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Anthocyanins are important compounds for fruit quality and nutrition. The R2R3 MYB transcription factor PpMYB10.1 is known to be critical for regulating anthocyanin accumulation in peach. However, regulatory factors upstream of PpMYB10.1which control temperature-dependent, cultivar-contrasted and tissue-specific anthocyanin accumulation remain to be determined. In this study, differential anthocyanin accumulation in the outer flesh near the peel (OF) of peach [Prunus persica(L.) Batsch] was observed between cultivars ‘Zhonghuashoutao’ and ‘Dongxuemi’, as well as among different storage temperatures and different fruit tissues of ‘Zhonghuashoutao’. By cross-comparisons of RNA-Seq data of samples with differential anthocyanin accumulation, transcription factor genes PpBBX32and PpZAT5were identified. These were functionally characterized as two positive regulators for anthocyanin accumulation via transient expression and genetic transformation. Various interaction assays revealed that both PpBBX32 and PpZAT5 can directly activate the PpMYB10.1promoter and meanwhile interact at protein level as a PpZAT5-PpBBX32-PpMYB10.1 complex. Furthermore, the results of in silicoanalysis and exogenous application of methyl jasmonate (MeJA) indicated that MeJA favored anthocyanin accumulation, while it was also found that anthocyanin accumulation as well as PpBBX32and PpZAT5expression correlated significantly with endogenous JA and JA-Ile in different fruit tissues. In summary, PpBBX32 and PpZAT5 are upstream activators of PpMYB10.1, allowing JAs to take part in temperature-dependent and tissue-specific anthocyanin accumulation by modulating their expression. This work enriches the knowledge of the transcriptional regulatory mechanisms for differential anthocyanin accumulation under internal and external factors.

Selection of fruits with enhanced health benefits and superior flavor is an important aspect of peach breeding. Understanding the genetic interplay between appearance and flavor chemicals remains a major challenge. We identify the most important volatiles contributing to consumer preferences for peach, thus establishing priorities for improving flavor quality. We quantify volatiles of a peach population consisting of 184 accessions and demonstrate major reductions in the important flavor volatiles linalool and Z-3-hexenyl acetate in red-fleshed accessions. We identify 474 functional gene regulatory networks (GRNs), among which GRN05 plays a crucial role in controlling both red flesh and volatile content through the NAM/ATAF1/2/CUC (NAC) transcription factor PpBL. Overexpressing PpBLresults in reduced expression of PpNAC1, a positive regulator for Z-3-hexenyl acetate and linalool synthesis. Additionally, we identify haplotypes for three tandem PpAATs that are significantly correlated with reduced gene expression and ester content. We develop genetic resources for improvement of fruit quality.

Flavonols are a class of flavonoids that play a crucial role in regulating plant growth and promoting stress resistance. They are also important dietary components in horticultural crops due to their benefits for human health. In past decades, research on the transcriptional regulation of flavonol biosynthesis in plants has increased rapidly. This review summarizes recent progress in flavonol-specific transcriptional regulation in plants, encompassing characterization of different categories of transcription factors (TFs) and microRNAs as well as elucidation of different transcriptional mechanisms, including direct and cascade transcriptional regulation. Direct transcriptional regulation involves TFs, such as MYB, AP2/ERF, and WRKY, which can directly target the key flavonol synthasegene or other early genes in flavonoid biosynthesis. In addition, different regulation modules in cascade transcriptional regulation involve microRNAs targeting TFs, regulation between activators, interaction between activators and repressors, and degradation of activators or repressors induced by UV-B light or plant hormones. Such sophisticated regulation of the flavonol biosynthetic pathway in response to UV-B radiation or hormones may allow plants to fine-tune flavonol homeostasis, thereby balancing plant growth and stress responses in a timely manner. Based on orchestrated regulation, molecular design strategies will be applied to breed horticultural crops with excellent health-promoting effects and high resistance.

The recent discovery of circular RNAs(circRNAs) and characterization of their functional roles have opened a new avenue for understanding the biology of genomes. circRNAs have been implicated to play important roles in a variety of biological processes, but their precise functions remain largely elusive. Currently, a few approaches are available for novel circRNA prediction, but almost all these methods are intended for animal genomes. Considering that the major differences between the organization of plantand mammal genomes cannot be neglected, a plant-specific method is needed to enhance the validity of plant circRNA identification. In this study, we present CircPlant, an integrated tool for the exploration of plant circRNAs, potentially acting as competing endogenous RNAs (ceRNAs), and their potential functions. With the incorporation of several unique plant-specific criteria, CircPlant can accurately detect plant circRNAs from high-throughput RNA-seqdata. Based on comparison tests on simulated and real RNA-seq datasets from Arabidopsis thalianaand Oryza sativa, we show that CircPlant outperforms all evaluated competing tools in both accuracy and efficiency. CircPlant is freely available at http://bis.zju.edu.cn/circplant.

The recent discovery of circular RNAs(circRNAs) and characterization of their functional roles have opened a new avenue for understanding the biology of genomes. circRNAs have been implicated to play important roles in a variety of biological processes, but their precise functions remain largely elusive. Currently, a few approaches are available for novel circRNA prediction, but almost all these methods are intended for animal genomes. Considering that the major differences between the organization of plantand mammal genomes cannot be neglected, a plant-specific method is needed to enhance the validity of plant circRNA identification. In this study, we present CircPlant, an integrated tool for the exploration of plant circRNAs, potentially acting as competing endogenous RNAs (ceRNAs), and their potential functions. With the incorporation of several unique plant-specific criteria, CircPlant can accurately detect plant circRNAs from high-throughput RNA-seqdata. Based on comparison tests on simulated and real RNA-seq datasets from Arabidopsis thalianaand Oryza sativa, we show that CircPlant outperforms all evaluated competing tools in both accuracy and efficiency. CircPlant is freely available at http://bis.zju.edu.cn/circplant.

The lignification triggered by biotic or abiotic stresses hardens fruits and vegetables and eventually influences their consumer appeal. Extensive prior efforts have been made to unveil the underlying mechanism of flesh lignification, primarily focused on its physicochemical and molecular biological properties. Nevertheless, most of these studies used destroyed and homogenized bulk tissues as analytes; as a result, potentially valuable spatial information was lost. In this study, the deposition of lignin in loquat flesh during lignification was visualized from the tissue level to the single-cell level by combining the advantages of stimulated Raman scattering (SRS) and spontaneous Raman microscopy using label-free in situ molecular imaging. SRS has the advantages of being fast and providing large-area chemical imaging to reveal the spatial heterogeneity of lignin and cell wall polysaccharide distribution in loquat flesh. After 2 days of storage at 0 °C, increased lignins were observed by large-area SRS imaging. In addition, microscopic SRS images of the flesh cells indicated that the increased lignins were trapped in the cell corner (CC) and middle lamella (ML). Furthermore, the compositional and structural features of lignified cells (LCs), CC and ML of loquat flesh were investigated by spontaneous Raman microscopy, and the results showed that the LCs were a combination of lignin, cellulose, and hemicellulose, whereas CC and ML showed only deposited lignin and pectin without cross-linked cellulose and hemicellulose. This result further suggests that the lignins in the CC and ML regions of loquats were later synthesized alone during postharvest storage. This innovative combination of SRS and spontaneous Raman microscopy allows the label-free macroscale and fine chemical imaging of plant cell walls and will enhance our fundamental understanding of the structures and functions of the plant cell wall.

Histone acetyltransferase (HAT) catalyzes histone acetylation and is involved in plant growth and development and stress responses. Here, 37 CitHATgenes were identified in Citrus clementina. Their physicochemical properties, chromosomal location, gene structure, conserved domain and motif, and cis-acting elements were characterized. CitHATswere classified into four subfamilies based on protein sequence homology, which was strongly supported by gene structure, conserved domain, and motif analysis. The cis-acting elements in gene promoter regions were predicted to be associated with the regulation of plant growth, stress resistance, and response to hormones. Phenotypic and transcriptomic analyses of citrus callus with mock treatment and HAT inhibitor treatment revealed that increased citric acid content in inhibitor treatment may be attributed to differential expression of CitPEPCK2and CitGS2, which may be due to the hypo-acetylation of histone H3. The expression patterns of CitHATsin citrus fruit development stages showed that CitHAG11and CitHAG28exhibited a negative correlation with citric acid content. Our study associates the potential function of histone acetyltransferases in citrate metabolism and extends the molecular mechanism of citrate metabolism in fruits.

Background: Apple is an economically important fruit crop. Changes in metabolism accompanying human-guided evolution can be revealed using a multiomics approach. We perform genome-wide metabolic analysis of apple fruits collected from 292 wild and cultivated accessions representing various consumption types. Results: We find decreased amounts of certain metabolites, including tannins, organic acids, phenolic acids, and flavonoids as the wild accessions transition to cultivated apples, while lysolipids increase in the “Golden Delicious” to “Ralls Janet” pedigree, suggesting better storage. We identify a total of 222,877 significant single-nucleotide polymorphisms that are associated with 2205 apple metabolites. Investigation of a region from 2.84 to 5.01 Mb on chromosome 16 containing co-mapping regions for tannins, organic acids, phenolic acids, and flavonoids indicates the importance of these metabolites for fruit quality and nutrition during breeding. The tannin and acidity-related genes Myb9-likeand PH4are mapped closely to fruit weight locus fw1from 3.41 to 3.76 Mb on chromosome 15, a region under selection during domestication. Lysophosphatidylethanolamine (LPE) 18:1, which is suppressed by fatty acid desaturase-2(FAD2), is positively correlated to fruit firmness. We find the fruit weight is negatively correlated with salicylic acid and abscisic acid levels. Further functional assays demonstrate regulation of these hormone levels by NAC-like activated by Apetala3/Pistillata(NAP) and ATP binding cassette G25(ABCG25), respectively. Conclusions: This study provides a metabolic perspective for selection on fruit quality during domestication and improvement, which is a valuable resource for investigating mechanisms controlling apple metabolite content and quality.

Qualitative and quantitative analysis of N-glycans by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is hampered mainly by the low ionization efficiency of analytes and their poor cocrystallization with traditional organic acid matrices. In the present study, a combination strategy of reactive and catalytic matrices (CSRCM) was proposed for the on-target derivatization and detection of reducing N-glycans: a novel reactive matrix, i.e., 2,5-dihydroxybenzohydrazide (DHBH), having a skeleton structure similar to that of DHB, was designed and synthesized, and this reactive matrix was mixed with catalytic matrix DHB to form a rationally combinatorial matrix (DHB/DHBH). Qualitatively, DHB/DHBH could improve the ionization efficiency of reducing carbohydrates significantly. Quantitatively, the acid–base chemistry of DHB/DHBH leads to a uniform cocrystallization of analytes-matrix mixtures. Consequently, CSRCM provides accurate quantitation for N-glycans with high derivatization efficiency and good linearity (R2> 0.99) within 2 orders of magnitude on the basis of an internal standard method. Furthermore, the CSRCM was successfully applied to evaluating N-glycan in serum samples of colorectal cancer patients, thus showing potential in clinical applications for biomarker discovery.

Peach fruit volatile acetate esters impact consumer sensory preference and contribute to defense against biotic stresses. Previous studies showed that alcohol acyltransferase (AAT) family PpAAT1is correlated with volatile ester formation in peach fruits. However, fruits also contain carboxylesterase (CXE) enzymes that hydrolyze esters. The functions of this family with regard to volatile ester content has not been explored. Here, we observed that content of acetate ester was negatively correlated with expression of PpCXE1. Recombinant PpCXE1 protein exhibited hydrolytic activity toward acetate esters present in peach fruit. Kinetic analysis showed that PpCXE1 showed the highest catalytic activity toward E-2-hexenyl acetate. Subcellular localization demonstrated that PpCXE1 is present in the cytoplasm. Transient expression in peach fruit and stable overexpression in tomato fruit resulted in significant reduction of volatile esters in vivo. Taken together, the results indicate that PpCXE1expression is associated with catabolism of volatile acetate esters in peach fruit.

Recently, DNA methylation was proposed to regulate fleshy fruit ripening. Fleshy fruits can be distinguished by their ripening process as climacteric fruits, such as tomatoes, or non-climacteric fruits, such as strawberries. Tomatoes undergo a global decrease in DNA methylation during ripening, due to increased expression of a DNA demethylase gene. The dynamics and biological relevance of DNA methylation during the ripening of non-climacteric fruits are unknown. Here, we generate single-base resolution maps of the DNA methylome in immature and ripe strawberry. We observe an overall loss of DNA methylation during strawberry fruit ripening. Thus, ripening-induced DNA hypomethylation occurs not only in climacteric fruit, but also in non-climacteric fruit. Application of a DNA methylation inhibitor causes an early ripening phenotype, suggesting that DNA hypomethylation is important for strawberry fruit ripening. The mechanisms underlying DNA hypomethylation during the ripening of tomato and strawberry are distinct. Unlike in tomatoes, DNA demethylase genes are not upregulated during the ripening of strawberries. Instead, genes involved in RNA-directed DNA methylation are downregulated during strawberry ripening. Further, ripening-induced DNA hypomethylation is associated with decreased siRNA levels, consistent with reduced RdDM activity. Therefore, we propose that a downregulation of RdDM contributes to DNA hypomethylation during strawberry ripening. Our findings provide new insight into the DNA methylation dynamics during the ripening of non-climacteric fruit and suggest a novel function of RdDM in regulating an important process in plant development.

Recently, increasing evidence suggests that DNA methylation plays a crucial role in fruit ripening. However, the role of DNA methylation in regulating specific traits, such as flavor, remains unclear. Here, we report a role of DNA methylation in affecting furanone biosynthesis in strawberry. Strawberry quinone oxidoreductase (FaQR) is a key enzyme in furanone biosynthesis. There are four FaQRhomologs in strawberry cultivar ‘Yuexin’, and one of them, FaQR3, contributes ~50% of FaQRtranscripts, indicating a major role of FaQR3in furanone biosynthesis. Through characterization of levels of DNA methylation and FaQR3transcript and furanone contents during fruit ripening and after the application of DNA methylation inhibitor, we found that the DNA methylation level of the FaQR3promoter was negatively correlated with FaQR3expression and furanone accumulation, suggesting that DNA methylation may be involved in furanone biosynthesis through adjusting FaQR3expression, and responded to different temperatures consistently. In addition, transient expression of a gene in the RNA-directed DNA methylation (RdDM) pathway, FaAGO4, and enrichment analysis of the 24-nucleotide siRNAs suggested that DNA methylation in the FaQR3promoter is mediated by the RdDM pathway. Transient RNA interference (RNAi) of FaDMLindicated that the demethylation pathway may be involved in regulating furanone accumulation. These findings provide new insights into the role of DNA methylation and demethylation in affecting flavor quality in strawberry during fruit ripening.

Cultivated hawthorn (Crataegus pinnatifidavar. major), the principal cultivated hawthorn species in China, is rich in phenolic compounds. These phytochemicals are considered essential bioactive ingredients in different organs of cultivated hawthorn, contributing to its health effects. However, there is lack of a comprehensive review that systematically summarizes the chemistry, health effects, and stability of phenolic substances. This review summarizes recent progress in the characterization, classification, and distribution of phenolic compounds in C. pinnatifidavar. major, including procyanidins, flavonoids, phenolic acids, lignans, and others. Importantly, the stability of these compounds was found to be influenced by factors such as the hawthorn development process, postharvest storage, postharvest processing, and the gastrointestinal tract environment. Additionally, the health effects of phenolic compounds in cultivated hawthorn and their underlying mechanisms were discussed. This review provides valuable insights into the utilization of hawthorn resources and the development of the hawthorn industry.

Bitter is generally undesirable, although it is an important part of flavor. Bitter substances exhibit diverse health-promoting activities, which is in line with the famous Chinese saying ‘a good medicine tastes bitter’. Naringin (NAG) and neohesperidin (NHP), two important flavanones that give bitterness to citrus fruits, show various pharmacological activities. Interestingly, their hydrogenation products, i.e. naringin dihydrochalcone (NDC) and neohesperidin dihydrochalcone (NHDC), undergo a dramatic taste shift from bitter to intensely sweet, which can be 300 and 1000 times sweeter than sucrose, respectively. Such sweeteners not only provide a sweet taste without the burden of increased calorie intake and glycemia, but also may exert multiple bioactivities. This review summarizes common dietary bitter and sweet compounds with sensory scores. Taste conversions induced by structural changes from bitter NAG and NHP to sweet NDC and NHDC are particularly discussed. In addition, the taste-sensing mechanisms, pharmacological characteristics, dietary distribution, synthesis, and food industry applications of these bitter–sweet interchangeable compounds are outlined. In conclusion, the bitter NAG and NHP are promising therapeutic candidates for management of diverse etiologically complex diseases while their corresponding dihydrochalcones NDC and NHDC are promising sweeteners, which might be a blessing for those who need to control sugar intake.

Cai et al report that a major anthocyanin extract from the Chinese bayberry, Myrica rubra, protects islets from ischemia-reperfusion injury and oxidative stress following their transplantation under the kidney capsule or into the portal vein of diabetic syngeneic recipients. Supplemental digital content is available in the text.

In this article, a simple and efficient protocol for rapid preparation and separation of neohesperidin from the albedo of Citrus reticulatacv. Suavissimawas established by the combination of macroporous resin column chromatography and high‐speed counter‐current chromatography (HSCCC). Six types of resin were investigated by adsorption and desorption tests, and D101 macroporous resin was selected for the first cleaning‐up procedure, in which 55% aqueous ethanol was used to elute neohesperidin. After treatment with D101 resin, the neohesperidin purity increased 11.83‐fold from 4.92% in the crude extract to 58.22% in the resin‐refined sample, with a recovery of 68.97%. The resin‐refined sample was directly subjected to HSCCC purification with a two‐phase solvent system composed of ethyl acetate–n‐butanol–water (4:1:5, v/v), and 23.6 mg neohesperidin with 97.47% purity was obtained from 60 mg sample in only one run. The recovery of neohesperidin in HSCCC separation procedure was 65.85%. The chemical structure of the purified neohesperidin was identified by both HPLC and LC‐MS. The established purification process will be helpful for further characterization and utilization of Citrusneohesperidin.

Flavonol glycosides are health-promoting phytochemicals important for human nutrition and plant defense against environmental stresses. Glycosylation modification greatly enriches the diversity of flavonols. Morella rubra, a member of the Myricaceae, contains high amounts of myricetin 3-O-rhamnoside (M3Rha), quercetin 3-O-rhamnoside (Q3Rha), and quercetin 3-O-galactoside (Q3Gal). In the present study, MrUGT78R1 and MrUGT78R2 were identified as two functional UDP-rhamnosyltransferases, while MrUGT78W1 was identified as a UDP-galactosyltransferase. Site-directed mutagenesis identified Pro143 and Asn386 as important residues for rhamnosyl transfer activity of MrUGT78R1, while the two corresponding positions in MrUGT78W1 (i.e. Ser147 and Asn370) also play important roles in galactosyl transfer activity. Transient expression data for these three MrUGTs in Nicotiana benthamianatested the function of MrUGT78R1 and MrUGT78R2 as rhamnosyltransferases and MrUGT78W1 as a galactosyltransferase in glycosylation of flavonols. This work enriches knowledge of the diversity of UDP-rhamnosyltransferase in plantaand identifies two amino acid positions important for both rhamnosyltransferase and galactosyltransferase.

Volatile organic compounds (VOCs) derived from fatty acids are major contributors to fruit flavor and affect human preferences. The ω-3 fatty acid linolenic acid 3 (18:3) serves as an important precursor for synthesis of (E)-2-hexenal and (Z)-3-hexenol. These short-chain C6 VOCs provide unique fresh notes in multiple fruit species. Metabolic engineering to improve fruit aroma requires knowledge of the regulation of fatty acid-derived VOCs. Here, we determined that ripe fruit-specific expression of PpFAD3-1contributes to 18:3 synthesis in peach fruit. However, no significant increases in (E)-2-hexenal and (Z)-3-hexenol were detected after overexpressing PpFAD3-1. Interestingly, overexpressing the PpNAC1transcription factor increased the content of 18:3 and enhanced the production of its derived volatiles. Moreover, induced expression of genes responsible for downstream VOC synthesis was observed for transgenic tomato fruit overexpressing PpNAC1, but not for transgenic fruit overexpressing PpFAD3-1. Electrophoretic mobility shift and ChIP-Seq assays showed that PpNAC1 activated PpFAD3-1expression via binding to its promoter. Therefore, PpNAC1plays an important role in modulating fatty acid flux to produce fruit flavor-related VOCs. In addition to PpNAC1, PpFAD3-1expression was also associated with epigenetic modifications during peach fruit ripening. Taken together, our results provide new insights into the molecular mechanisms regulating biosynthesis of fatty acid and short-chain VOCs in fruit.

Flavonoids are the most widespread polyphenolic compounds and are important dietary constituents present in horticultural crops such as fruits, vegetables, and tea. Natural flavonoids are responsible for important quality traits, such as food colors and beneficial dietary antioxidants, and numerous investigations have shown that intake of flavonoids can reduce the incidence of various non-communicable diseases. Analysis of the thousands of flavonoids reported so far has shown that different hydroxylation modifications affect their chemical properties and nutritional values. These diverse flavonoids can be classified based on different hydroxylation patterns in the B, C, and A rings and multiple structure–activity analyses have shown that hydroxylation decoration at specific positions markedly enhances their bioactivities. This review focuses on current knowledge concerning hydroxylation of flavonoids catalyzed by several different types of hydroxylase enzymes. Flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′5′-hydroxylase (F3′5′H) are important enzymes for the hydroxylation of the B ring of flavonoids. Flavanone 3-hydroxylase (F3H) is key for the hydroxylation of the C ring, while flavone 6-hydroxylase (F6H) and flavone 8-hydroxylase (F8H) are key enzymes for hydroxylation of the A ring. These key hydroxylases in the flavonoid biosynthesis pathway are promising targets for the future bioengineering of plants and mass production of flavonoids with designated hydroxylation patterns of high nutritional importance. In addition, hydroxylation in key places on the ring may help render flavonoids ready for degradation, and the catabolic turnover of flavonoids may open the door for new lines of inquiry.

Covalent organic frameworks (COFs) hold great potential in various applications because of their well-defined pore structures and morphologies. However, most COF materials demonstrate poor dispersibility in solvents that significantly limits their processing and applications. Herein, we report the synthesis of COF-based hollow nanoparticles (h-NPs) with good water dispersibility, high capacity, and thermal responsiveness to load essential oil molecules for longer-term preservation of fruits. Imine-based COF h-NPs possessing a pore width of 1.3 nm, inner/outer diameters of ∼150/239 nm, and high crystallinity were synthesized and grafted with water-soluble polymers such as polyethylene glycol or poly(N-isopropylacrylamide) (PNIPAM) with molecular weights of 1–3 kDa. The h-NP products with grafting densities of 0.6–2.1 nm–2can be well dispersed in water at room temperature. PNIPAM-grafted ones are temperature-responsive in that they can precipitate out from the dispersion at 40 °C and redisperse at 25 °C for at least 15 cycles. The h-NPs are used as nanocarriers to load essential oils such as hexanal and trans-2-hexenal with a high capacity of 1.1 g/g for fruit fresh-keeping, and the encapsulated preservatives can be released controllably at 25–40 °C as regulated by the grafted polymers. As a result, the storage time of cherry tomatoes can be prolonged by 4 days compared to the control run. Moreover, these h-NPs can be recycled and reused. Our work highlights the potential of COF nanomaterials grafting with stimuli-responsive polymers for controlled release application in various food preservation.

Loquat (Eriobotrya japonicaLindl. cv. Luoyangqing) is a chilling-sensitive fruit and therefore has a limited postharvest life. While fruit stored at 5 °C retained its acceptable quality after 39 days, fruit stored at 0 °C had chilling injury with the symptoms of tissue browning and lignification, decrease in percentage juice, increase in superoxide free radical production, electric conductivity and lignification enzyme activities, including phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and guaiacol-peroxidase (G-POD). Such chilling injury symptoms became more severe after fruit were moved to 20 °C shelf life. A postharvest application of 1 mmol/L aqueous acetylsalicylic acid (ASA, a derivative of salicylic acid) to loquat fruit significantly alleviated chilling injury symptoms, inhibited accumulation of superoxide free radical, and reduced PAL, CAD, and G-POD activities. ASA treatment impairing the accumulation of superoxide free radical may prevent chilling injury and lignification in loquat.Loquat (Eriobotrya japonicaLindl. cv. Luoyangqing) is a chilling-sensitive fruit and therefore has a limited postharvest life. While fruit stored at 5 °C retained its acceptable quality after 39 days, fruit stored at 0 °C had chilling injury with the symptoms of tissue browning and lignification, decrease in percentage juice, increase in superoxide free radical production, electric conductivity and lignification enzyme activities, including phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and guaiacol-peroxidase (G-POD). Such chilling injury symptoms became more severe after fruit were moved to 20 °C shelf life. A postharvest application of 1 mmol/L aqueous acetylsalicylic acid (ASA, a derivative of salicylic acid) to loquat fruit significantly alleviated chilling injury symptoms, inhibited accumulation of superoxide free radical, and reduced PAL, CAD, and G-POD activities. ASA treatment impairing the accumulation of superoxide free radical may prevent chilling injury and lignification in loquat.

The kinetics of polymerization of tributyltin methacrylate (TBTM) has been studied in benzene solution in the temperature range 60-75°C in the presence of azobisisobutyronitrile (AIBN). We have obtained the following polymerization rate equation: Rp = Kp [TBTM]1.5 [AIBN]0.5. It shows that the dependence of the polymerization rate on the concentrations of the monomer TBTM and the initiator AIBN are 1.5 and 0.5 order, respectively. The activation energy of polymerization was found to be 18.1 kcal/mol. The activation energy for the degree of polymerization is approximately -12.3 kcal/mol.

Mechanical damage to fruit causes flavor changes during post-harvest supply chains. It is important to identify the main volatiles and explore their biosynthesis mechanism. In this study, the volatile changes in apples caused by mechanical damage were analyzed by gas chromatography–ion mobility spectrometry. Hexanal and ethyl acetate were accumulated and identified as potential volatile biomarkers to detect damaged apples. The study on the lipoxygenase (LOX) pathway and transcription factors (TFs) shows that mechanical damage up-regulated the expression of MdLOX-like, MdLOX3b, MdLOX7b, MdLOX7c, MdLOX2a, and MdAATin the LOX pathway and that of one MYB TF (MdMYB-like), five ERF TFs (MdERF073, MdERF003, MdERF114, MdERF15, and MdERF2), and five WRKY TFs (MdWRKY23, MdWRKY17, MdWRKY46, MdWRKY48, and MdWRKY71). Notably, MdAATwas significantly correlated to MdMYB-like, MdWRKY23, MdWRKY71, MdERF15, and MdERF2. Thus, TFs may attribute to the accumulation of hexanal and ethyl acetate by regulating the expression of LOX pathway-related genes.

Chemical structural characterization of phenolic compounds from the red (“Biqi”) and white (“Shuijing”) bayberries was carried out in the present study. With the aid of Global Natural Products Social Molecular Networking (GNPS), 18 flavonoid glycosides and 13 proanthocyanidins (PACs) in bayberry extracts were tentatively identified. Three cyanidin-3-glucoside derivatives (cyanidin-acetylapiosyl-glucoside, catechin-cyanidin-3-glucoside, and gallocatechin-cyanidin-3-glucoside), two quercetin derivatives (quercetin-3-arabinoside and quercetin-3-glucuronide), patuletin-7-glucoside, and individual PACs consisting of (epi)catechin or (epi)gallocatechin units were reported for the first time in bayberry fruits. In addition, “Biqi” exhibited a considerable increase of flavonoid glycoside content together with a dramatic decrease in the content of PACs in mature fruits, while “Shuijing” showed a decrease in levels of PACs but failed to accumulate flavonoid glycosides during fruit development.

Loquat (Eriobotrya japonica) fruit accumulates lignin during postharvest storage under chilling conditions (0 °C), while low-temperature conditioning (LTC; 5 °C for 6 days followed by transfer to 0 °C) or heat treatment (HT; 40 °C for 4 h followed by transfer to 0 °C) can alleviate lignification. Here we compared transcriptome profiles of loquat fruit samples under LTC or HT to those stored at 0 °C at five time points from day 1 to day 8 after treatment. High-throughput transcriptome sequences were de novo assembled into 53,319 unique transcripts with an N50 length of 1306 bp. A total of 2235 differentially expressed genes were identified in LTC, and 1020 were identified in HT compared to 0 °C. Key genes in the lignin biosynthetic pathway, including EjPAL2, EjCAD1, EjCAD3, 4CL, COMT, and HCT, were responsive to LTC or HT treatment, but they showed different expression patterns during the treatments, indicating that different structural genes could regulate lignification at different treatment stages. Coexpression network analysis showed that these candidate biosynthetic genes were associated with a number of transcription factors, including those belonging to the AP2, MYB, and NAC families. Gene ontology (GO) enrichment analysis of differentially expressed genes indicated that biological processes such as stress responses, cell wall and lignin metabolism, hormone metabolism, and metal ion transport were significantly affected under LTC or HT treatment when compared to 0 °C. Our analyses provide insights into transcriptome responses to postharvest treatments in loquat fruit.