Pyrus Bretschneideri Research Articles

Telomere-to-telomere Genome Assembly of two representative Asian and European pear cultivars

As the third most important temperate fruit, Pear (Pyrus spp.) exhibits a remarkable genetic diversity and is classified into two mainly categories known as Asian pear and European pear. Although several pear genomes are available, most of the released versions are fragmented and not chromosome-level high-quality. In this study, we report two high-quality genomes for Pyrus bretschneideri Rhed. cv. ‘Danshansuli’ (DS) and Pyrus communis L. cv. ‘Conference’ (KFL), which represent the predominant Asian and European cultivars, respectively, with nearly telomere-to-telomere (T2T) gap-free level. The finally assembled genome sizes for DS and KFL were 510.98 Mb and 510.71 Mb, respectively, with Contig N50 of 29.47 Mb and 30.47 Mb, where each chromosome was represented by a single contig. The DS and KFL genomes yielded a total of 46,394 and 44,702 protein-coding genes, respectively. Among these genes, the functional annotation accounted for 96.47% and 96.46% in the DS and KFL genomes. The two novels nearly T2T genomic information offers an invaluable resource for comparative genomics, genetic diversity analysis, molecular breeding strategies, and functional exploration.

Integration of mRNA-miRNA Reveals the Possible Role of PyCYCD3 in Increasing Branches Through Bud-Notching in Pear (Pyrus bretschneideri Rehd.).

Bud-notching in pear varieties with weak-branches enhances branch development, hormone distribution, and germination, promoting healthier growth and improving early yield. To examine the regulatory mechanisms of endogenous hormones on lateral bud germination in Pyrus spp. (cv. 'Huangguan') (Pyrus bretschneideri Rehd.), juvenile buds were collected from 2-year-old pear trees. Then, a comprehensive study, including assessments of endogenous hormones, germination and branching rates, RNA-seq analysis, and gene function analysis in these lateral buds was conducted. The results showed that there was no significant difference in germination rate between the control and bud-notching pear trees, but the long branch rate was significantly increased in bud-notching pear trees compared to the control (p < 0.05). After bud-notching, there was a remarkable increase in IAA and BR levels in the pruned section of shoots, specifically by 141% and 93%, respectively. However, the content of ABA in the lateral buds after bud-notching was not significantly different from the control. Based on RNA-seq analysis, a notable proportion of the differentially expressed genes (DEGs) were linked to the plant hormone signal transduction pathway. Notably, the brassinosteroid signaling pathway seemed to have the closest connection with the branching ability of pear with the related genes encoding BRI1 and CYCD3, which showed significant differences between lateral buds. Finally, the heterologous expression of PyCYCD3 has a positive regulatory effect on the increased Arabidopsis growth and branching numbers. Therefore, the PyCYCD3 was identified as an up-regulated gene that is induced via brassinosteroid (BR) and could act as a conduit, transforming bud-notching cues into proliferative signals, thereby governing lateral branching mechanisms in pear trees.

Genome-wide identification of the Phospholipase D (PLD) gene family in Chinese white pear (Pyrus bretschneideri) and the role of PbrPLD2 in drought resistance

The Chinese white pear (Pyrus bretschneideri), a vital fruit crop, is highly susceptible to abiotic stresses, especially drought, which poses a major threat to its growth and productivity. Phospholipase D (PLD) genes are pivotal in orchestrating plant responses to abiotic stresses, acting as key regulators in stress adaptation mechanisms. This study systematically identified and functionally characterized the entire PLD gene family in P. bretschneideri through a comprehensive genome-wide analysis. A total of 20 PbrPLD genes were identified, and they were categorized into five subfamilies based on phylogenetic analysis. chromosome localization, gene structure, and conserved motif analyses revealed that these genes have diverse evolutionary histories. Cis-acting element analysis and expression profiling under drought stress indicated that several PbrPLD genes, particularly PbrPLD2, are strongly induced by drought. Overexpression of PbrPLD2 in both Arabidopsis thaliana and pear demonstrated enhanced drought tolerance through improved stomatal closure and increased expression of drought-responsive genes. These findings highlight the critical role of PbrPLD2 in drought resistance and provide a theoretical and experimental foundation for molecular breeding in pear and other fruit crops.

Glutamine Synthetase and Glutamate Synthase Family Perform Diverse Physiological Functions in Exogenous Hormones and Abiotic Stress Responses in Pyrus betulifolia Bunge (P.be)

The unscientific application of nitrogen (N) fertilizer not only increases the economic input of pear growers but also leads to environmental pollution. Improving plant N use efficiency (NUE) is the most effective economical method to solve the above problems. The absorption and utilization of N by plants is a complicated process. Glutamine synthetase (GS) and glutamate synthase (GOGAT) are crucial for synthesizing glutamate from ammonium in plants. However, their gene family in pears has not been documented. This study identified 29 genes belonging to the GS and GOGAT family in the genomes of Pyrus betulaefolia (P.be, 10 genes), Pyrus pyrifolia (P.py, 9 genes), and Pyrus bretschneideri (P.br, 10 genes). These genes were classified into two GS subgroups (GS1 and GS2) and two GOGAT subgroups (Fd–GOGAT and NADH–GOGAT). The similar exon–intron structures and conserved motifs within each cluster suggest the evolutionary conservation of these genes. Meanwhile, segmental duplication has driven the expansion and evolution of the GS and GOGAT gene families in pear. The tissue–specific expression dynamics of PbeGS and PbeGOGAT genes suggest significant roles in pear growth and development. Cis–acting elements of the GS and GOGAT gene promoters are crucial for plant development, hormonal responses, and stress reactions. Furthermore, qRT–PCR analysis indicated that PbeGSs and PbeGOGATs showed differential expression under exogenous hormones (GA3, IAA, SA, ABA) and abiotic stress (NO3− and salt stress). In which, the expression of PbeGS2.2 was up–regulated under hormone treatment and down–regulated under salt stress. Furthermore, physiological experiments demonstrated that GA3 and IAA promoted GS, Fd–GOGAT, and NADH–GOGAT enzyme activities, as well as the N content. Correlation analysis revealed a significant positive relationship between PbeGS1.1, PbeGS2.2, PbeNADH–GOGATs, and the N content. Therefore, PbeGS1.1, PbeGS2.2, and PbeNADH–GOGATs could be key candidate genes for improving NUE under plant hormone and abiotic stress response. To the best of our knowledge, our study provides valuable biological information about the GS and GOGAT family in the pear for the first time and establishes a foundation for molecular breeding aimed at developing high NUE pear rootstocks.

6-Methyl-5-hepten-2-one promotes programmed cell death during superficial scald development in pear

Plants possess the ability to induce programmed cell death (PCD) in response to abiotic and biotic stresses; nevertheless, the evidence on PCD initiation during pear scald development and the involvement of the scald trigger 6-methyl-5-hepten-2-one (MHO) in this process is rudimentary. Pyrus bretschneideri Rehd. cv. ‘Dangshansuli’ pear was used to validate such hypothesis. The results showed that superficial scald occurred after 120-d chilling exposure, which accompanied by typical PCD-associated morphological alterations, such as plasmolysis, cell shrinkage, cytosolic and nuclear condensation, vacuolar collapse, tonoplast disruption, subcellular organelle swelling, and DNA fragmentation. These symptoms were aggravated after MHO fumigation but alleviated by diphenylamine (DPA) dipping. Through transcriptome assay, 24 out of 146 PCD-related genes, which were transcribed during cold storage, were identified as the key candidate members responsible for these cellular biological alternations upon scald development. Among these, PbrCNGC1, PbrGnai1, PbrACD6, and PbrSOBIR1 were implicated in the MHO signaling pathway. Additionally, PbrWRKY2, 34 and 39 could bind to the W-box element in the promoter of PbrGnai1 or PbrSOBIR1 and activate their transcription, as confirmed by dual-luciferase, yeast one-hybrid, and transient overexpression assays. Hence, our study confirms the PCD initiation during scald development and explores the critical role of MHO in this process.

Variation in Bacterial and Fungal Communities in Soils from Three Major Apple Pear (Pyrus bretschneideri Rehd.) Orchards.

Microbial communities are closely related to the overall health and quality of soil, but studies on microbial ecology in apple pear orchard soils are limited. In the current study, 28 soil samples were collected from three apple pear orchards, and the composition and structure of fungal and bacterial communities were investigated by high-throughput sequencing. The molecular ecological network showed that the keystone taxa of bacterial communities were Actinobacteria, Proteobacteria, Gemmatimonadetes, Acidobacteria, Nitrospirae, and Chloroflexi, and the keystone taxon of fungal communities was Ascomycota. Mantel tests showed that soil texture and pH were important factors shaping soil bacterial and fungal communities, and soil water soluble organic carbon (WSOC) and nitrate nitrogen (NO3--N) were also closely related to soil bacterial communities. Canonical correspondence analysis (CCA) and variation partition analysis (VPA) revealed that geographic distance, soil texture, pH, and other soil properties could explain 10.55%, 13.5%, and 19.03% of the overall variation in bacterial communities, and 11.61%, 13.03%, and 20.26% of the overall variation in fungal communities, respectively. The keystone taxa of bacterial and fungal communities in apple pear orchard soils and their strong correlation with soil properties could provide useful clues toward sustainable management of orchards.

Molecular characterization of PSEUDO RESPONSE REGULATOR family in Rosaceae and function of PbPRR59a and PbPRR59b in flowering regulation

BackgroundPSEUDO RESPONSE REGULATOR (PRR) genes are essential components of circadian clock, playing vital roles in multiple processes including plant growth, flowering and stress response. Nonetheless, little is known about the evolution and function of PRR family in Rosaceae species.ResultsIn this study, a total of 43 PRR genes in seven Rosaceae species were identified through comprehensive analysis. The evolutionary relationships were analyzed with phylogenetic tree, duplication events and synteny. PRR genes were classified into three groups (PRR1, PRR5/9, PRR3/7). The expansion of PRR family was mainly derived from dispersed and whole-genome duplication events. Purifying selection was the major force for PRR family evolution. Synteny analysis indicated the existence of multiple orthologous PRR gene pairs between pear and other Rosaceae species. Moreover, the conserved motifs of eight PbPRR proteins supported the phylogenetic relationship. PRR genes showed diverse expression pattern in various tissues of pear (Pyrus bretschneideri). Transcript analysis under 12-h light/ dark cycle and constant light conditions revealed that PRR genes exhibited distinct rhythmic oscillations in pear. PbPRR59a and PbPRR59b highly homologous to AtPRR5 and AtPRR9 were cloned for further functional verification. PbPRR59a and PbPRR59b proteins were localized in the nucleus. The ectopic overexpression of PbPRR59a and PbPRR59b significantly delayed flowering in Arabidopsis transgenic plants by repress the expression of AtGI, AtCO and AtFT under long-day conditions.ConclusionsThese results provide information for exploring the evolution of PRR genes in plants, and contribute to the subsequent functional studies of PRR genes in pear and other Rosaceae species.

Distribution characteristics of selenium and influencing factors in the plant–soil system of an arid oasis

A total of 323 topsoil samples, 63 profile soil samples, and 55 plant root samples were collected from an oasis area on the eastern margin of the Tarim Basin in China and the selenium content and other physical and chemical indicators were analyzed. The results showed that the average selenium content in the surface soil was 0.15 mg/kg, which was lower than the national background value, and only about 4% of the surveyed land area was classified as rich in selenium. The vertical distribution of selenium was characterized by surface accumulation. The organic carbon and clay content were positively correlated and the pH levels negatively correlated with the selenium content. Soil type had little effect on selenium content, though the selenium levels in Anthrosols and Gleysols were relatively high. The selenium content for cultivated land and garden soil was higher than for other land use types. The enrichment of selenium in plant roots was highest for Apocynum venetum L., followed by Pulicaria dysenterica (L.). Bernh., Populus euphratica Olive, Tamarix chinensis Lour., Phragmites australis (Cav.) Trin. ex Steud, and Pyrus bretschneideri Rehder. Correlation analysis revealed that the enrichment of selenium in the soil was mainly controlled by supergenesis in conjunction with long-distance migration and deposition. Overall, this study provides useful information for the rational development and utilization of regional land resources.

R2R3-MYB transcription factor PbMYB5-like positively regulates the biosynthesis of phenylalanine-related metabolites in pear (Pyrus bretschneideri)

The red color of red pears is primarily attributed to the accumulation of anthocyanins, which are biosynthesized via the phenylalanine pathway. However, research into the regulation of these processes is currently limited. The study found that increasing the expression of the transcription factor PbMYB5-like resulted in increased expression of genes involved in anthocyanin, proanthocyanidin (PAs), and lignin biosynthesis, as well as anthocyanin accumulation in pear epidermis. The experiments demonstrated that PbMYB5-like interacts with bHLH3, resulting in the formation of the PbMYB5 like-bHLH3-WD40 complex, which regulates the expression of structural genes such as CCR, F5H, LAR, ANS, UFGT, and others. Furthermore, PbMYB5-like has been demonstrated to directly bind to the promoters of CHI, F3H, ANS, and UFGT genes, thereby regulating the synthesis of related metabolites. The findings of this study provide a foundation for understanding the mechanisms by which PbMYB5-like regulates pear skin color, which is a pivotal aspect in pear breeding and germplasm innovation.

Heat-shock transcription factor HsfA8a regulates heat stress response in Sorbus pohuashanensis.

The SpHsfA8a upregulated expression can induce the expression of multiple heat-tolerance genes, and increase the tolerance of Arabidopsis thaliana to high-temperature stress. Sorbus pohuashanensis is an ornamental tree used in courtyards. However, given its poor thermotolerance, the leaves experience sunburn owing to high temperatures in summer, severely affecting its ornamental value. Heat-shock transcription factors play a critical regulatory role in the plant response to heat stress. To explore the heat-tolerance-related genes of S. pohuashanensis to increase the tree's high-temperature tolerance, the SpHsfA8a gene was cloned from S. pohuashanensis, and its structure and expression patterns in different tissues and under abiotic stresswere analyzed, as well as its function in heat tolerance, was determined via overexpression in Arabidopsis thaliana. The results showed that SpHsfA8a encodes 416 amino acids with a predicted molecular weight of 47.18kDa and an isoelectric point of 4.63. SpHsfA8a is a hydrophilic protein without a signal peptide and multiple phosphorylation sites. It also contains a typical DNA-binding domain and is similar to MdHsfA8a in Malus domestica and PbHsfA8 in Pyrus bretschneideri. In S. pohuashanensis, SpHsfA8a is highly expressed in the roots and fruits and is strongly induced under high-temperature stress in leaves. The heterologous expression of SpHsfA8a in A. thaliana resulted in a considerably stronger growth status than that of the wild type after 6h of treatment at 45°C. Its proline content, catalase and peroxidase activities also significantly increased, indicating that the SpHsfA8a gene increased the tolerance of A. thaliana to high-temperature stress. SpHsfA8a could induce the expression of multiple heat-tolerance genes in A. thaliana, indicating that SpHsfA8a could strengthen the tolerance of A. thaliana to high-temperature stress through a complex regulatory network. The results of this study lay the foundation for further elucidation of the regulatory mechanism of SpHsfA8a in response of S. pohuashanensis to high-temperature stress.

Chloroplast Genome Profiling and Phylogenetic Insights of the “Qixiadaxiangshui” Pear (Pyrus bretschneideri Rehd.1)

The “Qixiadaxiangshui” pear (Pyrus bretschneideri Rehd.1) is a highly valued cultivar known for its crisp texture, abundant juice, and rich aroma. In this study, we reported the first complete chloroplast genome sequence of the “Qixiadaxiangshui” pear, which is 159,885 bp in length with a GC content of 36.58%. The genome exhibits a typical circular quadripartite structure, comprising a large single-copy region (LSC), a small single-copy region (SSC), and a pair of inverted repeat regions (IRs). A total of 131 genes were identified, including 84 protein-coding genes, 8 rRNA genes, and 37 tRNA genes. We also identified 209 simple sequence repeats (SSRs) and several mutation hotspots, such as ndhC-trnM-CAU and trnR-UCU-atpA, which can be applied in molecular identification and phylogenetic studies of Pyrus. Comparative genomic analysis showed high conservation among ten pear cultivars. Phylogenetic analysis indicated that the “Qixiadaxiangshui” pear is closely related to germplasm Dangshansuli, Wonwhang, and Yali, suggesting a recent common ancestor. These findings provided valuable insights into the genetic diversity and evolutionary dynamics of the Pyrus species and contribute to the conservation and breeding of pear germplasm resources.

PbbHLH137 interacts with PbGIF1 to regulate pear fruit development by promoting cell expansion to increase fruit size.

The regulation of fruit development is a complex process and a core issue in the fruit tree industry. To investigate the role of PbGIF1 in pear fruit development, we identified a transcription factor PbbHLH137 that regulates pear (Pyrus bretschneideri) fruit development by screening a yeast library constructed from fruit cDNA. Yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and split luciferase complementation (split-LUC) assays were performed to confirm the PbbHLH137-PbGIF1 interaction. By tracing the complete fruit development process, we found that PbbHLH137 expression was closely related to fruit size and highly involved at the late pear fruit development stage. Transgenic experiments showed that heterologous expression of PbbHLH137 or PbGIF1 promoted fruit enlargement. PbbHLH137 promoted mainly the expansion of fruit cell volume, whereas PbGIF1 mainly increased the number of cells. Further LUC experiments demonstrated that PbGIF1 promoted the transcriptional activation ability of PbbHLH137. Our work identified PbbHLH137 as a transcription factor that regulates fruit development, and showed that PbGIF1 played an ongoing role during fruit development, making it a candidate gene for genetic improvement of pear fruit development.

Genome-wide analysis of the family 10 plant pathogenesis-related proteins in Pyrus bretschneideri and functional analysis of PbrMLP for Colletotrichum fructicola resistance

Pathogenesis-related (PR) genes are key regulators of plant adaptation responses to biotic and abiotic stresses. Family 10 PRs (PR10s, also known as major latex proteins) are usually induced by pathogens and environmental stresses. However, the evolutionary trajectory and functional divergence of the PR10 gene family in Chinese white pear (Pyrus bretschneideri ‘Dangshan Suli’) remain uncharacterized. The presence of 61 PR10s was detected across six Rosaceae species. The PR10 gene family was classified into two distinct groups by employing phylogenetic analysis and the taxonomic criteria of model plants. Interspecies synchrony revealed an ancient origin of the PR10 family in the six Rosaceae species, with 18 synchronic gene pairs. The expansion and evolution of the PR10 family were driven by various types of gene duplication events, with whole-genome duplication (WGD) being the primary mechanism. A candidate Colletotrichum fructicola (C. fructicola) resistance gene Pyrusbretschneiderimajor latex-like proteins (PbrMLP) belonging to the PR10 family was screened through transcriptomics and qRT-PCR. In addition, PbrMLP-silenced pear seedlings were more sensitive to C. fructicola than the controls. These results showed that PbrMLP is a candidate gene vital for anthracnose resistance in pears. These findings offer novel insights into the molecular mechanisms underlying the resistance to pear anthracnose infection in Rosaceae species and identify potential target genes for developing disease-resistant cultivars through genetic engineering.

Transcriptome Profiling Reveals Potential Genes Involved in Salicylic Acid-Induced Arbutin Synthesis in Pear

Salicylic acid (SA) is known to be an efficient elicitor of secondary metabolism in plants. Arbutin, a characteristic phenolic glycoside found in ‘Yuluxiang’ pear (Pyrus bretschneideri Rehder × Pyrus sinkiangensis Yu), is widely used in lightening agents, in addition to cough, anti-inflammatory, and anti-microbial remedies, among other applications. However, research into the synthesis of arbutin in pear is limited. This study aimed to clarify the effect of exogenous SA on the arbutin content of pear using HPLC and investigate the mechanism for arbutin accumulation using RNA-Seq analysis. HPLC revealed that SA increased the arbutin contents of leaf, fruit, and callus in pear and demonstrated that the effect of SA is concentration and time dependent. RNA-Seq analysis of pear callus treated with or without SA revealed 380 differentially expressed genes (DEGs), 335 of which were up-regulated. According to a KEGG database analysis, the highest number of genes were annotated for phenylpropane biosynthesis. Overall, 21 DEGs were found to be involved in the synthesis of hydroquinone and UDP-glucose, which are substrates of arbutin synthesis. It is noteworthy that the expression levels of three up-regulated genes (Pbr006844.1, Pbr021064.1 and Pbr021069.1) related to hydroquinone glycosyltransferase were induced by SA and hydroquinone. Furthermore, transient overexpression of PbUGT72B1 (Pbr021069.1) increased the arbutin content in pear callus. These data explain the regulation of gene transcription associated with the promotive effect of SA on arbutin biosynthesis in pear, thus providing a theoretical foundation for enhancing the arbutin content of fruit through genetic engineering.

Genome-wide characterisation of HD-Zip transcription factors and functional analysis of PbHB24 during stone cell formation in Chinese white pear (Pyrus bretschneideri)

BackgroundThe homodomain-leucine zipper (HD-Zip) is a conserved transcription factor family unique to plants that regulate multiple developmental processes including lignificaion. Stone cell content is a key determinant negatively affecting pear fruit quality, which causes a grainy texture of fruit flesh, because of the lignified cell walls.ResultsIn this study, a comprehensive bioinformatics analysis of HD-Zip genes in Chinese white pear (Pyrus bretschneideri) (PbHBs) was performed. Genome-wide identification of the PbHB gene family revealed 67 genes encoding PbHB proteins, which could be divided into four subgroups (I, II, III, and IV). For some members, similar intron/exon structural patterns support close evolutionary relationships within the same subgroup. The functions of each subgroup of the PbHB family were predicted through comparative analysis with the HB genes in Arabidopsis and other plants. Cis-element analysis indicated that PbHB genes might be involved in plant hormone signalling and external environmental responses, such as light, stress, and temperature. Furthermore, RNA-sequencing data and quantitative real-time PCR (RT-qPCR) verification revealed the regulatory roles of PbHB genes in pear stone cell formation. Further, co-expression network analysis revealed that the eight PbHB genes could be classified into different clusters of co-expression with lignin-related genes. Besides, the biological function of PbHB24 in promoting stone cell formation has been demonstrated by overexpression in fruitlets.ConclusionsThis study provided the comprehensive analysis of PbHBs and highlighted the importance of PbHB24 during stone cell development in pear fruits.

The Fungal Diversity and Potential Pathogens Associated with Postharvest Fruit Rot of 'Huangguan' Pear (Pyrus bretschneideri) in Hebei Province, China.

Postharvest fruit rot caused by pathogens is a serious problem in the pear industry. This study investigated the fungal diversity and main pathogens and identified a new pathogen in the stored 'Huangguan' pear (Pyrus bretschneideri Rehd.), the dominant pear variety in northern China. We sampled 20 refrigeration houses from five main producing regions in Hebei Province and used Illumina sequencing technology to detect the fungal composition. Alternaria (56.3%) was the most abundant fungus, followed by Penicillium (9.2%) and Monilinia (6.2%). We also isolated and identified nine strains of Alternaria and four strains of Penicillium. Moreover, we observed a new postharvest fruit disease in 'Huangguan' pear caused by Stemphylium eturmiunum, which was confirmed by phylogenetic analysis by combining the sequences of three conserved genes, including internal transcribed spacer, gapdh, and calmodulin. This study marks the first documentation of S. eturmiunum causing fruit rot in 'Huangguan' pears, offering valuable insights for identifying and controlling this newly identified postharvest disease.

A Genome-Wide Analysis of the BAM Gene Family and Identification of the Cold-Responsive Genes in Pomegranate (Punica granatum L.).

Beta-amylases (BAMs, EC 3.2.1.2), belonging to a multigene family, play a pivotal role in starch breakdown and are also involved in hormonal and stress responses, notably to cold stress. Pomegranate trees (Punica granatum L.) are adapted to warm climates and are sensitive to cold temperatures. In this study, we analyzed eight PgBAM genes from the pomegranate genome dataset. These members unevenly distributed across chromosomes and were categorized into four groups based on their orthologous members. The motif composition was highly consistent among most members. In contrast, exon numbers and arrangements were conserved within groups or subgroups, whereas significant diversity was observed between different groups. A syntenic analysis revealed that three PgBAM members (PgBAM1/4/5) showed a total of 11 syntenic relationships with the BAM members from Arabidopsis, kiwifruit, and Chinese white pear, respectively. Promoter binding motif prediction suggested potential roles for PgBAMs' genes in light, stress, hormones, and development signaling. Gene expression indicated that PgBAM4 was predominantly expressed in leaves, PgBAM7 in flowers, and PgBAM8 in roots and leaves and during fruit ripening, particularly in pericarp development. A transcriptome analysis identified the starch and sucrose metabolism pathway (map00500) as a key factor in the cold stress response of cold-sensitive cultivar 'Tunisia' seedlings. PgBAM4 exhibited remarkable expression and was closely associated with the cold-responsive BAM genes, characterized by a closer phylogenetic relationship, conserved catalytic residues, and similar secondary and tertiary structures. Moreover, the differences in soluble sugar levels and PgBAM4 expression were closely associated with the varying cold stress resistance observed between 'Tunisia' and 'Sanbai' seedlings. Furthermore, yeast one-hybrid assays confirmed that PgCBF7, a critical transcription factor for enhancing freezing tolerance, binds to the promoter region of PgBAM4. Our findings provide a systematic overview of the PgBAM gene family and shed new light on the regulatory mechanisms underlying cold stress tolerance in pomegranate.

Profiling of soluble sugar compositions in mature fruits of a diverse pear (Pyrus spp.) germplasm by UPLC

Soluble sugars play a vital role as taste components in fruits, significantly contributing to fruit quality. Here, we employed ultraperformance liquid chromatography (UPLC) to determine the sugar composition of mature pear fruits from 142 cultivars. The results revealed that fructose, sorbitol, glucose, and sucrose were the primary soluble sugars present in pear fruit, and Pyrus pyrifolia (China) exhibited the highest total sugar content, followed by Pyrus ussuriensis, Pyrus bretschneideri, Pyrus communis, and Pyrus pyrifolia (Japanese and Korean (J&K)), Pyrus sinkiangensis, and the Hybrid Breeding (HB) cultivars. Furthermore, our study uncovered that the sampling time of these pear cultivars has a significant positive correlation with the content of sorbitol and glucose, respectively. Additionally, the soluble sugar content varied among pear fruits originating from different geographic positions, and the pear cultivars originating from the South China group presented the highest content of soluble sugar. In conclusion, these findings can provide valuable phenotypic data for studying sugar genetics and can also aid in selecting suitable parent cultivars in pear breeding programs.

Transposable elements in Rosaceae: insights into genome evolution, expression dynamics, and syntenic gene regulation.

Transposable elements (TEs) exert significant influence on plant genomic structure and gene expression. Here, we explored TE-related aspects across 14 Rosaceae genomes, investigating genomic distribution, transposition activity, expression patterns, and nearby differentially expressed genes (DEGs). Analyses unveiled distinct long terminal repeat retrotransposon (LTR-RT) evolutionary patterns, reflecting varied genome size changes among nine species over the past million years. In the past 2.5 million years, Rubus idaeus showed a transposition rate twice as fast as Fragaria vesca, while Pyrus bretschneideri displayed significantly faster transposition compared with Crataegus pinnatifida. Genes adjacent to recent TE insertions were linked to adversity resistance, while those near previous insertions were functionally enriched in morphogenesis, enzyme activity, and metabolic processes. Expression analysis revealed diverse responses of LTR-RTs to internal or external conditions. Furthermore, we identified 3695 pairs of syntenic DEGs proximal to TEs in Malus domestica cv. 'Gala' and M. domestica (GDDH13), suggesting TE insertions may contribute to varietal trait differences in these apple varieties. Our study across representative Rosaceae species underscores the pivotal role of TEs in plant genome evolution within this diverse family. It elucidates how these elements regulate syntenic DEGs on a genome-wide scale, offering insights into Rosaceae-specific genomic evolution.

Reactive Oxygen Species and Salicylic Acid Mediate the Responses of Pear to Venturia nashicola Infection

Reactive oxygen species (ROS) and salicylic acid (SA) are essential signaling molecules in plant cells that participate in responses to biotic and abiotic stresses. Changes in ROS and SA signals during interactions between pear and the pear scab pathogen Venturia nashicola remain unclear. Herein, we analyzed the roles of ROS in the signal transduction pathway of pear scab resistance using the highly resistant Huangguan and susceptible Xuehua cultivars of pear (Pyrus bretschneideri Rehd). Protoplasts, calluses, and leaves were obtained from 14-year-old pear trees and treated with V. nashicola for different periods. The results showed that ROS rapidly accumulated in protoplasts of both cultivars within a 120-min treatment period, but the fluorescence intensity of ROS differed between cultivars. The H2O2 content in fruit-derived calluses of Huangguan peaked at 48 h post-infection at levels 1.85 times higher than those in Xuehua. Induction of H2O2 by V. nashicola in Huangguan was more intense than in Xuehua over a 96-h treatment period. At 96 h post-infection, the malondialdehyde content in leaves of Huangguan was significantly lower than in Xuehua, while the activities of superoxide dismutase, peroxidase, and catalase, and the relative expression levels of PbMnSOD, PbPOD, and PbCAT genes were higher in Huangguan than Xuehua. V. nashicola infection also caused a continuous increase in the leaf SA content of Huangguan, which was 6.76 times higher than in Xuehua at 96 h post-infection, and V. nashicola exposure upregulated the expression of PbPAL, PbICS, PbPR1, and PbPR5. In summary, both ROS and SA participated in the responses of pear trees to V. nashicola infection and played vital roles in the signal transduction pathway of pear scab resistance.