Perturbation of IP3R-dependent endoplasmic reticulum calcium homeostasis by PPARδ-activated metabolic stress leads to mouse spermatocyte apoptosis: A direct mechanism for perfluorooctane sulfonic acid-induced spermatogenic disorders.

Perfluorooctane sulfonic acid (PFOS) as an archetypal representative of per- and polyfluoroalkyl substances (PFAS) is ubiquitously distributed in the environment and extensively detected in human bodies. Although accumulating evidence is suggestive of the deleterious effects of PFOS on male reproduction, the direct toxicity of PFOS towards spermatogenic cells and the relevant mechanisms remain poorly understood. The aims of the present study were to explore the direct effects and underlying molecular mechanisms of PFOS on spermatogenesis. Through integrating animal study, transcriptome profiling, in silico toxicological approaches, and in vitro validation study, we identified the molecular initiating event and key events contributing to PFOS-induced spermatogenic impairments. The mouse experiments revealed that spermatocytes were involved in PFOS-induced spermatogenic disorders and the activation of peroxisome proliferator-activated receptor delta (PPARδ) was linked to spermatocyte loss in PFOS-administrated mice. GC-2spd(ts) cells were treated with an increased gradient of PFOS, which was relevant to environmental and occupational exposure levels of PFOS in populations. Following 72-h treatment, cells was harvested for RNA sequencing. The transcriptome profiling and benchmark dose (BMD) modeling identified endoplasmic reticulum (ER) stress as the key event for PFOS-mediated spermatocyte apoptosis and determined the point-of-departure (PoD) for perturbations of ER stress signaling. Based on the calculated PoD value, further bioinformatics analyses combined with in vitro and in vivo validations showed that PFOS caused metabolic stress by activating PPARδ in mouse spermatocytes, which was responsible for Beclin 1-involved inositol 1,4,5-trisphosphate receptor (IP3R) sensitization. The disruption of IP3R-mediated ER calcium homeostasis triggered ER calcium depletion, leading to ER stress and apoptosis in mouse spermatocytes exposed to PFOS. This study systematically investigated the direct impacts of PFOS on spermatogenesis and unveiled the relevant molecular mechanism of PFOS-induced spermatogenic disorders, providing novel insights and potential preventive/therapeutic targets for PFAS-associated male reproductive toxicity.

TERT transcription and translocation into mitochondria regulate benzo[a]pyrene/BPDE-induced senescence and mitochondrial damage in mouse spermatocytes.

Telomere and mitochondria may be the targets of Benzo[a]pyrene (BaP) -induced male reproductive damage, and further elucidation of the toxic molecular mechanisms is necessary. In this study, we used in vivo and in vitro exposure models to explore the molecular mechanisms of TERT regulation in BaP-induced telomere and mitochondrial damage in spermatocytes. The results showed that the treatment of benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), the active metabolite of BaP, caused telomere dysfunction in mouse spermatocyte-derived GC-2 cells, resulting in S-phase arrest and increased senescence-associated secretory phenotype (SASP). These effects were significantly alleviated by telomerase agonist (ABG) pretreatment in GC-2 cells. SIRT1, FOXO3a, or c-MYC overexpressing GC-2 cell models were established to demonstrate that BPDE inhibited TERT transcriptional expression through the SIRT1/FOXO3a/c-MYC pathway, leading to telomere dysfunction. We also observed that BPDE induced mitochondrial compromise, including complex I damage, accompanied by reduced mitochondrial TERT expression. Based on this, we constructed wild-type TERT-overexpressing (OE-TERTwt) and mitochondria targeting TERT-overexpressing (OE-TERTmst) GC-2 cell models and found that OE-TERTmst GC-2 cells improved mitochondrial function better than OE-TERTwt GC-2 cells. Finally, ICR mice were given BaP by intragastric administration for 35 days, which verified the results of the in vitro study. The results shown that BaP exposure can lead to spermatogenesis disturbance, which is related to the telomere and mitochondrial damage in spermatocytes. In conclusion, our results suggest that BPDE causes telomere and mitochondrial damage in spermatocytes by inhibiting TERT transcription and mitochondrial TERT expression. This study elucidates the molecular mechanism of male reproductive toxicity due to environmental pollutant BaP, and also provides a new perspective for the exploration of interventions and protective measures against male reproductive damage by BaP.

PPARα/ACOX1 as a novel target for hepatic lipid metabolism disorders induced by per- and polyfluoroalkyl substances: An integrated approach.

BACKGROUND: Per- and polyfluoroalkyl substances (PFAS) are persistent and ubiquitous environmental contaminants with well-documented hepatotoxicity. However, the mechanistic linkage between PFAS exposure and non-alcoholic fatty liver disease (NAFLD) remains largely elusive. OBJECTIVES: This study aimed to explore PFAS-to-NAFLD link and the relevant molecular mechanisms. METHODS: The cross-sectional analyses using National Health and Nutrition Examination Survey (NHANES) data were conducted to investigate the association between PFAS exposure and NAFLD. A combination of in silico toxicological analyses, bioinformatics approaches, animal experiments, and in vitro assays was used to explore the molecular initiating events (MIEs) and key events (KEs) in PFAS-induced hepatic lipid metabolism disorders. RESULTS: The cross-sectional analyses with NHANES data revealed the significant association between PFAS exposure and hepatic steatosis/NAFLD. The in silico toxicological analyses showed that PPARα activation induced by perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), prototypical representatives of PFAS, is the critical MIE associated with NAFLD-predominant liver diseases. Transcriptome-based bioinformatic annotation and analyses identified that transcriptional upregulation of hepatic acyl-CoA oxidase 1 (ACOX1) in PPARα-regulated peroxisomal ß-oxidation pathway was the KE involved with PFOA/PFOS-perturbed hepatic lipid metabolic pathways in humans, mice and rats. The in vivo and in vitro assays further verified that ACOX1-mediated oxidative stress contributed to mitochondrial compromise and lipid accumulation in PFOA/PFOS-exposed mouse hepatocytes, which could be mitigated by co-treatment with ACOX1 inhibitor and mitochondria ROS scavenger. Additionally, we observed that besides PFOA and PFOS, hepatic ACOX1 exhibited good-fit response to short-term exposures of long-chain (C7-C10) perfluoroalkyl carboxylic acids (PFHpA, PFNA, PFDA) and perfluoroalkyl sulfonic acids (PFHpS, PFDS) in human hepatocyte spheroids through benchmark dose (BMD) modeling. CONCLUSION: Our study unveils a novel molecular target for PFAS-induced hepatic lipid metabolic disorders, shedding new light on prediction, assessment, and mitigation of PFAS hepatotoxicity.

Sperm telomere length is associated with sperm nuclear DNA integrity and mitochondrial DNA abnormalities among healthy male college students in Chongqing, China.

STUDY QUESTION: Is sperm telomere length (STL) associated with sperm nuclear DNA damage and mitochondrial DNA abnormalities? SUMMARY ANSWER: Sperm telomere length is related to sperm nuclear DNA integrity and mitochondrial DNA abnormalities in healthy young college students. WHAT IS KNOWN ALREADY: Many studies have revealed the correlations between sperm genetic alterations in both the nucleus and mitochondria and sperm functionality, however, the possible associations between the telomere, an important component of chromosome, and conventional indicators of mitochondrial DNA and nuclear DNA changes have not been investigated. STUDY DESIGN, SIZE, DURATION: A prospective cohort study, Male Reproductive Health in Chongqing College Students (MARHCS), was conducted from June 2013 to June 2015. We pooled data collected from the follow-up study in 2014 and a total of 444 participants were included. PARTICIPANTS/MATERIALS, SETTING, METHODS: STL was measured by quantitative (Q)-PCR. Sperm nuclear DNA integrity was determined using sperm chromatin structure assay (SCSA) and comet assay. Mitochondrial DNA damage was assessed by mitochondrial DNA copy number (mtDNAcn) evaluated with Q-PCR, and mtDNA integrity was determined with long PCR. MAIN RESULTS AND THE ROLE OF CHANCE: The univariable-linear regression analysis revealed that STL was significantly positively correlated with markers of sperm nuclear DNA damage including the DNA fragmentation index (DFI) and comet parameters (the percentage of DNA in the tail, tail length, comet length, and tail moment). Additionally, STL was also significantly positively correlated with mtDNAcn and significantly negatively correlated with mtDNA integrity. After adjustment for potential confounders, these relationships remained appreciable. Moreover, we investigated potential effects of biometric factors, including age, parental age at conception, and BMI on STL and found that STL was increased with paternal age at conception. LIMITATIONS, REASONS FOR CAUTION: A mechanistic explanation of the correlation between STL, sperm nuclear DNA integrity, and mtDNA abnormalities cannot be provided with a cross-sectional study design, so well-designed longitudinal studies are still necessary. In addition, a single semen samples were provided and were not all obtained at the same time point, which may increase the intraindividual bias in this study. WIDER IMPLICATIONS OF THE FINDINGS: The findings extend the literature including assessment of mitochondrial dysfunction, sperm nuclear DNA damage, and telomere length and provide new insights into the relevance of STL in male reproduction. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the National Natural Science Foundation of China (No. 82073590), the National Natural Science Foundation of China (No. 81903363), the National Natural Science Foundation of China (No. 82130097), and the National Key R&D Program of China (2022YFC2702900). The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

CsTRM5 regulates fruit shape via mediating cell division direction and cell expansion in cucumber.

Fruit shape and size are important appearance and yield traits in cucumber, but the underlying genes and their regulatory mechanisms remain poorly understood. Here we identified a mutant with spherical fruits from an Ethyl Methane Sulfonate (EMS)-mutagenized library, named the qiu mutant. Compared with the cylindrical fruit shape in 32X (wild type), the fruit shape in qiu was round due to reduced fruit length and increased fruit diameter. MutMap analysis narrowed the candidate gene in the 6.47 MB range on Chr2, harboring the FS2.1 locus reported previously. A single-nucleotide polymorphism (SNP) (11359603) causing a truncated protein of CsaV3_2G013800, the homolog of tomato fruit shape gene SlTRM5, may underlie the fruit shape variation in the qiu mutant. Knockout of CsTRM5 by the CRISPR-Cas9 system confirmed that CsaV3_2G013800/CsTRM5 was the causal gene responsible for qiu. Sectioning analysis showed that the spherical fruit in qiu resulted mainly from increased and reduced cell division along the transverse and longitudinal directions, respectively. Meanwhile, the repressed cell expansion contributed to the decreased fruit length in qiu. Transcriptome profiling showed that the expression levels of cell-wall-related genes and abscisic acid (ABA) pathway genes were significantly upregulated in qiu. Hormone measurements indicated that ABA content was greatly increased in the qiu mutant. Exogenous ABA application reduced fruit elongation by inhibiting cell expansion in cucumber. Taken together, these data suggest that CsTRM5 regulates fruit shape by affecting cell division direction and cell expansion, and that ABA participates in the CsTRM5-mediated cell expansion during fruit elongation in cucumber.

A recessive gene Cmpmr2F confers powdery mildew resistance in melon (Cucumis melo L.).

KEY MESSAGE: Identified a recessive gene (Cmpmr2F) associated with resistance to infection by the powdery mildew causing agent Podosphaera xanthii race 2F. Powdery mildew (PM) is one of the most destructive fungal diseases of melon, which significantly reduces the crop yield and quality. Multiple studies are being performed for in-depth genetic understandings of PM-susceptibility or -resistance mechanisms in melon plants, but the holistic knowledge of the precise genetic basis of PM-resistance is unexplored. In this study, we characterized the recessive gene "Cmpmr2F" and found its association with resistance against the PM causative agent "Podosphaera xanthii race 2F." Fine genetic mapping revealed the major-effect region of a 26.25-kb interval on chromosome 12, which harbored the Cmpmr2F gene corresponding to the MELO3C002403, encoding allantoate amidohydrolase. The functional gene annotation, expression pattern, and sequence alignment analyses were carried out using two contrast parent lines of melon "X055" PM-susceptible and "PI 124112" PM-resistant. Further, gene silencing of Cmpmr2F using virus-induced gene silencing (VIGS) significantly increased PM-resistance in the susceptible plant. In contrast to the previously reported studies, we identified that Cmpmr2F-silenced plants showed no impairment in growth due to less apparent negative effects in silenced melon plants. So, it is believed that the Cmpmr2F gene has great potential for further breeding studies to increase the P. xanthii race 2F resistance in melon. In short, our study provides new genetic resources and a solid foundation for further functional analysis of PM-resistance genes in melon, as well as powerful molecular markers for marker-assisted breeding aimed at developing new melon varieties resistant to PM infection.

Benzo[a]pyrene inhibits testosterone biosynthesis via NDUFA10-mediated mitochondrial compromise in mouse Leydig cells: Integrating experimental and in silico toxicological approaches.

Benzo[a]pyrene (B[a]P), a representative of polycyclic aromatic hydrocarbons (PAHs), is ubiquitously spread in the environment and showing deleterious impacts on male steroidogenesis, including testosterone synthesis disorder. However, the precise mechanisms involved in B[a]P-induced steroidogenesis perturbation remains obscure. In the present study, we integrated in vivo tests, transcriptome profiling, in vitro assays, and conjoint in silico toxicological approaches to delineate the detailed mechanisms. In mouse models, we observed that B[a]P administration remarkably inhibited testosterone synthesis accompanied by ultrastructural impairments of mitochondria and mitophagosome formation in mouse Leydig cells. Transcriptome profiling showed that B[a]P down-regulated the expression of Ndufa9, Ndufa6, Ndufa10, and Ndufa5 in mouse testes, which are identified as critical genes involved in the assembly and functionality of mitochondrial complex I. In the in vitro tests, the bioactive B[a]P metabolite BPDE induced perturbation of testosterone synthesis by NDUFA10-mediated mitochondrial impairment, which was further exacerbated by mitophagy in TM3 Leydig cells. The findings of in silico toxicological analyses were highly consistent with the experimental observations and further unveiled that B[a]P/BPDE-involved PPARα activation could serve as a molecular initiating event to trigger the decline in Ndufa10 expression and testosterone synthesis. Overall, we have shown the first evidence that mitochondrial compromise in Leydig cells is the extremely crucial target in B[a]P-induced steroidogenesis perturbation.

Natural Polysaccharide Strengthened Hydrogel Electrolyte and Biopolymer Derived Carbon for Durable Aqueous Zinc Ion Storage.

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) represent one of the current research subjects because of their flame retardancy, ease of manufacturing, and exceptional roundtrip efficiency. With the evolution into real useful energy storage cells, the bottleneck factors of the corrosion and dendrite growth problems must be properly resolved for largely boosting their cycling life and energy efficiency. Herein, a natural polysaccharide strengthened hydrogel electrolyte (denoted as PAAm/agar/Zn(CF3SO3)2) was engineered by designing an asymmetric dual network of covalently cross-linked polyacrylamide (denoted as PAAm) and physically cross-linked loose polysaccharide (e.g., agar) followed by intense uptake of Zn(CF3SO3)2 aqueous electrolyte. In this polymeric matrix, the PAAm chains are responsible for constructing the soft domains to immobilize the water molecules, and the agar component boosts the mechanical performance (by using its inherent reversible sacrificial bonds) and favors the electrolyte ion transport. Due to these reasons, the as-designed hydrogel electrolyte effectively inhibits the zinc dendrite growth, realizes the uniform Zn deposition, and affords a satisfactory ionic conductivity of 1.55 S m-1, excellent tensile strength (78.9 kPa at 507.7% stretchable), and high compression strength (118.0 kPa at 60.0% strain). Additionally, a biopolymer-derived N-doped carbon microsphere cathode material with a highly interconnected porous carbonaceous network (denoted as NC) was also synthesized, which delivers a high capacity of 92.8 mAh g-1, along with superb rate capability and long duration cycling lifespan (95.4% retention for 10000 cycles) in the aqueous Zn//NC ZHSC. More notably, with integrated merits of the PAAm/agar/Zn(CF3SO3)2 hydrogel electrolyte and NC, the as-built quasi-solid-state ZHSC achieves a high specific capacity of 73.4 mAh g-1 and superior energy density of 61.3 Wh kg-1 together with excellent cycling stability for 10000 cycles. This work demonstrated favorable practicability in the structural design of the hydrogel electrolytes and electrode materials for advanced ZHSC applications.

Analysis by transcriptomics and metabolomics for the proliferation inhibition and dysfunction through redox imbalance-mediated DNA damage response and ferroptosis in male reproduction of mice and TM4 Sertoli cells exposed to PM2.5.

Sertoli cells play a pivotal role in the complex spermatogenesis process. This study aimed to investigate the effects of PM2.5 on Sertoli cells using the TM4 cell line and a real time whole-body PM2.5 exposure mouse model, and further explore the underlying mechanisms through the application of metabolomics and transcriptomics. The results in vivo and in vitro showed that PM2.5 reduced Sertoli cells number in seminiferous tubules and inhibited cell proliferation. PM2.5 exposure also induced Sertoli cell dysfunction by increasing androgen binding protein (ABP) concentration, reducing the blood-testis barrier (BTB)-related protein expression, and decreasing glycolysis capacity and lactate production. The results of transcriptomics, metabolomics, and integrative analysis of multi-omics in the TM4 Sertoli cells revealed the activation of xenobiotic metabolism, and the disturbance of glutathione and purine metabolism after PM2.5 exposure. Further tests verified the reduced GSH/GSSG ratio and the elevation of xanthine oxidase (XO) activity in the PM2.5-exposed TM4 cells, indicating that excessive reactive oxygen species (ROS) was generated via metabolic disorder caused by PM2.5. Moreover, the redox imbalance was proved by the increase in the mitochondrial ROS level, superoxide dismutase (SOD) and catalase (CAT) activity, as well as the activation of the Nrf2 antioxidative pathway. Further study found that the redox imbalance caused by PM2.5 induced DNA damage response and cell cycle arrest. Additionally, PM2.5 induced ferroptosis through iron overload and lipid peroxidation. Taken all together, our study provided new insights for understanding proliferation inhibition and dysfunction of TM4 Sertoli cells exposed to PM2.5 via metabolic disorder and redox imbalance-mediated DNA damage response and ferroptosis.

CmPMRl and CmPMrs are responsible for resistance to powdery mildew caused by Podosphaera xanthii race 1 in Melon.

KEY MESSAGE: Two genes for resistance to Podosphaera xanthii race 1 in melon were identified on chromosomes 10 and 12 of the Cucumis melo cultivar MR-1. Cucumis melo L. is an economically important crop, the production of which is threatened by the prevalence of melon powdery mildew (PM) infections. We herein utilized the MR-1 (P1; resistant to PM) and M4-7 (P2; susceptible to PM) accessions to assess the heritability of PM (race 1) resistance in these melon plants. PM resistance in MR-1 leaves was linked to a dominant gene (CmPMRl), whereas stem resistance was under the control of a recessive gene (CmPMrs), with the dominant gene having an epistatic effect on the recessive gene. The CmPMRl gene was mapped to a 50 Kb interval on chromosome 12, while CmPMrs was mapped to an 89 Kb interval on chromosome 10. The CmPMRl candidate gene MELO3C002441 and the CmPMrs candidate gene MELO3C012438 were identified through sequence alignment, functional annotation, and expression pattern analyzes of all genes within these respective intervals. MELO3C002441 and MELO3C012438 were both localized to the cellular membrane and were contained conserved NPR gene-like and MLO domains, respectively, which were linked to PM resistance. In summary, we identified patterns of PM resistance in the disease-resistant MR-1 melon cultivar and identified two putative genes linked to resistance. Our results offer new genetic resources and markers to guide future marker-assisted breeding for PM resistance in melon.

Color-changing fluorescent DNA probe containing solvatochromic Dansyl-nucleoside surrogate for sensing local variation of DNA duplex.

A novel Dansyl-nucleoside surrogate (Dns) based on (±)-trans-4-(hydroxymethyl) piperidin-3-ol was designed and synthesized. The Dns exhibited excellent solvatochromic properties. About 90 nm of red-shift accompanied color change from green to orange could be achieved with an increase of solvent polarity. The Dns was incorporated into oligodeoxynucleotide by phosphoroamidite chemistry. Two kinds of Dns-incorporated fluorescent DNA probes were designed and synthesized for sensing variation of DNA duplexes based on color-changing manner. As a result, the color-changing DNA probe not only can detect complementary oligonucleotide, but also can distinguish mismatch flanked in Dansyl/nucleobase pair by naked eye. Moreover, the change of fluorescence color of sample solutions could be captured by smartphone, and the photographs could be digitalized by image-processing software. Thus, the Dns-incorporated fluorescent DNA probe is expected to open the way to point-of-care assays in the future.

A safe and robust dual-network hydrogel electrolyte coupled with multi-heteroatom doped carbon nanosheets for flexible quasi-solid-state zinc ion hybrid supercapacitors.

Aqueous zinc ion hybrid supercapacitors (ZHSCs) are receiving increasing research interest because of their superiority in safety, economy, and high water compatibility. However, the corrosion problems coupled with dendrite growth in an aqueous system severely limit the potential use of zinc storage systems with long service life. To delicately address the above obstacles, a κ-carrageenan/polyacrylamide/Zn(CF3SO3)2 hydrogel electrolyte (denoted as κ-CG/PAAm/Zn(CF3SO3)2) with an ionically and covalently double crosslinked network was constructed, which possesses a high ionic conductivity of 2.3 S m-1, a high tensile strength of 34.6 kPa with a superior stretchability of 599.0%, and an excellent compression strength of 75.3 kPa at 75.0% strain. The double crosslinked polymer chains realize uniform zinc deposition. In addition, the intrinsic hydrophilic groups in the κ-carrageenan (κ-CG) and polyacrylamide (PAAm) chains can well immobilize water molecules, which favor electrolyte ion transport. Moreover, nitrogen and sulphur co-doped carbon nanosheets (denoted as ACNS) characterized by the rich amorphous phase associated with lots of short-range ordered microcrystalline regions were prepared as the cathode material in this work, which exhibits a high capacity of 116.4 mA h g-1 coupled with superior rate performance and long-term cycling stability (108.0% capacity retention over 10 000 cycles) for an aqueous Zn//ACNS ZHSC. A quasi-solid-state ZHSC based on ACNS and κ-CG/PAAm/Zn(CF3SO3)2 exhibits a specific capacity of 100.5 mA h g-1 at 0.25 A g-1 with a high capacity retention of 50.8% at 20 A g-1. The as-fabricated ZHSC also shows excellent cycling stability of 10 000 cycles as well as a superior energy density of 86.5 W h kg-1 at a power density of 215.3 W kg-1. The ZHSC can also be used as a reliable source to drive various kinds of electronics (e.g., mobile phones and electronic timers), which uncovers a feasible strategy for engineering the high-performance hydrogel electrolytes and cathode materials for ZHSC applications.

Phosphate-modified Co-Ni phosphide heterostructure formed by interfacial and electronic tuning for boosted faradaic properties.

Rational structural and compositional modulation endows electrode materials with unique physicochemical characteristics due to their adjustable electronic properties. Herein, a phosphate-modified hierarchical nanoarray consisting of a heterojunction with a well-aligned cobalt phosphide nanowire core and nickel phosphide nanosheet shell on flexible carbon cloth (denoted as CoP@Ni2P-CC) is engineered. The phosphate-modulated heterogeneous phosphide with a tuned electronic structure, additional heterojunction interfaces, and high degree of covalency in the chemical bonds accelerates the reaction kinetics and enhances the energy storage performance. Due to these reasons, the as-obtained phosphide-based heterostructured CoP@Ni2P-CC electrode delivers a capacity of 475.9 C g-1 at 0.5 A g-1 with a satisfying rate capability, which is greatly superior to that of its transition metal counterparts (sulfide, selenide, and oxide). After being assembled into a flexible hybrid supercapacitor (FHSC), a wide operating voltage (1.8 V), high energy/power densities (49.8 W h kg-1/8.6 kW kg-1), and long-term stability (85.1% capacity retention after 10 000 cycles) were achieved. This work may provide a general method from multiple strategies for designing reliable pseudocapacitive materials for flexible electronics.

Comparative analysis of nuclear, chloroplast, and mitochondrial genomes of watermelon and melon provides evidence of gene transfer.

During plant evolution, there is genetic communication between organelle and nuclear genomes. A comparative analysis was performed on the organelle and nuclear genomes of the watermelon and melon. In the watermelon, chloroplast-derived sequences accounted for 7.6% of the total length of the mitochondrial genome. In the melon, chloroplast-derived sequences accounted for approximately 2.73% of the total mitochondrial genome. In watermelon and melon, the chloroplast-derived small-fragment sequences are either a subset of large-fragment sequences or appeared multiple times in the mitochondrial genome, indicating that these fragments may have undergone multiple independent migration integrations or emerged in the mitochondrial genome after migration, replication, and reorganization. There was no evidence of migration from the mitochondria to chloroplast genome. A sequence with a total length of about 73 kb (47%) in the watermelon chloroplast genome was homologous to a sequence of about 313 kb in the nuclear genome. About 33% of sequences in the watermelon mitochondrial genome was homologous with a 260 kb sequence in the nuclear genome. A sequence with a total length of about 38 kb (25%) in the melon chloroplast genome was homologous with 461 sequences in the nuclear genome, with a total length of about 301 kb. A 3.4 Mb sequence in the nuclear genome was homologous with a melon mitochondrial sequence. These results indicate that, during the evolution of watermelon and melon, a large amount of genetic material was exchanged between the nuclear genome and the two organelle genomes in the cytoplasm.

The complete chloroplast genome sequence of the Sechium edule (Jacq.) Swartz. (Cucurbitaceae).

Sechium edule (Jacq.) Swartz is an important vegetable with both food and medicinal values. The complete chloroplast genome sequence of S. edule has been reported in this study. The total genome size is 154,558 bp in length and contains a pair of inverted repeats (IRs) of 19,128 bp, which were separated by large single-copy (LSC) and small single-copy (SSC) of 98,806 and 17,496 bp, respectively. A total of 122 genes were predicted including 78 protein-coding genes, 8 rRNA genes, and 36 tRNA genes. Further, the phylogenetic analysis confirmed that S. edule belongs to the family Cucurbitaceae. The complete chloroplast genome of S. edule would play a significant role in the development of molecular markers for plant phylogenetic and population genetic studies.

Population structure and genetic diversity of watermelon (Citrullus lanatus) based on SNP of chloroplast genome.

Citrullus amarus (citronmelon) is an important crop with resistance to many diseases. The chloroplast genome is important in studying the genetic evolution of plants. The C. amarus chloroplast genome was first reported in this study using a novel assembly method based on whole genome sequencing. We identified 82 SNP sites in chloroplast genome with 313 watermelon materials. The 82 SNPs could effectively divide the natural watermelon population into four groups: C. lanatus subsp. lanatus, C. lanatus subsp. mucosospermus, C. lanatus subsp. vulgaris (ecologically from the Americas) and C. lanatus subsp. vulgaris (ecologically from Asia), with decreasing genetic diversity (π) (6.6 × 10-5, 2.4 × 10-5, 9.8 × 10-6 and 5.41 × 10-6, respectively). The single fruit weight, soluble solids, fruit color and 1000-seed weight of C. lanatus subsp. lanatus were significantly different from those of the other three groups. These results indicate that the complete chloroplast genome can be used in studying population genetics of watermelon, which is helpful for classification among intra species subgroups and identification of core germplasm resources.

Linkage Mapping and Comparative Transcriptome Analysis of Firmness in Watermelon (Citrullus lanatus).

Watermelon fruit texture and quality are determined by flesh firmness. As a quality trait, flesh firmness is controlled by multigenes. Defining the key regulatory factors of watermelon flesh firmness is of great significance for watermelon genetic breeding. In this study, the hard-flesh egusi seed watermelon PI186490 was used as the male parent, the soft-flesh cultivated watermelon W1-1 was used as the female parent, and 175 F2 generations were obtained from selfing F1. Primary mapping of the major genes controlling center flesh firmness was achieved by bulked-segregant analysis (BSA)-Seq analysis and molecular marker technology. Finally, major genes were delimited in the physical interval between 6,210,787 and 7,742,559 bp on chromosome 2 and between 207,553 and 403,137 bp on chromosome 8. The content of each cell wall component and hormone was measured, and comparative transcriptome analysis was performed during fruit development in watermelon. The protopectin, cellulose, hemicellulose, indole-3-acetic acid (IAA) and abscisic acid (ABA) contents were measured, and paraffin sections were made during the three fruit developmental stages. The results revealed that protopectin, celluloses, and hemicelluloses exhibited similar trends for flesh firmness, while the IAA and ABA concentrations continued to decrease with fruit ripening. Paraffin sections showed that PI186490 cells were more numerous, were more tightly packed, had clearer cell wall edges and had thicker cell walls than W1-1 cells at every developmental stage. Comparative transcriptome analysis was conducted on RNA samples of flesh during fruit development and ripening in W1-1 and PI186490. The results from the localization interval transcriptome analysis showed that Cla016033 (DUF579 family member), which may influence the cell wall component contents to adjust the flesh firmness in watermelon fruit, was different in W1-1 and PI186490 and that Cla012507 (MADS-box transcription factor) may be involved in the regulation of fruit ripening and affect the hardness of watermelon fruit.

Identification of lncRNAs and their regulatory relationships with target genes and corresponding miRNAs in melon response to powdery mildew fungi.

Melon (Cucumis melo L.), an economically beneficial crop widely cultivated around the world, is vulnerable to powdery mildew (PM). However, the studies on molecular mechanism of melon response to PM fungi is still limited. Long non coding RNAs (lncRNAs) have emerged as new regulators in plants response to biotic stresses. We predicted and identified the intricate regulatory roles of lncRNAs in melon response to PM fungi. A total of 539 lncRNAs were identified from PM-resistant (MR-1) and susceptible melon (Top Mark), in which 254 were significantly altered after PM fungi infection. Multiple target genes of lncRNAs were found to be involved in the hydrolysis of chitin, callose deposition and cell wall thickening, plant-pathogen interaction and plant hormone signal transduction pathway. Additionally, a total of 42 lncRNAs possess the various functions with microRNAs (miRNAs), including lncRNAs that are targeted by miRNAs and function as miRNA precursors or miRNA sponges. These findings provide a comprehensive view of potentially functional lncRNAs, corresponding target genes and related lncRNA-miRNA pairs, which will greatly increase our knowledge of the mechanism underlying susceptibility and resistance to PM in melon.