Biphenyls and dibenzofurans of the rosaceous subtribe Malinae and their role as phytoalexins.

MAIN CONCLUSION: Biphenyl and dibenzofuran phytoalexins are differentially distributed among species of the rosaceous subtribe Malinae, which includes apple and pear, and exhibit varying inhibitory activity against phytopathogenic microorganisms. Biphenyls and dibenzofurans are specialized metabolites, which are formed in species of the rosaceous subtribe Malinae upon elicitation by biotic and abiotic inducers. The subtribe Malinae (previously Pyrinae) comprises approximately 1000 species, which include economically important fruit trees such as apple and pear. The present review summarizes the current status of knowledge of biphenyls and dibenzofurans in the Malinae, mainly focusing on their role as phytoalexins. To date, 46 biphenyls and 41 dibenzofurans have been detected in 44 Malinae species. Structurally, 54 simple molecules, 23 glycosidic compounds and 10 miscellaneous structures were identified. Functionally, 21 biphenyls and 21 dibenzofurans were demonstrated to be phytoalexins. Furthermore, their distribution in species of the Malinae, inhibitory activities against phytopathogens, and structure-activity relationships were studied. The most widely distributed phytoalexins of the Malinae are the three biphenyls aucuparin (3), 2'-methoxyaucuparin (7), and 4'-methoxyaucuparin (9) and the three dibenzofurans α-cotonefuran (47), γ-cotonefuran (49), and eriobofuran (53). The formation of biphenyl and dibenzofuran phytoalexins appears to be an essential defense weapon of the Malinae against various stresses. Manipulating phytoalexin formation may enhance the disease resistance in economically important fruit trees. However, this approach requires an extensive understanding of how the compounds are formed. Although the biosynthesis of biphenyls was partially elucidated, formation of dibenzofurans remains largely unclear. Thus, further efforts have to be made to gain deeper insight into the distribution, function, and metabolism of biphenyls and dibenzofurans in the Malinae.

Anti-Diabetic Potential of Polyphenol-Rich Fruits from the Maleae Tribe-A Review of In Vitro and In Vivo Animal and Human Trials.

The Maleae tribe consists of over one thousand species, including many well-known polyphenol-containing fruit crops with wide-ranging biological properties, e.g., apples (Malus), chokeberries (Aronia), pears (Pyrus), quinces (Cydonia, Chaenomeles), saskatoon (Amelanchier), loquats (Eriobotrya), medlars (Mespilus), rowans (Sorbus), and hawthorns (Crataegus). Considering the current interest in the concept of functional foods and the still-insufficient methods of diabetes management, the anti-diabetic potential of fruits has been studied intensively, including those of the Maleae tribe. This paper is the first comprehensive overview of this selected topic, covering articles published from 2000 to 2023 (131 articles in total). The first part of this review focuses on the potential mechanisms of action of fruits investigated so far (46 species), including their effects on tissue-specific glucose transport and the expression or activity of proteins in the insulin signalling pathway. The second part covers the phytocompounds responsible for particular fruits' activity-primarily polyphenols (e.g., flavonols, dihydrochalcones, proanthocyanidins, anthocyanins, phenolic acids), but also polysaccharides, triterpenes, and their additive and synergistic effects. In summary, fruits from the Maleae tribe seem promising as functional foods and anti-diabetic agents; however, their prospects for more expansive pro-health application require further research, especially more profound in vivo trials.

The pear genomics database (PGDB): a comprehensive multi-omics research platform for Pyrus spp.

BACKGROUND: Pears are among the most important temperate fruit trees in the world, with significant research efforts increasing over the last years. However, available omics data for pear cannot be easily and quickly retrieved to enable further studies using these biological data. DESCRIPTION: Here, we present a publicly accessible multi-omics pear resource platform, the Pear Genomics Database (PGDB). We collected and collated data on genomic sequences, genome structure, functional annotation, transcription factor predictions, comparative genomics, and transcriptomics. We provide user-friendly functional modules to facilitate querying, browsing and usage of these data. The platform also includes basic and useful tools, including JBrowse, BLAST, phylogenetic tree building, and additional resources providing the possibility for bulk data download and quick usage guide services. CONCLUSIONS: The Pear Genomics Database (PGDB, http://pyrusgdb.sdau.edu.cn ) is an online data analysis and query resource that integrates comprehensive multi-omics data for pear. This database is equipped with user-friendly interactive functional modules and data visualization tools, and constitutes a convenient platform for integrated research on pear.

Dictamnine suppresses the development of pear ring rot induced by Botryosphaeria dothidea infection by disrupting the chitin biosynthesis.

Ring rot induced by Botryosphaeria dothidea is a major cause of growth and postharvest losses in various fruits. There is an urgent need to develop green fungicides due to pesticide resistance and environmental pressure. Here, we demonstrated the efficacy of dictamnine (DIC, 4-methoxyfuro [2,3-ß] quinoline, purity 98%), a compound isolated from the stems and leaves of Clausena lansium, in effectively suppressing pear ring rot by inhibiting the mycelial growth of B. dothidea. The median effective concentration of DIC was 15.48 µg/mL. Application of DIC to B. dothidea resulted in structural disruption of the cell wall and plasma membrane, leading to mycelial deformation, breakage, and cell death. Transcriptome analysis revealed significant inhibition of the synthetic pathways for fungal cell wall and membrane components by DIC. Particularly, the expression of chitin synthase, a key enzyme of chitin synthesis, was prominently down-regulated. Moreover, the chitin content in DIC-treated B. dothidea mycelia exhibited a substantial dose-dependent reduction. Based on these results, it is promising to develop DIC as an antifungal pesticide for controlling ring rot disease in pear fruits. Our study provides new insights into the underlying mechanism through which DIC inhibits the mycelial growth of B. dothidea.

PbWRKY26 positively regulates malate accumulation in pear fruit by activating PbMDH3.

Malate is the main organic acid that affects fruit acidity and flavor in pear (Pyrus spp.). However, the regulatory mechanism of malic acid accumulation in pear remains unclear. We identified PbWRKY26 as a candidate gene using mRNA-seq, and quantification analysis verified the expression level. The expression of PbWRKY26 was positively correlated with the malic acid content in two P. pyrifolia cultivars ('Cuiguan', 'Hongsucui') and two P. ussuriensis cultivars ('Qiuxiang', 'Hanhong'), with respective correlation coefficients of 0.748*, 0.871**, 0.889**, and 0.910** (*, P < 0.05; **, P < 0.01). The expression of PbWRKY26 enhanced the malate content in overexpression transgenic pear fruit and callus. In contrast, silencing PbWRKY26 decreased the pear fruit malic acid content. Analysis of the neighbor-joining phylogenetic tree indicated that PbWRKY26 was a PH3 homolog. The WRKY26 (PH3) has been identified to regulate a proton pump gene, PH5, in a lot of plant species, but the LUC and Y1H assays showed that PbWRKY26 could not bind to PbPH5 promoter in our study. Interestingly, a malate dehydrogenase gene, PbMDH3, was identified to be regulated by PbWRKY26. This study might be valuable to understand the metabolic regulatory network associated with malate accumulation.

Impact of Intron and Retransformation on Transgene Expression in Leaf and Fruit Tissues of Field-Grown Pear Trees.

Stable and high expression of introduced genes is a prerequisite for using transgenic trees. Transgene stacking enables combining several valuable traits, but repeated transformation increases the risk of unintended effects. This work studied the stability and intron-mediated enhancement of uidA gene expression in leaves and different anatomical parts of pear fruits during field trials over 14 years. The stability of reporter and herbicide resistance transgenes in retransformed pear plants, as well as possible unintended effects using high-throughput phenotyping tools, were also investigated. The activity of ß-glucuronidase (GUS) varied depending on the year, but silencing did not occur. The uidA gene was expressed to a maximum in seeds, slightly less in the peel and peduncles, and much less in the pulp of pear fruits. The intron in the uidA gene stably increased expression in leaves and fruits by approximately twofold. Retransformants with the bar gene showed long-term herbicide resistance and exhibited no consistent changes in leaf size and shape. The transgenic pear was used as rootstock and scion, but grafted plants showed no transport of the GUS protein through the graft in the greenhouse and field. This longest field trial of transgenic fruit trees demonstrates stable expression under varying environmental conditions, the expression-enhancing effect of intron and the absence of unintended effects in single- and double-transformed woody plants.

PearMODB: a multiomics database for pear (Pyrus) genomics, genetics and breeding study.

Pear (Pyrus ssp.) belongs to Rosaceae and is an important fruit tree widely cultivated around the world. Currently, challenges to cope with the burgeoning sets of multiomics data are rapidly increasing. Here, we constructed the Pear Multiomics Database (PearMODB) by integrating genome, transcriptome, epigenome and population variation data, and aimed to provide a portal for accessing and analyzing pear multiomics data. A variety of online tools were built including gene search, BLAST, JBrowse, expression heatmap, synteny analysis and primer design. The information of DNA methylation sites and single-nucleotide polymorphisms can be retrieved through the custom JBrowse, providing an opportunity to explore the genetic polymorphisms linked to phenotype variation. Moreover, different gene families involving transcription factors, transcription regulators and disease resistance (nucleotide-binding site leucine-rich repeat) were identified and compiled for quick search. In particular, biosynthetic gene clusters (BGCs) were identified in pear genomes, and specialized webpages were set up to show detailed information of BGCs, laying a foundation for studying metabolic diversity among different pear varieties. Overall, PearMODB provides an important platform for pear genomics, genetics and breeding studies. Database URL http://pearomics.njau.edu.cn.

Development of a novel, sustainable, cellulose-based food packaging material and its application for pears.

This study aimed to develop a cellulose-based active food packaging material using paper, a biodegradable, sustainable, recyclable, renewable, and relatively low-cost material. For electrospray coating, fulvic acid (FA), which has antioxidant and antimicrobial properties, and sericin (S) were used as an active agent and a carrier medium, respectively. Solutions prepared at various concentrations and ratios of FA and S were analyzed, the properties of the active packaging material were examined, and the effect on the quality of pears was studied. The optimum conditions of electrospraying for minimum droplet size and maximum antibacterial effect were 0.8 g/mL concentration of solutions, 1:1 FA:S ratio, 20 kV voltage, 0.75 mL/h flow rate, and 23 cm collector-needle tip distance. FA had static, lethal, and inhibitory effects on Pseudomonas syringae and P. digitatum, the common pathogenic microorganisms on pears. The antioxidant activity of FA was higher than that of S (872.96 mM vs. 239.36 mM). At the end of the 90-day storage period, pears stored in the active packaging material at 7 °C and 90% RH showed better preserved color and texture, matured later, had a lower antimicrobial load, and were more appreciated in sensory evaluation than other samples.

Comprehensive analysis of KCS gene family in pear reveals the involvement of PbrKCSs in cuticular wax and suberin synthesis and pear fruit skin formation.

Cuticular wax, cutin and suberin polyesters covering the surface of some fleshy fruit are tightly associated with skin color and appearance. ß-Ketoacyl-CoA synthase (KCS) is a rate-limiting enzyme participating in the synthesis of very-long-chain fatty acids (VLCFAs), the essential precursors of cuticular waxes and aliphatic monomers of suberin. However, information on the KCS gene family in pear genome and the specific members involved in pear fruit skin formation remain unclear. In the present study, we performed an investigation of the composition and amount of cuticular waxes, cutin and aliphatic suberin in skins of four sand pear varieties with distinct colors (russet, semi-russet, and green) and demonstrated that the metabolic shifts of cuticular waxes and suberin leading to the significant differences of sand pear skin color. A genome-wide identification of KCS genes from the pear genome was conducted and 35 KCS coding genes were characterized and analyzed. Expression profile analysis revealed that the KCS genes had diverse expression patterns among different pear skins and the transcript abundance of PbrKCS15, PbrKCS19, PbrKCS24, and PbrKCS28 were consistent with the accumulation of cuticular waxes and suberin in fruit skin respectively. Subcellular localization analysis demonstrated that PbrKCS15, PbrKCS19, PbrKCS24 and PbrKCS28 located on the endoplasmic reticulum (ER). Further, transient over-expression of PbrKCS15, PbrKCS19, and PbrKCS24 in pear fruit skins significantly increased cuticular wax accumulation, whereas PbrKCS28 notably induced suberin deposition. In conclusion, pear fruit skin color and appearance are controlled in a coordinated way by the deposition of the cuticular waxes and suberin. PbrKCS15, PbrKCS19, and PbrKCS24 are involved in cuticular wax biosynthesis, and PbrKCS28 is involved in suberin biosynthesis, which play essential roles in pear fruit skin formation. Moreover, this work provides a foundation for further understanding the functions of KCS genes in pear.

PEARS: A Web Tool for Fitting Time-Resolved Photoluminescence Decays of Perovskite Materials.

Time-resolved photoluminescence (TRPL) is a powerful tool to investigate charge carrier recombination processes in emissive materials. Perovskite materials are extremely promising for applications in solar cells; however, the interpretation of their TRPL is arduous due to the complicated nature of the recombination processes occurring in these materials. We present here the PErovskite cArrier Recombination Simulator (PEARS) web tool for effortlessly and quickly fitting TRPL of perovskite materials using advanced charge carrier recombination models, allowing for the extraction of recombination rate constants and trap state concentration. PEARS is flexible and can adapt to different situations, by ignoring recombination processes or fixing known parameters (e.g., the doping concentration). The tool is publicly available at https://pears-tool.herokuapp.com.

The PcMYB44-mediated miR397-PcLACs module regulates defence-induced lignification in pear resistance to fungal disease.

Diseases caused by Alternaria alternata and Botryosphaeria dothidea diminish pear yield and quality, and restrict the pear agricultural industry. Lignification is a conserved mechanism for plant resistance against pathogen invasion. The regulatory mechanisms underlying defence-induced lignification in pear in response to fungal pathogen infection remain unknown. In this study, analysis of lignification level and lignin content in pear revealed that A. alternata and B. dothidea induced lignification, and transcriptomics showed that lignin biosynthesis was affected. To explore whether laccases (LACs) mediated by miR397 regulate lignification in pear, we investigated the role of PcmiR397 in repressing the expression of PcLACs using 5'-RNA ligase-mediated-RACE and co-transformation in tobacco. Opposite expression patterns for PcmiR397 and PcLAC target genes were observed in pear in response to pathogens. Transient transformation in pear demonstrated that silencing PcmiR397 and overexpressing a single PcLAC enhanced resistance to pathogens via lignin synthesis. To further reveal the mechanism underpinning the PcMIR397 response of pear to pathogens, the PcMIR397 promoter was analysed, and pMIR397-1039 was found to be inhibited by pathogen infection. The transcription factor PcMYB44 was up-regulated, and it bound to the PcMIR397 promoter and inhibited transcription following pathogen infection. The results demonstrate the role of PcmiR397-PcLACs in broad-spectrum resistance to fungal disease, and the potential role of PcMYB44 involved in the miR397-PcLAC module in regulating defence-induced lignification. The findings provide valuable candidate gene resources and guidance for molecular breeding to improve resistance to fungal disease in pear.

Fruit Characteristics of Transgenic pear (Pyrus communis L.) Trees During Long-Term Field Trials.

The quality of transgenic fruits was studied only for apple, plum and citrus. We first evaluated the transgenic fruit characteristics of pear, which is one of the most consumed fruit crops. The size, shape and biochemical composition of fruits from field-grown pear trees with marker genes were analyzed for 5 years. Soluble solids, vitamin C, and phenolic compounds varied significantly between transgenic lines, but these deviations were inconsistent. Arbutin content and sugar:acidity ratio were the most stable parameters. One transgenic line showed a stable increase in fruit weight (by 12.2-21.2%). The extremely dry and hot season increased the total phenolics (2.6-3.6 times) and tannin (3.2-3.6 times) levels, but not flavonoids. The harvest year had a stronger effect on analyzed fruit parameters than the genotype. Our study found no unintended effects of genetic transformation on pear fruit quality and confirms the importance of long-term field tests for perennial transgenic plants.

Planting and mowing cover crops as livestock feed to synergistically optimize soil properties, economic profit, and environmental burden on pear orchards in the Yangtze River Basin.

BACKGROUND: Pears, as an important cash crop, are currently facing great issues due to unsustainable management practices. Cover cropping is a sustainable management strategy that can improve soil fertility and increase fruit yield, while it may also stimulate greenhouse gas emissions. Therefore, synergizing multiple indicators to achieve sustainable development is critical. This study introduces a new management system, namely the planting and mowing of ryegrass as a livestock feed system (PRSS), and analyzes its impact on soil quality, economic benefits, and environmental burdens. RESULTS: Our results indicated that PRSS could increase soil pH from 5.08 to 5.48 and decrease the content of soil alkali-hydrolyzable nitrogen, total phosphate, and available phosphate (26.96-59.89%) while also enhancing yield (+38.51%) compared with the traditional natural grass management system (TMS). The average soil methane fluxes in PRSS were 72.67 µg m-2 day-1 , higher than those of TMS (61.28 µg m-2 day-1 ). However, the gross primary production was lower than TMS (-37.24%), and no significant difference was observed in soil nitrous oxide fluxes. In different scenarios, the total profit of PRSS mode 1 (mowing ryegrass and selling to a livestock company) and PRSS mode 2 (mowing ryegrass and feeding own sheep) were 10 706.21 $ ha-1 and 26 592.87 $ ha-1 respectively. These values are respectively2.36 times and 5.85 times higher than that of TMS. The total global warming potential of TMS (18.19 t CO2 -eq ha-1 ) was 1.29 t CO2 -eq ha-1 higher and 2.89 t CO2 -eq ha-1 lower than that of PRSS mode 1 and mode 2 respectively. CONCLUSION: Compared with traditional natural grass, planting and mowing ryegrass in pear orchards can optimize soil properties, increase fruit yield, and reduce global warming potential. Different modes can greatly increase revenue but have varying impacts on environmental burdens. These findings can help rebuild the links between farmland and specialized livestock production, contributing to sustainable development in the pear industries. © 2023 Society of Chemical Industry.

Acetylation of inorganic pyrophosphatase by S-RNase signaling induces pollen tube tip swelling by repressing pectin methylesterase.

Self-incompatibility (SI) is a widespread genetically determined system in flowering plants that prevents self-fertilization to promote gene flow and limit inbreeding. S-RNase-based SI is characterized by the arrest of pollen tube growth through the pistil. Arrested pollen tubes show disrupted polarized growth and swollen tips, but the underlying molecular mechanism is largely unknown. Here, we demonstrate that the swelling at the tips of incompatible pollen tubes in pear (Pyrus bretschneideri [Pbr]) is mediated by the SI-induced acetylation of the soluble inorganic pyrophosphatase (PPA) PbrPPA5. Acetylation at Lys-42 of PbrPPA5 by the acetyltransferase GCN5-related N-acetyltransferase 1 (GNAT1) drives accumulation of PbrPPA5 in the nucleus, where it binds to the transcription factor PbrbZIP77, forming a transcriptional repression complex that inhibits the expression of the pectin methylesterase (PME) gene PbrPME44. The function of PbrPPA5 as a transcriptional repressor does not require its PPA activity. Downregulating PbrPME44 resulted in increased levels of methyl-esterified pectins in growing pollen tubes, leading to swelling at their tips. These observations suggest a mechanism for PbrPPA5-driven swelling at the tips of pollen tubes during the SI response. The targets of PbrPPA5 include genes encoding cell wall-modifying enzymes, which are essential for building a continuous sustainable mechanical structure for pollen tube growth.

Pandora cacopsyllae Eilenberg, Keller & Humber (Entomophthorales: Entomophthoraceae), a new species infecting pear psyllid Cacopsylla pyri L. (Hemiptera: Psyllidae).

The new species Pandora cacopsyllae Eilenberg, Keller & Humber (Entomophthorales) is described. The fungus was found on infected pear psyllids Cacopsylla pyri (Hemiptera: Psyllidae) in a pear orchard in Zealand, Denmark. Morphological structures (conidia, rhizoids, cystidia) were described on the designated type host C. pyri. In addition, conidia from an in vitro culture were described. Pandora cacopsyllae differs from other Pandora species by a) C. pyri is the natural host; b) conidia are different from other Pandora species infecting Psylloidea; c) ITS differs from other Pandora species infecting Hemiptera. The fungus has a high potential for future use in biological control of Cacopsylla pest species as well as other psyllids.

Exploring the Aroma Fingerprint of Various Chinese Pear Cultivars through Qualitative and Quantitative Analysis of Volatile Compounds Using HS-SPME and GC×GC-TOFMS.

To comprehensively understand the volatile compounds and assess the aroma profiles of different types of Pyrus ussuriensis Maxim. Anli, Dongmili, Huagai, Jianbali, Jingbaili, Jinxiangshui, and Nanguoli were detected via headspace solid phase microextraction (HS-SPME) coupled with two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS). The aroma composition, total aroma content, proportion and number of different aroma types, and the relative quantities of each compound were analyzed and evaluated. The results showed that 174 volatile aroma compounds were detected in various cultivars, mainly including esters, alcohols, aldehydes, and alkenes: Jinxiangshui had the highest total aroma content at 2825.59 ng/g; and Nanguoli had the highest number of aroma species detected at 108. The aroma composition and content varied among pear varieties, and the pears could be divided into three groups based on principal component analysis. Twenty-four kinds of aroma scents were detected; among them, fruit and aliphatic were the main fragrance types. The proportions of aroma types also varied among different varieties, visually and quantitatively displaying changes of the whole aroma of the different varieties of pears brought by the changes in aroma composition. This study contributes to further research on volatile compound analysis, and provides useful data for the improvement of fruit sensory quality and breeding work.

Effects of vacuum microwave combined with freeze-drying on the physicochemical properties, phenolic compounds, and antioxidant capacity of pear fruit slices.

The effects of freeze-drying (FD), vacuum microwave drying after freeze-drying (FD-VMD), and freeze-drying after vacuum microwave drying (VMD-FD) on the physicochemical properties, phenolic compounds, and antioxidant capacity of pear fruit slices were investigated. The results showed that FD samples had the highest crispness value (116.30 N·sec) and the lowest volume shrinkage ratio value (5.48%). Compared to FD, the VMD-FD and FD-VMD methods could save drying time without affecting the color of dried samples. FD-VMD samples had the lowest rehydration capacity and maintained a homogeneous porous structure, while the VMD-FD samples had obvious collapse. Compared to VMD-FD samples, FD-VMD samples had higher contents of ascorbic acid (20.91 mg/100 g), total phenolic (7.62 mg/g), total anthocyanin (0.21 mg/g), and gallic acid (1.21 µg/g). Moreover, FD-VMD samples showed the highest antioxidant capacity as evaluated by the 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl scavenging activity, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) scavenging capacity, and H2 O2 content. Compared with FD and VMD-FD, FD-VMD was most effective in maintaining better quality and shortening drying time of pear fruit slices. These findings suggested that FD-VMD might be a promising drying technique in the fruits and vegetable processing industries.

Pear psylla and natural enemy thresholds for successful integrated pest management in pears.

Pear psylla, Cacopsylla pyricola (Förster), is the most economically challenging pest of commercial pears in Washington and Oregon, the top producers of pears in the United States. The objective of this study was to quantify economic injury levels and thresholds for pear psylla. We used the relationship between pear psylla adult and nymph densities, and fruit downgraded due to psylla honeydew marking to identify injury levels. We calculated economic injury levels using the cost of downgraded fruit and average management costs (spray materials and labor). Using economic injury levels, we determined economic thresholds for pear psylla, which include predicted pest population growth, natural enemy predation, and anticipated delays between when pest populations are measured and when managers apply interventions. Economic thresholds generated by this study were 0.1-0.3 second-generation nymphs per leaf and 0.2-0.8 third-generation nymphs per leaf depending on predicted price and yield for insecticide applications at 1,300 pear psylla degree days in the second generation and 2,600 pear psylla degree days in the third generation. Natural enemy inaction thresholds identified by this study were 6 Deraeocoris brevis or 3 Campylomma verbasci immatures per 30 trays or 2 earwigs per trap for third-generation optional insecticide applications.