The dynamic changes of mango (Mangifera indica L.) epicuticular wax during fruit development and effect of epicuticular wax on Colletotrichum gloeosporioides invasion.

Mango fruits are susceptible to diseases, such as anthracnose, during fruit development, leading to yield reduction. Epicuticular wax is closely related to resistance of plants to pathogenic bacterial invasion. In this study, the effect of mango fruit epicuticular wax on the invasion of Colletotrichum gloeosporioides was investigated, followed by to understand the changes of wax chemical composition and crystal morphology during mango fruit development using GC-MS and SEM. Results showed that the epicuticular wax of mango fruits can prevent the invasion of C. gloeosporioides, and 'Renong' showed the strongest resistance to C. gloeosporioides. The wax content of four mango varieties first increased and then decreased from 40 days after full bloom (DAFB) to 120 DAFB. In addition, 95 compounds were detected in the epicuticular wax of the four mango varieties at five developmental periods, in which primary alcohols, terpenoids and esters were the main wax chemical composition. Furthermore, the surface wax structure of mango fruit changed dynamically during fruit development, and irregular platelet-like crystals were the main wax structure. The present study showed the changes of wax content, chemical composition and crystal morphology during mango fruit development, and the special terpenoids (squalene, farnesyl acetate and farnesol) and dense crystal structure in the epicuticular wax of 'Renong' fruit may be the main reason for its stronger resistance to C. gloeosporioides than other varieties. Therefore, these results provide a reference for the follow-up study of mango fruit epicuticular wax synthesis mechanism and breeding.

Transcriptomic and proteomic analyses of Mangifera indica in response to Xanthomonas critis pv. mangiferaeindicae.

Mango is an important tropical fruit with the reputation of "Tropical Fruit King." It is widely cultivated in tropical and subtropical regions. Mango bacterial leaf spot, which is caused by Xanthomonas critis pv. mangiferaeindicae (Xcm), poses a great threat to the development of mango planting industry. In this study, we used RNA sequencing and data-independent acquisition techniques to compare the transcriptome and proteome of the highly resistant cultivar "Renong No.1" (RN) and the highly susceptible cultivar "Keitt" (KT) in response to Xcm infection at different stages (0, 2, and 6 days). A total of 14,397 differentially expressed genes (DEGs) were identified in the transcriptome of the two varieties, and 4,400 and 8,926 genes were differentially expressed in RN and KT, respectively. Among them, 217 DEGs were related to plant hormone signaling pathway, and 202 were involved in the maintenance of cellular redox homeostasis. A total of 3,438 differentially expressed proteins (DEPs) were identified in the proteome of the two varieties. Exactly 1,542 and 1,700 DEPs were detected in RN and KT, respectively. In addition, 39 DEPs were related to plant hormone signaling pathway, whereas 68 were involved in the maintenance of cellular redox homeostasis. Through cross-validation of the two omics, 1,470 genes were found to be expressed in both groups, and a large number of glutathione metabolism-related genes, such as HSP26-A, G6PD4, and GPX2, were up-regulated in both omics. Peroxisome-related genes, such as LACS6, LACS9, PED1, GLO4, and HACL, were up-regulated or down-regulated in both omics. ABCB11, SAPK2, MYC2, TAG7, PYL1, and other genes related to indole-3-acetic acid and abscisic acid signal transduction and plant-pathogen interaction were up-regulated or down-regulated in both omics. We also used weighted gene co-expression network analysis to combine physiological and biochemical data (superoxide dismutase and catalase activity changes) with transcriptome and proteome data and finally identified three hub genes/proteins (SAG113, SRK2A, and ABCB1) that play an important role in plant hormone signal transduction. This work was the first study of gene/protein changes in resistant and susceptible mango varieties, and its results improved our understanding of the molecular mechanism of mango resistance to Xcm.

Identification of the passion fruit (Passiflora edulis Sims) MYB family in fruit development and abiotic stress, and functional analysis of PeMYB87 in abiotic stresses.

Environmental stresses are ubiquitous in agricultural cultivation, and they affect the healthy growth and development of edible tissues in passion fruit. The study of resistance mechanisms is important in understanding the adaptation and resistance of plants to environmental stresses. In this work, two differently resistant passion fruit varieties were selected, using the expression characteristics of the transcription factor MYB, to explore the resistance mechanism of the MYB gene under various environmental stresses. A total of 174 MYB family members were identified using high-quality passion fruit genomes: 98 2R-MYB, 5 3R-MYB, and 71 1R-MYB (MYB-relate). Their family information was systematically analyzed, including subcellular localization, physicochemical properties, phylogeny at the genomic level, promoter function, encoded proteins, and reciprocal regulation. In this study, bioinformatics and transcriptome sequencing were used to identify members of the PeMYB genes in passion fruit whole-genome data, and biological techniques, such as qPCR, gene clone, and transient transformation of yeast, were used to determine the function of the passion fruit MYB genes in abiotic stress tolerance. Transcriptomic data were obtained for differential expression characteristics of two resistant and susceptible varieties, three expression patterns during pulp development, and four induced expression patterns under abiotic stress conditions. We further focused on the resistance mechanism of PeMYB87 in environmental stress, and we selected 10 representative PeMYB genes for quantitative expression verification. Most of the genes were differentially induced by four abiotic stresses, among which PeMYB87 responded significantly to high-temperature-induced expression and overexpression of the PeMYB87 gene in the yeast system. The transgenic PeMYB87 in yeast showed different degrees of stress resistance under exposure to cold, high temperatures, drought, and salt stresses. These findings lay the foundation for further analysis of the biological functions of PeMYBs involved in stress resistance in passion fruit.

Transcriptome and Metabolome Analyses Reveal the Involvement of Multiple Pathways in Flowering Intensity in Mango.

Mango (Mangifera indica L.) is famous for its sweet flavor and aroma. China is one of the major mango-producing countries. Mango is known for variations in flowering intensity that impacts fruit yield and farmers' profitability. In the present study, transcriptome and metabolome analyses of three cultivars with different flowering intensities were performed to preliminarily elucidate their regulatory mechanisms. The transcriptome profiling identified 36,242 genes. The major observation was the differential expression patterns of 334 flowering-related genes among the three mango varieties. The metabolome profiling detected 1,023 metabolites that were grouped into 11 compound classes. Our results show that the interplay of the FLOWERING LOCUS T and CONSTANS together with their upstream/downstream regulators/repressors modulate flowering robustness. We found that both gibberellins and auxins are associated with the flowering intensities of studied mango varieties. Finally, we discuss the roles of sugar biosynthesis and ambient temperature pathways in mango flowering. Overall, this study presents multiple pathways that can be manipulated in mango trees regarding flowering robustness.

First report of Bougainvillea spectabilis Willd bacterial leaf spot caused by Pantoea stewartii subspecies indologenes in China.

Bougainvillea spectabilis Willd. is an important ornamental flowering plant belonging to the family Nyctaginaceae. It is widely used in landscape designs in tropical and subtropical regions. In December 2020, severe disease-causing leaf spots were discovered on the leaves of B. spectabilis in the Modern Agricultural Park (110°19' E, 21°26' N) Zhanjiang City, Guangdong Province, China. Field surveys revealed that the disease was widespread, with an incidence of 60-80%. Early symptoms on the leaves appeared as tiny leaf spots that later developed into concentric circles surrounded by a yellowish halo (Fig. 1). Diseased leaves with typical symptoms were collected for pathogen isolation. The leading edges of the lesions were excised, sanitized in 75% ethanol for 30 s and in 3% sodium hypochlorite for 3 min, and rinsed three times with sterile distilled water (SDW). The diseased tissue was crushed in 1 mL SDW, soaked for 15 min, and then spread onto nutrient agar medium on a petri dish. Circular, bright yellow colonies with smooth margins were observed after 24 h of incubation at 28 °C. The isolate (SJM1) was a gram-negative bacillus with positive results for catalase, indole synthesis, maltose, and arbutin and negative results for sorbitol, lactose, salicin, and starch hydrolysis. The SJM1 genomic DNA was extracted using the TIANamp Bacterial DNA Kit, and partial 16S rDNA gene segments were amplified using the bacterial generic primers 27F and 1492R. The collated 16S rDNA gene sequences were submitted to the NCBI GenBank (MZ723935). BLAST analysis of the sequences revealed 99.38% identity with Pantoea stewartii (MG517424.1). Amplification using subspecies-specific primers galE (#562/564; Gehring et al. 2014), glmS (#356/341; Wensing et al. 2010), and pstC + pstS (#338/339; Wensing et al. 2010) revealed that the genes showed 99-100% identity with P. stewartii subsp. indologenes (galE = 100%, MZ754494.1; glmS = 99.79%, MZ75496.1; and pstC + pstS = 99.89%, MZ754495.1). Phylogenetic trees were constructed using the neighbor-joining method (MEGA X), with both the 16S rDNA sequence (Fig. 2 2A) and the concatenated 16S rDNA, galE, pstC + pstS, and glmS sequences (Fig.2 2B). The SJM1 isolate belonged to the same clade as P. stewartii subsp. indologenes and was 99% homologous to P. stewartii subsp. indologenes strain ZJ-FGZX1 (Fig. 2 2B; Ren et al. 2020). Pathogenicity tests were performed through prick wound inoculation. Sterile needles were used to create fresh wounds on healthy young leaves of one-year-old B. spectabilis plants. Wounds were inoculated with 20 µl bacterial suspension (1 × 108 CFU/ml) or SDW. Four leaves per plant and three plants per treatment were evaluated. The plants were incubated at 28 °C temperature and 80-90% relative humidity. After 4-7 days of inoculation, all plants inoculated with the bacterial suspension had spot symptoms with a halo, similar to those observed in the field. However, leaves inoculated with SDW alone did not show any symptoms. Furthermore, the colony morphology and 16S rDNA sequences of the strains isolated from the inoculated leaves were identical to those of the original isolates. These results verified Koch's postulates. Based on biochemical identification and sequencing analysis, the pathogen causing B. spectabilis leaf spot was identified as P. stewartii subsp. indologenes. Previous reports have shown that P. stewartii subsp. indologenes can cause diseases in Dracaena sanderiana, Cenchrus americanus, and Allium cepa (Zhang et al. 2020, Ashajyothi et al. 2021, Stumpf et al. 2018). To our knowledge, this is the first report of P. stewartii subsp. indologenes causing B. spectabilis leaf spot disease in China.

Comparative Metabolic Profiling in Pulp and Peel of Green and Red Pitayas (Hylocereus polyrhizus and Hylocereus undatus) Reveals Potential Valorization in the Pharmaceutical and Food Industries.

Pitaya (Hylocereus genus) is a popular plant with exotic and nutritious fruit, which has widespread uses as a source of nutrients and raw materials in the pharmaceutical industry. However, the potential of pitaya peel as a natural source of bioactive compounds has not yet fully been explored. Recent advances in metabolomics have paved the way for understanding and evaluating the presence of diverse sets of metabolites in different plant parts. This study is aimed at exploring the diversity of primary and secondary metabolites in two commercial varieties of pitaya, i.e., green pitaya (Hylocereus undatus) and red pitaya (Hylocereus polyrhizus). A total of 433 metabolites were identified using a widely targeted metabolomic approach and classified into nine known diverse classes of metabolites, including flavonoids, amino acids and its derivatives, alkaloids, tannins, phenolic acids, organic acids, nucleotides and derivatives, lipids, and lignans. Red pitaya peel and pulp showed relatively high accumulation of metabolites viz. alkaloids, amino acids and its derivatives, and lipids. Differential metabolite landscape of pitaya fruit indicated the presence of key bioactive compounds, i.e., L-tyrosine, L-valine, DL-norvaline, tryptophan, γ-linolenic acid, and isorhamnetin 3-O-neohesperidoside. The findings in this study provide new insight into the broad spectrum of bioactive compounds of red and green pitaya, emphasizing the valorization of the biowaste pitaya peel as raw material for the pharmaceutical and food industries.

Chromosome-scale genome assembly provides insights into the evolution and flavor synthesis of passion fruit (Passiflora edulis Sims).

Passion fruit (Passiflora edulis Sims) is an economically valuable fruit that is cultivated in tropical and subtropical regions of the world. Here, we report an ~1341.7 Mb chromosome-scale genome assembly of passion fruit, with 98.91% (~1327.18 Mb) of the assembly assigned to nine pseudochromosomes. The genome includes 23,171 protein-coding genes, and most of the assembled sequences are repetitive sequences, with long-terminal repeats (LTRs) being the most abundant. Phylogenetic analysis revealed that passion fruit diverged after Brassicaceae and before Euphorbiaceae. Ks analysis showed that two whole-genome duplication events occurred in passion fruit at 65 MYA and 12 MYA, which may have contributed to its large genome size. An integrated analysis of genomic, transcriptomic, and metabolomic data showed that 'alpha-linolenic acid metabolism', 'metabolic pathways', and 'secondary metabolic pathways' were the main pathways involved in the synthesis of important volatile organic compounds (VOCs) in passion fruit, and this analysis identified some candidate genes, including GDP-fucose Transporter 1-like, Tetratricopeptide repeat protein 33, protein NETWORKED 4B isoform X1, and Golgin Subfamily A member 6-like protein 22. In addition, we identified 13 important gene families in fatty acid pathways and eight important gene families in terpene pathways. Gene family analysis showed that the ACX, ADH, ALDH, and HPL gene families, especially ACX13/14/15/20, ADH13/26/33, ALDH1/4/21, and HPL4/6, were the key genes for ester synthesis, while the TPS gene family, especially PeTPS2/3/4/24, was the key gene family for terpene synthesis. This work provides insights into genome evolution and flavor trait biology and offers valuable resources for the improved cultivation of passion fruit.

Genomic analysis of WD40 protein family in the mango reveals a TTG1 protein enhances root growth and abiotic tolerance in Arabidopsis.

WD40 domain-containing proteins constitute one of the most abundant protein families in all higher plants and play vital roles in the regulation of plant growth and developmental processes. To date, WD40 protein members have been identified in several plant species, but no report is available on the WD40 protein family in mango (Mangifera indica L.). In this study, a total of 315 WD40 protein members were identified in mango and further divided into 11 subgroups according to the phylogenetic tree. Here, we reported mango TRANSPARENT TESTA GLABRA 1 (MiTTG1) protein as a novel factor that functions in the regulation of Arabidopsis root growth and development. Bimolecular fluorescence complementation (BiFC) assay in tobacco leaves revealed that MiTTG1 protein physically interacts with MiMYB0, MiTT8 and MibHLH1, implying the formation of a new ternary regulatory complex (MYB-bHLH-WD40) in mango. Furthermore, the MiTTG1 transgenic lines were more adapted to abiotic stresses (mannitol, salt and drought stress) in terms of promoted root hairs and root lengths. Together, our findings indicated that MiTTG1 functions as a novel factor to modulate protein-protein interactions and enhance the plants abilities to adjust different abiotic stress responses.

Morphological description of a novel synthetic allotetraploid(A1A1G3G3) of Gossypium herbaceum L.and G.nelsonii Fryx. suitable for disease-resistant breeding applications.

Wild species of Gossypium ssp. are an important source of traits for improving commercial cotton cultivars. Previous reports show that Gossypium herbaceum L. and Gossypium nelsonii Fryx. have better disease resistance characteristics than commercial cotton varieties. However, chromosome ploidy and biological isolation make it difficult to hybridize diploid species with the tetraploid Gossypium hirsutum L. We developed a new allotetraploid cotton genotype (A1A1G3G3) using a process of distant hybridization within wild cotton species to create new germplasms. First of all, G. herbaceum and G. nelsonii were used for interspecific hybridization to obtain F1 generation. Afterwards, apical meristems of the F1 diploid cotton plants were treated with colchicine to induce chromosome doubling. The new interspecific F1 hybrid and S1 cotton plants originated from chromosome duplication, were tested via morphological and molecular markers and confirmed their tetraploidy through flowrometric and cytological identification. The S1 tetraploid cotton plants was crossed with a TM-1 line and fertile hybrid offspring were obtained. These S2 offsprings were tested for resistance to Verticillium wilt and demonstrated adequate tolerance to this fungi. The results shows that the new S1 cotton line could be used as parental material for hybridization with G. hirsutum to produce pathogen-resistant cotton hybrids. This new S1 allotetraploid genotype will contributes to the enrichment of Gossypium germplasm resources and is expected to be valuable in polyploidy evolutionary studies.

Comprehensive ESI-Q TRAP-MS/MS based characterization of metabolome of two mango (Mangifera indica L) cultivars from China.

Polyphenols based bioactive compounds from vegetables and fruits are known for impressive antioxidant activity. Ingestion of these antioxidants may promote human health against cardiovascular diseases and cancer. Mango is a popular tropical fruit with special taste, high nutritional value and health-enhancing metabolites. The aim was to investigate the diversity of phytochemicals between two mango cultivars of china at three stages of fruit maturity. We used ESI-QTRAP-MS/MS approach to characterize comprehensively the metabolome of two mango cultivars named Hongguifei (HGF) and Tainong (TN). HPLC was used to quantify selected catechin based phenolic compounds. Moreover, real-time qPCR was used to study the expression profiles of two key genes (ANR and LAR) involved in proanthocyanidin biosynthesis from catechins and derivatives. A total of 651 metabolites were identified, which include at least 257 phenolic compounds. Higher number of metabolites were differentially modulated in peel as compared to pulp. Overall, the relative quantities of amino acids, carbohydrates, organic acids, and other metabolites were increased in the pulp of TN cultivar. While the contents of phenolic compounds were relatively higher in HGF cultivar. Moreover, HPLC based quantification of catechin and derivatives exhibited cultivar specific variations. The ANR and LAR genes exhibited an opposite expression profile in both cultivars. Current study is the first report of numerous metabolites including catechin-based derivatives in mango fruit. These findings open novel possibilities for the use of mango as a source of bioactive compounds.

Combined Transcriptome and Metabolome analysis of Pitaya fruit unveiled the mechanisms underlying Peel and pulp color formation.

BACKGROUND: Elucidating the candidate genes and key metabolites responsible for pulp and peel coloration is essential for breeding pitaya fruit with new and improved appeal and high nutritional value. Here, we used transcriptome (RNA-Seq) and metabolome analysis (UPLC-MS/MS) to identify structural and regulatory genes and key metabolites associated with peel and pulp colors in three pitaya fruit types belonging to two different Hylocereus species. RESULT: Our combined transcriptome and metabolome analyses suggest that the main strategy for obtaining red color is to increase tyrosine content for downstream steps in the betalain pathway. The upregulation of CYP76ADs is proposed as the color-breaking step leading to red or colorless pulp under the regulation by WRKY44 transcription factor. Supported by the differential accumulation of anthocyanin metabolites in red pulped pitaya fruit, our results showed the regulation of anthocyanin biosynthesis pathway in addition to betalain biosynthesis. However, no color-breaking step for the development of anthocyanins in red pulp was observed and no biosynthesis of anthocyanins in white pulp was found. Together, we propose that red pitaya pulp color is under the strict regulation of CYP76ADs by WRKYs and the anthocyanin coexistence with betalains is unneglectable. We ruled out the possibility of yellow peel color formation due to anthocyanins because of no differential regulation of chalcone synthase genes between yellow and green and no detection of naringenin chalcone in the metabolome. Similarly, the no differential regulation of key genes in the carotenoid pathway controlling yellow pigments proposed that the carotenoid pathway is not involved in yellow peel color formation. CONCLUSIONS: Together, our results propose several candidate genes and metabolites controlling a single horticultural attribute i.e. color formation for further functional characterization. This study presents useful genomic resources and information for breeding pitaya fruit with commercially attractive peel and pulp colors. These findings will greatly complement the existing knowledge on the biosynthesis of natural pigments for their applications in food and health industry.

Transcriptional mechanism of differential sugar accumulation in pulp of two contrasting mango (Mangifera indica L.) cultivars.

Temporal transcriptome analysis combined with targeted metabolomics was employed to investigate the mechanisms of high sugar accumulation in fruit pulp of two contrasting mango cultivars. Ten sugar metabolites were identified in mango pulp with the most dominant being d-glucose. Analysis of the gene expression patterns revealed that the high-sugar cultivar prioritized the conversion of sucrose to d-glucose by up-regulating invertases and ß-glucosidases and increased other genes directly contributing to the synthesis of sucrose and d-glucose. In contrast, it repressed the expression of genes converting sucrose, d-glucose and other sugars into intermediates compounds for downstream processes. It also strongly increased the expression of alpha-amylases which may promote high degradation of starch into d-glucose. Besides, ¾ of the sugar transporters was strongly up-regulated, indicative of their preponderant role in sugar accumulation in mango fruit. Overall, this study provides a good insight into the regulation pattern of high sugar accumulation in mango pulp.

Evolutionary analysis of six chloroplast genomes from three Persea americana ecological races: Insights into sequence divergences and phylogenetic relationships.

Chloroplasts significantly influence species phylogenies because of their maternal inheritance and the moderate evolutionary rate of their genomes. Avocado, which is a member of the family Lauraceae, has received considerable attention from botanists, likely because of its position as a basal angiosperm. However, there is relatively little avocado genomic information currently available. In this study, six complete avocado chloroplast genomes from three ecological races were assembled to examine the sequence diversity among the three avocado ecological races. A comparative genomic analysis revealed that 515 simple sequence repeat loci and 176 repeats belonging to four other types were polymorphic across the six chloroplast genomes. Three highly variable regions (trnC-GCA-petN, petN-psbM, and petA-psbJ) were identified as highly informative markers. A phylogenetic analysis based on 79 common protein-coding genes indicated that the six examined avocado accessions from three ecological races form a monophyletic clade. The other three genera belonging to the Persea group clustered to form a sister clade with a high bootstrap value. These chloroplast genomes provide important genetic information for future attempts at identifying avocado races and for the related biological research.

Transcriptome Profiling Provides Insight into the Genes in Carotenoid Biosynthesis during the Mesocarp and Seed Developmental Stages of Avocado (Persea americana).

Avocado (Persea americana Mill.) is an economically important crop because of its high nutritional value. However, the absence of a sequenced avocado reference genome has hindered investigations of secondary metabolism. For next-generation high-throughput transcriptome sequencing, we obtained 365,615,152 and 348,623,402 clean reads as well as 109.13 and 104.10 Gb of sequencing data for avocado mesocarp and seed, respectively, during five developmental stages. High-quality reads were assembled into 100,837 unigenes with an average length of 847.40 bp (N50 = 1725 bp). Additionally, 16,903 differentially expressed genes (DEGs) were detected, 17 of which were related to carotenoid biosynthesis. The expression levels of most of these 17 DEGs were higher in the mesocarp than in the seed during five developmental stages. In this study, the avocado mesocarp and seed transcriptome were also sequenced using single-molecule long-read sequencing to acquired 25.79 and 17.67 Gb clean data, respectively. We identified 233,014 and 238,219 consensus isoforms in avocado mesocarp and seed, respectively. Furthermore, 104 and 59 isoforms were found to correspond to the putative 11 carotenoid biosynthetic-related genes in the avocado mesocarp and seed, respectively. The isoform numbers of 10 out of the putative 11 genes involved in the carotenoid biosynthetic pathway were higher in the mesocarp than those in the seed. Besides, alpha- and beta-carotene contents in the avocado mesocarp and seed during five developmental stages were also measured, and they were higher in the mesocarp than in the seed, which validated the results of transcriptome profiling. Gene expression changes and the associated variations in gene dosage could influence carotenoid biosynthesis. These results will help to further elucidate carotenoid biosynthesis in avocado.

Whole-genome sequence and genome annotation of Xanthomonas citri pv. mangiferaeindicae, causal agent of bacterial black spot on Mangifera indica.

A newly isolated strain XC01 was identified as Xanthomonas citri pv. mangiferaeindicae, isolated from an infected mango fruit in Guangxi, China. The complete genome sequence of XC01 was carried out using the PacBio RSII platform. The genome contains a circular chromosome with 3,865,165 bp, 3442 protein-coding genes, 53 tRNAs, and 2 rRNA operons. Phylogenetic analysis revealed that this pathogen is very close to the soybeans bacterial pustule pathogen X. citri pv. glycines CFBP 2526, with a completely different host range. The genome sequence of XC01 may shed a highlight genes with a demonstrated or proposed role in on the pathogenesis.

Profiling of volatile fragrant components in a mini-core collection of mango germplasms from seven countries.

Aroma is important in assessing the quality of fresh fruit and their processed products, and could provide good indicators for the development of local cultivars in the mango industry. In this study, the volatile diversity of 25 mango cultivars from China, America, Thailand, India, Cuba, Indonesia, and the Philippines was investigated. The volatile compositions, their relative contents, and the intervarietal differences were detected with headspace solid phase microextraction tandem gas chromatography-mass spectrometer methods. The similarities were also evaluated with a cluster analysis and correlation analysis of the volatiles. The differences in mango volatiles in different districts are also discussed. Our results show significant differences in the volatile compositions and their relative contents among the individual cultivars and regions. In total, 127 volatiles were found in all the cultivars, belonging to various chemical classes. The highest and lowest qualitative abundances of volatiles were detected in 'Zihua' and 'Mallika' cultivars, respectively. Based on the cumulative occurrence of members of the classes of volatiles, the cultivars were grouped into monoterpenes (16 cultivars), proportion and balanced (eight cultivars), and nonterpene groups (one cultivars). Terpene hydrocarbons were the major volatiles in these cultivars, with terpinolene, 3-carene, caryophyllene and α-Pinene the dominant components depending on the cultivars. Monoterpenes, some of the primary volatile components, were the most abundant aroma compounds, whereas aldehydes were the least abundant in the mango pulp. ß-Myrcene, a major terpene, accounted for 58.93% of the total flavor volatile compounds in 'Xiaofei' (Philippens). γ-Octanoic lactone was the only ester in the total flavor volatile compounds, with its highest concentration in 'Guiya' (China). Hexamethyl cyclotrisiloxane was the most abundant volatile compound in 'Magovar' (India), accounting for 46.66% of the total flavor volatiles. A typical aldehydic aroma 2,6-di-tert-butyl-4-sec-butylphenol, was detected in 'Gleck'. A highly significant positive correlation was detected between Alc and K, Alk and Nt, O and L. Cultivars originating from America, Thailand, Cuba, India, Indonesia and the Philippines were more similar to each other than to those from China. This study provides a high-value dataset for use in development of health care products, diversified mango breeding, and local extension of mango cultivars.

Identification and Characterization of Phospholipase D Genes Putatively Involved in Internal Browning of Pineapple during Postharvest Storage.

Phospholipase D (PLD) in plants plays vital roles in growth, development, and stress responses. However, the precise role of PLDs in pineapple remains poorly understood. In this study, 10 putative PLD genes, designated as AcPLD1-AcPLD10, were identified based on the pineapple genome database. The 10 AcPLDs could be clustered into five of the six known PLD families according to sequence characterization. Their deduced amino acid sequences displayed similarities to PLDs from other plant species. Expression analyses of PLD mRNAs from pineapple pulp were performed. The 10 PLDs exhibited differential expression patterns during storage periods of fruits treated with hexaldehyde (a specific PLD inhibitor) which could alleviate internal browning (IB) of pineapple after harvest. Functional subcellular localization signaling assays of two PLD proteins (AcPLD2 and AcPLD9) were performed by fluorescence microscopy. To further detect the potential action mechanism underlying PLD involved in the IB defense response, PLD, hydrogen peroxide (H2O2) and H2O2 associated with antioxidative enzymes such as superoxide dismutase, catalase, NADPH, and ascorbate peroxidase were quantified by enzyme-linked immunosorbent assay. This report is the first to provide a genome-wide description of the pineapple PLD gene family, and the results should expand knowledge of this family.

Transcription Profiling Analysis of Mango-Fusarium mangiferae Interaction.

Malformation caused by Fusarium mangiferae is one of the most destructive mango diseases affecting the canopy and floral development, leading to dramatic reduction in fruit yield. To further understand the mechanism of interaction between mango and F. mangiferae, we monitored the transcriptome profiles of buds from susceptible mango plants, which were challenged with F. mangiferae. More than 99 million reads were deduced by RNA-sequencing and were assembled into 121,267 unigenes. Based on the sequence similarity searches, 61,706 unigenes were identified, of which 21,273 and 50,410 were assigned to gene ontology categories and clusters of orthologous groups, respectively, and 33,243 were mapped to 119 KEGG pathways. The differentially expressed genes of mango were detected, having 15,830, 26,061, and 20,146 DEGs respectively, after infection for 45, 75, and 120 days. The analysis of the comparative transcriptome suggests that basic defense mechanisms play important roles in disease resistance. The data also show the transcriptional responses of interactions between mango and the pathogen and more drastic changes in the host transcriptome in response to the pathogen. These results could be used to develop new methods to broaden the resistance of mango to malformation, including the over-expression of key mango genes.

Development of a sensitive molecular detection assay for mango malformation disease caused by Fusarium mangiferae.

OBJECTIVES: To develop a sensitive and specific molecular assay for detection of mango malformation disease (MMD), which is caused primarily by Fusarium mangiferae. RESULTS: We screened 100 ISSR primers and identified one (UBC888) that directed the stable amplification of a specific gene fragment of 479 bp (GenBank accession number KJ526382). Based on the DNA sequence of this fragment, a pair of SCAR primers (W342 and W1772) were designed to amplify another gene fragment of 1376 bp (GenBank accession number KJ526383), demonstrating the successful conversion of an ISSR marker to a SCAR marker. An effective and simple detection assay for MMD was established based on this pair of PCR primers, with a high level of specificity and sensitivity to the DNA of F. mangiferae and other species of Fusarium both in vitro and in vivo. It can detect as little as 10 pg fungal DNA from the DNA of mango's tissues. CONCLUSIONS: Our assay provides a practical method for the early diagnosis so that proper prevention of the mango malformation disease can be developed.

Transcriptome and proteomic analysis of mango (Mangifera indica Linn) fruits.

Here we used Illumina RNA-seq technology for transcriptome sequencing of a mixed fruit sample from 'Zill' mango (Mangifera indica Linn) fruit pericarp and pulp during the development and ripening stages. RNA-seq generated 68,419,722 sequence reads that were assembled into 54,207 transcripts with a mean length of 858bp, including 26,413 clusters and 27,794 singletons. A total of 42,515(78.43%) transcripts were annotated using public protein databases, with a cut-off E-value above 10(-5), of which 35,198 and 14,619 transcripts were assigned to gene ontology terms and clusters of orthologous groups respectively. Functional annotation against the Kyoto Encyclopedia of Genes and Genomes database identified 23,741(43.79%) transcripts which were mapped to 128 pathways. These pathways revealed many previously unknown transcripts. We also applied mass spectrometry-based transcriptome data to characterize the proteome of ripe fruit. LC-MS/MS analysis of the mango fruit proteome was using tandem mass spectrometry (MS/MS) in an LTQ Orbitrap Velos (Thermo) coupled online to the HPLC. This approach enabled the identification of 7536 peptides that matched 2754 proteins. Our study provides a comprehensive sequence for a systemic view of transcriptome during mango fruit development and the most comprehensive fruit proteome to date, which are useful for further genomics research and proteomic studies. BIOLOGICAL SIGNIFICANCE: Our study provides a comprehensive sequence for a systemic view of both the transcriptome and proteome of mango fruit, and a valuable reference for further research on gene expression and protein identification. This article is part of a Special Issue entitled: Proteomics of non-model organisms.