Fruit sugar hub: gene regulatory network associated with soluble solids content (SSC) in Prunus persica.

Chilean peach growers have achieved worldwide recognition for their high-quality fruit products. Among the main factors influencing peach fruit quality, sweetness is pivotal for maintaining the market's competitiveness. Numerous studies have been conducted in different peach-segregating populations to unravel SSC regulation. However, different cultivars may also have distinct genetic conformation, and other factors, such as environmental conditions, can significantly impact SSC. Using a transcriptomic approach with a gene co-expression network analysis, we aimed to identify the regulatory mechanism that controls the sugar accumulation process in an 'O × N' peach population. This population was previously studied through genomic analysis, associating LG5 with the genetic control of the SSC trait. The results obtained in this study allowed us to identify 91 differentially expressed genes located on chromosome 5 of the peach genome as putative new regulators of sugar accumulation in peach, together with a regulatory network that involves genes directly associated with sugar transport (PpSWEET15), cellulose biosynthesis (PpCSLG2), flavonoid biosynthesis (PpPAL1), pectin modifications (PpPG, PpPL and PpPMEi), expansins (PpEXPA1 and PpEXPA8) and several transcription factors (PpC3H67, PpHB7, PpRVE1 and PpCBF4) involved with the SSC phenotype. These results contribute to a better understanding of the genetic control of the SSC trait for future breeding programs in peaches.

Phenotyping 172 strawberry genotypes for water soaking reveals a close relationship with skin water permeance.

Water soaking is a commercially important disorder of field-grown strawberries that is exacerbated by surface wetness and high humidity. The objective was to establish the effect of genotype on susceptibility to water soaking. Three greenhouse-grown model 'collections' were used comprising a total of 172 different genotypes: (1) a segregating F2 population, (2) a collection of strawberry cultivars and breeding clones, and (3) a collection of wild Fragaria species. A standardized immersion assay was used to induce water soaking. Potential relationships between water soaking and water uptake characteristics, depth of the achene depressions, fruit firmness, cuticle mass and strain relaxation and microcracking were investigated. Further, the effect of downregulating the polygalacturonase genes (FaPG1 and FaPG2) on the susceptibility to water soaking was investigated. The collection of wild species was most susceptible to water soaking. This was followed by the collection of cultivars and breeding clones, and by the F2 population. Susceptibility to water soaking was strongly correlated with water uptake rate (mass of water, per fruit, per time). For the pooled dataset of 172 genotypes, 46% of the variability in water soaking was accounted for by the permeance of the skin to osmotic water uptake. Susceptibility to water soaking was not, or was only poorly correlated with measurements of fruit surface area or of the osmotic potential of the expressed fruit juice. The only exceptions were the wild Fragaria species which were highly variable in fruit size and also in fruit osmotic potential. For genotypes from the F2 and the wild species collections, firmer fruit were less susceptible to water soaking than softer fruit. There were no relationships between fruit firmness and susceptibility to water soaking in transgenic plants in which FaPG1 and FaPG2 were down-regulated. Susceptibility to water soaking was not related to cuticle mass per unit fruit surface area, nor to strain relaxation of the cuticle upon isolation, nor to achene position. In summary, strawberry's susceptibility to water soaking has a significant genetic component and is closely and consistently related to the skin's permeance to osmotic water uptake.

Comparative analysis of physical traits, mineral compositions, antioxidant contents, and metabolite profiles in five cherry tomato cultivars.

Cherry tomatoes (Solanum lycopersicum var. cerasiforme) are cultivated and consumed worldwide. While numerous cultivars have been bred to enhance fruit quality, few studies have comprehensively evaluated the fruit quality of cherry tomato cultivars. In this study, we assessed fruits of five cherry tomato cultivars (Qianxi, Fengjingling, Fushan88, Yanyu, and Qiyu) at the red ripe stage through detailed analysis of their physical traits, mineral compositions, antioxidant contents, and metabolite profiles. Significant variations were observed among the cultivars in terms of fruit size, shape, firmness, weight, glossiness, and sepal length, with each cultivar displaying unique attributes. Mineral analysis revealed distinct patterns of essential and trace element accumulation, with notable differences in calcium, sodium, manganese, and selenium concentrations. Fenjingling was identified as a selenium enriched cultivar. Analysis of antioxidant contents highlighted Yanyu as particularly rich in vitamin C and Fenjingling as having elevated antioxidant enzyme activities. Metabolomics analysis identified a total number of 3,396 annotated metabolites, and the five cultivars showed distinct metabolomics profiles. Amino acid analysis showed Fushan88 to possess a superior profile, while sweetness and tartness assessments indicated that Yanyu exhibited higher total soluble solids (TSS) and acidity. Notably, red cherry tomato cultivars (Fushan88, Yanyu, and Qiyu) accumulated significantly higher levels of eugenol and α-tomatine, compounds associated with undesirable flavors, compared to pink cultivars (Qianxi and Fengjingling). Taken together, our results provide novel insights into the physical traits, nutritional value, and flavor-associated metabolites of cherry tomatoes, offering knowledge that could be implemented for the breeding, cultivation, and marketing of cherry tomato cultivars.

Metabolites profiling of Sapota fruit pulp via a multiplex approach of gas and ultra performance liquid chromatography/mass spectroscopy in relation to its lipase inhibition effect.

Background: Sapota, Manilkara zapota L., are tasty, juicy, and nutrient-rich fruits, and likewise used for several medicinal uses. Methods: The current study represents an integrated metabolites profiling of sapota fruits pulp via GC/MS and UPLC/MS, alongside assessment of antioxidant capacity, pancreatic lipase (PL), and α-glucosidase enzymes inhibitory effects. Results: GC/MS analysis of silylated primary polar metabolites led to the identification of 68 compounds belonging to sugars (74%), sugar acids (18.27%), and sugar alcohols (7%) mediating the fruit sweetness. Headspace SPME-GC/MS analysis led to the detection of 17 volatile compounds belonging to nitrogenous compounds (72%), ethers (7.8%), terpenes (7.6%), and aldehydes (5.8%). Non-polar metabolites profiling by HR-UPLC/MS/MS-based Global Natural Products Social (GNPS) molecular networking led to the assignment of 31 peaks, with several novel sphingolipids and fatty acyl amides reported for the first time. Total phenolic content was estimated at 6.79 ± 0.12 mg gallic acid equivalent/gram extract (GAE/g extract), but no flavonoids were detected. The antioxidant capacities of fruit were at 1.62 ± 0.2, 1.49 ± 0.11, and 3.58 ± 0.14 mg Trolox equivalent/gram extract (TE/g extract) via DPPH, ABTS, and FRAP assays, respectively. In vitro enzyme inhibition assays revealed a considerable pancreatic lipase inhibition effect (IC50 = 2.2 ± 0.25 mg/mL), whereas no inhibitory effect towards α-glucosidase enzyme was detected. This study provides better insight into sapota fruit's flavor, nutritional, and secondary metabolites composition mediating for its sensory and health attributes.

Auxin responsive factor MdARF17 promotes ethylene synthesis in apple fruits by activating MdERF003 expression.

KEY MESSAGE: Auxin (AUX) promotion of apple fruit ripening is ethylene-dependent, and AUX-MdARF17-MdERF003 plays a role in AUX-promoted ethylene synthesis in apple. Phytohormones play important roles in plant growth and fleshy fruit ripening, and the phytohormone auxin (AUX) can either promote or inhibit the ripening of fleshy fruits. Although AUX can influence ethylene (ETH) synthesis in apple (Malus domestica) fruits by affecting ETH system II, this mechanism remains to be explored. Here, we identified an ETH response factor (ERF) family transcription factor, MdERF003, whose expression could be activated by naphthalene acetic acid. The transient silencing of MdERF003 inhibited ETH synthesis in fruits, and MdERF003 could bind to the MdACS1 promoter. To explore the upstream target genes of MdERF003, we screened the MdARF family members by yeast one-hybrid assays of the MdERF003 promoter, and found that the transcription factor MdARF17, which showed AUX-promoted expression, could bind to the MdERF003 promoter and promote its expression. Finally, we silenced MdERF003 in apple fruits overexpressing MdARF17 and found that MdERF003 plays a role in MdARF17-promoted ETH synthesis in apple. Thus, AUX-MdARF17-MdERF003 promotes ETH synthesis in apple fruits.

Enrichment of Fruit Peels' Nutritional Value by Solid-State Fermentation with Aspergillus ibericus and Rhizopus oryzae.

The fruit processing industry is responsible for disposing of huge amounts of byproducts, especially fruit peels (FPs), which are often discarded in landfills. Using FPs in biotechnological processes contributes to a circular economy, reducing the environmental burden of FPs and increasing the revenue of the fruit processing industry. This study was focused on upgrading the nutritional value of orange (OPs) and banana (BPs) peels by solid-state fermentation (SSF) with filamentous fungi. SSF factors (moisture, fermentation time, inoculum size, ammonium sulfate (AS), and corn steep liquor (CSL)) and fungi species (Aspergillus ibericus and Rhizopus oryzae) were studied by a variable screening Plackett-Burman design. Both fungi grew on untreated FPs, increasing their protein content and antioxidant activity. Moisture, AS, and CSL were further studied by a Box-Behnken design with A. ibericus. Fermented OPs at 70% moisture and 0.005 g/g AS increased their protein content by 200%, whereas BPs at 70% moisture and 0.005 g/g CSL increased by 123%. Fermented peels were enriched in protein, fiber, and minerals, with a low content of carbohydrates and soluble sugars. Fermented OPs and BPs showed higher antioxidant activity than unfermented peels. The SSF of these FPs is an innovative approach that contributes to obtaining rich nutrient-fermented peels for food.

Search for Expression Marker Genes That Reflect the Physiological Conditions of Blossom End Enlargement Occurrence in Cucumber.

Blossom end enlargement (BEE) is a postharvest deformation that may be related to the influx of photosynthetic assimilates before harvest. To elucidate the mechanism by which BEE occurs, expression marker genes that indicate the physiological condition of BEE-symptomatic fruit are necessary. First, we discovered that preharvest treatment with a synthetic cytokinin, N-(2-Chloro-4-pyridyl)-N'-phenylurea (CPPU), promoted fruit growth and suppressed BEE occurrence. This suggests that excessive assimilate influx is not a main cause of BEE occurrence. Subsequently, the expression levels of seven sugar-starvation marker genes, CsSEF1, AS, CsFDI1, CsPID, CsFUL1, CsETR1, and CsERF1B, were compared among symptomatic and asymptomatic fruits, combined with and without CPPU treatment. Only CsSEF1 showed a higher expression level in asymptomatic fruits than in symptomatic fruits, regardless of CPPU treatment. This was then tested using fruits stored via the modified-atmosphere packaging technique, which resulted in a lower occurrence of BEE, and the asymptomatic fruits showed a higher CsSEF1 expression level than symptomatic fruits, regardless of the packaging method. CsSEF1 codes a CCCH-type zinc finger protein, and an increase in the expression of CsSEF1 was correlated with a decrease in the fruit respiration rate. Thus, CsSEF1 may be usable as a BEE expression marker gene.

Genome-Wide Identification, Expression, and Interaction Analysis of the Auxin Response Factor and AUX/IAA Gene Families in Vaccinium bracteatum.

BACKGROUND: Auxin, a plant hormone, plays diverse roles in the modulation of plant growth and development. The transport and signal transduction of auxin are regulated by various factors involved in shaping plant morphology and responding to external environmental conditions. The auxin signal transduction is primarily governed by the following two gene families: the auxin response factor (ARF) and auxin/indole-3-acetic acid (AUX/IAA). However, a comprehensive genomic analysis involving the expression profiles, structures, and functional features of the ARF and AUX/IAA gene families in Vaccinium bracteatum has not been carried out to date. RESULTS: Through the acquisition of genomic and expression data, coupled with an analysis using online tools, two gene family members were identified. This groundwork provides a distinguishing characterization of the chosen gene families in terms of expression, interaction, and response in the growth and development of plant fruits. In our genome-wide search of the VaARF and VaIAA genes in Vaccinium bracteatum, we identified 26 VaARF and 17 VaIAA genes. We analyzed the sequence and structural characteristics of these VaARF and VaIAA genes. We found that 26 VaARF and 17 VaIAA genes were divided into six subfamilies. Based on protein interaction predictions, VaIAA1 and VaIAA20 were designated core members of VaIAA gene families. Moreover, an analysis of expression patterns showed that 14 ARF genes and 12 IAA genes exhibited significantly varied expressions during fruit development. CONCLUSION: Two key genes, namely, VaIAA1 and VaIAA20, belonging to a gene family, play a potentially crucial role in fruit development through 26 VaARF-IAAs. This study provides a valuable reference for investigating the molecular mechanism of fruit development and lays the foundation for further research on Vaccinium bracteatum.

How Nano-ZnO Affect Tomato Fruits (Solanum lycopersicum L.)? Analysis of Selected Fruit Parameters.

Tomato (Solanum lycopersicum L.), as one of the most valuable horticulture crops, was chosen to investigate the effect of nanoparticles (NPs) in the form of nano-ZnO combined with conventional fertilizer on the quality of tomato fruits, including their antioxidant potential (total antioxidant activity, lycopene and ß-carotene content), sugars content and allergenic potential (profilin and Bet v 1 content). Nano-ZnO was implemented during plant cultivation, applied by foliar spraying or directly via soil, at three different concentrations (50, 150 and 250 mg/L). The obtained results suggest that the usage of NPs during tomato plant cultivation had minor impacts on parameters such as total antioxidant activity or the content of selected allergens. Even though the total antioxidant activity was not affected by nano-ZnO, the malondialdehyde activity (MDA) content was notably decreased in fruits under nano-ZnO treatment. The content of lycopene and ß-carotene was significantly affected by the use of nano-ZnO. Moreover, the usage of nano-ZnO significantly increased the total sugar content in fruits treated with nanoparticles via foliar spraying. Based on the obtained results, it can be stated that nano-ZnO, regardless of the method of application, significantly affected tomato fruits which can be beneficial for fruit production.

Integrated transcriptome and targeted metabolome analyses provide insights into flavonoid biosynthesis in kiwifruit (Actinidia chinensis).

So far, a variety of metabolite components of kiwifruit have been elucidated. However, the identification and analysis of flavonoids in different tissues of kiwifruit are rarely carried out. In this study, we performed transcriptome and metabolome analyses of roots (Gkf_R), stems (Gkf_T), leaves (Gkf_L), and fruits (Gkf_F) to provide insights into the differential accumulation and regulation mechanisms of flavonoids in kiwifruit. Results showed that a total of 301 flavonoids were identified, in four tissues with different accumulation trends, and a large proportion of flavonoids had high accumulation in Gkf_L and Gkf_R. A total of 84 genes have been identified involved in the flavonoid biosynthesis pathway, and the expression levels of five LAR, two DFR, and one HCT were significantly correlated with the accumulation of 16 flavonoids and co-localized in the flavonoid biosynthesis pathway. In addition, a total of 2362 transcription factor genes were identified, mainly MYBs, bHLHs, ERFs, bZIPs and WRKYs, among which the expression level of bHLH74, RAP2.3L/4L/10L, MYB1R1, and WRKY33 were significantly correlated with 25, 56, 43, and 24 kinds of flavonoids. Our research will enrich the metabolomic data and provide useful information for the directed genetic improvement and application in the pharmaceutical industry of kiwifruit.

Functional analysis of two caffeoyl-coenzyme 3 a-o-methyltransferase involved in pear lignin metabolism.

Caffeoyl-coenzyme 3 A-O-methyltransferase (CCoAOMT) plays a crucial role in the lignin synthesis in many higher plants. In this study, nine PbCCoAOMT genes in total were identified from pear, and classified into six categories. We treated pear fruits with hormones abscisic acid (ABA) and methyl jasmonate (MeJA) and salicylic acid (SA) and observed differential expression levels of these genes. Through qRT-PCR, we also preliminarily identified candidate PbCCoAOMT gene, potentially involved in lignin synthesis in pear fruits. Additionally, the overexpression of PbCCoAOMT1/2 in Arabidopsis and pear fruits increased in lignin content. Enzymatic assays showed that recombinant PbCCoAOMT1/2 proteins have similar enzymatic activity in vitro. The Y1H (Yeast one-hybrid) and dual luciferase (dual-LUC) experiments demonstrated that PbMYB25 can bind to the AC elements in the promoter region of the PbCCoAOMT1 gene. Our findings suggested that the PbCCoAOMT1 and PbCCoAOMT2 genes may contribute to the synthesis of lignin and provide insights into the mechanism of lignin biosynthesis and stone cell development in pear fruits.

Metabolomic profiling analysis reveals the benefits of ginseng berry intake on mitochondrial function and glucose metabolism in the liver of obese mice.

INTRODUCTION: Ginseng berry (GB) has previously been demonstrated to improve systemic insulin resistance and regulate hepatic glucose metabolism and steatosis in mice with diet-induced obesity (DIO). OBJECTIVES: In this study, the role of GB in metabolism was assessed using metabolomics analysis on the total liver metabolites of DIO mice. METHODS: Metabolomic profiling was performed using capillary electrophoresis time-of-flight mass spectrometry (CE-TOF/MS) of liver tissue from mice on a 12-wk normal chow diet (NC), high-fat diet (HFD), and HFD supplemented with 0.1% GB (HFD + GB). The detected metabolites, its pathways, and functions were analyzed through partial least square discriminant analysis (PLS-DA), the small molecular pathway database (SMPDB), and MetaboAnalyst 5.0. RESULTS: The liver metabolite profiles of NC, HFD, and GB-fed mice (HFD + GB) were highly compartmentalized. Metabolites involved in major liver functions, such as mitochondrial function, gluconeogenesis/glycolysis, fatty acid metabolism, and primary bile acid biosynthesis, showed differences after GB intake. The metabolites that showed significant correlations with fasting blood glucose (FBG), insulin, and homeostatic model assessment for insulin resistance (HOMA-IR) were highly associated with mitochondrial membrane function, energy homeostasis, and glucose metabolism. Ginseng berry intake increased the levels of metabolites involved in mitochondrial membrane function, decreased the levels of metabolites related to glucose metabolism, and was highly correlated with metabolic phenotypes. CONCLUSION: This study demonstrated that long-term intake of GB changed the metabolite of hepatosteatotic livers in DIO mice, normalizing global liver metabolites involved in mitochondrial function and glucose metabolism and indicating the potential mechanism of GB in ameliorating hyperglycemia in DIO mice.

Comprehensive analysis of transcriptomics and metabolomics provides insights into the mechanism by plant growth regulators affect the quality of jujube (Ziziphus jujuba Mill.) fruit.

A comprehensively analysis of the transcriptomics and metabolomics was conducted to investigate the mechanism of plant growth regulators on the quality of jujube fruit. After the application of plant growth regulators, a total of 3097 differentially expressed genes (DEGs) were identified, which were mainly annotated in 123 pathways such as flavonoid biosynthesis, metabolism of alanine, aspartate, and glutamate. In addition, 1091 differential expressed metabolites (DEMs), including 519 up-regulated and 572 down-regulated metabolites, were significantly altered after application of plant growth regulators. DEGs and DEMs simultaneously annotated 69 metabolic pathways, including biosynthesis of phenylpropane, flavonoid, starch and sucrose. The key genes in flavonoid biosynthesis pathway were revealed, which may play an important role in plant growth regulator regulation quality of jujube fruit. Besides, the application of plant growth regulator during the jujube flowering period increased the contents of gibberellin and indole-3-acetic acid in leaves, and decreased the contents of abscisic acid. The results may help to reveal the metabolic network and molecular mechanism of plant growth regulators in jujube fruit.

A new raspberry ketone synthesis gene RinPKS4 identified in Rubus idaeus L. by transcriptome analysis.

Raspberry ketone accounts for the characteristic aroma of the raspberry fruit. In order to explore the genes involved in raspberry ketone synthesis, the transcriptome in fruit tissues of two red raspberry varieties "Polka" and "Orange legend", were sequenced and 24213 single genes were obtained. As the red raspberry fruit ripening, genes involved in flavonoid and anthocyanin synthesis were up-regulated, while those associated with lignin synthesis were down-regulated. A gene (RinPKS4) highly related to raspberry ketone synthesis was identified by transcriptome analysis, and RinPKS4 gene was over-expressed in raspberry in order to further understand the function of RinPKS4 gene in raspberry ketone synthesis. The results showed that the gene expression level of RinPKS4 in the leaf tissues of a transgenic lines increased by about 4-fold and the content of raspberry ketone increased by 42.64% compared with the wide type. This study lays a theoretical foundation for further study on the synthesis and regulation of raspberry ketone in red raspberry.

Insight into the changes in active metabolite profiles of noni (Morinda citrifolia L.) fruit subjected to different drying treatments.

Noni fruit is renowned for its abundance of bioactive compounds. Drying is an important method for processing functional products derived from noni. However, limited information exists on how drying methods affect the active metabolite profiles of noni fruit. This study investigated the impact of four common drying methods, including hot-air drying (HAD), vacuum freeze drying (VFD), microwave drying (MWD), and far infrared drying (FID), on the physicochemical indexes, bioactive components, and functional properties of dried noni fruit slices using targeted and untargeted metabonomics analysis. The results showed significant variations in appearance, water migration, and microstructure of dried noni fruit slices subjected to the four drying methods. VFD treatment yielded better dried noni fruit products when compared to other drying methods. The superiority of VFD treatment was due to its uniform stratification, reduced collapse, better retention of bioactive components and antioxidants, and higher enzyme inhibitory rates. These findings suggest that VFD method is ideal for obtaining premium bioactive profiles and maintaining the biological activity of noni fruit.

Unveiling the regulatory role of DzAGL6-1 in carotenoid biosynthesis during durian (Durio zibethinus) fruit development.

KEY MESSAGE: Approximately 119 MADS-box genes have been identified in durian. Moreover, DzAGL6-1 primarily expressed during fruit development, activates the DzPSY promoter. Transient expression of DzAGL6-1 in tomatoes influences carotenoid production. MADS-box transcription factors play a crucial role in regulating plant biological processes, including fruit ripening and associated events. This study aimed to comprehend the mechanisms involved in durian fruit development and ripening and carotenoid production by conducting a genome-wide analysis of MADS-box proteins in durian (Durio zibethinus L.), an economically important fruit in Southeast Asia. A total of 119 durian MADS-box proteins were identified from the genome of the 'Musang King' cultivar. Based on the phylogenetic analysis, the proteins were classified into types I and II, which exhibited similar conserved motif compositions. Notably, only 16 durian MADS-box genes exhibited fruit-specific expression patterns. Among these genes, DzAGL6-1 was predominantly expressed during fruit development, a stage at which carotenoid biosynthesis is activated. Transient expression of DzAGL6-1 in tomato fruit increased the transcript level of the carotenoid biosynthetic gene phytoene synthase (PSY) and the ß-carotene content. Furthermore, DzAGL6-1 activated the promoter activity of DzPSY, as demonstrated by a dual-luciferase assay. These findings provide insights into the role of MADS-box transcription factors in regulating carotenoid biosynthesis during durian fruit development.

Intra-canopy LED lighting outperformed top LED lighting in improving tomato yield and expression of the genes responsible for lycopene, phytoene and vitamin C synthesis.

Greenhouses located at high latitudes and in cloudy areas often experience a low quality and quantity of light, especially during autumn and winter. This low daily light integral (DLI) reduces production rate, quality, and nutritional value of many crops. This study was conducted on Sakhiya RZ F1 tomato plants to evaluate the impact of LED lights on the growth and nutritional value of tomatoes in a greenhouse with low daily light due to cloudy weather. The treatments included LED growth lights in three modes: top lighting, intra-canopy lighting, and combined top and intra-canopy lighting. The results showed that although the combined top and intra-canopy lighting reached the maximum increase in tomato yield, exposure to intra-canopy LED lighting alone outperformed in tomato fruit yield increase (28.46%) than exposure to top LED lighting alone (12.12%) when compared to no supplemental lighting during the entire production year. Intra-canopy exposure demonstrated the highest increase in tomato lycopene (31.3%), while top and intra-canopy lighting exhibited the highest increase in vitamin C content (123.4%) compared to the control. The LED light treatment also had a very positive effect on the expression of genes responsible for metabolic cycles, including Psy1, LCY-ß, and VTC2 genes, which had collinearity with the increase in tomato fruit production.

Sorbitol metabolism plays a key role in the differential accumulation of sugar in two plum cultivars.

Sugar is vital for plant growth and determines fruit quality via its content and composition. This study explores the differential sugar accumulation in two plum varieties, 'Fengtangli (FTL)' and 'Siyueli (SYL)'. The result showed that 'FTL' fruit displayed higher soluble solids and sugar content at various development stages. Metabolomic analysis indicated increased sorbitol in 'FTL', linked to elevated sorbitol-6-phosphate-dehydrogenase (S6PDH) activity. Transcriptome analysis identified a key gene for sorbitol synthesis, PsS6PDH4, which was significantly higher expressed in 'FTL' than in 'SYL'. The function of the PsS6PDH4 gene was verified in strawberry, apple, and plum fruits using transient overexpression and virus-induced gene silencing techniques. The results showed that overexpression of the PsS6PDH4 gene in strawberry, apple, and plum fruits promoted the accumulation of soluble solids content and sorbitol, while inhibition of the gene reduced soluble solids content and sorbitol content. Meanwhile, analysis of the relationship between PsS6PDH4 gene expression, sorbitol, and soluble solids content in four different plum varieties revealed a significant correlation between PsS6PDH4 gene expression and soluble solids content as well as sorbitol content. This research discovered PsS6PDH4 as a crucial regulator of sugar metabolism in plum, with potential applications in improving fruit sweetness and nutritional value in various fruit species. Understanding these molecular pathways can lead to innovative approaches for enhancing fruit quality, benefiting sustainable agriculture and consumer preferences in the global fruit industry.

Fruit-In-Sight: A deep learning-based framework for secondary metabolite class prediction using fruit and leaf images.

Fruits produce a wide variety of secondary metabolites of great economic value. Analytical measurement of the metabolites is tedious, time-consuming, and expensive. Additionally, metabolite concentrations vary greatly from tree to tree, making it difficult to choose trees for fruit collection. The current study tested whether deep learning-based models can be developed using fruit and leaf images alone to predict a metabolite's concentration class (high or low). We collected fruits and leaves (n = 1045) from neem trees grown in the wild across 0.6 million sq km, imaged them, and measured concentration of five metabolites (azadirachtin, deacetyl-salannin, salannin, nimbin and nimbolide) using high-performance liquid chromatography. We used the data to train deep learning models for metabolite class prediction. The best model out of the seven tested (YOLOv5, GoogLeNet, InceptionNet, EfficientNet_B0, Resnext_50, Resnet18, and SqueezeNet) provided a validation F1 score of 0.93 and a test F1 score of 0.88. The sensitivity and specificity of the fruit model alone in the test set were 83.52 ± 6.19 and 82.35 ± 5.96, and 79.40 ± 8.50 and 85.64 ± 6.21, for the low and the high classes, respectively. The sensitivity was further boosted to 92.67± 5.25 for the low class and 88.11 ± 9.17 for the high class, and the specificity to 100% for both classes, using a multi-analyte framework. We incorporated the multi-analyte model in an Android mobile App Fruit-In-Sight that uses fruit and leaf images to decide whether to 'pick' or 'not pick' the fruits from a specific tree based on the metabolite concentration class. Our study provides evidence that images of fruits and leaves alone can predict the concentration class of a secondary metabolite without using expensive laboratory equipment and cumbersome analytical procedures, thus simplifying the process of choosing the right tree for fruit collection.

Microalgae-based biofertilizer improves fruit yield and controls greenhouse gas emissions in a hawthorn orchard.

Raising attentions have focused on how to alleviate greenhouse gas (GHG) emissions from orchard system while simultaneously increase fruit production. Microalgae-based biofertilizer represents a promising resource for improving soil fertility and higher productivity. However, the effects of microalgae application more especially live microalgae on GHG emissions are understudied. In this study, fruit yield and quality, GHG emissions, as well as soil organic carbon and nitrogen fractions were examined in a hawthorn orchard, under the effects of live microalgae-based biofertilizer applied at three doses and two modes. Compared with conventional fertilization, microalgae improved hawthorn yield by 15.7%-29.6% with a maximal increment at medium dose by root application, and significantly increased soluble and reducing sugars contents at high dose. While microalgae did not increase GHG emissions except for nitrous oxide at high dose by root application, instead it significantly increased methane uptake by 1.5-2.3 times in root application. In addition, microalgae showed an increasing trend in soil organic carbon content, and significantly increased the contents of soil dissolved organic carbon and microbial biomass carbon, as well as soil ammonium nitrogen and dissolved organic nitrogen at medium dose with root application. Overall, the results indicated that the live microalgae could be used as a green biofertilizer for improving fruit yield without increasing GHG emissions intensity and the comprehensive greenhouse effect, in particular at medium dose with root application. We presume that if lowering chemical fertilizer rates, application of the live microalgae-based biofertilizer may help to reduce nitrous oxide emissions without compromising fruit yield and quality.