Proteomic analysis of the effects of ABA treatments on ripening Vitis vinifera berries

Preharvest and Postharvest Applications of Fe-Based Nanomaterials: A Potent Strategy for Improving Pepper Storage

Nanomaterials (NMs) hold significant potential for enhancing agricultural production, extending the shelf life, and maintaining the quality of postharvest vegetables and fruits. In this study, after foliar spraying with 1, 10, and 50 mg of L-1 Fe-P NMs at different stages (seedling, flowering, and fruit stage), the pepper plant growth was significantly improved. In particular, the foliar application of 10 mg of L-1 Fe-P NMs during the flowering stage was found to be an optimal cultivation approach to promote the growth, yield, and freshness of peppers. Compared with the control group, Fe-P NMs increased net photosynthetic rate, plant height, and fruit number by 132.7%, 40.4%, and 265.7%, respectively. The applied Fe-P NMs, at the flowering stage, altered the capsaicin metabolic pathway, upregulating the genes for the synthesis of total phenols, flavonoids, lignans, and capsaicinoids. Consequently, these metabolites, which are beneficial for maintaining the freshness of pepper fruits, were increased. Furthermore, Fe-P NMs at the flowering stage downregulated the abundance of rot-causing microorganisms (Enterobacter and Chryseobacterium) and upregulated beneficial microorganisms (Pseudomonas, Arthrobacter, Sphingobacterium, and Paenibacillus) to change the microbial community structure. This ultimately created a micro-ecological environment conducive to the preservation of pepper fruits. For comparison, during pepper fruit storage, dipping and spraying with Fe-P NM suspensions effectively delayed weight loss and enhanced the growth of beneficial bacteria. Nevertheless, the effect was less pronounced than preharvest foliar application. This study provides insights into the pre- or postharvest application of NMs for improving the preservation performance of pepper fruits.

Integrative molecular and physiological insights into the phytotoxic impact of liquid crystal monomer exposure and the protective strategy in plants

Liquid crystal monomers (LCMs), the integral components in the manufacture of digital displays, have engendered environmental concerns due to extensive utilization and intensive emission. Despite their prevalence and ecotoxicity, the LCM impacts on plant growth and agricultural yield remain inadequately understood. In this study, we investigated the specific response mechanisms of tobacco, a pivotal agricultural crop and model plant, to four representative LCMs (2OdF3B, 5CB, 4PiMeOP, 2BzoCP) through integrative molecular and physiological approaches. The findings reveal specific impacts, with 4PiMeOP exerting the most pronounced effects, followed by 2BzoCP, 5CB, and 2OdF3B. LCM exposure disrupts the photosynthetic apparatus, exacerbating reactive oxygen species (ROS) levels in leaves, which in turn triggers the upregulation of antioxidative enzymes and the synthesis of antioxidant substances. Additionally, LCMs strongly stimulate the expression of genes involved in abscisic acid (ABA) biosynthesis and signalling pathways. The AI-assisted meta-analysis implicates ABA as a critical regulator in the tobacco response to LCMs. Notably, exogenous application of ABA alleviates LCM-induced toxicities, highlighting the pivotal role of ABA in stress amelioration. Our study provides novel insights into the toxicity and tolerance mechanisms of LCMs in plants, shedding light on both their harmful effects on the ecosystems and potential adaptation responses. This is crucial to develop sustainable agricultural systems by reducing the negative environmental impacts caused by emerging organic pollutants.

Abscisic acid and ethylene coordinating fruit ripening under abiotic stress

Fleshy fruit metabolism is intricately influenced by environmental changes, yet the hormonal regulations underlying these responses remain poorly elucidated. ABA and ethylene, pivotal in stress responses across plant vegetative tissues, play crucial roles in triggering fleshy fruit ripening. Their actions are intricately governed by complex mechanisms, influencing key aspects such as nutraceutical compound accumulation, sugar content, and softening parameters. Both hormones are essential orchestrators of significant alterations in fruit development in response to stressors like drought, salt, and temperature fluctuations. These alterations encompass colour development, sugar accumulation, injury mitigation, and changes in cell-wall degradation and ripening progression. This review provides a comprehensive overview of recent research progress on the roles of ABA and ethylene in responding to drought, salt, and temperature stress, as well as the molecular mechanisms controlling ripening in environmental cues. Additionally, we propose further studies aimed at genetic manipulation of ABA and ethylene signalling, offering potential strategies to enhance fleshy fruit resilience in the face of future climate change scenarios.

Quantitative Proteomics Analysis of ABA- and GA3-Treated Malbec Berries Reveals Insights into H2O2 Scavenging and Anthocyanin Dynamics

Abscisic acid (ABA) and gibberellic acid (GA3) are regulators of fruit color and sugar levels, and the application of these hormones is a common practice in commercial vineyards dedicated to the production of table grapes. However, the effects of exogenous ABA and GA3 on wine cultivars remain unclear. We investigated the impact of ABA and GA3 application on Malbec grapevine berries across three developmental stages. We found similar patterns of berry total anthocyanin accumulation induced by both treatments, closely associated with berry H2O2 levels. Quantitative proteomics from berry skins revealed that ABA and GA3 positively modulated antioxidant defense proteins, mitigating H2O2. Consequently, proteins involved in phenylpropanoid biosynthesis were downregulated, leading to decreased anthocyanin content at the almost ripe stage, particularly petunidin-3-G and peonidin-3-G. Additionally, we noted increased levels of the non-anthocyanins E-viniferin and quercetin in the treated berries, which may enhance H2O2 scavenging at the almost ripe stage. Using a linear mixed-effects model, we found statistical significance for fixed effects including the berry H2O2 and sugar contents, demonstrating their roles in anthocyanin accumulation. In conclusion, our findings suggest a common molecular mechanism by which ABA and GA3 influence berry H2O2 content, ultimately impacting anthocyanin dynamics during ripening.

Abscisic acid activates transcription factor module MdABI5-MdMYBS1 during carotenoid-derived apple fruit coloration

Carotenoids are major pigments contributing to fruit coloration. We previously reported that the apple (Malus domestica Borkh.) mutant fruits of "Beni Shogun" and "Yanfu 3" show a marked difference in fruit coloration. However, the regulatory mechanism underlying this phenomenon remains unclear. In this study, we determined that carotenoid is the main factor influencing fruit flesh color. We identified an R1-type MYB transcription factor (TF), MdMYBS1, which was found to be highly associated with carotenoids and abscisic acid (ABA) contents of apple fruits. Overexpression of MdMYBS1 promoted, and silencing of MdMYBS1 repressed, β-branch carotenoids synthesis and ABA accumulation. MdMYBS1 regulates carotenoid biosynthesis by directly activating the major carotenoid biosynthetic genes encoding phytoene synthase (MdPSY2-1) and lycopene β-cyclase (MdLCYb). 9-cis-epoxycarotenoid dioxygenase 1 (MdNCED1) contributes to ABA biosynthesis, and MdMYBS1 enhances endogenous ABA accumulation by activating the MdNCED1 promoter. In addition, the basic leucine zipper domain TF ABSCISIC ACID-INSENSITIVE5 (MdABI5) was identified as an upstream activator of MdMYBS1, which promotes carotenoid and ABA accumulation. Furthermore, ABA promotes carotenoid biosynthesis and enhances MdMYBS1 and MdABI5 promoter activities. Our findings demonstrate that the MdABI5-MdMYBS1 cascade activated by ABA regulates carotenoid-derived fruit coloration and ABA accumulation in apple, providing avenues in breeding and planting for improvement of fruit coloration and quality.

Grape SnRK2.7 Positively Regulates Drought Tolerance in Transgenic Arabidopsis

In this study, we obtained and cloned VvSnRK2.7 by screening transcriptomic data to investigate the function of the grape sucrose non-fermenting kinase 2 (SnRK2) gene under stress conditions. A yeast two-hybrid (Y2H) assay was used to further screen for interaction proteins of VvSnRK2.7. Ultimately, VvSnRK2.7 was heterologously expressed in Arabidopsis thaliana, and the relative conductivity, MDA content, antioxidant enzyme activity, and sugar content of the transgenic plants were determined under drought treatment. In addition, the expression levels of VvSnRK2.7 in Arabidopsis were analyzed. The results showed that the VvSnRK2.7-EGFP fusion protein was mainly located in the cell membrane and nucleus of tobacco leaves. In addition, the VvSnRK2.7 protein had an interactive relationship with the VvbZIP protein during the Y2H assay. The expression levels of VvSnRK2.7 and the antioxidant enzyme activities and sugar contents of the transgenic lines were higher than those of the wild type under drought treatment. Moreover, the relative conductivity and MDA content were lower than those of the wild type. The results indicate that VvSnRK2.7 may activate the enzyme activity of the antioxidant enzyme system, maintain normal cellular physiological metabolism, stabilize the berry sugar metabolism pathway under drought stress, and promote sugar accumulation to improve plant resistance.

Unveiling the toxic effects, physiological responses and molecular mechanisms of tobacco (Nicotiana tabacum) in exposure to organic ultraviolet filters

Exposure to organic ultraviolet (UV) filters has raised concerns due to their potential adverse effects on environments. However, their toxic mechanisms on plants remain elusive. In this study, using integrative physiological and transcriptomic approaches we investigated the physiological and molecular responses to three representative UV filters, namely oxybenzone (OBZ), avobenzone (AVB), and octinoxate (OMC), in an agricultural model plant tobacco. The exposure to UV filters disrupts the functionality of photosystem reaction centers and the light-harvesting apparatus. Concurrently, UV filters exert a suppressive effect on the expression of genes encoding Rubisco and Calvin-Benson cycle enzymes, resulting in a decreased efficiency of the Calvin-Benson cycle and consequently hampering the process of photosynthesis. Exposure to UV filters leads to significant generation of reactive oxygen species within tobacco leaves and downregulation of oxidoreductase activities. Moreover, UV filters promote abscisic acid (ABA) accumulation by inducing the expression of ABA biosynthesis genes whereas repress indole-3-acetic acid (IAA) biosynthesis gene expression, which induce leaf yellowing and slow plant growth. In summary, the organic UV filters exert toxic effects on tobacco growth by inhibiting chlorophyll synthesis, photosynthesis, and the Calvin-Benson cycle, while generating excessive reactive oxygen species. This study sheds light on the toxic and tolerance mechanisms of UV filters in agricultural crops.

Regulation of carotenoid metabolism and ABA biosynthesis during blueberry fruit ripening

Carotenoids and their derivates play critical physiologic roles in plants. However, these substrates and their metabolism have not been elucidated in fruit of blueberry (Vaccinium corymbosum). In this study, carotenoids and ABA were investigated by LC-MS and their biosynthesis were subject to proteomic analysis during fruit ripening. Activity of CCD1 and NCED1/3 were studied in vivo or in vitro. Also, effects of ethephon and 1-MCP on biosynthesis of carotenoid and ABA were investigated through the expression of corresponding genes using qPCR. As a result, carotenoid biosynthesis was prominently mitigated whereas its metabolism was enhanced during fruit ripening, which resulted in a decrease in the carotenoids. VcCCD1 could both cleave β-carotene, zeaxanthin and lutein at positions of 9, 10 (9', 10'), which was mainly responsible for the degradation of these carotenoids. Interestingly, in the situation of mitigation of carotenoid biosynthesis, ABA still rapidly accumulated, which was mainly attributed to the upregulated expression of VcNCED1/3. Notably, VcNCED1/3 also showed a cleavage activity of all-trans-zeaxanthin and a stereospecific cleavage activity of 9-cis-carotene to generate C15-carotenal. The C15-carotenal could be potentially converted to ABA through ZEP-independent ABA biosynthetic pathway during blueberry fruit ripening. Similar to a nature natural maturation, ethylene accelerated the carotenoid degradation and ABA biosynthesis trough downregulating the expression of genes in carotenoid biosynthesis and upregulating the expression of genes in ABA biosynthesis. These information help understand the regulation of carotenoids and ABA, and effects of ethylene on the regulation during blueberry fruit ripening.

Non-climacteric fruit development and ripening regulation: 'the phytohormones show'

Fruit ripening involves numerous physiological, structural, and metabolic changes that result in the formation of edible fruits. This process is controlled at different molecular levels, with essential roles for phytohormones, transcription factors, and epigenetic modifications. Fleshy fruits are classified as either climacteric or non-climacteric species. Climacteric fruits are characterized by a burst in respiration and ethylene production at the onset of ripening, while regulation of non-climacteric fruit ripening has been commonly attributed to abscisic acid (ABA). However, there is controversy as to whether mechanisms regulating fruit ripening are shared between non-climacteric species, and to what extent other hormones contribute alongside ABA. In this review, we summarize classic and recent studies on the accumulation profile and role of ABA and other important hormones in the regulation of non-climacteric fruit development and ripening, as well as their crosstalk, paying special attention to the two main non-climacteric plant models, strawberry and grape. We highlight both the common and different roles of these regulators in these two crops, and discuss the importance of the transcriptional and environmental regulation of fruit ripening, as well as the need to optimize genetic transformation methodologies to facilitate gene functional analyses.

MaABI5 and MaABF1 transcription factors regulate the expression of MaJOINTLESS during fruit abscission in mulberry (Morus alba L.)

Mulberry holds significant economic value. However, during the ripening stage of its fruit, the phenomenon of abscission, resulting in heavy fruit drop, can severely impact the yield. The formation of off-zone structures is a critical factor in the fruit abscission process, and this process is regulated by multiple transcription factors. One such key gene that plays a significant role in the development of the off-zone in the model plant tomato is JOINTLESS, which promotes the expression of abscission-related genes and regulates the differentiation of abscission zone tissue cells. However, there is a lack of information about fruit abscission mechanism in mulberry. Here, we analyzed the MaJOINTLESS promoter and identified the upstream regulators MaABF1 and MaABI5. These two regulators showed binding with MaJOINTLESS promoter MaABF1 (the ABA Binding Factor/ABA-Responsive Element Binding Proteins) activated the expression of MaJOINTLESS, while MaABI5 (ABSCISIC ACID-INSENSITIVE 5) inhibited the expression of MaJOINTLESS. Finally, the differentially expressed genes (DEGs) were analyzed by transcriptome sequencing to investigate the expression and synergistic relationship of endogenous genes in mulberry during abscission. GO classification and KEGG pathway enrichment analysis showed that most of the DEGs were concentrated in MAPK signaling pathway, flavonoid biosynthesis, citric acid cycle, phytohormone signaling, amino acid biosynthesis, and glycolysis. These results provide a theoretical basis for subsequent in-depth study of physiological fruit abscission in mulberry.

Dynamic Changes of Endogenous Hormones in Different Seasons of Idesia polycarpa Maxim

Idesia polycarpa Maxim is a native dioecious tree from East Asia cultivated for its fruits and as an ornamental plant throughout temperate regions. Given the economic potential, comparative studies on cultivated genotypes are of current interest. This study aims to discover the dynamic changes and potential functions of endogenous hormones in I. polycarpa, as well as the differences in endogenous hormone contents in different growth stages among different I. polycarpa provenances. We used High-Performance Liquid Chromatography (HPLC) to measure and compare the levels of abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellin A3 (GA3), and trans-Zeatin-riboside (tZR) in the leaves, flowers, and fruits of I. polycarpa from various provenances between April and October. Our findings indicated that changes in the ABA and GA3 content of plants from Jiyuan and Tokyo were minimal from April to October. However, the levels of these two hormones in Chengdu plants vary greatly at different stages of development. The peak of IAA content in the three plant materials occurred primarily during the early fruit stage and the fruit expansion stage. The concentration of tZR in the three plant materials varies greatly. Furthermore, we discovered that the contents of endogenous hormones in I. polycarpa leaves, flowers, and fruits from Chengdu provenances were slightly higher than those from Tokyo and Jiyuan provenances. The content of IAA was higher in male flowers than in female flowers, and the content of ABA, GA3, and tZR was higher in female flowers than in male flowers. According to the findings, the contents of these four endogenous hormones in I. polycarpa are primarily determined by the genetic characteristics of the trees and are less affected by cultivation conditions. The gender of I. polycarpa had a great influence on these four endogenous hormones. The findings of this study will provide a theoretical foundation and practical guidance for artificially regulating the flowering and fruiting of I. polycarpa.

Transcriptomic and metabolomic integration as a resource in grapevine to study fruit metabolite quality traits

Transcriptomics and metabolomics are methodologies being increasingly chosen to perform molecular studies in grapevine (Vitis vinifera L.), focusing either on plant and fruit development or on interaction with abiotic or biotic factors. Currently, the integration of these approaches has become of utmost relevance when studying key plant physiological and metabolic processes. The results from these analyses can undoubtedly be incorporated in breeding programs whereby genes associated with better fruit quality (e.g., those enhancing the accumulation of health-promoting compounds) or with stress resistance (e.g., those regulating beneficial responses to environmental transition) can be used as selection markers in crop improvement programs. Despite the vast amount of data being generated, integrative transcriptome/metabolome meta-analyses (i.e., the joint analysis of several studies) have not yet been fully accomplished in this species, mainly due to particular specificities of metabolomic studies, such as differences in data acquisition (i.e., different compounds being investigated), unappropriated and unstandardized metadata, or simply no deposition of data in public repositories. These meta-analyses require a high computational capacity for data mining a priori, but they also need appropriate tools to explore and visualize the integrated results. This perspective article explores the universe of omics studies conducted in V. vinifera, focusing on fruit-transcriptome and metabolome analyses as leading approaches to understand berry physiology, secondary metabolism, and quality. Moreover, we show how omics data can be integrated in a simple format and offered to the research community as a web resource, giving the chance to inspect potential gene-to-gene and gene-to-metabolite relationships that can later be tested in hypothesis-driven research. In the frame of the activities promoted by the COST Action CA17111 INTEGRAPE, we present the first grapevine transcriptomic and metabolomic integrated database (TransMetaDb) developed within the Vitis Visualization (VitViz) platform (https://tomsbiolab.com/vitviz). This tool also enables the user to conduct and explore meta-analyses utilizing different experiments, therefore hopefully motivating the community to generate Findable, Accessible, Interoperable and Reusable (F.A.I.R.) data to be included in the future.

Changes and response mechanism of sugar and organic acids in fruits under water deficit stress

The content and the ratio of soluble sugars and organic acids in fruits are significant indicators for fruit quality. They are affected by multiple environmental factors, in which water-deficient is the most concern. Previous studies found that the content of soluble sugars and organic acids in fruit displayed great differences under varied water stress. It is important to clarify the mechanism of such difference and to provide researchers with systematic knowledge about the response to drought stress and the mechanism of sugar and acid changes in fruits, so that they can better carry out the study of fruit quality under drought stress. Therefore, the researchers studied dozens of research articles about the content of soluble sugar and organic acid, the activity of related metabolic enzymes, and the expression of related metabolic genes in fruits under water stress, and the stress response of plants to water stress. We found that after plants perceived and transmitted the signal of water deficit, the expression of genes related to the metabolism of soluble sugars and organic acids changed. It was then affected the synthesis of metabolic enzymes and changed their metabolic rate, ultimately leading to changes in soluble sugar and organic acid content. Based on the literature review, we described the pathway diagrams of sugar metabolism, organic acid metabolism, mainly malic acid, tartaric acid, and citric acid metabolism, and of the response to drought stress. From many aspects including plants' perception of water stress signal, signal conversion and transmission, induced gene expression, the changes in soluble sugar and the enzyme activities of organic acids, as well as the final sugar and acid content in fruits, this thesis summarized previous studies on the influence of water stress on soluble sugars and the metabolism of organic acids in fruits.

Transcriptome and metabolite integrated analysis reveals that exogenous ethylene controls berry ripening processes in grapevine

Although grapevine (Vitis vinifera L.) is generally classified as a non-climacteric fruit, the regulatory mechanisms of ethylene in the ripening of non-climacteric fruit are still poorly understood. In this study, exogenous ethephon (ETH) strongly stimulated fruit color and anthocyanin accumulation, which was consistent with the increased expression of anthocyanin structural, regulatory, and transport genes. ETH application increased ABA content and decreased IAA content by coordinating ABA and auxin biosynthesis regulatory network. ETH treatment also accelerated sugar (glucose and fructose) accumulation by enhancing the gene expression involved in sugar transport and sucrose cleavage. ETH treatment blocked the synthesis of cellulose and accelerated the degradation of pectin, which was strongly associated with berry softening. To further confirm the function of ethylene biosynthesis and signaling genes, transient overexpression of VvACO4 and VvEIL3 were performed in both in tomato and strawberry fruits. These findings of the ethylene cascade add to our understanding of ethylene in non-climacteric berry ripening regulation and revealed a complex involvement of ethylene and its interplay with phytohormones during grapevine berry ripening.

Genome-scale transcriptomic insights into the gene co-expression network of seed abortion in triploid Siraitia grosvenorii

BACKGROUND

Siraitia grosvenorii (Swingle) C. Jeffrey, also known as Luohanguo or monk fruit, is a famous traditional Chinese medicine ingredient with important medicinal value and broad development prospects. Diploid S. grosvenorii has too many seeds, which will increase the utilization cost of active ingredients. Thus, studying the molecular mechanism of seed abortion in triploid S. grosvenorii, identifying the abortion-related genes, and regulating their expression will be a new direction to obtain seedless S. grosvenorii. Herein, we examined the submicroscopic structure of triploid S. grosvenorii seeds during abortion.

RESULTS

Upon measuring the endogenous hormone content, we found that abscisic acid (ABA) and trans-zeatin (ZR) levels were significantly downregulated after days 15 and 20 of flowering. RNA sequencing of triploid seeds at different developmental stages was performed to identify key genes regulating abortion in triploid S. grosvenorii seeds. Multiple genes with differential expression between adjacent stages were identified; seven genes were differentially expressed across all stages. Weight gene co-expression network analysis revealed that the enhancement of monoterpene and terpene metabolic processes might lead to seed abortion by reducing the substrate flow to ABA and ZR.

CONCLUSIONS

These findings provide insights into the gene-regulatory network of seed abortion in triploid S. grosvenorii from different perspectives, thereby facilitating the innovation of the breeding technology of S. grosvenorii.

Abscisic Acid: Role in Fruit Development and Ripening

Abscisic acid (ABA) is a plant growth regulator known for its functions, especially in seed maturation, seed dormancy, adaptive responses to biotic and abiotic stresses, and leaf and bud abscission. ABA activity is governed by multiple regulatory pathways that control ABA biosynthesis, signal transduction, and transport. The transport of the ABA signaling molecule occurs from the shoot (site of synthesis) to the fruit (site of action), where ABA receptors decode information as fruit maturation begins and is significantly promoted. The maximum amount of ABA is exported by the phloem from developing fruits during seed formation and initiation of fruit expansion. In the later stages of fruit ripening, ABA export from the phloem decreases significantly, leading to an accumulation of ABA in ripening fruit. Fruit growth, ripening, and senescence are under the control of ABA, and the mechanisms governing these processes are still unfolding. During the fruit ripening phase, interactions between ABA and ethylene are found in both climacteric and non-climacteric fruits. It is clear that ABA regulates ethylene biosynthesis and signaling during fruit ripening, but the molecular mechanism controlling the interaction between ABA and ethylene has not yet been discovered. The effects of ABA and ethylene on fruit ripening are synergistic, and the interaction of ABA with other plant hormones is an essential determinant of fruit growth and ripening. Reaction and biosynthetic mechanisms, signal transduction, and recognition of ABA receptors in fruits need to be elucidated by a more thorough study to understand the role of ABA in fruit ripening. Genetic modifications of ABA signaling can be used in commercial applications to increase fruit yield and quality. This review discusses the mechanism of ABA biosynthesis, its translocation, and signaling pathways, as well as the recent findings on ABA function in fruit development and ripening.

Effects of exogenous methyl jasmonate and light condition on grape berry coloration and endogenous abscisic acid content

Suitable postharvest treatment methods were investigated to improve the color of grape berries. Culture solutions containing jasmonic acid (JA), methyl jasmonate (MeJA), and prohydrojasmon (PDJ) enhanced the skin coloration of grape berries ('Pione') harvested at the initial stage of coloration. MeJA vapor treatment under sealed conditions increased anthocyanin accumulation in grape berries ('AkiQueen' and 'Pione') harvested at the early stage of skin coloration. Furthermore, promoting skin coloration by MeJA vapor treatment was as effective in mature clusters as it was in detached berries. These effects were confirmed in light conditions but not in constant darkness. Our results showed that postharvest MeJA vapor treatment improved skin coloration in grapes. In addition, postharvest treatment with MeJA was found to have no effect on the endogenous abscisic acid content of grape berry skins. Therefore, we suggest that MeJA vapor treatment can be a useful and labor-saving method for the horticultural industry.

Exogenous Abscisic Acid Mediates Berry Quality Improvement by Altered Endogenous Plant Hormones Level in "Ruiduhongyu" Grapevine

Abscisic acid (ABA) plays a key role in fruit development and ripening in non-climacteric fruit. A variety of metabolites such as sugars, anthocyanins, fatty acids, and several antioxidants, which are regulated by various phytohormones, are important components of fruit quality in grape. Here, grape cultivar "Ruiduhongyu" was used to investigate the relationship between endogenous phytohormones and metabolites associated to grape berry quality under exogenous ABA treatment. 500 mg/L ABA significantly improved the appearance parameters and the content of many metabolites including sugar, anthocyanin, and other compounds. Exogenous ABA also increased the contents of ABA, auxin (IAA), and cytokinins (CTKs), and transcription level of ABA biosynthesis and signaling related genes in fruit. Furthermore, a series of genes involved in biosynthesis and the metabolite pathway of sugars, anthocyanins, and fatty acids were shown to be significantly up-regulated under 500 mg/L ABA treatment. In addition, Pearson correlation analysis demonstrated that there existed relatively strong cooperativities in the ABA/kinetin (KT)-appearance parameters, ABA/IAA/KT-sugars, ABA/indolepopionic acid (IPA)/zeatin riboside (ZR)-anthocyanins, and gibberellin 3 (GA₃)/methyl jasmonate (MeJA)-fatty acids, indicating that 13 kinds of endogenous phytohormones induced by ABA had different contributions to the accumulation of quality-related metabolites, while all of them were involved in regulating the overall improvement of grape fruit quality. These results laid a primary foundation for better understanding that exogenous ABA improves fruit quality by mediating the endogenous phytohormones level in grape.

ABA signaling pathway genes and function during abiotic stress and berry ripening in Vitis vinifera

Abscisic acid (ABA) plays important roles in plant development and tolerance to abiotic stresses. Limited information is available regarding ABA signaling pathway genes in grape. In this study, 9 VvPYR/PYLs, 85 VvPP2Cs, 7 VvABIs, 7 VvSnRK2s, and 8 VvABFs were identified in the grape genome. Duplication analysis indicated that whole genome duplication might contribute to the expansion of these gene families. The comprehensive transcriptome analysis in various organs/tissues implied that most of these genes were tissue-specific, and few were environment-specific genes. Exogenous ABA treatment reduced the grape maturation period. VvPP2C59, VvPP2C60, VvPP2C66, and VvABF8 were all involved in tolerance to cold, heat, and drought stresses, revealing their crucial roles in regulating environmental stress responses. This work provides detailed information of ABA signaling pathway genes and new insights regarding their expression patterns during grape development and abiotic stress treatment.

Transcriptome analysis of strawberry fruit in response to exogenous arginine

Transcriptome and physiological analysis showed that exogenous arginine can delay the ripening process of postharvest strawberry fruit. Arginine (Arg) plays an important role in the growth and development of plants, but its growth and development regulatory mechanisms in strawberry fruit are unknown. In this study, we found that the content of Arg decreased after the onset of fruit coloration and exogenous Arg inhibited fruit coloration. We comprehensively analyzed the transcriptome of 'Sweet Charlie' strawberry fruit with or without Arg treatment and identified a large number of differential genes and metabolites. Based on the transcriptome data, we also found that Arg inhibited ripening, which coincided with changes in several physiological parameters and their corresponding gene transcripts, including firmness, anthocyanin content, sugar content, Arg content, indole-acetic acid (IAA) content, abscisic acid (ABA) content, and ethylene emissions. We also found that Arg induced the expression of heat-shock proteins (HSPs) and antioxidant enzyme genes, which improved strawberry stress resistance. This study elucidated the molecular mechanism by which exogenous Arg delays strawberry fruit ripening, providing some genetic information to help guide the future improvement and cultivation of strawberry.

Long-Term Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Berry Transcriptome

Viticulture is one of the horticultural systems in which antifungal treatments can be extremely frequent, with substantial economic and environmental costs. New products, such as biofungicides, resistance inducers and biostimulants, may represent alternative crop protection strategies respectful of the environmental sustainability and food safety. Here, the main purpose was to evaluate the systemic molecular modifications induced by biocontrol products as laminarin, resistance inducers (i.e., fosetyl-Al and potassium phosphonate), electrolyzed water and a standard chemical fungicide (i.e., metiram), on the transcriptomic profile of ‘Nebbiolo’ grape berries at harvest. In addition to a validation of the sequencing data through real-time polymerase chain reaction (PCR), for the first-time the expression of some candidate genes in different cell-types of berry skin (i.e., epidermal and hypodermal layers) was evaluated using the laser microdissection approach. Results showed that several considered antifungal treatments do not strongly affect the berry transcriptome profile at the end of season. Although some treatments do not activate long lasting molecular defense priming features in berry, some compounds appear to be more active in long-term responses. In addition, genes differentially expressed in the two-cell type populations forming the berry skin were found, suggesting a different function for the two-cell type populations.

The physiology of drought stress in grapevine: towards an integrative definition of drought tolerance

Water availability is arguably the most important environmental factor limiting crop growth and productivity. Erratic precipitation patterns and increased temperatures resulting from climate change will likely make drought events more frequent in many regions, increasing the demand on freshwater resources and creating major challenges for agriculture. Addressing these challenges through increased irrigation is not always a sustainable solution so there is a growing need to identify and/or breed drought-tolerant crop varieties in order to maintain sustainability in the context of climate change. Grapevine (Vitis vinifera), a major fruit crop of economic importance, has emerged as a model perennial fruit crop for the study of drought tolerance. This review synthesizes the most recent results on grapevine drought responses, the impact of water deficit on fruit yield and composition, and the identification of drought-tolerant varieties. Given the existing gaps in our knowledge of the mechanisms underlying grapevine drought responses, we aim to answer the following question: how can we move towards a more integrative definition of grapevine drought tolerance?

Transcriptome profiling of non-climacteric 'yellow' melon during ripening: insights on sugar metabolism

BACKGROUND

The non-climacteric 'Yellow' melon (Cucumis melo, inodorus group) is an economically important crop and its quality is mainly determined by the sugar content. Thus, knowledge of sugar metabolism and its related pathways can contribute to the development of new field management and post-harvest practices, making it possible to deliver better quality fruits to consumers.

RESULTS

The RNA-seq associated with RT-qPCR analyses of four maturation stages were performed to identify important enzymes and pathways that are involved in the ripening profile of non-climacteric 'Yellow' melon fruit focusing on sugar metabolism. We identified 895 genes 10 days after pollination (DAP)-biased and 909 genes 40 DAP-biased. The KEGG pathway enrichment analysis of these differentially expressed (DE) genes revealed that 'hormone signal transduction', 'carbon metabolism', 'sucrose metabolism', 'protein processing in endoplasmic reticulum' and 'spliceosome' were the most differentially regulated processes occurring during melon development. In the sucrose metabolism, five DE genes are up-regulated and 12 are down-regulated during fruit ripening.

CONCLUSIONS

The results demonstrated important enzymes in the sugar pathway that are responsible for the sucrose content and maturation profile in non-climacteric 'Yellow' melon. New DE genes were first detected for melon in this study such as invertase inhibitor LIKE 3 (CmINH3), trehalose phosphate phosphatase (CmTPP1) and trehalose phosphate synthases (CmTPS5, CmTPS7, CmTPS9). Furthermore, the results of the protein-protein network interaction demonstrated general characteristics of the transcriptome of young and full-ripe melon and provide new perspectives for the understanding of ripening.

Exogenous Abscisic Acid Regulates Distribution of 13C and 15N and Anthocyanin Synthesis in 'Red Fuji' Apple Fruit Under High Nitrogen Supply

In order to improve the problem of poor coloring caused by high fruit nitrogen in apple production, we studied the effects of different concentrations of abscisic acid (ABA: 0, 50, 100, and 150 mg/L) and fluridone (ABA biosynthesis inhibitor) on the fruit of 'Red Fuji' apple (Malus Domestica Borkh.) in the late stage of apple development (135 days after blooming) in 2017 and 2018. The effects of these treatments on the distribution of 13C and 15N and anthocyanin synthesis in fruit were studied. The results showed that the expression levels of ABA synthesis and receptor genes in the peel and flesh were upregulated by exogenous ABA treatment. An appropriate concentration of ABA significantly increased the expression of anthocyanin synthesis genes and transcription factors and increased the content of anthocyanin in the peel. The results of 13C and 15N double isotope labeling showed that exogenous ABA coordinated the carbon-nitrogen nutrient of apple fruit in the late stage of the development, reduced the accumulation of fruit nitrogen, increased the accumulation of fruit carbon and sugar, provided a substrate for anthocyanin synthesis, or promoted anthocyanin synthesis through the sugar signal regulation mechanism. Comprehensive analysis showed that the application of 100 mg/L ABA effectively improved the problem of poor coloring caused by high fruit nitrogen in the late stage of apple development and is beneficial to the accumulation of carbon in fruit and the formation of color.

Distinct Metabolic Signals Underlie Clone by Environment Interplay in "Nebbiolo" Grapes Over Ripening

Several research studies were focused to understand how grapevine cultivars respond to environment; nevertheless, the biological mechanisms tuning this phenomenon need to be further deepened. Particularly, the molecular processes underlying the interplay between clones of the same cultivar and environment were poorly investigated. To address this issue, we analyzed the transcriptome of berries from three "Nebbiolo" clones grown in different vineyards, during two ripening seasons. RNA-sequencing data were implemented with analyses of candidate genes, secondary metabolites, and agronomical parameters. This multidisciplinary approach helped to dissect the complexity of clone × environment interactions, by identifying the molecular responses controlled by genotype, vineyard, phenological phase, or a combination of these factors. Transcripts associated to sugar signalling, anthocyanin biosynthesis, and transport were differently modulated among clones, according to changes in berry agronomical features. Conversely, genes involved in defense response, such as stilbene synthase genes, were significantly affected by vineyard, consistently with stilbenoid accumulation. Thus, besides at the cultivar level, clone-specific molecular responses also contribute to shape the agronomic features of grapes in different environments. This reveals a further level of complexity in the regulation of genotype × environment interactions that has to be considered for orienting viticultural practices aimed at enhancing the quality of grape productions.

Genome-wide identification and transcriptome profiling reveal that E3 ubiquitin ligase genes relevant to ethylene, auxin and abscisic acid are differentially expressed in the fruits of melting flesh and stony hard peach varieties

Background

Ubiquitin ligases (E3) are the enzymes in the ubiquitin/26S proteasome pathway responsible for targeting proteins to the degradation pathway and play major roles in multiple biological activities. However, the E3 family and their functions are yet to be identified in the fruit of peach.

Results

In this study, genome-wide identification, classification and characterization of the E3 ligase genes within the genome of peach (Prunus persica) was carried out. In total, 765 E3 (PpE3) ligase genes were identified in the peach genome. The PpE3 ligase genes were divided into eight subfamilies according to the presence of known functional domains. The RBX subfamily was not detected in peach. The PpE3 ligase genes were not randomly distributed among the 8 chromosomes, with a greater concentration on the longer chromosomes. The primary mode of gene duplication of the PpE3 ligase genes was dispersed gene duplication (DSD). Four subgroups of the BTB subfamily never characterized before were newly identified in peach, namely BTBAND, BTBBL, BTBP and BTBAN. The expression patterns of the identified E3 ligase genes in two peach varieties that display different types of fruit softening (melting flesh, MF, and stony hard, SH) were analyzed at 4 different stages of ripening using Illumina technology. Among the 765 PpE3 ligase genes, 515 (67.3%) were expressed (FPKM > 1) in the fruit of either MF or SH during fruit ripening. In same-stage comparisons, 231 differentially expressed genes (DEGs) were identified between the two peach cultivars. The number of DEGs in each subfamily varied. Most DEGs were members of the BTB, F-box, U-box and RING subfamilies. PpE3 ligase genes predicted to be involved in ethylene, auxin, or ABA synthesis or signaling and DNA methylation were differentially regulated. Eight PpE3 ligase genes with possible roles in peach flesh texture and fruit ripening were discussed.

Conclusions

The results of this study provide useful information for further understanding the functional roles of the ubiquitin ligase genes in peach. The findings also provide the first clues that E3 ligase genes may function in the regulation of peach ripening.

A low temperature promotes anthocyanin biosynthesis but does not accelerate endogenous abscisic acid accumulation in red-skinned grapes

The effect of temperature on the concentrations of anthocyanins and endogenous plant hormones [abscisic acid (ABA), auxin, and cytokinin] were investigated using the detached berries of two related red-skinned cultivars cv. 'Aki Queen' and 'Ruby Roman' of the table grape Vitis labrusca L. × Vitis vinifera L. The total anthocyanin concentration of both cultivars was lower when exposed to high rather than low temperatures after véraison (the onset of ripening). However, the responses to temperature differed between the two cultivars, and anthocyanin accumulation could occur in 'Ruby Roman' at a higher temperature than in 'Aki Queen'. High temperatures increased the expression of VlMybA1-2 and VlMybA1-3, which encode myeloblastosis (MYB)-related transcription factors; however, the expression of the anthocyanin biosynthesis-related structural genes uridine diphosphate-d-glucose: flavonoid 3-O-glucosyltransferase, flavonoid 3'5' hydroxylase, and flavonoid O-methyltransferase at different temperatures did not correspond with that of the expression of MybAs. The concentration of ABA and its derivatives increased under high temperatures, but that of auxin and cytokinin decreased. The observation that high temperatures induced the accumulation of ABA and expression of VlMybA1s but not the expression of anthocyanin biosynthesis-related structural genes implied the operation of a mechanism different from up-regulation of anthocyanin synthesis by VlMybA1s in the temperature response of grape berries.

Fruit ripening: the role of hormones, cell wall modifications, and their relationship with pathogens

Fruits result from complex biological processes that begin soon after fertilization. Among these processes are cell division and expansion, accumulation of secondary metabolites, and an increase in carbohydrate biosynthesis. Later fruit ripening is accomplished by chlorophyll degradation and cell wall lysis. Fruit maturation is an essential step to optimize seed dispersal, and is controlled by a complex network of transcription factors and genetic regulators that are strongly influenced by phytohormones. Abscisic acid (ABA) and ethylene are the major regulators of ripening and senescence in both dry and fleshy fruits, as demonstrated by numerous ripening-defective mutants, effects of exogenous hormone application, and transcriptome analyses. While ethylene is the best characterized player in the final step of a fruit's life, ABA also has a key regulatory role, promoting ethylene production and acting as a stress-related hormone in response to drought and pathogen attack. In this review, we focus on the role of ABA and ethylene in relation to the interconnected biotic and abiotic phenomena that affect ripening and senescence. We integrate and discuss the most recent data available regarding these biological processes, which are crucial for post-harvest fruit conservation and for food safety.

PpERF3 positively regulates ABA biosynthesis by activating PpNCED2/3 transcription during fruit ripening in peach

The plant hormone ethylene regulates ripening in climacteric fruits. The phytohormone abscisic acid (ABA) affects ethylene biosynthesis, but whether ethylene influences ABA biosynthesis is unknown. To explore this possibility, we investigated the interactions between the ABA biosynthesis genes PpNCED2/3 and the ethylene response transcription factor PpERF3 in peach fruit. The ABA content increased during fruit maturation and reached a peak at stage S4 III. The increase was greatly inhibited by the ethylene inhibitor 1-MCP, which also suppressed PpERF3 expression. PpERF3 shared a similar expression profile with PpNCED2/3, encoding a rate-limiting enzyme involved in ABA biosynthesis, during fruit ripening. A yeast one-hybrid assay suggested that the nuclear-localized PpERF3 might bind to the promoters of PpNCED2/3. PpERF3 increased the expression of PpNCED2/3 as shown by dual-luciferase reporters, promoter-GUS assays and transient expression analyses in peach fruit. Collectively, these results suggest that ethylene promotes ABA biosynthesis through PpERF3's regulation of the expression of ABA biosynthesis genes PpNCED2/3.

The distinct ripening processes in the reproductive and non-reproductive parts of the fig syconium are driven by ABA

The common fig bears a unique closed inflorescence structure, the syconium, composed of small individual drupelets that develop from the ovaries, which are enclosed in a succulent receptacle of vegetative origin. The fig ripening process is traditionally classified as climacteric; however, recent studies have suggested that distinct mechanisms exist in its reproductive and non-reproductive parts. We analysed ABA and ethylene production, and expression of ABA-metabolism, ethylene-biosynthesis, MADS-box, NAC, and ethylene response-factor genes in inflorescences and receptacles of on-tree fruit treated with ABA, ethephon, fluridone, and nordihydroguaiaretic acid (NDGA). Exogenous ABA and ethephon accelerated fruit ripening and softening, whereas fluridone and NDGA had the opposite effect, delaying endogenous ABA and ethylene production compared to controls. Expression of the ABA-biosynthesis genes FcNCED2 and FcABA2, ethylene-biosynthesis genes FcACS4, FcACOL, and FcACO2, FcMADS8, 14, 15, FcNAC1, 2, 5, and FcERF9006 was up-regulated by exogenous ABA and ethephon. NDGA down-regulated FcNCED2 and FcABA2, whereas fluridone down-regulated FcABA2; both down-regulated the ethylene-related genes. These results demonstrate the key role of ABA in regulation of ripening by promoting ethylene production, as in the climacteric model plant tomato, especially in the inflorescence. However, increasing accumulation of endogenous ABA until full ripeness and significantly low expression of ethylene-biosynthesis genes in the receptacle suggests non-climacteric, ABA-dependent ripening in the vegetative-originated succulent receptacle part of the fruit.

Transcriptomic analysis of light-dependent anthocyanin accumulation in bicolored cherry fruits

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.

Osmotic Stress and ABA Affect Immune Response and Susceptibility of Grapevine Berries to Gray Mold by Priming Polyamine Accumulation

Abiotic factors inducing osmotic stress can affect plant immunity and resistance against pathogen attack. Although a number of studies have characterized grapevine responses to various forms of biotic and abiotic stresses, the relationships between osmotic stress response and susceptibility of mature berries to Botrytis cinerea still remain unknown. In this study, we investigated the effects of osmotic stress and abscisic acid (ABA) on defense responses of mature grapevine berries before and after B. cinerea infection. We focused on the possible involvement of polyamines in the interaction between osmotic stress response and susceptibility to B. cinerea. We showed that osmotic stress induced by PEG or sucrose, and exogenous ABA induce transient but low defense responses, including weak expression of PR genes and phytoalexin synthesis in mature berries. This was accompanied by an upregulation of NCED2 involved in ABA biosynthesis and a large production of free polyamines. However, osmotic stress followed by B. cinerea infection primed berries for enhanced accumulation of polyamines, but slowed down the defense responses and increased susceptibility to the pathogen. A weak increase of diamine- and polyamine-oxidase activities was also recorded in stressed berries, but declined after pathogen infection. The pretreatment of stressed berries with appropriate inhibitors of diamine- and polyamine-oxidases further increased polyamine level and greatly lowered defense responses, leading to higher susceptibility to B. cinerea. These results suggest that increased polyamine titer through low activation of their oxidative degradation in grape berries may contribute at least in part to the weakening of defense responses and subsequent disease susceptibility.

Exogenous strigolactone interacts with abscisic acid-mediated accumulation of anthocyanins in grapevine berries

Besides signalling to soil organisms, strigolactones (SLs) control above- and below-ground morphology, in particular shoot branching. Furthermore, SLs interact with stress responses, possibly thanks to a crosstalk with the abscisic acid (ABA) signal. In grapevine (Vitis vinifera L.), ABA drives the accumulation of anthocyanins over the ripening season. In this study, we investigated the effects of treatment with a synthetic strigolactone analogue, GR24, on anthocyanin accumulation in grape berries, in the presence or absence of exogenous ABA treatment. Experiments were performed both on severed, incubated berries, and on berries attached to the vine. Furthermore, we analysed the corresponding transcript concentrations of genes involved in anthocyanin biosynthesis, and in ABA biosynthesis, metabolism, and membrane transport. During the experiment time courses, berries showed the expected increase in soluble sugars and anthocyanins. GR24 treatment had no or little effect on anthocyanin accumulation, or on gene expression levels. Exogenous ABA treatment activated soluble sugar and anthocyanin accumulation, and enhanced expression of anthocyanin and ABA biosynthetic genes, and that of genes involved in ABA hydroxylation and membrane transport. Co-treatment of GR24 with ABA delayed anthocyanin accumulation, decreased expression of anthocyanin biosynthetic genes, and negatively affected ABA concentration. GR24 also enhanced the ABA-induced activation of ABA hydroxylase genes, while it down-regulated the ABA-induced activation of ABA transport genes. Our results show that GR24 affects the ABA-induced activation of anthocyanin biosynthesis in this non-climacteric fruit. We discuss possible mechanisms underlying this effect, and the potential role of SLs in ripening of non-ABA-treated berries.

A Multi-Omics Analysis of Glycine max Leaves Reveals Alteration in Flavonoid and Isoflavonoid Metabolism Upon Ethylene and Abscisic Acid Treatment

Phytohormones are central to plant growth and development. Despite the advancement in our knowledge of hormone signaling, downstream targets, and their interactions upon hormones action remain largely fragmented, especially at the protein and metabolite levels. With an aim to get new insight into the effects of two hormones, ethylene (ET) and abscisic acid (ABA), this study utilizes an integrated proteomics and metabolomics approach to investigate their individual and combined (ABA+ET) signaling in soybean leaves. Targeting low-abundance proteins, our previously established protamine sulfate precipitation method was applied, followed by label-free quantification of identified proteins. A total of 4129 unique protein groups including 1083 differentially modulated in one (individual) or other (combined) treatments were discerned. Functional annotation of the identified proteins showed an increased abundance of proteins related to the flavonoid and isoflavonoid biosynthesis and MAPK signaling pathway in response to ET treatment. HPLC analysis showed an accumulation of isoflavones (genistin, daidzein, and genistein) upon ET treatment, in agreement with the proteomics results. A metabolome analysis assigned 79 metabolites and further confirmed the accumulation of flavonoids and isoflavonoids in response to ET. A potential cross-talk between ET and MAPK signaling, leading to the accumulation of flavonoids and isoflavonoids in soybean leaves is suggested.

Abscisic Acid Regulates Anthocyanin Biosynthesis and Gene Expression Associated With Cell Wall Modification in Ripening Bilberry (Vaccinium myrtillus L.) Fruits

Ripening of non-climacteric bilberry (Vaccinium myrtillus L.) fruit is characterized by a high accumulation of health-beneficial anthocyanins. Plant hormone abscisic acid (ABA) and sucrose have been shown to be among the central signaling molecules coordinating non-climacteric fruit ripening and anthocyanin accumulation in some fruits such as strawberry. Our earlier studies have demonstrated an elevation in endogenous ABA level in bilberry fruit at the onset of ripening indicating a role for ABA in the regulation of bilberry fruit ripening. In the present study, we show that the treatment of unripe green bilberry fruits with exogenous ABA significantly promotes anthocyanin biosynthesis and accumulation both in fruits attached and detached to the plant. In addition, ABA biosynthesis inhibitor, fluridone, delayed anthocyanin accumulation in bilberries. Exogenous ABA also induced the expression of several genes involved in cell wall modification in ripening bilberry fruits. Furthermore, silencing of VmNCED1, the key gene in ABA biosynthesis, was accompanied by the down-regulation in the expression of key anthocyanin biosynthetic genes. In contrast, the treatment of unripe green bilberry fruits with exogenous sucrose or glucose did not lead to an enhancement in the anthocyanin accumulation neither in fruits attached to plant nor in post-harvest fruits. Moreover, sugars failed to induce the expression of genes associated in anthocyanin biosynthesis or ABA biosynthesis while could elevate expression of some genes associated with cell wall modification in post-harvest bilberry fruits. Our results demonstrate that ABA plays a major role in the regulation of ripening-related processes such as anthocyanin biosynthesis and cell wall modification in bilberry fruit, whereas sugars seem to have minor regulatory roles in the processes. The results indicate that the regulation of bilberry fruit ripening differs from strawberry that is currently considered as a model of non-climacteric fruit ripening. In this study, we also identified transcription factors, which expression was enhanced by ABA, as potential regulators of ABA-mediated bilberry fruit ripening processes.

Abscisic acid stimulates anthocyanin accumulation in 'Jersey' highbush blueberry fruits during ripening

Non-climacteric blueberry (Vaccinium spp.) fruits accumulate high levels of anthocyanins during ripening, which are a good source of dietary antioxidants. This study examined the effects of exogenous abscisic acid (ABA) application on fruit characteristics and anthocyanin accumulation in a northern highbush blueberry (V. corymbosum 'Jersey') during development. Fruits on shrubs were treated with 1gL^-1 ABA before the initiation of fruit colouration. Application of ABA temporarily increased the level of ABA in the fruits during development. Exogenous ABA had no obvious effect on fruit growth, but stimulated fruit colouration by accelerating the accumulation of individual anthocyanins, mainly malvidin, delphinidin and petunidin glycosides. This is the first report to show that ABA promotes the accumulation of anthocyanins in blueberry fruits. However, exogenous ABA also promoted fruit softening, which is undesirable during harvest and shelf life.

The Influence of Lead on Generation of Signalling Molecules and Accumulation of Flavonoids in Pea Seedlings in Response to Pea Aphid Infestation

The aim of this study was to investigate the effect of an abiotic factor, i.e., lead at various concentrations (low causing a hormesis effect and causing high toxicity effects), on the generation of signalling molecules in pea (Pisum sativum L. cv. Cysterski) seedlings and then during infestation by the pea aphid (Acyrthosiphon pisum Harris). The second objective was to verify whether the presence of lead in pea seedling organs and induction of signalling pathways dependent on the concentration of this metal trigger defense responses to A. pisum. Therefore, the profile of flavonoids and expression levels of genes encoding enzymes of the flavonoid biosynthesis pathway (phenylalanine ammonialyase and chalcone synthase) were determined. A significant accumulation of total salicylic acid (TSA) and abscisic acid (ABA) was recorded in the roots and leaves of pea seedlings growing on lead-supplemented medium and next during infestation by aphids. Increased generation of these phytohormones strongly enhanced the biosynthesis of flavonoids, including a phytoalexin, pisatin. This research provides insights into the cross-talk between the abiotic (lead) and biotic factor (aphid infestation) on the level of the generation of signalling molecules and their role in the induction of flavonoid biosynthesis.

Resveratrol accumulation and its involvement in stilbene synthetic pathway of Chinese wild grapes during berry development using quantitative proteome analysis

Attention has become focused on resveratrol not only because of its role in grapevine fungal resistance but also because of its benefits in human health. This report describes the Chinese wild grapevine Vitis quinquangularis accession Danfeng-2 in relation to the high resveratrol content of its ripe berries. In this study, we used isobaric tags for relative and absolute quantification (iTRAQ) tandem mass spectrometry strategy to quantify and identify proteome changes, resulting in the detection of a total of 3,751 proteins produced under natural conditions. Among the proteins quantified, a total of 578 differentially expressed proteins were detected between Danfeng-2 and Cabernet Sauvignon during berry development. Differentially expressed proteins are involved in secondary metabolism, biotic stress, abiotic stress and transport activity and indicate novel biological processes in Chinese wild grapevine. Eleven proteins involved in phenylpropanoid metabolism and stilbene synthesis were differently expressed between Danfeng-2 and Cabernet Sauvignon at the veraison stage of berry development. These findings suggest that Chinese wild V. quinquangularis accession Danfeng-2 is an extremely important genetic resource for grape breeding and especially for increasing the resveratrol content of European grape cultivars for disease resistance and for improved human nutritional benefits.

Changes in ABA, IAA and JA levels during calyx, fruit and leaves development in cape gooseberry plants (Physalis peruviana L.)

Changes in abscisic acid (ABA), indole-3-acetic acid (IAA) and jasmonic acid (JA) content in developing calyx, fruits and leaves of Physalis peruviana L. plants were analysed. Plant hormones have been widely studied for their roles in the regulation of various aspects related to plant development and, in particular, into their action during development and ripening of fleshly fruits. The obtained evidences suggest that the functions of these hormones are no restricted to a particular development stage, and more than one hormone is involved in controlling various aspects of plant development. Our results will contribute to understand the role of these hormones during growth and development of calyx, fruits and leaves in cape gooseberry plants. This work offers a good, quickly and efficiently protocol to extract and quantify simultaneously ABA, IAA and JA in different tissues of cape gooseberry plants.

Grape hexokinases are involved in the expression regulation of sucrose synthase- and cell wall invertase-encoding genes by glucose and ABA

Hexokinase (HXK, EC 2.7.1.1) is a multifunctional protein that both is involved in catalyzing the first step of glycolysis and plays an important role in sugar signaling. However, the supporting genetic evidence on hexokinases (CsHXKs) from grape (Vitis vinifera L. cv. Cabernet Sauvignon) berries has been lacking. Here, to investigate the role of CsHXK isoforms as glucose (Glc) and abscisic acid (ABA) sensors, we cloned two hexokinase isozymes, CsHXK1 and CsHXK2 with highly conserved genomic structure of nine exons and eight introns. We also found adenosine phosphate binding, substrate recognition and connection sites in their putative proteins. During grape berry development, the expression profiles of two CsHXK isoforms, sucrose synthases (SuSys) and cell wall invertase (CWINV) genes increased concomitantly with high levels of endogenous Glc and ABA. Furthermore, we showed that in wild type grape berry calli (WT), glucose repressed the expression levels of sucrose synthase (SuSy) and cell wall invertase (CWINV) genes, while ABA increased their expression levels. ABA could not only effectively improve the expression levels of SuSy and CWINV, but also block the repression induced by glucose on the expression of both genes. However, after silencing CsHXK1 or CsHXK2 in grape calli, SuSy and CWINV expression were enhanced, and the expressions of the two genes are insensitive in response to Glc treatment. Interestingly, exogenous ABA alone could not or less increase SuSy and CWINV expression in silencing CsHXK1 or CsHXK2 grape calli compared to WT. Meantime, ABA could not block the repression induced by glucose on the expression of SuSy and CWINV in CsHXK1 or CsHXK2 mutants. Therefore, Glc signal transduction depends on the regulation of CsHXK1 or CsHXK2. ABA signal was also disturbed by CsHXK1 or CsHXK2 silencing. The present results provide new insights into the regulatory role of Glc and ABA on the enzymes related to sugar metabolism in grape berry.

Regulation of Banana Phytoene Synthase (MaPSY) Expression, Characterization and Their Modulation under Various Abiotic Stress Conditions

Phytoene synthase (PSY) is a key regulatory enzyme of carotenoid biosynthesis pathway in plants. The present study examines the role of PSY in carotenogenesis and stress management in banana. Germplasm screening of 10 Indian cultivars showed that Nendran (3011.94 μg/100 g dry weight) and Rasthali (105.35 μg/100 g dry weight) contained the highest and lowest amounts of β-carotene, respectively in ripe fruit-pulp. Nendran ripe pulp also showed significantly higher antioxidant activity as compared to Rasthali. Meta-analysis of three banana PSY genes (MaPSY1, MaPSY2, and MaPSY3) was performed to identify their structural features, subcellular, and chromosomal localization in banana genome. The distinct expression patterns of MaPSY1, MaPSY2, and MaPSY3 genes were observed in various tissues, and fruit developmental stages of these two contrasting cultivars, suggesting differential regulation of the banana PSY genes. A positive correlation was observed between the expression of MaPSY1 and β-carotene accumulation in the ripe fruit-peel and pulp of Nendran. The presence of stress responsive cis-regulatory motifs in promoter region of MaPSY genes were correlated with the expression pattern during various stress (abscisic acid, methyl jasmonate, salicylic acid and dark) treatments. The positive modulation of MaPSY1 noticed under abiotic stresses suggested its role in plant physiological functions and defense response. The amino acid sequence analysis of the PSY proteins in contrasting cultivars revealed that all PSY comprises conserved domains related to enzyme activity. Bacterial complementation assay has validated the functional activity of six PSY proteins and among them PSY1 of Nendran (Nen-PSY1) gave the highest activity. These data provide new insights into the regulation of PSY expression in banana by developmental and stress related signals that can be explored in the banana improvement programs.

Omics Approaches for Understanding Grapevine Berry Development: Regulatory Networks Associated with Endogenous Processes and Environmental Responses

Grapevine fruit development is a dynamic process that can be divided into three stages: formation (I), lag (II), and ripening (III), in which physiological and biochemical changes occur, leading to cell differentiation and accumulation of different solutes. These stages can be positively or negatively affected by multiple environmental factors. During the last decade, efforts have been made to understand berry development from a global perspective. Special attention has been paid to transcriptional and metabolic networks associated with the control of grape berry development, and how external factors affect the ripening process. In this review, we focus on the integration of global approaches, including proteomics, metabolomics, and especially transcriptomics, to understand grape berry development. Several aspects will be considered, including seed development and the production of seedless fruits; veraison, at which anthocyanin accumulation begins in the berry skin of colored varieties; and hormonal regulation of berry development and signaling throughout ripening, focusing on the transcriptional regulation of hormone receptors, protein kinases, and genes related to secondary messenger sensing. Finally, berry responses to different environmental factors, including abiotic (temperature, water-related stress and UV-B radiation) and biotic (fungi and viruses) stresses, and how they can significantly modify both, development and composition of vine fruit, will be discussed. Until now, advances have been made due to the application of Omics tools at different molecular levels. However, the potential of these technologies should not be limited to the study of single-level questions; instead, data obtained by these platforms should be integrated to unravel the molecular aspects of grapevine development. Therefore, the current challenge is the generation of new tools that integrate large-scale data to assess new questions in this field, and to support agronomical practices.

Sequence Polymorphisms and Structural Variations among Four Grapevine (Vitis vinifera L.) Cultivars Representing Sardinian Agriculture

The genetic diversity among grapevine (Vitis vinifera L.) cultivars that underlies differences in agronomic performance and wine quality reflects the accumulation of single nucleotide polymorphisms (SNPs) and small indels as well as larger genomic variations. A combination of high throughput sequencing and mapping against the grapevine reference genome allows the creation of comprehensive sequence variation maps. We used next generation sequencing and bioinformatics to generate an inventory of SNPs and small indels in four widely cultivated Sardinian grape cultivars (Bovale sardo, Cannonau, Carignano and Vermentino). More than 3,200,000 SNPs were identified with high statistical confidence. Some of the SNPs caused the appearance of premature stop codons and thus identified putative pseudogenes. The analysis of SNP distribution along chromosomes led to the identification of large genomic regions with uninterrupted series of homozygous SNPs. We used a digital comparative genomic hybridization approach to identify 6526 genomic regions with significant differences in copy number among the four cultivars compared to the reference sequence, including 81 regions shared between all four cultivars and 4953 specific to single cultivars (representing 1.2 and 75.9% of total copy number variation, respectively). Reads mapping at a distance that was not compatible with the insert size were used to identify a dataset of putative large deletions with cultivar Cannonau revealing the highest number. The analysis of genes mapping to these regions provided a list of candidates that may explain some of the phenotypic differences among the Bovale sardo, Cannonau, Carignano and Vermentino cultivars.

The Synthesis and Accumulation of Resveratrol Are Associated with Veraison and Abscisic Acid Concentration in Beihong (Vitis vinifera × Vitis amurensis) Berry Skin

Resveratrols are polyphenolic secondary metabolites that can benefit human health, and only occur in a few plant families including Vitaceae. It has been reported that abscisic acid (ABA) can induce veraison (the onset of grape berry ripening) and may induce the accumulation of resveratrol in berry skin. However, the relationships between ABA, veraison, the accumulation of anthocyanins and the accumulation of resveratrol in the berry are poorly understood. This study attempted to answer this question through an investigation of the effect of applied ABA and fluridone (a synthetic inhibitor of ABA) on the biosynthesis and accumulation of ABA, anthocyanin, and resveratrol in Beihong (Vitis vinifera × Vitis amurensis) berry skin. Under natural conditions, resveratrol concentration was very low before 91 DAA (days after anthesis), i.e., 2 weeks after veraison, however, it increased sharply from this point to 126 DAA (maturity). Exogenous ABA applications all resulted in an increase in berry skin ABA and anthocyanin concentration, irrespective of the developmental stage at which the treatment occurred (20 and 10 days pre-veraison, veraison or 7 days post-veraison), thereby advancing veraison. In contrast, resveratrol concentration increased only when ABA was applied at 10 days pre-veraison or at veraison. As a result, the accumulation of resveratrol was associated with veraison in grape berry skin and this accumulation, together with that of anthocyanins, was associated with ABA concentration. The response of resveratrol biosynthesis in the berry skin to manipulation of ABA varied during berry development and was less sensitive to ABA than the response of anthocyanin biosynthesis.

Long-term effects of abscisic acid (ABA) on the grape berry phenylpropanoid pathway: Gene expression and metabolite content

ABA has been proposed as the main signal triggering the onset of the ripening process in grapes, and modulating the secondary metabolism in grape berry skins. To determine the effect of ABA on secondary metabolism in berries, clusters of Carménère were sprayed with 0 μLL(-1) ABA; 50 μLL(-1) ABA and 100 μLL(-1) ABA during pre-véraison, and the gene expression of the transcription factors and enzymes of the phenylpropanoid pathway were assessed from véraison to 70 days after véraison (DAV). Additionally, flavonols, tannins and anthocyanins were assessed from véraison until harvest (110 DAV). ABA accelerated sugar and anthocyanin accumulation at véraison. The grape transcript abundance of VvDFR, VvANS, VvUFGT and VvMybA1, all peaking around véraison mimicked the concentration of ABA throughout the season. The highest anthocyanin concentration occurred 35 DAV for all treatments, but higher pigment concentrations were observed in ABA-treated berries at véraison and from 60 to 70 DAV to harvest. VvPAL was also increased by treatment at the higher concentration of ABA from véraison to 40 DAV. Regarding flavanol synthesis, VvLAR2 and VvMyb4A decreased from véraison until 40 DAV and then increased again until 70 DAV. Compared to the control, both ABA treatments resulted in a less-than-proportional reduction of the expression of both genes compared to the control and, after 40 DAV, in a more-than-proportional increase compared to the control, suggesting a long-term effect of the pre-véraison ABA spray on the berries. A concomitant increase in flavanols was observed in berries after 40 DAV, and this occurred at a higher extent in berries treated with the highest ABA concentration.

Proteomic Response and Quality Maintenance in Postharvest Fruit of Strawberry (Fragaria × ananassa) to Exogenous Cytokinin

The limitations in current understanding of the molecular mechanisms underlying fruit response to the application of plant growth regulators have increasingly become major challenges in improvement of crop quality. This study aimed to evaluate the response of strawberry to the preharvest application of exogenous cytokinin known as forchlorfenuron (CPPU). Postharvest internal and physiological quality attributes were characterized following storage under different conditions. Hierarchical clustering analysis via a label-free proteomic quantitative approach identified a total of 124 proteins in strawberries across all treatments. The expression profiles of both proteins and genes spanned the ranged role of cytokinin involved in primary and secondary metabolism, stress response, and so on. Eighty-eight proteins and fifty-six proteins were significantly regulated immediately at harvest and after storage, respectively. In general, the glycolysis in strawberry was only regulated by CPPU before storage; in addition to the accelerated photosynthesis and acid metabolism, CPPU application maintained higher capacity of resistance in strawberry to stress stimuli after storage, in comparison to control. Nevertheless, the volatile biosynthesis in strawberry has been suppressed by exogenous CPPU. Novel cytokinin response proteins and processes were identified in addition to the main transcriptomic expression to gain insights into the phytohormone control of fruit postharvest quality.

Abscisic acid transcriptomic signaling varies with grapevine organ

BACKGROUND

Abscisic acid (ABA) regulates various developmental processes and stress responses over both short (i.e. hours or days) and longer (i.e. months or seasons) time frames. To elucidate the transcriptional regulation of early responses of grapevine (Vitis vinifera) responding to ABA, different organs of grape (berries, shoot tips, leaves, roots and cell cultures) were treated with 10 μM (S)-(+)-ABA for 2 h. NimbleGen whole genome microarrays of Vitis vinifera were used to determine the effects of ABA on organ-specific mRNA expression patterns.

RESULTS

Transcriptomic analysis revealed 839 genes whose transcript abundances varied significantly in a specific organ in response to ABA treatment. No single gene exhibited the same changes in transcript abundance across all organs in response to ABA. The biochemical pathways affected by ABA were identified using the Cytoscape program with the BiNGO plug-in software. The results indicated that these 839 genes were involved in several biological processes such as flavonoid metabolism, response to reactive oxygen species, response to light, and response to temperature stimulus. ABA affected ion and water transporters, particularly in the root. The protein amino acid phosphorylation process was significantly overrepresented in shoot tips and roots treated with ABA. ABA affected mRNA abundance of genes (CYP707As, UGTs, and PP2Cs) associated with ABA degradation, conjugation, and the ABA signaling pathway. ABA also significantly affected the expression of several transcription factors (e.g. AP2/ERF, MYC/MYB, and bZIP/AREB). The greatest number of significantly differentially expressed genes was observed in the roots followed by cell cultures, leaves, berries, and shoot tips, respectively. Each organ had a unique set of gene responses to ABA.

CONCLUSIONS

This study examined the short-term effects of ABA on different organs of grapevine. The responses of each organ were unique indicating that ABA signaling varies with the organ. Understanding the ABA responses in an organ-specific manner is crucial to fully understand hormone action and plant responses to water deficit.