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 comparisons with the domesticated Vaccinium species. Bilberry is prized for its taste and health properties and has provided essential nutrition for Northern European indigenous populations. It contains high concentrations of phytonutrients, with perhaps the most important being the purple colored anthocyanins, found in both skin and flesh. Here, we present the first bilberry genome assembly, comprising 12 pseudochromosomes assembled using Oxford Nanopore (ONT) and Hi‐C Technologies. The pseudochromosomes represent 96.6% complete BUSCO genes with an assessed LAI score of 16.3, showing a high conservation of synteny against the blueberry genome. Kmer analysis showed an unusual third peak, indicating the sequenced samples may have been from two individuals. The alternate alleles were purged so that the final assembly represents only one haplotype. A total of 36,404 genes were annotated after nearly 48% of the assembly was masked to remove repeats. To illustrate the genome quality, we describe the complex MYBA locus, and identify the key regulating MYB genes that determine anthocyanin production. The new bilberry genome builds on the genomic resources and knowledge of Vaccinium species, to help understand the genetics underpinning some of the quality attributes that breeding programs aspire to improve. The high conservation of synteny between bilberry and blueberry genomes means that comparative genome mapping can be applied to transfer knowledge about marker‐trait association between these two species, as the loci involved in key characters are orthologous.
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 its effects in transgenic fruit skin and flesh using two approaches. Firstly, the effects of PSY overexpression on carotenoid accumulation and gene expression was assessed in fruit at different development stages. Secondly, the effect of light exclusion on PSY1-induced fruit carotenoid accumulation was examined. PSY1 overexpression increased carotenoid content in transgenic fruit skin and flesh, with beta-carotene being the most prevalent carotenoid compound. Light exclusion by fruit bagging reduced carotenoid content overall, but carotenoid content was still higher in bagged PSY fruit than in bagged controls. In tissues overexpressing
PSY1
, plastids showed accelerated chloroplast to chromoplast transition as well as high fluorescence intensity, consistent with increased number of chromoplasts and carotenoid accumulation. Surprisingly, the expression of other carotenoid pathway genes was elevated in PSY fruit, suggesting a feed-forward regulation of carotenogenesis when this enzyme step is mis-expressed. Transcriptome profiling of fruit flesh identified differentially expressed transcription factors (TFs) that also were co-expressed with carotenoid pathway genes. A comparison of differentially expressed genes from both the developmental series and light exclusion treatment revealed six candidate TFs exhibiting strong correlation with carotenoid accumulation. This combination of physiological, transcriptomic and metabolite data sheds new light on plant carotenogenesis and TFs that may play a role in regulating apple carotenoid biosynthesis.
Wufanshu (
Thunb.), which is a wild member of the genus
, 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 transcriptome of Wufanshu berries. qRT-PCR analyses showed that the expression of anthocyanin structural genes correlated with anthocyanin accumulation in berries. The R2R3-MYB,
, which is a homolog of anthocyanin promoting R2R3-MYBs from other
species, was also identified. Transient expression of
in
leaves confirmed its role as an anthocyanin regulator, and produced a higher anthocyanin concentration when compared with blueberry
expression. Dual-luciferase assays further showed that VbMYBA can activate the
and
promoters from other
species. VbMYBA has an additional 23 aa at the N terminus compared with blueberry VcMYBA, but this was shown not to affect the ability to regulate anthocyanins. Taken together, our results provide important information on the molecular mechanisms responsible for the high anthocyanin content in Wufanshu berries.
Fruit quality is dependent on various factors including flavour, texture and colour. These factors are determined by the ripening process, either climacteric or non-climacteric. In grape berry, which ...is non-climacteric, the process is signalled by a complex set of hormone changes. Abscisic acid (ABA) is one of the key hormones involved in ripening, while sugar availability also plays a significant role in certain ripening aspects such as anthocyanin production. To understand the relative influence of hormone and sugar signalling
can prove problematic due to the physiological and environmental (abiotic and biotic) factors at play in vineyards. Here we report on the use of
detached berry culture to investigate the comparative significance of ABA and sugar in the regulation of Pinot noir berry anthocyanin production under controlled conditions. Using a factorial experimental design, pre-véraison berries were cultured on media with various concentrations of sucrose and ABA. After 15 days of
culture, the berries were analysed for changes in metabolites, hormones and gene expression. Results illustrated a stimulatory effect of sucrose and ABA on enhancing berry colour and a corresponding increase in anthocyanins. Increased ABA concentration was able to boost anthocyanin production in berries when sucrose supply was low. The sucrose and ABA effects on berry anthocyanins were primarily manifested through the up-regulation of transcription factors and other genes in the phenylpropanoid pathway, while in other parts of the pathway a down-regulation of key proanthocyanindin transcription factors and genes corresponded to sharp reduction in berry proanthocyanidins, irrespective of sucrose supply. Similarly, increased ABA was correlated with a significant reduction in berry malic acid and associated regulatory genes. These findings suggest a predominance of berry ABA over berry sugar in coordinating the physiological and genetic regulation of anthocyanins and proanthocyanins in Pinot noir grape berries.
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, hence studied their role and associated gene expression patterns in comparison with skin-specific anthocyanin biosynthesis during fruit ripening. In ripening berries, active abscisic acid (ABA) concentrations were highest at the onset of anthocyanin biosynthesis, suggesting a role for ABA in regulating anthocyanins during at the onset of fruit ripening. Concentrations of active ABA, however, were comparable between fruit tissues during berry development, while genes and metabolites associated with ABA catabolism and reversible conjugation were up to 10-fold higher in fruit skin and correlated strongly with anthocyanins. Thus, increased amounts of ABA were processed in fruit skin, likely impacting on tissue-specific pigmentation during fruit development. In response to biotic stress, however, salicylic acid (SA) concentrations increased in fruit flesh and correlated strongly with anthocyanin biosynthesis, while ABA was actively catabolised and concentrations reduced, indicating a role for SA in activating stress-anthocyanin production. Application of SA and ABA showed that both phytohormones increased flavonoid gene expression and anthocyanin accumulation, thus indicating that anthocyanin biosynthesis can be regulated by alternate signals.
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•Biotic stress induced anthocyanin biosynthesis in non-pigmented blueberry flesh.•In stressed fruit, abscisic acid was catabolised and salicylic acid content increased.•In ripening fruit, abscisic acid metabolism was higher in fruit skin than flesh.•Alternate signals induced stress-related and ripening-related anthocyanins.
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