Richard Espley

Plant and Food Research · Department of Breeding and Genomics

Daily intake of polyphenols, especially anthocyanins that colour our fruits and vegetables, is considered suboptimal for human health in many western countries. We sought to deploy biofortification breeding strategies to improve anthocyanin content in blueberries. Our aim was to understand the genetic regulation of the phytochemical differences bet...

For many fruit crops, the colour of the fruit outwardly defines its eating quality. Fruit pigments provide reproductive advantage for the plant as well as providing protection against unfavourable environmental conditions and pathogens. For consumers these colours are considered attractive and provide many of the dietary benefits derived from fruit...

Domestication of cranberry and blueberry began in the United States in the early 1800s and 1900s, respectively, and in part owing to their flavors and health-promoting benefits are now cultivated and consumed worldwide. The industry continues to face a wide variety of production challenges (e.g. disease pressures) as well as a demand for higher-yie...

Vaccinium myrtillus, known as bilberry or European blueberry, is highly valued by consumers for its berries that are rich in health-promoting compounds. However, bilberry production remains largely wild, as the low fruit yield and soft berry characteristics impede its domestication and commercialization. A robust gene transformation system, which i...

The genus Vaccinium L. (Ericaceae) contains premium berryfruit crops including blueberry, cranberry, bilberry and lingonberry. Consumption of Vaccinium berries is strongly associated with various potential health and many of these benefits are attributed to the relatively high concentrations of flavonoids, including the anthocyanins that provide th...

Anthocyanins are a major group of red to blue spectrum plant pigments with many consumer health benefits. Anthocyanins are derived from the flavonoid pathway and diversified by glycosylation and methylation, involving the concerted action of specific enzymes. Blueberry and bilberry ( Vaccinium spp.) are regarded as ‘superfruits’ owing to their high...

Wild berries are abundant in health-beneficial bioactive compounds, such as flavonoids, carotenoids, vitamins, and polyphenolic compounds, which accumulate during the fruit ripening process. Interestingly, wild Vaccinium berries from northern latitudes are found to contain more bioactive compounds compared to southern clones. The genetic adaptation...

Sieboldin is a specialised secondary metabolite of the group of dihydrochalcones (DHC), found in high concentrations only in some wild Malus species, closely related to the domesticated apple ( Malus × domestica L.). To date, the first committed step towards the biosynthesis of sieboldin remains unknown. In this study, we combined transcriptomic an...

Phloridzin is the most abundant polyphenolic compound in apple (Malus x domestica Borkh.), which results from the action of a key phloretin‐specific UDP‐2′‐O‐glucosyltransferase (MdPGT1). Here, we simultaneously assessed the effects of targeting MdPGT1 by conventional transgenesis and CRISPR/Cas9‐mediated genome editing. To this end, we conducted t...

DNA methylation, an epigenetic mark, is proposed to regulate plant anthocyanin biosynthesis. It well known that light induces anthocyanin accumulation, with bagging treatments commonly used to investigate light-controlled anthocyanin biosynthesis. We studied the DNA methylome landscape during pear skin coloration under various conditions (fruits re...

During ripening blueberries accumulate high amounts of flavonoid-derived anthocyanin pigments in fruit skin, but not in flesh. However, we found that anthocyanin biosynthesis was induced in fruit flesh in response to infiltration with Agrobacterium and even with sterile water. We hypothesised that this stress-response was mediated by phytohormones,...

Knowledge of the transcriptional regulation of the carotenoid metabolic pathway is still emerging and here, we have misexpressed a key biosynthetic gene in apple to highlight potential transcriptional regulators of this pathway. We overexpressed phytoene synthase (PSY1), which controls the key rate-limiting biosynthetic step, in apple and analyzed...

Highbush blueberry (Vaccinium corymbosum, 2n = 4x = 48) is the most cultivated type of blueberry, both in New Zealand and overseas. Its perceived nutritional value is conferred by phytonutrients, particularly anthocyanins. Identifying the genetic mechanisms that control the biosynthesis of these metabolites would enable faster development of cultiv...

The genetic link between apple red flesh (RF) coloration and the internal flesh browning disorder (FBD) is a major challenge when breeding high fruit quality RF apple cultivars. A genome-wide association study (GWAS) was conducted in a population of about 900 red-leaved seedlings to identify genomic regions and putative candidate genes using whole...

Light spectral quality is known to affect flavonoid biosynthesis during fruit ripening. However, the response of fruits to different light conditions, when ripening autonomously from the parent plant (detached), has been less explored. In this study, we analyzed the effect of light quality on detached and naturally ripening (attached) non-climacter...

The ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) plays a central role in light-induced anthocyanin biosynthesis. However, the upstream regulatory factors of COP1 remain poorly understood, particularly in horticultural plants. Here, we identified a MdCOP1-interacting protein, BROAD-COMPLEX, TRAMTRACK AND BRIC A BRAC2 (MdBT2), in apple (...

Vaccinium berries are regarded as “superfoods” owing to their high concentrations of anthocyanins, flavonoid metabolites that provide pigmentation and positively affect human health. Anthocyanin localization differs between the fruit of cultivated highbush blueberry (V. corymbosum) and wild bilberry (V. myrtillus), with the latter having deep red f...

The genus Vaccinium L. (Ericaceae) contains a wide diversity of culturally and economically important berry crop species. Consumer demand and scientific research in blueberry (Vaccinium spp.) and cranberry (Vaccinium macrocarpon) have increased worldwide over the crops’ relatively short domestication history (~100 years). Other species, including b...

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 underst...

MicroRNA172 (miR172) plays a role in regulating a diverse range of plant developmental processes, including flowering, fruit development and nodulation. However, its role in regulating flavonoid biosynthesis is unclear. In this study, we show that transgenic apple plants over-expressing miR172 show a reduction in red coloration and anthocyanin accu...

Chinese plum (Prunus salicina Lindl.) is a stone fruit that belongs to the Prunus genus and plays an important role in the global production of plum. In this study, we report the genome sequence of the Chinese plum ‘Sanyueli’, which is known to have a low-chill requirement for flower bud break. The assembled genome size was 282.38 Mb, with a contig...

Pear, belonging to the genus Pyrus, is one of the most economically important temperate fruit crops. Pyrus is an important genus of the Rosaceae family, subfamily Maloideae, and has at least 22 different species with over 5000 accessions maintained or identified worldwide. With the release of draft whole-genome sequences for Pyrus, opportunities fo...

MYB transcription factors regulate diverse aspects of plant development and secondary metabolism, often by partnering in transcriptional regulatory complexes. Here, we harness genomic resources to identify novel MYBs, thereby producing an updated eudicot MYB phylogeny with revised relationships among subgroups as well as new information on sequence...

Waxy apple cuticles predominantly accumulate ursane-type triterpenes, but the profile shifts with the induction of skin russeting towards lupane-type triterpenes. We previously characterised several key enzymes in the ursane-type and lupane-type triterpene pathways, but this switch in triterpene metabolism associated with loss of cuticle integrity...

Flavonoids play important roles in regulating plant growth and development. In this study, three kaempferol 3-O-glycosides were identified and mainly accumulated in flowers but not in leaves or fruits of Malus. In Malus, flower petal color is normally white, but some genotypes have red flowers containing anthocyanin. Anthocyanin biosynthesis appear...

Some cultivars of pear ( Pyrus L.) show attractive red fruit skin due to anthocyanin accumulation. This pigmentation can be affected by environmental conditions, especially light. To explore the light-induced regulation network for anthocyanin biosynthesis and fruit coloration in pear, small RNA libraries and mRNA libraries from fruit skins of ‘Yun...

Wufanshu (Vaccinium bracteatum Thunb.), which is a wild member of the genus Vaccinium, accumulates high concentration of anthocyanin in its berries. In this study, the accumulated anthocyanins and their derivatives in Wufanshu berries were identified through UHPLC–MS/MS analysis. Candidate anthocyanin biosynthetic genes were identified from the tra...

Bilberry (Vaccinium myrtillus) is a commercially important wild berry species, which accumulates high amounts of polyphenols, particularly anthocyanins, in the skin and flesh. Whilst a number of studies have quantified these phytochemicals in intact ripe bilberry fruit, we extend the current knowledge by investigating the spatial distribution of an...

Anthocyanin accumulation is responsible for red pigmentation in plum peel and affected by light and temperature. We investigated the effects of temperature and LED light (400−800 nm, with following red: green: blue ratio 20.9: 75.7: 3.4 respectively) with total radiant flux adjusted at 150 mol m⁻² s⁻¹ on anthocyanin accumulation in postharvest ‘Aki...

The biosynthesis of anthocyanins has been shown to be influenced by light quality. However, the molecular mechanisms underlying the light-mediated regulation of fruit anthocyanin biosynthesis are not well understood. In this study, we analyzed the effects of supplemental red and blue light on the anthocyanin biosynthesis in non-climacteric bilberry...

The regulatory network of R2R3 MYB transcription factors in anthocyanin biosynthesis is not fully understood in blue‐coloured berries containing delphinidin compounds. We used blue berries of bilberry ( Vaccinium myrtillus ) to comprehensively characterise flavonoid‐regulating R2R3 MYBs, which revealed a new type of co‐regulation in anthocyanin bio...

Overexpression of a VcMYBA anthocyanin transcription factor in Vaccinium corymbosum produces dark red shoots in vitro.

Bilberry (Vaccinium myrtillus L.) belongs to the Vaccinium genus, which includes blueberries (Vaccinium spp.) and cranberry (V. macrocarpon). Unlike its cultivated relatives, bilberry remains largely undomesticated, with berry harvesting almost entirely from the wild. As such, it represents an ideal target for genomic analysis, providing comparison...

Plum is one of the most important stone fruits in the world and anthocyanin-rich plums are increasingly popular due to their health-promoting potential. In this study, we investigated the mechanisms of anthocyanin accumulation in the flesh of the red-fleshed mutant of the yellow-fleshed plum ‘Sanyueli’. RNA-Seq and qRT-PCR showed that anthocyanin b...

The biosynthesis of anthocyanins has been shown to be influenced by light quality. However, the molecular mechanisms underlying the light-mediated regulation of fruit anthocyanin biosynthesis are not well understood. In this study, we analyzed the effects of supplemental red and blue light on the anthocyanin biosynthesis in non-climacteric bilberry...

Although taste is an important aspect of fruit quality, our understanding of its genetic control remains elusive in apple and other fruit crops. Genomic sequence analysis of 497 Malus accessions revealed an erosion of genetic diversity caused by apple breeding and possible independent domestication events of dessert and cider apples. Signatures of...

Polyphenols within fruits and vegetables may contribute to health benefits due to their consumption, with the anthocyanin sub-set also adding colour. The Lemonade™ apple variety has green skin and white flesh, with low anthocyanin content, while some apple varieties have high anthocyanin content in both the skin and flesh. Effects of red compared w...

The groups of plant flavonoid metabolites termed anthocyanins and proanthocyanins (PA) are responsible for pigmentation in seeds, flowers and fruits. Anthocyanins and PAs are produced by a pathway of enzymes which are transcriptionally regulated by transcription factors (TFs) that form the MYB-bHLH-WD40 (MBW) complex. In this study, transcriptomic...

Chinese plum (Prunus salicina Lindl.) is a stone fruit that belongs to the Prunus genus and plays an important role in the global production of plum. In this study, we report the genome sequence of the Chinese plum ′Sanyueli′ (P. salicina Lindl.), which is known to have a low-chill requirement. The assembled genome size was 308.06 Mb, with a contig...

The MYB transcription factors (TFs) comprise a major TF family in the plant kingdom. Studies increasingly show that MYB-related genes drive physiological functions in plants. However, little is known regarding their regulatory networks and downstream pathways in potato. We conducted a genome-wide analysis of MYB TFs and related proteins in potato (...

Blueberries are distinguished by their purple-blue fruit color, which develops during ripening and is derived from a characteristic composition of flavonoid-derived anthocyanin pigments. The production of anthocyanins is confined to fruit skin, leaving the colorless fruit flesh devoid of these compounds. By linking accumulation patterns of phenolic...

Non-targeted LC-MS metabolomics on fruit of three wild and domesticated apple species (Malus sylvestris, M. sieversii and M. domestica) showed that two crab apple (M. sylvestris) accessions were distinguished by high concentrations of an ascorbic acid glycoside (AAG). This was partly purified, but key NMR signals were masked by inseparable sucrose....

Anthocyanins are a group of secondary metabolites that colour fruit and flowers orange, red, purple or blue depending on a number of factors, such as the basic structure, co-pigmentation, metal ion complexation and vacuolar pH. The biosynthesis of anthocyanin is regulated at the transcriptional level by a group of transcription factors, the MYB–bHL...

Red skin colour is an important target trait in various pear breeding programmes. In this study, the genetic control of red skin colour was investigated in an interspecific population derived using the descendants of the red sport European pear cultivar ‘Max Red Bartlett’ (MRB) and the red-blushed Chinese pear cultivar ‘Huobali’. Approximately 550...

Fruit with stripes, which are generally longitudinal, can occur naturally, but the bioprocesses underlying this phenomenon are unclear. Previously, we observed an atypical anthocyanin distribution that caused red-striped fruit on the spontaneous pear bud sport “Red Zaosu” (Pyrus bretschneideri Rehd.). In this study, comparative transcriptome analys...

Asthma is an allergic lung inflammation characterised by the influx of eosinophils at the infected site recruited by the chemokine, CCL11. During inflammation, the transcription factor Nuclear Factor kappa B (NF-κB) initiates a series of pro-inflammatory responses. Natural compounds that could modulate CCL11 levels and/or NF-κB activation have pote...

Environmentally-responsive genes can affect fruit red colour via the activation of MYB transcription factors. The apple B-box (BBX) gene, BBX33/CONSTANS-like 11 (COL11) has been reported to influence apple red-skin colour in a light- and temperature-dependent manner. To further understand the role of apple BBX genes, other members of the BBX family...

The elevation of anthocyanin contents in fruits and vegetables is a breeding target for many crops. In some fruit, such as tomato, higher anthocyanin concentrations enhance storage and shelf life. In contrast, highly anthocyanic red-fleshed apples (Malus x domestica) have an increased incidence of internal browning flesh disorder (IBFD). To determi...

As an important environment factor, light affects plant growth and development throughout life. B-BOX (BBX) proteins play key roles in the regulation of light signaling. Although the multiple roles of BBX proteins have been extensively studied in Arabidopsis, the research in apple is much less extensive. In this study, we systematically characteriz...

High temperatures are known to reduce anthocyanin accumulation in a number of diverse plant species. In potato (Solanum tuberosum L.), high temperature significantly reduces tuber anthocyanin pigment content. However, the mechanism of anthocyanin biosynthesis in potato tuber under heat stress remains unknown. Here we show that high temperature caus...

Radula marginata Taylor is a subtropical liverwort, endemic to the Northern island of New Zealand in the Pacific region. Despite its significant potential as an alternative source of a THC-like phytocannabinoid, the biosynthesis of this compound remains elusive. Following the discovery of a bibenzyl cis-tetrahydrocannabinol (perrottetinene) in R. m...

Fruits and vegetables are a major source of phytochemicals. One class of flavonoids, the anthocyanins, provide both novelty and health effects to the consumer. For many of these horticultural products, all varieties (or most of the varieties) accumulate anthocyanins only in the skin and have white flesh, such as apples (Malus × domestica), pears (P...

Chinese narcissus (Narcissus tazetta L. var. chinensis Roem.) is a popular flower in Asia. However, flower colors are limited with all cultivars having a white perianth and yellow corona. Previous studies have shown no anthocyanin accumulation in this species. The reason for an absence of anthocyanins remains unknown, with the flavonoid biosyntheti...

Full list of differentially expressed genes in the skin and flesh of mature-stage blueberry fruit, with a differential greater than 2 log2fold.

MYBA orthologs from rabbiteye blueberry and cranberry. Nucleotide alignment of the coding sequence of MYBA from highbush blueberry (Vaccinium corymbosum; Vc) and orthologs from rabbiteye blueberry (V. ashei; Va) and cranberry (V. macrocarpon; Vm). Sequence identity between VcMYBA and the orthologs from rabbiteye blueberry and cranberry are 97 and 9...

Alignment of the deduced amino acid sequence of VcMYBA with those of selected flavonoid-related R2R3MYBs. The deduced amino acid sequence of VcMYBA was aligned with representative R2R3MYB genes from SGs 4, 5, 6 and the PA1-type clade using MUSCLE. Sequences from Vaccinium species are in bold. The C-terminal motifs that define each SG (Stracke et al...

MYBA induces anthocyanin biosynthesis in blueberry petals. Petals from V. corymbosum were biolistically transformed with either 35S:GFP-ER alone or 35S:VcMYBA + 35S:GFP-ER. Transformed cells were identified by GFP fluorescence, observed with blue light. Transformation with VcMYBA induced pink pigmentation in transformed cells, while GFP-ER alone di...