Methylation of a MITE insertion in the MdRFNR1-1 promoter is positively associated with its allelic expression in apple in response to drought stress.

Miniature inverted-repeat transposable elements (MITEs) are widely distributed in the plant genome and can be methylated. However, whether DNA methylation of MITEs is associated with induced allelic expression and drought tolerance is unclear. Here, we identified the drought-inducible MdRFNR1 (root-type ferredoxin-NADP+ oxidoreductase) gene in apple (Malus domestica). MdRFNR1 plays a positive role in drought tolerance by regulating the redox system, including increasing NADP+ accumulation and catalase and peroxidase activities and decreasing NADPH levels. Sequence analysis identified a MITE insertion (MITE-MdRF1) in the promoter of MdRFNR1-1 but not the MdRFNR1-2 allele. MdRFNR1-1 but not MdRFNR1-2 expression was significantly induced by drought stress, which was positively associated with the MITE-MdRF1 insertion and its DNA methylation. The methylated MITE-MdRF1 is recognized by the transcriptional anti-silencing factors MdSUVH1 and MdSUVH3, which recruit the DNAJ domain-containing proteins MdDNAJ1, MdDNAJ2, and MdDNAJ5, thereby activating MdRFNR1-1 expression under drought stress. Finally, we showed that MdSUVH1 and MdDNAJ1 are positive regulators of drought tolerance. These findings illustrate the molecular roles of methylated MITE-MdRF1 (which is recognized by the MdSUVH-MdDNAJ complex) in induced MdRFNR1-1 expression as well as the drought response of apple and shed light on the molecular mechanisms of natural variation in perennial trees.

Genome-wide identification and expression analysis of the glycosyl hydrolase family 1 genes in Medicago sativa revealed their potential roles in response to multiple abiotic stresses.

Glycoside hydrolase family 1 (GH1) ß-glucosidases (BGLUs), are encoded by a large number of genes, which participate in the development and stress response of plants, particularly under biotic and abiotic stresses through the activation of phytohormones. However, there are few studies systematically analyzing stress or hormone-responsive BGLU genes in alfalfa. In this study, a total of 179 BGLU genes of the glycoside hydrolase family 1 were identified in the genome of alfalfa, and then were classified into five distinct clusters. Sequence alignments revealed several conserved and unique motifs among these MsBGLU proteins. Many cis-acting elements related to abiotic stresses and phytohormones were identified in the promoter of some MsBGLUs. Moreover, RNA-seq and RT-qPCR analyses showed that these MsBGLU genes exhibited distinct expression patterns in response to different abiotic stress and hormonal treatments. In summary, this study suggests that MsBGLU genes play crucial roles in response to various abiotic stresses and hormonal responses, and provides candidate genes for stress tolerance breeding in alfalfa.

Integrated physiological, metabolomic, and transcriptomic analyses elucidate the regulation mechanisms of lignin synthesis under osmotic stress in alfalfa leaf (Medicago sativa L.).

Alfalfa, an essential forage crop known for its high yield, nutritional value, and strong adaptability, has been widely cultivated worldwide. The yield and quality of alfalfa are frequently jeopardized due to environmental degradation. Lignin, a constituent of the cell wall, enhances plant resistance to abiotic stress, which often causes osmotic stress in plant cells. However, how lignin responds to osmotic stress in leaves remains unclear. This study explored the effects of osmotic stress on lignin accumulation and the contents of intermediate metabolites involved in lignin synthesis in alfalfa leaves. Osmotic stress caused an increase in lignin accumulation and the alteration of core enzyme activities and gene expression in the phenylpropanoid pathway. We identified five hub genes (CSE, CCR, CADa, CADb, and POD) and thirty edge genes (including WRKYs, MYBs, and UBPs) by integrating transcriptome and metabolome analyses. In addition, ABA and ethylene signaling induced by osmotic stress regulated lignin biosynthesis in a contradictory way. These findings contribute to a new theoretical foundation for the breeding of high-quality and resistant alfalfa varieties.

Global hypermethylation of the N6-methyladenosine RNA modification associated with apple heterografting.

Grafting can facilitate better scion performance and is widely used in plants. Numerous studies have studied the involvement of mRNAs, small RNAs, and epigenetic regulations in the grafting process. However, it remains unclear whether the mRNA N6-methyladenosine (m6A) modification participates in the apple (Malus x domestica Borkh.) grafting process. Here, we decoded the landscape of m6A modification profiles in 'Golden delicious' (a cultivar, Gd) and Malus prunifolia 'Fupingqiuzi' (a unique rootstock with resistance to environmental stresses, Mp), as well as their heterografted and self-grafted plants. Interestingly, global hypermethylation of m6A occurred in both heterografted scion and rootstock compared with their self-grafting controls. Gene Ontology (GO) term enrichment analysis showed that grafting-induced differentially m6A-modified genes were mainly involved in RNA processing, epigenetic regulation, stress response, and development. Differentially m6A-modified genes harboring expression alterations were mainly involved in various stress responses and fatty acid metabolism. Furthermore, grafting-induced mobile mRNAs with m6A and gene expression alterations mainly participated in ABA synthesis and transport (e.g. carotenoid cleavage dioxygenase 1 [CCD1] and ATP-binding cassette G22 [ABCG22]) and abiotic and biotic stress responses, which might contribute to the better performance of heterografted plants. Additionally, the DNA methylome analysis also demonstrated the DNA methylation alterations during grafting. Downregulated expression of m6A methyltransferase gene MdMTA (ortholog of METTL3) in apples induced the global m6A hypomethylation and distinctly activated the expression level of DNA demethylase gene MdROS1 (REPRESSOR OF SILENCING 1) showing the possible association between m6A and 5mC methylation in apples. Our results reveal the m6A modification profiles in the apple grafting process and enhance our understanding of the m6A regulatory mechanism in plant biological processes.

Fine-tuning of SUMOylation modulates drought tolerance of apple.

SUMOylation is involved in various aspects of plant biology, including drought stress. However, the relationship between SUMOylation and drought stress tolerance is complex; whether SUMOylation has a crosstalk with ubiquitination in response to drought stress remains largely unclear. In this study, we found that both increased and decreased SUMOylation led to increased survival of apple (Malus × domestica) under drought stress: both transgenic MdSUMO2A overexpressing (OE) plants and MdSUMO2 RNAi plants exhibited enhanced drought tolerance. We further confirmed that MdDREB2A is one of the MdSUMO2 targets. Both transgenic MdDREB2A OE and MdDREB2AK192R OE plants (which lacked the key site of SUMOylation by MdSUMO2A) were more drought tolerant than wild-type plants. However, MdDREB2AK192R OE plants had a much higher survival rate than MdDREB2A OE plants. We further showed SUMOylated MdDREB2A was conjugated with ubiquitin by MdRNF4 under drought stress, thereby triggering its protein degradation. In addition, MdRNF4 RNAi plants were more tolerant to drought stress. These results revealed the molecular mechanisms that underlie the relationship of SUMOylation with drought tolerance and provided evidence for the tight control of MdDREB2A accumulation under drought stress mediated by SUMOylation and ubiquitination.

A genome-wide association study provides insights into fatty acid synthesis and metabolism in Malus fruits.

As a precursor of aromatic compounds, fatty acids play important roles in apple fruit quality; however, the genetic and molecular basis underlying fatty acid synthesis and metabolism is largely unknown. In this study, we conducted a genome-wide association study (GWAS) of seven fatty acids using genomic data of 149 Malus accessions and identified 232 significant signals (-log10P>5) associated with 99 genes from GWAS of four fatty acids across 2 years. Among these, a significant GWAS signal associated with linoleic acid was identified in the transcriptional regulator SUPERMAN-like (SUP) MD13G1209600 at chromosome 13 of M. × domestica. Transient overexpression of MdSUP increased the contents of linoleic and linolenic acids and of three aromatic components in the fruit. Our study provides genetic and molecular information for improving the flavor and nutritional value of apple.

Hybrid-plane spectrum slicing for sequentially timed all-optical mapping photography.

Sequentially timed all-optical mapping photography (STAMP) is an effective tool for observing ultrafast and non-repetitive events. In the classical design of STAMP, the spatial resolution of the acquired images is different in two directions, severely limiting the scalability of STAMP. Here, by introducing an asymmetric optical design, we make the slicing mirror locate in the hybrid plane of the system, i.e., the image plane in the direction of the short edge, while the Fourier plane is in the direction of the long edge. This avoids the loss of the high-frequency components of the images and hence offers the possibility to further extend the frame number of the system.

Genome-wide analysis of SET-domain group histone methyltransferases in apple reveals their role in development and stress responses.

BACKGROUND: Histone lysine methylation plays an important role in plant development and stress responses by activating or repressing gene expression. Histone lysine methylation is catalyzed by a class of SET-domain group proteins (SDGs). Although an increasing number of studies have shown that SDGs play important regulatory roles in development and stress responses, the functions of SDGs in apple remain unclear. RESULTS: A total of 67 SDG members were identified in the Malus×domestica genome. Syntenic analysis revealed that most of the MdSDG duplicated gene pairs were associated with a recent genome-wide duplication event of the apple genome. These 67 MdSDG members were grouped into six classes based on sequence similarity and the findings of previous studies. The domain organization of each MdSDG class was characterized by specific patterns, which was consistent with the classification results. The tissue-specific expression patterns of MdSDGs among the 72 apple tissues in the different apple developmental stages were characterized to provide insight into their potential functions in development. The expression profiles of MdSDGs were also investigated in fruit development, the breaking of bud dormancy, and responses to abiotic and biotic stress; the results indicated that MdSDGs might play a regulatory role in development and stress responses. The subcellular localization and putative interaction network of MdSDG proteins were also analyzed. CONCLUSIONS: This work presents a fundamental comprehensive analysis of SDG histone methyltransferases in apple and provides a basis for future studies of MdSDGs involved in apple development and stress responses.

Insights into the effect of human civilization on Malus evolution and domestication.

The evolutionary history of the Malus genus has not been well studied. In the current study, we presented genetic evidence on the origin of the Malus genus based on genome sequencing of 297 Malus accessions, revealing the genetic relationship between wild species and cultivated apples. Our results demonstrated that North American and East Asian wild species are closer to the outgroup (pear) than Central Asian species, and hybrid species including natural (separated before the Pleistocene, about 2.5 Mya) and artificial hybrids (including ornamental trees and rootstocks) are between East and Central Asian wild species. Introgressions from M. sylvestris in cultivated apples appeared to be more extensive than those from M. sieversii, whose genetic background flowed westward across Eurasia and eastward to wild species including M. prunifolia, M. × asiatica, M. × micromalus, and M. × robust. Our results suggested that the loss of ancestral gene flow from M. sieversii in cultivated apples accompanied the movement of European traders around the world since the Age of Discovery. Natural SNP variations showed that cultivated apples had higher nucleotide diversity than wild species and more unique SNPs than other apple groups. An apple ERECTA-like gene that underwent selection during domestication on 15th chromosome was identified as a likely major determinant of fruit length and diameter, and an NB-ARC domain-containing gene was found to strongly affect anthocyanin accumulation using a genome-wide association approach. Our results provide new insights into the origin and domestication of apples and will be useful in new breeding programmes and efforts to increase fruit crop productivity.

Abscisic acid homeostasis is mediated by feedback regulation of MdMYB88 and MdMYB124.

The phytohormone abscisic acid (ABA) is involved in various plant processes. In response to drought stress, plants quickly accumulate ABA, but the regulatory mechanism of ABA accumulation is largely unknown, especially in woody plants. In this study, we report that MdMYB88 and MdMYB124 are myeloblastosis (MYB) transcription factors critical for ABA accumulation in apple trees (Malus x domestica) following drought, and this regulation is negatively controlled by ABA. MdMYB88 and MdMYB124 positively regulate leaf water transpiration, photosynthetic capacity, and stress endurance in apple trees under drought conditions. MdMYB88 and MdMYB124 regulate the expression of biosynthetic and catabolic genes of ABA, as well as drought- and ABA- responsive genes. MdMYB88 associates with promoter regions of the ABA biosynthetic gene 9-cis-epoxycarotenoid dioxygenase 3 (NCED3). Finally, expression of MdMYB88 and MdMYB124 is repressed by ABA. Our results identify a feedback regulation of MdMYB88 and MdMYB124 in modulating ABA homeostasis in apple trees.

Silenced lncRNA SNHG14 restrains the biological behaviors of bladder cancer cells via regulating microRNA-211-3p/ESM1 axis.

BACKGROUND: Bladder cancer (BCa) is a malignant tumor that occurs on the mucosa of the bladder, in which dysregulated long non-coding RNAs (lncRNAs) are involved. This study investigated the effect of lncRNA small nucleolar RNA host gene 1 (SNHG14) on the biological characteristics of BCa cells from microRNA (miR)-211-3p/ESM1 signaling axis. METHODS: BCa tissues and the matched normal tissues were collected to test SNHG14, miR-211-3p and ESM1 levels. SNHG14, miR-211-3p and ESM1 levels in BCa cell lines (T24, 5637, UMUC-3 and EJ) and normal bladder epithelial cells SV-HVC-1 were detected for screening the cell lines for follow-up experiments. T24 and UMUC-3 cells were transfected with different plasmids of SNHG14, miR-211-3p or ESM1 to observe the biological characteristics of BCa cells by MTT, colony formation, Transwell assays and flow cytometry. Tumor xenograft was implemented to inspect tumor growth in vivo. The targeting relationships of SNHG14, miR-211-3p and ESM1 were verified by bioinformatics software, RNA pull down assay and luciferase reporter assay. RESULTS: Enhanced SNHG14, ESM1 and suppressed miR-211-3p were found in BCa tissues and cells. SNHG14 up-regulated ESM1 via competitive binding with miR-211-3p. Decreased SNHG14 or up-regulated miR-211-3p depressed cell cycle entry, colony formation, invasion, migration and proliferation abilities, and facilitated apoptosis of BCa cells. Decreased SNHG14 or up-regulated miR-211-3p reduced the tumor volume and weight of nude mice with BCa, as well as promoted apoptosis and restrained proliferation of tumor cells. miR-211-3p inhibition or ESM1 overexpression reversed the effects of down-regulation of SNHG14 on BCa, and miR-211-3p up-regulation or ESM1 downregulation reversed the effect of SNHG14 overexpression on BCa. SNHG14 targeted miR-211-3p to regulate ESM1 expression. CONCLUSION: Our study highlights that silenced SNHG14 or elevated miR-211-3p represses the tumorigenic ability of BCa cells, which may be linked to ESM1 knockdown.

[Expression of vasodilator-stimulated phosphoprotein relates to prostate cancer metastasis].

OBJECTIVE: To investigate the relationship of the expression of vasodilator-stimulated phosphoprotein (VASP) with the metastasis and prognosis of prostate cancer. METHODS: Prostate cancer PC3 cells were infected with VASP shRNA and control shRNA lentiviruses, respectively. The invasive ability of the PC3 cells was determined by transwell migration assay, the expression of VASP in the prostate cancer tissue from 56 patients was detected by immunohistochemistry, and the survival rate of the patients was analyzed according to the VASP expression levels and follow-up data after radical prostatectomy. RESULTS: VASP shRNA lentivirus significantly inhibited the expression of VASP and decreased the invasive ability of the PC3 cells as compared with the results obtained in the scramble shRNA and blank control groups (P<0.05). The survival analysis of the 56 prostate cancer patients showed that the time of biochemical recurrence was markedly shorter in the VASP positive and strongly positive groups than in the VASP-negative cases (P<0.05), but with no statistically significant difference between the former two groups (P>0.05). CONCLUSIONS: VASP is involved in the regulation of the invasive ability of prostate cancer PC3 cells, and the differences in the VASP expression are related to the prognosis of prostate cancer.

Cyclooxygenase-2 and B-cell lymphoma-2 expression in cystitis glandularis and primary vesicle adenocarcinoma.

BACKGROUND: Although cystitis glandularis (CG) is a common benign urinary bladder epithelial abnormality, it remains unclear whether CG is a premalignant lesion. Cyclooxygenase-2 (COX-2) and B-cell lymphoma-2 (Bcl-2) overexpression has recently been reported as a potential tumor initiator or promoter. We evaluated and compared COX-2 and Bcl-2 expression in CG, chronic cystitis (CC), and primary vesicle adenocarcinoma (ADC) tissues. METHODS: We conducted a retrospective study to investigate COX-2 and Bcl-2 levels in CG and ADC. We obtained tissue samples from 75 patients (including 11 cases of CC, 30 typical cases of CG (CGTP), 30 cases of intestinal CG (CGIT), and 4 cases of ADC) between 1989 and 2009 from the Surgical Pathology Archives of the No. 2 People's Hospital of Zhenjiang, affiliated with Jiangsu University. COX-2 and Bcl-2 immunohistochemical staining was performed on all tissues. Nine normal bladder epithelial specimens were evaluated as control samples. Correlations between COX-2 and Bcl-2 expression in CG were also analyzed. RESULTS: COX-2 and Bcl-2 expression was higher in the ADC group compared to other groups (p < 0.05). COX-2 and Bcl-2 levels were higher in the CGIT group compared to the CGTP group (p = 0.000 for both). The CGIT and CGTP groups both showed higher COX-2 expression compared to the CC group (p = 0.000 for both). There was no difference in Bcl-2 expression between the CGTP and CC groups (p = 0.452). Additionally, the difference in COX-2 and Bcl-2 expression between the control and CC groups was also insignificant (p = 0.668 and p = 0.097, respectively). Finally, we found that COX-2 and Bcl-2 levels were positively related (r = 0.648, p = 0.000). CONCLUSION: COX-2 and Bcl-2 overexpression in the CG group suggests that CG, particularly the intestinal type, may be a premalignant lesion that converts into a tumor in the presence of carcinogens.

Clinical aspects and molecular genetics of persistent müllerian duct syndrome associated with transverse testicular ectopia: report of three cases.

Persistent müllerian duct syndrome (PMDS) is a rare form of male pseudohermaphroditism, characterized by the presence of a uterus and fallopian tubes owing to failure of müllerian duct regression in genotypically normal males. The association between a persistent müllerian duct and transverse testicular ectopia (TTE) is even more uncommon. PMDS with TTE is a very rare pathological association, often discovered during repair for inguinal hernia or cryptorchidism. We report 3 cases of Chinese patients with PMDS associated with TTE. Hysterectomy was performed, with resection of the underdeveloped fallopian tubes. Both gonads were placed into subdartos pouches in each scrotum by the transseptal approach. PMDS with TTE is a rarely encountered form of male pseudohermaphroditism usually unexpectedly found at surgery for cryptorchidism or inguinal hernia. Surgical treatment should avoid damage of fertile testes and vasa deferens.

NEDD4L represses prostate cancer cell proliferation via modulating PHF8 through the ubiquitin-proteasome pathway.

PURPOSE: Prostate cancer (PC) is a heterogeneous malignancy that greatly threatens man's health. E3 ubiquitin-protein ligase neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) imparts an regulatory role in various malignancies. This study focused on the modulatory mechanism of NEDD4L in proliferation of prostate cancer cells (PCCs) via regulating histone demethylase plant homeodomain finger protein 8 (PHF8/KDM7B) through the ubiquitin-proteasome system. METHODS: The expression levels of NEDD4L, PHF8, H3 lysine 9 dimethylation (H3K9me2) and activating transcription factor 2 (ATF2) in PC tissues and cell lines were detected via real-time quantitative polymerase chain reaction and Western blotting. After transfection of pcDNA3.1-NEDD4L, pcDNA3.1-PHF8, and pcDNA3.1-ATF2 into PCCs, cell proliferation was assessed via the cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Interaction between NEDD4L and PHF8 was identified via the protein immunoprecipitation. The ubiquitination level of PHF8 was determined via the ubiquitination detection. The enrichments of H3K9me2 and PHF8 in the ATF2 promotor region were detected via the chromatin-immunoprecipitation assay. RESULTS: PHF8 and ATF2 were highly expressed while NEDD4L was poorly expressed in PC tissues and cells. NEDD4L overexpression reduced proliferation of PCCs. NEDD4Linduced degradation of PHF8 via ubiquitination. PHF8 limited the enrichment of H3K9me2 in the ATF2 promotor region and enhanced ATF2 transcription. Upregulation of PHF8 or ATF2 abolished the inhibitory role of NEDD4L in proliferation of PCCs. CONCLUSION: NEDD4L facilitated degradation of PHF8 to limit ATF2 transcription, thereby suppressing proliferation of PCCs.

Cancer-associated Fibroblast-derived Extracellular Vesicles Mediate Immune Escape of Bladder Cancer via PD-L1/PD-1 Expression.

OBJECTIVE: Bladder cancer (BCa) is a malignant urological tumor with a high prevalence and poor prognosis. Extracellular vesicles (EVs) are increasingly becoming current hotspots owing to their involvement in cancer progression. This paper probed into the action of cancer-associated fibroblast-derived EVs (CAF-EVs) in the immune escape of BCa. METHODS: CAFs were identified by immunofluorescence. EVs were extracted from CAFs via ultracentrifugation and later characterized. BCa cells (T24 cell line) were co-cultured with CD8+ T cells and then treated with CAF-EVs. The uptake of EVs by T24 cells was examined by confocal laser microscopy. T24 cell apoptosis and invasion were assessed using flow cytometry and invasion assay. CD8+ T cell proliferation was evaluated using CFSE staining. The levels of cytokines (IFN-γ, IL-2, and TNF-α) were measured by ELISA. PD-L1 and PD-1 levels were determined utilizing RT-qPCR and flow cytometry. BCa mouse models were established to identify the effect of CAF-EVs on BCa progression in vivo. RESULTS: CAF-EVs decreased apoptosis and enhanced invasion of T24 cells, reduced proliferation of CD8+ T cells, and diminished levels of IFN-γ, IL-2, and TNF-α secreted by CD8+ T cells. CAF-EVs promoted the immune escape of T24 cells by carrying PD-L1. Downregulation of PDL1 expression in T24 cells or EVs partially counteracted the promotion of CAF-EVs on immune escape by reducing the binding of PD-L1 and PD-1. Additionally, CAF-EVs raised tumor volume and weight, upregulated PD-L1 expression, and weakened CD8+ T cell infiltration in BCa mice. CONCLUSION: CAF-EVs facilitate the immune escape of BCa by upregulating PD-L1/PD-1.

4-methylumbelliferone (4-MU) enhances drought tolerance of apple by regulating rhizosphere microbial diversity and root architecture.

The dwarfing rootstocks-mediated high-density apple orchard is becoming the main practice management. Currently, dwarfing rootstocks are widely used worldwide, but their shallow root system and drought sensitivity necessitate high irrigation requirements. Here, the root transcriptome and metabolome of dwarfing (M9-T337, a drought-sensitive rootstock) and vigorous rootstocks (Malus sieversii, a drought-tolerant species, is commonly used as a rootstock) showed that a coumarin derivative, 4-Methylumbelliferon (4-MU), was found to accumulate significantly in the roots of vigorous rootstock under drought condition. When exogenous 4-MU was applied to the roots of dwarfing rootstock under drought treatment, the plants displayed increased root biomass, higher root-to-shoot ratio, greater photosynthesis, and elevated water use efficiency. In addition, diversity and structure analysis of the rhizosphere soil microbial community demonstrated that 4-MU treatment increased the relative abundance of putatively beneficial bacteria and fungi. Of these, Pseudomonas, Bacillus, Streptomyces, and Chryseolinea bacterial strains and Acremonium, Trichoderma, and Phoma fungal strains known for root growth, or systemic resistance against drought stress, were significantly accumulated in the roots of dwarfing rootstock after 4-MU treatment under drought stress condition. Taken together, we identified a promising compound-4-MU, as a useful tool, to strengthen the drought tolerance of apple dwarfing rootstock.

Study on Pressure Propagation in Tight Oil Reservoirs with Stimulated Reservoir Volume Development.

The stimulated reservoir volume fracturing development in tight oil reservoirs is characterized by multiscale flow of the reservoir matrix, fracture network, and hydraulic fracture. Therefore, the flow field structure is extremely complex. Multiscale flow characteristics have been revealed through the systematical experiments including the threshold pressure gradient and the stress sensitivity. Based on the theory of elliptical flow, a comprehensive and practical mathematical model of multiregion coupling flow is established to characterize the multiscale flow, and the pressure distribution equation is derived. The calculation method of moving boundary is established to simulate the dynamic supply boundary and the dynamic pressure distribution by using the steady-state sequential replacement method. The characteristics of multiscale flow, multistage development state, and stress sensitivity are considered, especially the different stress sensitivity characteristics in different regions. Finally, the pressure propagation in tight reservoirs is clarified and the influence of matrix permeability, stress sensitivity characteristics, and drawdown pressure on the distance at the dynamic supply boundary are revealed. The research results provide theoretical basis for the development effect evaluation.

Genome-wide association study (GWAS) of leaf wax components of apple.

The wax layer of apple leaves plays an important role in improving stress resistance, but relatively little is known about the mechanisms of wax synthesis and transport in apple leaves. In this study, 17 wax components, including alcohols, alkanes, fatty acids and terpenes, were analyzed by gas chromatography-tandem mass spectrometry (GC-MS) from the leaves of 123 apple germplasms. Whole-genome sequencing of these apple accessions yielded 5.9 million high-quality single nucleotide polymorphisms (SNPs). We performed a genome-wide association study (GWAS) on 17 wax components and identified several genes related to wax synthesis and transport, including MdSHN1 (SHINE1), MdLTP4 (LIPID TRANSFER PROTEIN4), MdWSD1 (WAX ESTER SYNTHASE/ACYL-COA DIAC-YLGLYCEROL ACYLTRANSFERASE1), MdRDR1 (RNA-DEPENDENT RNA POLYMERASE1), MdACBP6 (ACYL-COA-BINDING PROTEIN6), MdNLE (NOTCHLESS) and MdABCG21 (ATP-BINDING CASSETTE G21). Moreover, we identified some prominent SNPs that may affect gene expression and protein function. These results provide insights into mechanisms of wax synthesis and transport in apple leaves and broaden the genetic resources and basis for facilitating resistance breeding.