Review of the health effects of berries and their phytochemicals on the digestive and immune systems

Berries as Foods: Processing, Products, and Health Implications

Berries are highly regarded as flavorful and healthy fruits that may prevent or delay some chronic diseases attributed to oxidative stress and inflammation. Berries are low in calories and harbor diverse bioactive phytochemicals, antioxidants, dietary fibers, and vitamins. This review delves into the main characteristics of fresh berries and berry products as foods and the technologies associated with their production. The main effects of processing operations and related variables on bioactive components and antioxidants are described. This review critically discusses why some health claims based on in vitro antioxidant data and clinical studies and intervention trials are difficult to assess. The review suggests that the beneficial health effects of berries are derived from a multifactorial combination of complex mixtures of abundant phenolic components, antioxidants, and their metabolites acting synergistically or additively with other nutrients like fibers and vitamins and possibly by modulating the gut microbiota.

Vegetables, fruits, and berries - a scoping review for Nordic Nutrition Recommendations 2023

Vegetables, fruits, and berries comprise a large variety of foods and are recognised to play an important role in preventing chronic diseases. Many observational studies have been published during the last decade, and the aim of this scoping review is to describe the overall evidence for the role of vegetables, fruits, and berries for health-related outcomes as a basis for setting and updating food-based dietary guidelines. A scoping review was conducted according to the protocol developed within the Nordic Nutrition Recommendations 2023 project. Current available evidence strengthens the role of consuming vegetables, fruits, and berries in preventing chronic diseases. The most robust evidence is found for cancer in the gastric system and lung cancer, cardiovascular disease, and all-cause mortality. Steeper risk reductions are generally seen at the lower intake ranges, but further reductions have been seen for higher intakes for cardiovascular disease. Weaker associations are seen for type 2 diabetes. There is evidence that suggests a beneficial role also for outcomes such as osteoporosis, depression, cognitive disorders, and frailty in the elderly. The observed associations are supported by several mechanisms, indicting causal effects. Some subgroups of vegetables, fruits, and berries may have greater benefits than other subgroups, supporting a recommendation to consume a variety of these foods.

Blueberry, cranberry, raspberry, and strawberry as modulators of the gut microbiota: target for treatment of gut dysbiosis in chronic kidney disease? From current evidence to future possibilities

Gut dysbiosis is common in patients with chronic kidney disease (CKD) and is associated with uremic toxin production, inflammation, oxidative stress, and cardiovascular disease development. Therefore, healthy dietary patterns are essential modulators of gut microbiota. In this context, studies suggest that consuming berry fruits, rich in polyphenols and nutrients, may positively affect the gut microbiota, promoting the selective growth of beneficial bacteria and improving clinical status. However, studies on the effects of berry fruits on gut microbiota in CKD are scarce, and a better understanding of the possible mechanisms of action of berry fruits on gut microbiota is needed to guide future clinical studies and clinical practice in CKD. The objective was to discuss how berry fruits (blueberry, cranberry, raspberry, and strawberry) could be a therapeutic strategy to modulate the gut microbiota and possibly reverse the dysbiosis in CKD. Overall, available evidence shows that berry fruits can promote an increase in diversity by affecting the abundance of mucus-producing bacteria and short-chain fatty acids. Moreover, these fruits can increase the expression of mRNA involved in tight junctions in the gut such as occludin, tight junction protein 1 (TJP1), and mucin. Studies on the exact amount of berries leading to these effects show heterogeneous findings. However, it is known that, with 5 mg/day, it is already possible to observe some effects in animal models. Wild berries could possibly improve the uremic condition by reducing the levels of uremic toxins via modulation of the gut microbiota. In the long term, this could be an excellent strategy for patients with CKD. Therefore, clinical studies are encouraged to evaluate better these effects on CKD as well as the safe amount of these fruits in order to promote a better quality of life or even the survival of these patients.

Decoding the enhanced antioxidant activities of the combined small berry pomaces by widely targeted metabolomics analysis

Small berry pomaces (SBPs) are poorly utilized as an inexpensive source of bioactive compounds. This study investigated the impact of compounding treatment on nutritional and antioxidant characteristics of combined SBPs, in comparison with single SBP. The results showed that the amounts of protein, minerals, dietary fiber (DF) and anthocyanidins were significantly (p < 0.05) higher in combined SBPs than in combined fruits. Moreover, the combined SBPs were characterized by an elevated abundance of minerals and anthocyanidins (6 kinds, and 5 kinds, respectively), substantiating the effectiveness of compounding treatment on SBP nutrition. A total of 776 secondary phytochemicals were detected in combined SBPs by a widely targeted metabolomics approach. Each SBP contained approximately 100 kinds of unique natural antioxidants. Furthermore, the combined SBPs group had the highest antioxidant activity compared with single SBP. Meanwhile, the antioxidant activities determined in combined SBPs were higher than arithmetic mean value of single SBP. The synergism and interaction of active components in different sources of SBPs play vital role in the high antioxidant capacity of combined SBPs. All the results provide reference for the comprehensive development and utilization of fruit residues. The SBPs should be highly prized for their substantial amount of nutritional and bioactive constituents, including protein, DF, essential minerals and secondary metabolites. These secondary metabolites are positively associated with antioxidant benefits. The present study summarizes the knowledge about bioactive compounds and antioxidant activities of combined SBPs group and discusses the relevant mechanisms. A conclusion can be educed that combined process is an effective way to improve properties of the pomaces.

The Stability of Phenolic Compounds in Fruit, Berry, and Vegetable Purees Based on Accelerated Shelf-Life Testing Methodology

Evaluating the stability of polyphenols in fruit, berry, and vegetable purees helps to assess the quality of these products during storage. This study aimed to (1) monitor the stability of total phenolic content (TPC) in four-grain puree with banana and blueberry (FGBB), mango-carrot-sea buckthorn puree (MCB), and fruit and yogurt puree with biscuit (FYB); (2) study the effect of aluminum-layered vs. aluminum-free packaging on the changes in TPC; and (3) assess the suitability of accelerated shelf-life testing (ASLT) methodology to evaluate the stability of polyphenols. The samples were stored at 23 °C for 182, 274, 365, and 427 days. The corresponding time points during ASLT at 40 °C were 28, 42, 56, and 66 days, calculated using Q₁₀ = 3. The TPC was determined with Folin-Ciocalteu method. The results revealed that the biggest decrease in TPC took place with high-pH FGBB, which contained fewer ingredients with bioactive compounds. Minor changes were seen in FYB and MCB, which had lower pH values, and contained a larger amount of ingredients that include polyphenols. In addition, the choice of packaging material did not affect the TPC decrease in each puree. Finally, it was concluded that the ASLT methodology is suitable for studying the TPC changes in such purees, but the corresponding Q₁₀ factors may vary and should be determined based on the chemical profile and ingredient list of the product.

'Superfoods': Reliability of the Information for Consumers Available on the Web

The term 'superfoods', used frequently with marketing purposes, is usually associated with foodstuffs with beneficial health properties. 'Superfoods' appears in many information sources, including digital media. The information they provide is easily accessible for consumers through Internet search engines. The objective of this work is to investigate the data that web pages offer to consumers and their accuracy according to current scientific knowledge. The two main search engines were utilized for English language websites search, introducing the term 'superfoods'. In total, 124 search results were found. After applying the selection criteria, 45 web pages were studied. A total of 136 foods were considered as 'superfoods' by sites; 10 of them (kale, spinach, salmon, blueberries, avocado, chia, walnuts, beans, fermented milks and garlic) were mentioned on at least 15 sites. Nutritional and healthy properties displayed on sites were compared to scientific information. In conclusion, websites present the information in a very simplified manner and it is generally not wrong. However, they should offer to consumers comprehensible information without raising false expectations regarding health benefits. In any case, 'superfoods' consumption can have salutary effects as part of a balanced diet.

Wild berries and related wild small fruits as traditional healthy foods

The consumption of cultivated berry species (e.g., strawberries, blueberries) has increased dramatically in the last two decades after consumers appreciated them as flavorful, convenient and healthy fruits. Wild berries and similar small wild fruits are traditionally consumed around the world by local people as safe, nutritious, tasty, and versatile foods. These wild fruits have played an important role in the nutrition and bio-cultural aspects of rural communities. Like their commercial counterparts, wild berries contain important nutrients and bioactive compounds that may prevent or delay some chronic diseases attributed to oxidative stress and chronic inflammation. This review provides a comprehensive appraisal of the chemical and bioactive components in wild berry species and their traditional uses as foods around the globe. Presently, wild berries and similar wild small fruits are novel food sources that inspire applications as culinary products, processed foods, and nutraceuticals. Further research is needed to validate the content and action of bioactive components responsible for health claims. Sustainable commercial exploitation of wild berries should consider biocultural, environmental, and socio-economic aspects.

A rational definition for functional foods: A perspective

Many foods are described as “functional foods”. However, the term is poorly defined. A commonly used definition is that they contain substances that have positive effects on health “beyond basic nutrition”. However, there are several problems with this definition. In many cases, healthy foods are included under the term functional foods. A new definition is proposed as follows. Functional foods are novel foods that have been formulated so that they contain substances or live microorganisms that have a possible health-enhancing or disease-preventing value, and at a concentration that is both safe and sufficiently high to achieve the intended benefit. The added ingredients may include nutrients, dietary fiber, phytochemicals, other substances, or probiotics.

"True" Helicobacter pylori infection and non-cardia gastric cancer: A pooled analysis within the Stomach Cancer Pooling (StoP) Project

BACKGROUND

Helicobacter pylori is the most important risk factor for non-cardia gastric cancer (NCGC); however, the magnitude of the association varies across epidemiological studies. This study aimed to quantify the association between H. pylori infection and NCGC, using different criteria to define infection status.

METHODS

A pooled analysis of individual-level H. pylori serology data from eight international studies (1325 NCGC and 3121 controls) from the Stomach Cancer Pooling (StoP) Consortium was performed. Cases and controls with a negative H. pylori infection status were reclassified as positive considering the presence of anti-Cag A antibodies, gastric atrophy, or advanced stage at diagnosis, as available and applicable. A two-stage approach was used to pool study-specific adjusted odds ratios (OR), and 95% confidence intervals (95% CI). A meta-analysis of published prospective studies assessing H. pylori seropositivity in NCGCs was conducted.

RESULTS

The OR for the association between serology-defined H. pylori and NCGC was 1.45 (95% CI: 0.87-2.42), which increased to 4.79 (95% CI: 2.39-9.60) following the reclassification of negative H. pylori infection. The results were consistent across strata of sociodemographic characteristics, clinical features and lifestyle factors, though significant differences were observed according to geographic region-a stronger association in Asian studies. The pooled risk estimates from the literature were 3.01 (95% CI: 2.22-4.07) for ELISA or EIA and 9.22 (95% CI: 3.12-27.21) for immunoblot or multiplex serology.

CONCLUSION

The NCGC risk estimate from StoP based on the reclassification of H. pylori seronegative individuals is consistent with the risk estimates obtained from the literature. Our classification algorithm may be useful for future studies.

Evaluation of Antioxidant Capacity and Gut Microbiota Modulatory Effects of Different Kinds of Berries

Berries are fairly favored by consumers. Phenolic compounds are the major phytochemicals in berries, among which anthocyanins are one of the most studied. Phenolic compounds are reported to have prebiotic-like effects. In the present study, we identified the anthocyanin profiles, evaluated and compared the antioxidant capacities and gut microbiota modulatory effects of nine common berries, namely blackberry, black goji berry, blueberry, mulberry, red Chinese bayberry, raspberry, red goji berry, strawberry and white Chinese bayberry. Anthocyanin profiles were identified by UPLC-Triple-TOF/MS. In vitro antioxidant capacity was evaluated by four chemical assays (DPPH, ABTS, FRAP and ORAC). In vivo antioxidant capacity and gut microbiota modulatory effects evaluation was carried out by treating healthy mice with different berry extracts for two weeks. The results show that most berries could improve internal antioxidant status, reflected by elevated serum or colonic T-AOC, GSH, T-SOD, CAT, and GSH-PX levels, as well as decreased MDA content. All berries significantly altered the gut microbiota composition. The modulatory effects of the berries were much the same, namely by the enrichment of beneficial SCFAs-producing bacteria and the inhibition of potentially harmful bacteria. Our study shed light on the gut microbiota modulatory effect of different berries and may offer consumers useful consumption guidance.

Dietary proanthocyanidins on gastrointestinal health and the interactions with gut microbiota

Many epidemiological and experimental studies have consistently reported the beneficial effects of dietary proanthocyanidins (PAC) on improving gastrointestinal physiological functions. This review aims to present a comprehensive perspective by focusing on structural properties, interactions and gastrointestinal protection of PAC. In brief, the main findings of this review are summarized as follows: (1) Structural features are critical factors in determining the bioavailability and subsequent pharmacology of PAC; (2) PAC and/or their bacterial metabolites can play a direct role in the gastrointestinal tract through their antioxidant, antibacterial, anti-inflammatory, and anti-proliferative properties; (3) PAC can reduce the digestion, absorption, and bioavailability of carbohydrates, proteins, and lipids by interacting with them or their according enzymes and transporters in the gastrointestinal tract; (4). PAC showed a prebiotic-like effect by interacting with the microflora in the intestinal tract, and the enhancement of PAC on a variety of probiotics, such as Bifidobacterium spp. and Lactobacillus spp. could be associated with potential benefits to human health. In conclusion, the potential effects of PAC in prevention and alleviation of gastrointestinal diseases are remarkable but clinical evidence is urgently needed.

Angioprevention of Urologic Cancers by Plant-Derived Foods

The number of cancer cases worldwide keeps growing unstoppably, despite the undeniable advances achieved by basic research and clinical practice. Urologic tumors, including some as prevalent as prostate, bladder or kidney tumors, are no exceptions to this rule. Moreover, the fact that many of these tumors are detected in early stages lengthens the duration of their treatment, with a significant increase in health care costs. In this scenario, prevention offers the most cost-effective long-term strategy for the global control of these diseases. Although specialized diets are not the only way to decrease the chances to develop cancer, epidemiological evidence support the role of certain plant-derived foods in the prevention of urologic cancer. In many cases, these plants are rich in antiangiogenic phytochemicals, which could be responsible for their protective or angiopreventive properties. Angiogenesis inhibition may contribute to slow down the progression of the tumor at very different stages and, for this reason, angiopreventive strategies could be implemented at different levels of chemoprevention, depending on the targeted population. In this review, epidemiological evidence supporting the role of certain plant-derived foods in urologic cancer prevention are presented, with particular emphasis on their content in bioactive phytochemicals that could be used in the angioprevention of cancer.

Recent Studies on Berry Bioactives and Their Health-Promoting Roles

Along with the increased knowledge about the positive health effects of food bioactives, the eating habits of many individuals have changed to obtain higher nutritional benefits from foods. Fruits are among the most preferred food materials in this regard. In particular, berry fruits are important sources in the diet in terms of their high nutritional content including vitamins, minerals, and phenolic compounds. Berry fruits have remedial effects on several diseases and these health-promoting impacts are associated with their phenolic compounds which may vary depending on the type and variety of the fruit coupled with other factors including climate, agricultural conditions, etc. Most of the berries have outstanding beneficial roles in many body systems of humans such as gastrointestinal, cardiovascular, immune, and nervous systems. Furthermore, they are effective on some metabolic disorders and several types of cancer. In this review, the health-promoting effects of bioactive compounds in berry fruits are presented and the most recent in vivo, in vitro, and clinical studies are discussed from a food science and nutrition point of view.

Small berries as health-promoting ingredients: a review on anti-aging effects and mechanisms in Caenorhabditis elegans

Aging is an inevitable, irreversible, and complex process of damage accumulation and functional decline, increasing the risk of various chronic diseases. However, for now no drug can delay aging process nor cure aging-related diseases. Nutritional intervention is considered as a key and effective strategy to promote healthy aging and improve life quality. Small berries, as one of the most common and popular fruits, have been demonstrated to improve cognitive function and possess neuroprotective activities. However, the anti-aging effects of small berries have not been systematically elucidated yet. This review mainly focuses on small berries' anti-aging activity studies involving small berry types, active components, the utilized model organism Caenorhabditis elegans (C. elegans), related signaling pathways, and molecular mechanisms. The purpose of this review is to propose effective strategies to evaluate the anti-aging effects of small berries and provide guidance for the development of anti-aging supplements from small berries.

Review of Functional and Pharmacological Activities of Berries

Functional plant-based foods (such as fruits, vegetables, and berries) can improve health, have a preventive effect, and diminish the risk of different chronic diseases during in vivo and in vitro studies. Berries contain many phytochemicals, fibers, vitamins, and minerals. The primary phytochemicals in berry fruits are phenolic compounds including flavonoids (anthocyanins, flavonols, flavones, flavanols, flavanones, and isoflavonoids), tannins, and phenolic acids. Since berries have a high concentration of polyphenols, it is possible to use them for treating various diseases pharmacologically by acting on oxidative stress and inflammation, which are often the leading causes of diabetes, neurological, cardiovascular diseases, and cancer. This review examines commonly consumed berries: blackberries, blackcurrants, blueberries, cranberries, raspberries, black raspberries, and strawberries and their polyphenols as potential medicinal foods (due to the presence of pharmacologically active compounds) in the treatment of diabetes, cardiovascular problems, and other diseases. Moreover, much attention is paid to the bioavailability of active berry components. Hence, this comprehensive review shows that berries and their bioactive compounds possess medicinal properties and have therapeutic potential. Nevertheless, future clinical trials are required to study and improve the bioavailability of berries' phenolic compounds and extend the evidence that the active compounds of berries can be used as medicinal foods against various diseases.

Fruits and vegetables intake and gastric cancer risk: A pooled analysis within the Stomach cancer Pooling Project

A low intake of fruits and vegetables is a risk factor for gastric cancer, although there is uncertainty regarding the magnitude of the associations. In our study, the relationship between fruits and vegetables intake and gastric cancer was assessed, complementing a previous work on the association betweenconsumption of citrus fruits and gastric cancer. Data from 25 studies (8456 cases and 21 133 controls) with information on fruits and/or vegetables intake were used. A two-stage approach based on random-effects models was used to pool study-specific adjusted (sex, age and the main known risk factors for gastric cancer) odds ratios (ORs) and the corresponding 95% confidence intervals (CIs). Exposure-response relations, including linear and nonlinear associations, were modeled using one- and two-order fractional polynomials. Gastric cancer risk was lower for a higher intake of fruits (OR: 0.76, 95% CI: 0.64-0.90), noncitrus fruits (OR: 0.86, 95% CI: 0.73-1.02), vegetables (OR: 0.68, 95% CI: 0.56-0.84), and fruits and vegetables (OR: 0.61, 95% CI: 0.49-0.75); results were consistent across sociodemographic and lifestyles categories, as well as study characteristics. Exposure-response analyses showed an increasingly protective effect of portions/day of fruits (OR: 0.64, 95% CI: 0.57-0.73 for six portions), noncitrus fruits (OR: 0.71, 95% CI: 0.61-0.83 for six portions) and vegetables (OR: 0.51, 95% CI: 0.43-0.60 for 10 portions). A protective effect of all fruits, noncitrus fruits and vegetables was confirmed, supporting further dietary recommendations to decrease the burden of gastric cancer.

Berry polyphenols metabolism and impact on human gut microbiota and health

Berries are rich in phenolic compounds such as phenolic acids, flavonols and anthocyanins. These molecules are often reported as being responsible for the health effects attributed to berries. However, their poor bioavailability, mostly influenced by their complex chemical structures, raises the question of their actual direct impact on health. The products of their metabolization, however, may be the most bioactive compounds due to their ability to enter the blood circulation and reach the organs. The main site of metabolization of the complex polyphenols to smaller phenolic compounds is the gut through the action of microorganisms, and reciprocally polyphenols and their metabolites can also modulate the microbial populations. In healthy subjects, these modulations generally lead to an increase in Bifidobacterium, Lactobacillus and Akkermansia, therefore suggesting a prebiotic-like effect of the berries or their compounds. Finally, berries have been demonstrated to alleviate symptoms of gut inflammation through the modulation of pro-inflammatory cytokines and have chemopreventive effects towards colon cancer through the regulation of apoptosis, cell proliferation and angiogenesis. This review recapitulates the knowledge available on the interactions between berries polyphenols, gut microbiota and gut health and identifies knowledge gaps for future research.

Organic cranberry pomace and its ethanolic extractives as feed supplement in broiler: impacts on serum Ig titers, liver and bursal immunity

With the pressure to reduce antibiotics use in poultry production, cost-effective alternative products need to be developed to enhance the bird's immunity. The present study evaluated the efficacy of cranberry fruit by-products to modulate immunity in broiler chickens. Broiler Cobb 500 chicks were fed a control basal diet, basal diet supplemented with bacitracin (BACI, 55 ppm), cranberry pomace at 1% and 2% (CP2), or cranberry pomace ethanolic extract at 150 and 300 ppm (COH300) for 30 d. Blood sera were analyzed at days 21 and 28 of age for Ig levels by ELISA. The innate and adaptive immune-related gene expression levels in the liver and bursa of Fabricius were investigated at 21 d of age by quantitative polymerase chain reaction arrays. At day 21, the highest IgY level was found in the blood serum of the CP2-fed birds. In the liver, 13 of the 22 differentially expressed genes were downregulated across all treatments compared with the control. Expression of genes belonging to innate immunity such as caspase 1 apoptosis–related cysteine peptidase, chemokine receptor 5, interferon gamma, myeloid differentiation primary response gene 88, and Toll-like receptor 3 were significantly downregulated mainly in BACI- and COH300-fed birds. In the bursa, 5 of 9 genes associated with the innate immunity were differentially expressed. The expression of anti-inflammatory IL-10 gene was upregulated in all treatment groups in bursa compared with the control. The expression of transferrin gene was significantly upregulated in livers of birds fed COH300 and in bursa of birds fed BACI, indicating feeding practices and organ-dependant modulation of this gene in broiler. Overall results of this study showed that cranberry product feed supplementation modulated the innate immune and suppressed proinflammatory cytokines in broilers, providing a platform for future investigations to develop berry products in poultry feeding.

Comparison of the Effect of Acids in Solvent Mixtures for Extraction of Phenolic Compounds From Aronia melanocarpa

Thirty-two different solvent mixtures containing methanol and acid (acetic, formic, and hydrochloric); methanol, water, and acid; and pure methanol were tested for their efficiency for extraction of phenolic compounds from aronia ( Aronia melanocarpa) belonging to the groups of anthocyanins, flavonols, and hydroxycinnamic acid derivatives. Thirteen compounds were detected and quantified in the extracts using HPLC/DAD/ESI-MS n. The yield of each compound and group was evaluated with regard to the extraction solvent composition. Extraction mixtures containing HCl were superior to the ones containing acetic or formic acid for the extraction yield of total phenolic compounds, which was especially pronounced for anthocyanins. The solvent mixture containing methanol/water/HCl (90:8:2, v/v/v) gave best results for the qualitative and quantitative assay of anthocyanins. However, this solvent mixture caused O-methylation of 3- and 5-caffeoylquinic acids transforming them to 3- and 5-feruloylquinic acids, respectively, during extraction. This peculiar finding must be taken into account during sample preparation for the analysis of polyphenols in any sample. It was observed that this O-methylation is specific for dihydroxycinnamic acid compounds containing neighboring hydroxyl groups. These results suggest the need for a detailed study of the behavior of various polyphenolic compounds during extraction with solvent mixtures containing methanol/HCl since it is very often used for the analysis of anthocyanins.

HAV detection from milk-based products containing soft fruits: Comparison between four different extraction methods

Virus detection in food requires appropriate elution and concentration techniques which need to be adapted for different food matrices. ISO/TS-15216-1:2017 and ISO/TS-15216-2:2019 describe standard methods for hepatitis A virus (HAV) research in some food only. Milk-based products containing one or more types of fruit are not covered by ISO procedures, even though they can be contaminated by fruit added to these products or by the food handlers. The aim of this work was to identify an efficient method for the detection of HAV in milk-based products. Four methods were tested to recover HAV from artificially contaminated milk, yoghurt and ice cream containing soft fruits. Results showed that the efficiency of the tested methods depends on the analyzed matrix. In milk we obtained a mean recovery from 13.4% to 1.9%; method based on high speed centrifuge gave the best values. The average recovery in yoghurt was between 3.3% and 114.4%, the latter value achieved by method with beef extract at 3% as eluent. Finally, two methods gave the best results in ice cream with similar recoveries: 29.1% and 27.7% respectively. The first method used glycine as eluent while the other one was based on high speed centrifugation. The ISO method has never proved to be the most efficient in the matrices studied. Therefore, based on the results obtained, a complete rethinking of the ISO method may be necessary to improve its recovery for some products such as milk, while only small changes would be sufficient for other products, such as yoghurt and ice cream.

MYBA From Blueberry (Vaccinium Section Cyanococcus) Is a Subgroup 6 Type R2R3MYB Transcription Factor That Activates Anthocyanin Production

The Vaccinium genus in the family Ericaceae comprises many species, including the fruit-bearing blueberry, bilberry, cranberry, huckleberry, and lingonberry. Commercially, the most important are the blueberries (Vaccinium section Cyanococcus), such as Vaccinium corymbosum (northern highbush blueberry), Vaccinium virgatum (rabbiteye blueberry), and Vaccinium angustifolium (lowbush blueberry). The rising popularity of blueberries can partly be attributed to their "superfood" status, with an increasing body of evidence around human health benefits resulting from the fruit metabolites, particularly products of the phenylpropanoid pathway such as anthocyanins. Activation of anthocyanin production by R2R3-MYB transcription factors (TFs) has been characterized in many species, but despite recent studies on blueberry, cranberry, and bilberry, no MYB anthocyanin regulators have been reported for Vaccinium. Indeed, there has been conjecture that at least in bilberry, MYB TFs divergent to the usual type are involved. We report identification of MYBA from blueberry, and show through sequence analysis and functional studies that it is homologous to known anthocyanin-promoting R2R3-MYBs of subgroup 6 of the MYB superfamily. In transient assays, MYBA complemented an anthocyanin MYB mutant of Antirrhinum majus and, together with a heterologous bHLH anthocyanin regulator, activated anthocyanin production in Nicotiana benthamiana. Furthermore anthocyanin accumulation and anthocyanin structural gene expression (assayed by qPCR and RNA-seq analyses) correlated with MYBA expression, and MYBA was able to transactivate the DFR promoter from blueberry and other species. The RNA-seq data also revealed a range of other candidate genes involved in the regulation of anthocyanin production in blueberry fruit. The identification of MYBA will help to resolve the regulatory mechanism for anthocyanin pigmentation in the Vaccinium genus. The sequence information should also prove useful in developing tools for the accelerated breeding of new Vaccinium cultivars.