycerides was prevented by anthocyanins. CONCLUSIONS: Anthocyanin supplementation did not prevent RT-induced local skin toxicity. The supplementation was well tolerated and safe.

The Therapeutic Potential of Anthocyanins: Current Approaches Based on Their Molecular Mechanism of Action.

Anthocyanins are natural phenolic pigments with biological activity. They are well-known to have potent antioxidant and antiinflammatory activity, which explains the various biological effects reported for these substances suggesting their antidiabetic and anticancer activities, and their role in cardiovascular and neuroprotective prevention. This review aims to comprehensively analyze different studies performed on this class of compounds, their bioavailability and their therapeutic potential. An in-depth look in preclinical, in vitro and in vivo, and clinical studies indicates the preventive effects of anthocyanins on cardioprotection, neuroprotection, antiobesity as well as their antidiabetes and anticancer effects.

Maize adaptation across temperate climates was obtained via expression of two florigen genes.

Expansion of the maize growing area was central for food security in temperate regions. In addition to the suppression of the short-day requirement for floral induction, it required breeding for a large range of flowering time that compensates the effect of South-North gradients of temperatures. Here we show the role of a novel florigen gene, ZCN12, in the latter adaptation in cooperation with ZCN8. Strong eQTLs of ZCN8 and ZCN12, measured in 327 maize lines, accounted for most of the genetic variance of flowering time in platform and field experiments. ZCN12 had a strong effect on flowering time of transgenic Arabidopsis thaliana plants; a path analysis showed that it directly affected maize flowering time together with ZCN8. The allelic composition at ZCN QTLs showed clear signs of selection by breeders. This suggests that florigens played a central role in ensuring a large range of flowering time, necessary for adaptation to temperate areas.

Nutritional intervention with cyanidin hinders the progression of muscular dystrophy.

Muscular Dystrophies are severe genetic diseases due to mutations in structural genes, characterized by progressive muscle wasting that compromises patients' mobility and respiratory functions. Literature underlined oxidative stress and inflammation as key drivers of these pathologies. Interestingly among different myofiber classes, type I fibers display a milder dystrophic phenotype showing increased oxidative metabolism. This work shows the benefits of a cyanidin-enriched diet, that promotes muscle fiber-type switch and reduced inflammation in dystrophic alpha-sarcoglyan (Sgca) null mice having, as a net outcome, morphological and functional rescue. Notably, this benefit is achieved also when the diet is administered in dystrophic animals when the signs of the disease are seriously evident. Our work provides compelling evidence that a cyanidin-rich diet strongly delays the progression of muscular dystrophies, paving the way for a combinatorial approach where nutritional-based reduction of muscle inflammation and oxidative stress facilitate the successful perspectives of definitive treatments.

Purple corn extract induces long-lasting reprogramming and M2 phenotypic switch of adipose tissue macrophages in obese mice.

BACKGROUND: Obesity is a chronic and systemic inflammatory disorder and an important risk factor for the onset of several chronic syndromes. Adipose tissue (AT) plays a crucial role in the development of obesity, promoting the infiltration and accumulation of leukocytes in the tissue and sustaining adipocyte expansion. Anthocyanins exert a broad range of health benefits, but their effect in improving obesity-related inflammation in vivo has been poorly characterized. We examined the effects of a purple corn cob extract in the context of AT inflammation in a murine diet-induced obesity (DIO) model. METHODS: Male C57BL/6J mice were subjected to control diet (CTR + H2O), high fat diet (HF + H2O) or high fat diet plus purple corn extract (HF + RED) for 12 weeks. Blood glucose, AT, and liver gene expression, metabolism, biochemistry, and histology were analysed and flow cytometry was performed on AT leukocytes and Kupffer cells. RESULTS: RED extract intake resulted in lower MCP-1 mediated recruitment and proliferation of macrophages into crown-like structures in the AT. AT macrophages (ATM) of HF + RED group upregulated M2 markers (ArgI, Fizz1, TGFß), downregulating inflammatory mediators (TNF-α, IL-6, IL-1ß, COX-2) thanks to the suppression of NF-kB signalling. ATM also increased the expression of iron metabolism-related genes (FABP4, Hmox1, Ferroportin, CD163, TfR1, Ceruloplasmin, FtL1, FtH1) associated with a reduction in iron storage and increased turnover. ATM from HF + RED mice did not respond to LPS treatment ex vivo, confirming the long-lasting effects of the treatment on M2 polarization. Adipocytes of HF + RED group improved lipid metabolism and displayed a lower inflammation grade. Liver histology revealed a remarkable reduction of steatosis in the HF + RED group, and Kupffer cell profiling displayed a marked switch towards the M2 phenotype. CONCLUSIONS: RED extract attenuated AT inflammation in vivo, with a long-lasting reprogramming of ATM and adipocyte profiles towards the anti-inflammatory phenotype, therefore representing a valuable supplement in the context of obesity-associated disorders.

Purple Corn Extract as Anti-allodynic Treatment for Trigeminal Pain: Role of Microglia.

Natural products have attracted interest in the search for new and effective analgesics and coadjuvant approaches to several types of pain. It is in fact well known that many of their active ingredients, such as anthocyanins (ACNs) and polyphenols, can exert potent anti-inflammatory actions. Nevertheless, their potential beneficial effects in orofacial painful syndromes have not been assessed yet. Here, we have evaluated the preventive effect of an ACN-enriched purple corn extract against the development of orofacial allodynia, in comparison with isogenic yellow corn extract containing only polyphenols. Orofacial allodynia developed following induction of temporomandibular joint (TMJ) inflammation in male rats, due to the injection of Complete Freund's Adjuvant (CFA), and was evaluated by von Frey filaments. Animals drank purple or yellow corn extracts or water starting from 11 days before induction of inflammation and up to the end of the experiment 3 days later. To highlight possible additive and/or synergic actions, some animals also received the anti-inflammatory drug acetyl salicylic acid (ASA). In parallel with the evaluation of allodynia, we have focused our attention on the activation of microglia cells in the central nervous system (CNS), as it is well-known that they significantly contribute to neuronal sensitization and pain. Our data demonstrate that purple corn extract is as effective as ASA in preventing the development of orofacial allodynia, and only partial additive effect is observed when the two agents are co-administered. Yellow corn exerted no effect. Multiple mechanisms are possibly involved in the action of purple corn, including reduction of trigeminal macrophage infiltration and the shift of microglia cell polarization to an anti-inflammatory phenotype. In fact, in rats receiving yellow corn or water microglia cells show thick, short cell processes typical of activated cells. Conversely, thinner and longer microglia cell processes are observed in the brainstem of animals drinking purple corn extract; shape changes are accompanied by a reduction in the expression of pro-inflammatory molecules and increased production of anti-inflammatory mediators. Administration of purple corn extracts therefore represents a possible low-cost and easy way to reduce trigeminal-associated pain in various pathological conditions also thanks to the modulation of microglia reactivity.

Abscisic Acid Is a Major Regulator of Grape Berry Ripening Onset: New Insights into ABA Signaling Network.

Grapevine is a world-wide cultivated economically relevant crop. The process of berry ripening is non-climacteric and does not rely on the sole ethylene signal. Abscisic acid (ABA) is recognized as an important hormone of ripening inception and color development in ripening berries. In order to elucidate the effect of this signal at the molecular level, pre-véraison berries were treated ex vivo for 20 h with 0.2 mM ABA and berry skin transcriptional modulation was studied by RNA-seq after the treatment and 24 h later, in the absence of exogenous ABA. This study highlighted that a small amount of ABA triggered its own biosynthesis and had a transcriptome-wide effect (1893 modulated genes) characterized by the amplification of the transcriptional response over time. By comparing this dataset with the many studies on ripening collected within the grapevine transcriptomic compendium Vespucci, an extended overlap between ABA- and ripening modulated gene sets was observed (71% of the genes), underpinning the role of this hormone in the regulation of berry ripening. The signaling network of ABA, encompassing ABA metabolism, transport and signaling cascade, has been analyzed in detail and expanded based on knowledge from other species in order to provide an integrated molecular description of this pathway at berry ripening onset. Expression data analysis was combined with in silico promoter analysis to identify candidate target genes of ABA responsive element binding protein 2 (VvABF2), a key upstream transcription factor of the ABA signaling cascade which is up-regulated at véraison and also by ABA treatments. Two transcription factors, VvMYB143 and VvNAC17, and two genes involved in protein degradation, Armadillo-like and Xerico-like genes, were selected for in vivo validation by VvABF2-mediated promoter trans-activation in tobacco. VvNAC17 and Armadillo-like promoters were induced by ABA via VvABF2, while VvMYB143 responded to ABA in a VvABF2-independent manner. This knowledge of the ABA cascade in berry skin contributes not only to the understanding of berry ripening regulation but might be useful to other areas of viticultural interest, such as bud dormancy regulation and drought stress tolerance.

SUMO proteases OTS1 and 2 control filament elongation through a DELLA-dependent mechanism.

KEY MESSAGE: SUMOylation and anther growth. During fertilization, stamen elongation needs to be synchronized with pistil growth. The phytohormone gibberellic acid (GA) promotes stamen growth by stimulating the degradation of growth repressing DELLA proteins. DELLA accumulation is negatively regulated by GAs through the ubiquitin-proteasome system. In Arabidopsis thaliana, a proportion of DELLAs is also conjugated to the small ubiquitin-like modifier (SUMO) protein, which stabilizes DELLAs. Increased DELLA levels occur in the SUMO protease-deficient OVERLY TOLERANT TO SALT 1 and 2 (ots1 ots2) double mutants, especially under salt stress conditions. Here, we show that OTS genes play a redundant role in the control of plant fertility under non-stress conditions. Mutants of ots1 ots2 display reduced fertility compared with the wild type, owing to reduced stamen elongation. Stamen growth, pollination rate and seed production are restored in ots1 ots2 della mutants, thus linking OTS1 function to the control of DELLA activity in the context of filament elongation. OTS levels appear to be developmentally regulated as OTS1/2 transcript upregulation during stamen development overlaps with GAs accumulations. We propose that OTS genes enable synchronization of stamen development by facilitating DELLA degradation at a specific developmental stage.

ABA-dependent control of GIGANTEA signalling enables drought escape via up-regulation of FLOWERING LOCUS T in Arabidopsis thaliana.

One strategy deployed by plants to endure water scarcity is to accelerate the transition to flowering adaptively via the drought escape (DE) response. In Arabidopsis thaliana, activation of the DE response requires the photoperiodic response gene GIGANTEA (GI) and the florigen genes FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF). The phytohormone abscisic acid (ABA) is also required for the DE response, by promoting the transcriptional up-regulation of the florigen genes. The mode of interaction between ABA and the photoperiodic genes remains obscure. In this work we use a genetic approach to demonstrate that ABA modulates GI signalling and consequently its ability to activate the florigen genes. We also reveal that the ABA-dependent activation of FT, but not TSF, requires CONSTANS (CO) and that impairing ABA signalling dramatically reduces the expression of florigen genes with little effect on the CO transcript profile. ABA signalling thus has an impact on the core genes of photoperiodic signalling GI and CO by modulating their downstream function and/or activities rather than their transcript accumulation. In addition, we show that as well as promoting flowering, ABA simultaneously represses flowering, independent of the florigen genes. Genetic analysis indicates that the target of the repressive function of ABA is the flowering-promoting gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), a transcription factor integrating floral cues in the shoot meristem. Our study suggests that variations in ABA signalling provide different developmental information that allows plants to co-ordinate the onset of the reproductive phase according to the available water resources.

A novel role for STOMATAL CARPENTER 1 in stomata patterning.

BACKGROUND: Guard cells (GCs) are specialised cells within the plant epidermis which form stomatal pores, through which gas exchange can occur. The GCs derive through a specialised lineage of cell divisions which is specified by the transcription factor SPEECHLESS (SPCH), the expression of which can be detected in undifferentiated epidermal cells prior to asymmetric division. Other transcription factors may act before GC specification and be required for correct GC patterning. Previously, the DOF transcription factor STOMATAL CARPENTER 1 (SCAP1) was shown to be involved in GC function, by activating a set of GC-specific genes required for GC maturation and activity. It is thus far unknown whether SCAP1 can also affect stomatal development. RESULTS: Here we show that SCAP1 expression can also be observed in young leaf primordia, before any GC differentiation occurs. The study of transgenic plants carrying a proSCAP1:GUS-GFP transcriptional fusion, coupled with qPCR analyses, indicate that SCAP1 expression peaks in a temporal window which is coincident with expression of stomatal patterning genes. Independent scap1 loss-of-function mutants have a reduced number of GCs whilst SCAP1 over expression lines have an increased number of GCs, in addition to altered GC distribution and spacing patterns. The study of early markers for stomatal cell lineage in a background carrying gain-of-function alleles of SCAP1 revealed that, compared to the wild type, an increased number of protodermal cells are recruited in the GC lineage, which is reflected in an increased number of meristemoids. CONCLUSIONS: Our results suggest an early role for SCAP1 in GC differentiation. We propose that a function of SCAP1 is to integrate different aspects of GC biology including specification, spacing, maturation and function.

Hydroxycinnamic acids and UV-B depletion: Profiling and biosynthetic gene expression in flesh and peel of wild-type and hp-1.

Hydroxycinnamic acids (HCAs) are phenolic compounds widely found in most plant families. Aim of the present work was to investigate their accumulation and biosynthetic gene expression in presence or absence of UV-B radiation in tomato fruits of wild-type and hp-1, a mutant characterized by exaggerated photoresponsiveness and increased fruit pigmentation. Gene expression and HCAs content were higher in hp-1 than in wild type peel and UV-B depletion determined a decrease in HCAs accumulation in wild-type and an increase in hp-1 fruits, generally in accordance with biosynthetic gene expression. In flesh, despite a similar transcript level of most genes between the two genotypes, HCAs content was generally higher in wild type than in hp-1, although remaining at a lower level with respect to wild type peel. Under UV-B depletion, a general reduction of HCAs content was observed in wild-type flesh, whereas an increase in the content of p-coumaric acid and caffeic acid was observed in hp-1 flesh.