Although the effects of melatonin on plant abiotic and biotic stress resistance have been explored in recent decades, the accumulation of endogenous melatonin in plants and its influence on fruit ...quality remains unclear. In the present study, melatonin accumulation levels and the expression profiles of five synthesis genes were investigated during fruit and leaf development in sweet cherry (
L.). Melatonin was strongly accumulated in young fruits and leaves, then decreased steadily with maturation. Transcript levels of
and
were highly correlated with melatonin content in both fruit and leaves, indicating their importance in melatonin accumulation. Furthermore, application of 50 and 100 μmol·L
of melatonin to leaves had a greater influence on fruit quality than treatments applied to fruits, by significantly improving fruit weight, soluble solids content, and phenolic content including total phenols, flavanols, total anthocyanins, and ascorbic acid. Meanwhile, melatonin application promoted the antioxidant capacity of fruit assayed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis (3-ethylben zothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP). These results provide insights into the physiological and molecular mechanisms underlying melatonin metabolism of sweet cherry.
Abscisic acid (ABA) is a key signaling molecule promoting ripening of non-climacteric fruits such as sweet cherry (
L.). To shed light on the role of other hormones on fruit development, ripening and ...anthocyanin production, the synthetic auxin 1-naphthaleneacetic acid (NAA) was applied to sweet cherry trees during the straw-color stage of fruit development. NAA-treated fruits exhibited higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC) and ABA-glucose ester (ABA-GE), which are a precursor of ethylene and a primary storage form of ABA, respectively. Consistent with these observations, transcript levels of genes encoding ACC synthase and ACC oxidase, both involved in ethylene biosynthesis, were increased after 6 days of NAA treatment, and both ABA concentration and expression of the regulator gene of ABA biosynthesis (
encoding 9-cis-epoxycarotenoid dioxygenase) were highest during early fruit ripening. In addition, transcript levels of key anthocyanin regulatory, biosynthetic and transport genes were significantly upregulated upon fruit exposure to NAA. This was accompanied by an increased anthocyanin concentration and fruit weight whilst fruit firmness and cracking index decreased. Altogether our data suggest that NAA treatment alters ethylene production, which in turn induces ripening in sweet cherry and enhanced anthocyanin production, possibly through ABA metabolism. The results from our study highlight the potential to use a single NAA treatment for manipulation of cherry ripening.
Sweet cherry (Prunus avium L.) fruits are classified into dark-red and bicolored cultivars based on their anthocyanin contents; however, the mechanisms regulating the accumulation of these pigments ...are unclear. Here, we reveal that anthocyanin accumulation is highly dependent on light in bicolored ‘Rainier’ cherries, while it is only slightly light dependent in the dark-red ‘Hongdeng’ fruits. To reveal the transcriptional mechanisms regulating light-dependent anthocyanin accumulation in bicolored ‘Rainier’ cherries, we sequenced the transcriptomes of fruits grown in light or in darkness. Genes encoding the anthocyanin biosynthesis enzymes chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, and flavonoid 3′-hydroxylase were significantly upregulated by light in the bicolored fruits. Most of the differentially expressed regulatory genes were known to be involved in the light or hormone signal transduction pathways, such as those encoding protein phosphatase 2Cs, PHYTOCHROME INTERACTING FACTOR 3, phytochromes, and ELONGATED HYPOCOTYL 5. The expression levels of 32 highly expressed transcription factors were found to be significantly altered by light in the bicolored fruits, including members of the basic leucine zipper, R2R3-MYB, and WRKY transcription factor families. A co-expression network analysis further revealed that many of the light-regulated genes were co-expressed with genes involved in the abscisic acid and gibberellic acid signaling pathways, suggesting that these phytohormones play important roles in light-dependent anthocyanin biosynthesis. Together, our data reveal multiple roles for light in regulating anthocyanin biosynthesis in differently colored cherries.
•Fruit coloration is light-dependent in bicolored cherries but not in dark-red ones.•The response to light of anthocyanin synthetic genes in different cherries is varied.•The regulatory proteins in light-dependent anthocyanin accumulation are identified.•Hormone signaling may play crucial roles in light-dependent anthocyanin biosynthesis.
Bud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production. Recent work highlighted physiological and molecular events ...occurring during bud dormancy in trees. However, they usually examined bud development or bud dormancy in isolation. In this work, we aimed to further explore the global transcriptional changes happening throughout bud development and dormancy onset, progression and release.
Using next-generation sequencing and modelling, we conducted an in-depth transcriptomic analysis for all stages of flower buds in several sweet cherry (Prunus avium L.) cultivars that are characterized for their contrasted dates of dormancy release. We find that buds in organogenesis, paradormancy, endodormancy and ecodormancy stages are defined by the expression of genes involved in specific pathways, and these are conserved between different sweet cherry cultivars. In particular, we found that DORMANCY ASSOCIATED MADS-box (DAM), floral identity and organogenesis genes are up-regulated during the pre-dormancy stages while endodormancy is characterized by a complex array of signalling pathways, including cold response genes, ABA and oxidation-reduction processes. After dormancy release, genes associated with global cell activity, division and differentiation are activated during ecodormancy and growth resumption. We then went a step beyond the global transcriptomic analysis and we developed a model based on the transcriptional profiles of just seven genes to accurately predict the main bud dormancy stages.
Overall, this study has allowed us to better understand the transcriptional changes occurring throughout the different phases of flower bud development, from bud formation in the summer to flowering in the following spring. Our work sets the stage for the development of fast and cost effective diagnostic tools to molecularly define the dormancy stages. Such integrative approaches will therefore be extremely useful for a better comprehension of complex phenological processes in many species.
Key message
This work provides the first system-wide datasets concerning metabolic changes in calcium-treated fruits, which reveal that exogenously applied calcium may specifically reprogram sweet ...cherry development and ripening physiognomy.
Calcium modulates a wide range of plant developmental processes; however, the regulation of fruit ripening by calcium remains largely uncharacterized. In this study, transcriptome, proteome and metabolome profiling was used to document the responses of sweet cherry fruit to external calcium application (0.5% CaCl
2
) at 15, 27 and 37 days after full blossom. Endogenous calcium loading in fruit across development following external calcium feeding was accompanied by a reduction in respiration rate. Calcium treatment strongly impaired water-induced fruit cracking tested by two different assays, and this effect depended on the fruit size, water temperature and light/dark conditions. Substantial changes in the levels of numerous polar/non-polar primary and secondary metabolites, including malic acid, glucose, cysteine, epicatechin and neochlorogenic acid were noticed in fruits exposed to calcium. At the onset of ripening, we identified various calcium-affected genes, including those involved in ubiquitin and cysteine signaling, that had not been associated previously with calcium function in fruit biology. Calcium specifically increased the abundance of a significant number of proteins that classified as oxidoreductases, transferases, hydrolases, lyases, and ligases. The overview of temporal changes in gene expression and corresponding protein abundance provided by interlinked analysis revealed that oxidative phosphorylation, hypersensitive response, DNA repair, stomata closure, biosynthesis of secondary metabolites, and proton-pump activity were mainly affected by calcium. This report provides the fullest characterization of expression patterns in calcium-responsive genes, proteins and metabolites currently available in fruit ripening and will serve as a blueprint for future biological endeavors.
MYB Transcription factors (TFs) are most imperative and largest gene family in plants, which participate in development, metabolism, defense, differentiation and stress response. The MYB TFs has been ...studied in various plant species. However, comprehensive studies of MYB gene family in the sweet cherry (Prunus avium L.) are still unknown.
In the current study, a total of 69 MYB genes were investigated from sweet cherry genome and classified into 28 subfamilies (C1-C28 based on phylogenetic and structural analysis). Microcollinearity analysis revealed that dispersed duplication (DSD) events might play an important role in the MYB genes family expansion. Chromosomal localization, the synonymous (Ks) and nonsynonymous (Ka) analysis, molecular characteristics (pI, weight and length of amino acids) and subcellular localization were accomplished using several bioinformatics tools. Furthermore, the members of distinct subfamilies have diverse cis-acting regions, conserved motifs, and intron-exon architectures, indicating functional heterogeneity in the MYB family. Moreover, the transcriptomic data exposed that MYB genes might play vital role in bud dormancy. The quantitative real-time qRT-PCR was carried out and the expression pattern indicated that MYB genes significantly expressed in floral bud as compared to flower and fruit.
Our comprehensive findings provide supportive insights into the evolutions, expansion complexity and functionality of PavMYB genes. These PavMYB genes should be further investigated as they seem to be brilliant candidates for dormancy manipulation in sweet cherry.
Plant R2R3-MYB transcription factors play crucial roles in stress responses. We previously isolated a R2R3-MYB homolog from sweet cherry cv. Hong Deng, designated PacMYBA (GenBank accession No. ...KF974774). To explore the role of PacMYBA in the plant stress response, we heterologously expressed PacMYBA in transgenic Arabidopsis thaliana plants. In a previous study, we demonstrated that PacMYBA is mainly localized to the nucleus and could be induced by abscisic acid (ABA). Analysis of the promoter sequence of PacMYBA revealed that it contains several stress-related cis-elements. QPCR results showed that PacMYBA is induced by salt, salicylic (SA), and jasmonic acid (JA) in sweet cherry leaves. Transgenic Arabidopsis plants heterologously expressing PacMYBA exhibited enhanced salt-tolerance and increased resistance to Pseudomonas syringe pv. tomato (Pst) DC3000 infection. Overexpression of PacMYBA decreased the osmotic potential (OP), increased the free proline content, and increased the peroxidase content in transgenic Arabidopsis plants. Furthermore, overexpression of PacMYBA also affected the expression levels of salt stress- and pathogen defense-related genes in the transgenic plants. These results indicate that PacMYBA is a positive regulator of salt stress tolerance and pathogen resistance.
•PacMYBA, a sweet cherry R2R3-MYB transcription factor, functions as a positive regulator of stress response.•PacMYBA enhances salt stress tolerance and pathogen resistance in transgenic Arabidopsis plants.•The increased stress tolerance of the transgenic plants may be due to increased anthocyanin accumulation.
•Anthocyanins but not carotenoids determine the color of sweet cherry fruits.•The difference between red-yellow and red sweet cherry may be attributed to seven anthocyanins.•The content of 85 ...flavonols differed between red and red-yellow sweet cherries.•Fifteen key structural genes were involved in the flavonoid metabolic pathway.
The color of a fruit is an important contributor to the perception of its nutritional value. It is widely acknowledged that the color of sweet cherry changes obviously during ripening. Variations in anthocyanins and flavonoids account for the heterogeneous color of sweet cherries. In this study, we showed that anthocyanins but not carotenoids determine the color of sweet cherry fruits. The difference between red-yellow and red sweet cherry may be attributed to seven anthocyanins, including Cyanidin-3-O-arabinoside, Cyanidin-3,5-O-diglucoside, Cyanidin 3-xyloside, Peonidin-3-O-glucoside, Peonidin-3-O-rutinoside, Cyanidin-3-O-galactoside, Cyanidin-3-O-glucoside (Kuromanin), Peonidin-3-O-rutinoside-5-O-glucoside, Pelargonidin-3-O-glucoside and Pelargonidin-3-O-rutinoside. The content of 85 flavonols differed between red and red-yellow sweet cherries. The transcriptional analysis identified 15 key structural genes involved in the flavonoid metabolic pathway and four R2R3-MYB transcription factors. The expression level of Pac4CL, PacPAL, PacCHS1, PacCHS2, PacCHI, PacF3H1, PacF3H2, PacF3′H, PacDFR, PacANS1, PacANS2, PacBZ1 and four R2R3-MYB were positively correlated with anthocyanin content (ps < 0.05). PacFLS1, PacFLS2 and PacFLS3 expression was negatively correlated with anthocyanin content but positively correlated with flavonols content (ps < 0.05). Overall, our findings suggests that the heterogeneous expression of structural genes in the flavonoid metabolic pathway accounts for the variation in levels of final metabolites, leading to differences between red ‘Red-Light’ and red-yellow ‘Bright Pearl’.
Summary
Sweet cherry is a diploid tree species and its fruit skin has rich colours from yellow to blush to dark red. The colour is closely related to anthocyanin biosynthesis and is mainly regulated ...at the transcriptional level by transcription factors that regulate the expression of multiple structural genes. However, the genetic and molecular bases of how these genes ultimately determine the fruit skin colour traits remain poorly understood. Here, our genetic and molecular evidences identified the R2R3 MYB transcription factor PavMYB10.1 that is involved in anthocyanin biosynthesis pathway and determines fruit skin colour in sweet cherry. Interestingly, we identified three functional alleles of the gene causally leading to the different colours at mature stage. Meanwhile, our experimental results of yeast two‐hybrid assays and chromatin immunoprecipitation assays revealed that PavMYB10.1 might interact with proteins PavbHLH and PavWD40, and bind to the promoter regions of the anthocyanin biosynthesis genes PavANS and PavUFGT; these findings provided to a certain extent mechanistic insight into the gene's functions. Additionally, genetic and molecular evidences confirmed that PavMYB10.1 is a reliable DNA molecular marker to select fruit skin colour in sweet cherry.
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