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

Identification and characterization of SWEET gene family in passion fruit reveals the involvement of PeSWEET3 in soluble sugar accumulation

The sugars will eventually be exported transporters (SWEET) family is a class of sugar transporters that play crucial roles in plant growth, reproduction, and stresses response. The characteristics of 21 PeSWEETs, identified in passion fruit (Passiflora edulis Sims) and divided into four clades, were evaluated. Structural feature analysis showed that exon numbers ranged from 4 to 12, while motif 1, 2, and 3 were highly conserved. Analysis of RNA-seq from different tissues revealed that PeSWEETs showed tissue-specificity. Additionally, Cis-acting regulatory element analysis indicated that abundant hormone-response and stress response elements were enriched in promoters of PeSWEETs. Exogenous abscisic acid (ABA) treatment led to an increase in the soluble sugar accumulation and up-regulated the expression level of PeSWEET3. The PeSWEET3 protein localizes on the plasma membrane and exhibits transport activity of fructose, glucose, and mannose. Furthermore, ectopic expression of PeSWEET3 significantly enhanced soluble sugar accumulation in leaves of transgenic tobacco. Collectively, these results lay a solid foundation for further exploration on the role of PeSWEETs.

Integrated metabolomics and transcriptomics analysis reveals the potential mechanism by which Methyl jasmonate enhances the pungent flavor of soilless-cultivated Chinese chives (Allium tuberosum)

BACKGROUND

Methyl jasmonate (MeJA) is an effective plant elicitor that enhances secondary metabolism. Chinese chives are prized for their pungent flavor, yet the biosynthetic pathways and regulatory mechanisms of flavor compounds induced by MeJA remain unclear.

METHODOLOGY

This study integrated metabolomic and transcriptomic analyses to elucidate how MeJA modulates the biosynthesis of flavor substance precursors in soilless-cultivated Chinese chives.

RESULTS

MeJA treatment improved the dry matter content and nutritional quality of Chinese chives. We identified 36 volatile and 183 nonvolatile differentially abundant metabolites between the MeJA-treated and control groups. Gene expression analysis revealed 193 candidate genes associated with flavor formation. Among all the genes, a total of 2,667 DEGs were enriched primarily in metabolic pathways, including secondary metabolite biosynthesis, linoleic acid metabolism, and phenylpropanoid biosynthesis. Furthermore, exogenous MeJA inhibited the synthesis of endogenous jasmonic acid as well as enzyme activity and gene expression related to metabolic pathways. It also promoted the conversion of S-alkyl-L-cysteine to S-alk(en)ylcysteine sulfoxides (CSOs), increasing the accumulation of the flavor precursor CSOs and increasing the levels of S-methyl-L-cysteine. This led to increased concentrations of the key garlic flavor compounds methiin and alliin, intensifying the pungent flavor of Chinese chives. Notably, MeJA-induced AtuFMO1 was associated with enhanced pungent flavor and may be regulated by AtuPHL7 and AP2/ERF-ERF transcription factors.

CONCLUSION

In conclusion, exogenous MeJA activates key enzyme-encoding genes involved in the biosynthesis of garlic flavor precursor CSOs, leading to increased accumulation of the spicy compounds Methiin and Alliin. These findings establish AtuFMO1 as a central hub linking hormonal signaling to flavor biosynthesis and provide molecular targets for improving Allium crop flavor and quality through precision horticulture.

Functional Characterization of PeVLN4 Involved in Regulating Pollen Tube Growth from Passion Fruit

Passion fruit (Passiflora edulis), mainly distributed in tropical and subtropical regions, is popular for its unique flavor and health benefits. The actin cytoskeleton plays a crucial role in plant growth and development, and villin is a key regulator of actin dynamics. However, the mechanism underlying the actin filament regulation of reproductive development in passion fruit remains poorly understood. Here, we characterized a villin isovariant in passion fruit, Passiflora edulis VLN4 (PeVLN4), highly and preferentially expressed in pollen. Subcellular localization analysis showed that PeVLN4 decorated distinct filamentous structures in pollen tubes. We next introduced PeVLN4 into Arabidopsis villin mutants to explore its functions on the growing pollen tubes. PeVLN4 rescued defects in the elongation of villin mutant pollen tubes. Pollen tubes expressing PeVLN4 were revealed to be less sensitive to latrunculin B, and PeVLN4 partially rescued defects in the actin filament organization of villin mutant pollen tubes. Additionally, biochemical assays revealed that PeVLN4 bundles actin filaments in vitro. Thus, PeVLN4 is an important regulator of F-actin stability and is required for normal pollen tube growth in passion fruit. This study provides a new insight into the function of the actin regulator villin involved in the reproduction development of passion fruit.

Differential gene expression and metabolic pathways in Toona sinensis: Influence on colour and aroma

Toona sinensis, a plant species renowned for its culinary and medicinal properties, exhibits diverse colour variations that contribute to its aesthetic appeal and commercial value. Understanding the molecular mechanisms underlying colour and aroma traits in Toona sinensis is crucial for breeding programs and quality regulation in agriculture and the food industry. The present investigation included a comprehensive analysis of the transcriptomic and metabolomic profiles of Toona sinensis with different colours, including green, red, and red leaves with green stems. Metabolic analysis revealed that the flavonoid biosynthesis pathway governs the colour distinction between green and red Toona sinensis. The top 10 metabolites influenced by transcriptome include terpenoids (5), heterocyclic compounds (1), phenol (1), ketone (1), aldehyde (1), and alcohol (1). Fifteen highly expressed genes impacted by phenylpropanoid, sesquiterpenoid, and triterpenoid biosynthesis in coloured Toona sinensis. Functional annotation and pathway analysis revealed that terpene metabolites are predominantly synthesized via terpene metabolic pathway, involving eight key gene families. This study underscores the importance of multi-omics approaches in unravelling the genetic and metabolic basis of phenotypic traits in plant species aimed at improving colour, aroma, and nutritional quality in plants and derived products. HIGHLIGHTS: Flavonoid biosynthesis pathway governs the colour distinction between green and red Toona sinensis. The top 10 metabolites influenced by transcriptome include five terpenoids, one heterocyclic compound, one phenol, one ketone, one aldehyde, and one alcohol. Fifteen highly expressed genes impacted by phenylpropanoid, sesquiterpenoid, and triterpenoid biosynthesis in coloured Toona sinensis. Terpene metabolites are predominantly synthesized via the terpene metabolic pathway, involving eight key gene families. The net photosynthetic rate and intercellular CO2 concentration are relatively high in the red Toon sinensis morph.

Microbiome and Metabolome Illustrate the Correlations Between Endophytes and Flavor Metabolites in Passiflora ligularis Fruit Juice

This study investigates the interplay between volatile and non-volatile flavor metabolites and endophytic microbial communities during three developmental stages of Passiflora ligularis fruit juice. Using bioinformatics and metabolomics, we characterize microbial diversity and metabolic variations to understand flavor development. A total of 1490 bacterial and 1158 fungal operational taxonomic units (OTUs) were identified. Young fruits had higher microbial diversity, dominated by Proteobacteria and Firmicutes (bacteria) and Ascomycota and Basidiomycota (fungi). As the fruit matured, Proteobacteria increased while Firmicutes decreased, indicating that microbial succession is tied to development. Metabolomic profiling identified 87 volatile and 1002 non-volatile metabolites, with distinct chemical classes varying across stages. Saturated hydrocarbons and fatty alcohols were the main volatile metabolites, while organic acids and lipids among non-volatile metabolites showed stage-dependent changes, influencing flavor complexity. Correlation analysis showed microbial-flavor interactions: Proteobacteria negatively correlated with metabolites, while Firmicutes positively correlated with metabolites. Ascomycota positively correlated with volatile metabolites, whereas Basidiomycota showed an inverse relationship, highlighting their differential contributions to flavor biosynthesis. This study enhances understanding of microbial and metabolic factors shaping P. ligularis fruit flavor, highlighting the importance of microbial influence on fruit metabolomics. The findings suggest the potential for microbiome engineering to improve flavor quality, aiding postharvest management and industrial processing in the food and beverage industry.

Genome-Wide Identification and Functional Analysis of AP2/ERF Gene Family in Passiflora edulis Sims

The Apetala2/Ethylene Responsive Factor (AP2/ERF) family represents a critical group of transcription factors in plants, recognized for their roles in growth, development, fruit ripening, and postharvest processes. This study aimed to identify and characterize the AP2/ERF gene family in passion fruit (Passiflora edulis Sims) and investigate their potential roles in flavor enhancement. A total of 91 PeAP2/ERF genes were identified and classified into five subfamilies. Chromosome localization and collinearity analysis demonstrated their distribution across all nine chromosomes of passion fruit, with tandem duplication events identified as a key driver of family expansion. Exon-intron configurations and motif compositions were highly conserved among PeAP2/ERF genes. Promoter cis-acting element analysis indicated potential regulation by environmental signals, including abiotic and biotic stresses, as well as hormonal cues. Postharvest storage induced the expression of 59 PeAP2/ERF genes over time. Notably, PeAP2-10 was found to enhance the expression of PeSTP6, a gene associated with sugar transport, suggesting its potential influence on the flavor profile of passion fruit. These findings provide valuable insights into the functional roles of PeAP2/ERF genes in passion fruit, highlighting their significance in postharvest management and flavor quality enhancement strategies.

Detection and comparative analysis of VOCs between tomato and pepper based on GC×GC-TOFMS

This study aimed to identify and compare the flavor substances in mature tomato and pepper fruits using flavoromics based on GC×GC-TOF-MS. A total of 1560 volatile substances were identified, including 627 tomato specific substances and 534 pepper specific substances. Esters were identified as the distinguishing factor in the aroma profiles of the two. ROAV, an effective flavor evaluation criterion, can help identify the main contributors to flavor that can be detected by the taste buds. VOCs with ROAV > 1 are typically regarded as the key flavor contributors. Interestingly, it was found that tomato and pepper shared three common VOCs (2-nonenal, (E)-; 2-octenal, (E)-; and furan, 2-pentyl-.), which exhibited higher ROAV in both. Except for the three common VOCs, heptanal; 2-dodecenal, (E)-; 1-octen-3-one; 2-undecanone in tomato and pyrazine, 2-methoxy-3-(2-methylpropyl)- in pepper were identified to be contributive to their corresponding aromatic flavor (ROVA > 1), respectively. The contents of 138 volatile metabolites differ between tomato and pepper. Among them, acetoin, dodecanal and 1-decanol demonstrated highest fold change (Log2FC > 10). The flavor wheel shows the most obvious flavor characteristic of both tomato and pepper is sweet flavor. In addition, green, fruity, herbal, woody and apple flavors are prominent in pepper, while waxy, citrus and fatty flavors are prominent in tomato.

Identification and characterization of GRAS genes in passion fruit (Passiflora edulis Sims) revealed their roles in development regulation and stress response

KEY MESSAGE

Twenty-nine GRAS genes were identified in passion fruit, the N-terminal regions and 3D (three-dimensional) structures were closely related with their tissue-specific expression patterns. Candidate PeGRASs for enhancing stress resistance were identified. Passion fruit (Passiflora edulis Sims) is a tropical fruit crop with significant edible and ornamental value, but its growth and development are highly sensitive to environmental conditions. The plant-specific GRAS gene family plays critical roles in regulating growth, development, and stress responses. Here, we performed the first comprehensive analysis of the GRAS gene family in passion fruit. A total of 29 GRAS genes were identified and named PeGRAS1 to PeGRAS29 based on their chromosomal locations. Phylogenetic analysis using GRAS proteins from passion fruit, Arabidopsis, and rice revealed that PeGRAS proteins could be classified into 10 subfamilies. Compared to Arabidopsis, passion fruit lacked members from the LAS subfamily but gained one GRAS member (PeGRAS9) clustered with the rice-specific Os4 subfamily. Structural analysis performed in silico revealed that most PeGRAS members were intron less and exhibited conserved motif patterns near the C-terminus, while the N-terminal regions varied in sequence length and composition. Members within certain subfamilies including DLT, PAT1, and LISCL with similar unstructured N-terminal regions and 3D structures, exhibited similar tissue-specific expression patterns. While PeGRAS members with difference in these structural features, even within the same subfamily (e.g., DELLA), displayed distinct expression patterns. These findings highlighted that the N-terminal regions of GRAS proteins may be critical for their specific functions. Moreover, many PeGRAS members, particularly those from the PAT1 subfamily, were widely involved in stress responses, with PeGRAS19 and PeGRAS26 likely playing roles in cold tolerance, and PeGRAS25 and PeGRAS28 in drought resistance. This study provides a foundation for further functional research on PeGRASs and offers potential candidates for molecular breeding aimed at enhancing stress tolerance in passion fruit.

Primary metabolomics and transcriptomic techniques were used to explore the regulatory mechanisms that may influence the flavor characteristics of fresh Corylus heterophylla × Corylus avellana

To explore the flavor related regulatory mechanisms of fresh Corylus heterophylla × Corylus avellana, a joint analysis of metabolome and transcriptome were utilized to compare the two typical C. heterophylla × C. avellana varieties with different flavors ('yuzhui' and 'pingou21') in this paper. The results showed that the genes including E2.4.1.67-1, E2.4.1.67-2, SUS-1, SUS-2, SUS-4, SUS-5, SUS-7, SUS-8, SUS-9, UGP2-2 were identified as responsible for regulating the levels of stachyose, manninotriose and raffinose in hazelnuts. CS and OGDH were deemed as the genes involved in the citric acid cycle, which was a central metabolic pathway that generated energy through the oxidation of carbohydrates, fats and proteins in hazelnuts. The genes trpD, ALDO, PK-1, PK-2, ilvH, argE-1, argE-4, argE-5, argD, PDAH, GLTI were regarded as involved in the biosynthesis of various amino acids like tryptophan, valine, alanine, and arginine. These amino acids determined the taste of C. heterophylla × C. avellana and were important precursors of other flavor-related compounds. The genes LOX2S-2, LOX2S-3, LOX2S-4 and LCAT3 were viewed as involved in the regulation of lipid biosynthesis, specifically involving 13(S)-HPODE, 9,10,13-trihome and 13(S)-HOTrE in C. heterophylla × C. avellana. These findings highlight the significance of genes and metabolites and internal regulatory mechanisms in shaping the flavor of fresh C. heterophylla × C. avellana cultivated in temperate continents. This study provides the theoretical basis for breeding excellent food functional hazelnut varieties.

Construction of a High-Density Genetic Linkage Map and QTL Mapping for Stem Rot Resistance in Passion Fruit (Passiflora edulis Sims)

BACKGROUND

The passion fruit (Passiflora edulis Sims) is a diploid plant (2n = 2x = 18) and is a perennial scrambling vine in Southern China. However, the occurrence and spread of stem rot in passion fruit severely impact its yield and quality.

METHODS

In this study, we re-sequenced a BC1F1 population consisting of 158 individuals using whole-genome resequencing. We constructed a high-density genetic linkage map and identified the quantitative trait locus (QTL), and analyzed candidate genes associated with stem rot resistance in passion fruit.

RESULTS

Based on the passion fruit reference genome (MER), a high-density genetic linkage map was constructed with 1,180,406 single nucleotide polymorphisms (SNPs). The map contains nine linkage groups, covering a total genetic distance of 1559.03 cM, with an average genetic distance of 311.81 cM. The average genetic distance between 4206 bins was 0.404 cM, and the average gap length was 10.565 cM. The collinearity correlation coefficient between the genetic map and the passion fruit genome was 0.9994. Fusarium solani was used to infect the BC1F1 population, and the resistance to stem rot showed a continuous distribution. A QTL, qPSR5, was mapped to the 113,377,860 bp-114,811,870 bp genomic region on chromosome 5. We performed RNA sequencing (RNA-seq) and real-time quantitative polymerase chain reaction (RT-qPCR) to analyze the expression levels of predicted genes in the candidate region and identified ZX.05G0020740 and ZX.05G0020810 as ideal candidate genes for stem rot resistance in passion fruit.

CONCLUSIONS

The findings in this study not only lay the foundation for cloning the qPSR5 responsible for stem rot resistance but also provide genetic resources for the genetic improvement of passion fruit.

Comprehensive insights on association mapping in perennial fruit crops breeding - Its implications, current status and future perspectives

In order to provide food and nutritional security for the world's rapidly expanding population, fruit crop researchers have identified two critical priorities: increasing production and preserving fruit quality during the pre- and post-harvest periods. The genetic basis of these complex, commercially important fruit traits which are uniquely regulated by polygenes or multi-allelic genes that interact with one another and the environment can be analyzed with the aid of trait mapping tools. The most interesting trait mapping approach that offers the genetic level investigation for marker-trait associations (MTAs) for these complex fruit traits, without the development of mapping population, is association mapping. This approach was used during the genetic improvement program, emphasizing the obstacles (breeding strategies adopted, generation interval, and their genomic status) pertaining to perennial fruit crops. This method of studying population diversity and linkage disequilibrium in perennial fruit crops has been made possible by recent developments in genotyping, phenotyping, and statistical analysis. Thus, the purpose of this review is to provide an overview of different trait mapping techniques, with a focus on association mapping (method, essential components, viability, constraints, and future perspective) and its advantages, disadvantages, and possibilities for breeding perennial fruit crops.

Genome-wide identification and expression profiling of MST, SUT and SWEET transporters in Dendrobium catenatum

BACKGROUND

Sugar transporters (STs) play a critical role in the transportation of sugar, participating in plant growth and development, stress/defense responses, and signal transduction processes. Dendrobium catenatum (also known as Dendrobium officinale, hereinafter referred to as D. catenatum) is an important traditional Chinese medicinal herb with remarkable medicinal properties and possessing high economic value. Polysaccharides are the primary active components in D. catenatum, exhibiting diverse pharmacological activities. Sugar transporters function as material supplier and may play the essential roles in the polysaccharide biosynthesis, as well as the key reulators in the signaling and responses to abiotic stresses in Dendrobium plants. However, a comprehensive analysis of sugar transporters in D. catenatum remains elusive, thereby hindering our understanding of sugar partitioning within this species.

RESULTS

In this work, the members belonging to MST, SUT, and SWEET gene families were identified in four Dendrobium plants. A comprehensive study of sugar transporters was conducted in D. catenatum, including phylogenetic relationship, structural arrangement, regulatory networks, expression profiles, and potential functions analysis. Seven sugar transporters were found to be involved in the process of polysaccharide biosynthesis in D. catenatum. Red-blue light is an effective way to enhance the accumulation of polysaccharides, and exerts an influence on the expression of polysaccharide biosynthesis related genes.

CONCLUSIONS

This study provide insight into the evolution and functional annotation of sugar transporters in Dendrobium, and establishing a foundation for future functional research of sugar transporters involved in polysaccharide biosynthesis and stress response.

Comprehensive Genome-Wide Analysis of the Receptor-like Protein Gene Family and Functional Analysis of PeRLP8 Associated with Crown Rot Resistance in Passiflora edulis

Passion fruit (Passiflora edulis Sims) is a Passifloraceae plant with high economic value. Crown rot caused by Rhizoctonia solani is a major fungal disease, which can seriously reduce the yield and quality of passion fruit. Receptor-like proteins (RLPs), which act as pathogen recognition receptors, are widely involved in plant immune responses and developmental processes. However, the role of RLP family members of passion fruit in resistance to crown rot remains unclear. In this study, evolutionary dynamics analysis and comprehensive genomic characterization of the RLP genes family were performed on passion fruit. A total of 141 PeRLPs in the genome of the 'Zixiang' cultivar and 79 PesRLPs in the genome of the 'Tainong' cultivar were identified, respectively. Evolutionary analysis showed that proximal and dispersed duplication events were the primary drivers of RLP family expansion. RNA-seq data and RT-qPCR analysis showed that PeRLPs were constitutively expressed in different tissues and induced by low temperature, JA, MeJA, and SA treatments. The PeRLP8 gene was identified as the hub gene by RNA-seq analysis of passion fruit seedlings infected by Rhizoctonia solani. The expression levels of PeRLP8 of the resistant variety Passiflora maliformis (LG) were significantly higher than those of the sensitive variety Passiflora edulis f. flavicarpa (HG). Transient overexpression of PeRLP8 tobacco and passion fruit leaves enhanced the resistance to Rhizoctonia solani, resulting in reduced lesion areas by 52.06% and 54.17%, respectively. In addition, it can increase reactive oxygen species levels and upregulated expression of genes related to active oxygen biosynthesis and JA metabolism in passion fruit leaves. Our research provides new insights into the molecular mechanism and breeding strategy of passion fruit resistance to crown rot.

Research Progress on Viruses of Passiflora edulis

Passiflora edulis, also known as passion fruit, is celebrated for its rich nutritional content, distinctive flavour, and significant medicinal benefits. At present, viral diseases pose a major challenge to the passion fruit industry, affecting both the production and quality of the fruit. These diseases impede the sustainable and healthy growth of the passion fruit sector. In recent years, with the expansion of P. edulis cultivation areas, virus mutations, and advances in virus detection technology, an increasing number of virus species infecting P. edulis have been discovered. To date, more than 40 different virus species have been identified; however, there are different strains within the same virus. This poses a challenge for the control and prevention of P. edulis virus disease. Therefore, this review discusses the different types of viruses and their characteristics, modes of transmission, and effects on the growth of the passion fruit plant, as well as the mechanisms of virus generation and preventive measures, with the hope that these discussions will provide a comprehensive understanding of and countermeasures for viruses in passion fruit.

Chromosome-scale genome assembly of Docynia delavayi provides new insights into the α-farnesene biosynthesis

Docynia delavayi is an economically significant fruit species with a high market potential due to the special aroma of its fruit. Here, a 653.34 Mb high-quality genome of D. delavayi was first reported, of which 93.8 % of the sequences (612.98 Mb) could be anchored to 17 chromosomes, containing 48,325 protein-coding genes. Ks analysis proved that two whole genome duplication (WGD) events occurred in D. delavayi, resulting in the expansion of genes associated with terpene biosynthesis, which promoted its fruit-specific aroma production. Combined multi-omics analysis, α-farnesene was detected as the most abundant aroma substance emitted by D. delavayi fruit during storage, meanwhile one α-farnesene synthase gene (AFS) and 15 transcription factors (TFs) were identified as the candidate genes potentially involved in α-farnesene biosynthesis. Further studies for the regulation network of α-farnesene biosynthesis revealed that DdebHLH, DdeERF1 and DdeMYB could activate the transcription of DdeAFS. To our knowledge, it is the first report that MYB TF plays a regulatory role in α-farnesene biosynthesis, which will greatly facilitate future breeding programs for D. delavayi.

Evolution and Functional Dynamics of TCP Transcription Factor Gene Family in Passion Fruit (Passiflora edulis)

Passion fruit is a valued tropical fruit crop that faces environment-related growth strains. TCP genes are important for both growth modulation and stress prevention in plants. Herein, we systematically analyzed the TCP gene family in passion fruit, recognizing 30 members. Genes exhibiting closer phylogenetic relationships exhibited similar protein and gene structures. Gene members of the TCP family showed developmental-stage- or tissue-specific expression profiles during the passion fruit life cycle. Transcriptome data also demonstrated that many PeTCPs showed induced expression in response to hormonal treatments and cold, heat, and salt stress. Based on transcriptomics data, eight candidate genes were chosen for preferential gene expression confirmation under cold stress conditions. The qRT-PCR assays suggested PeTCP15/16/17/19/23 upregulation, while PeTCP1/11/25 downregulation after cold stress. Additionally, TCP19/20/29/30 exhibited in silico binding with cold-stress-related miRNA319s. GFP subcellular localization assays exhibited PeTCP19/1 were localized at the nucleus. This study will aid in the establishment of novel germplasm, as well as the further investigation of the roles of PeTCPs and their cold stress resistance characteristics.

Integration of full-length Iso-Seq, Illumina RNA-Seq, and flavor testing reveals potential differences in ripened fruits between two Passiflora edulis cultivars

Background

Passion fruit (Passiflora edulis) is loved for its delicious flavor and nutritious juice. Although studies have delved into the cultivation and enhancement of passion fruit varieties, the underlying factors contributing to the fruit's appealing aroma remain unclear.

Methods

This study analyzed the full-length transcriptomes of two passion fruit cultivars with different flavor profiles: "Tainong 1" (TN1), known for its superior fruit flavor, and "Guihan 1" (GH1), noted for its strong environmental resilience but lackluster taste. Utilizing PacBio Iso-Seq and Illumina RNA-Seq technologies, we discovered terpene synthase (TPS) genes implicated in fruit ripening that may help explain the flavor disparities.

Results

We generated 15,913 isoforms, with N50 lengths of 1,500 and 1,648 bp, and mean lengths of 1,319 and 1,463 bp for TN1 and GH1, respectively. Transcript and isoform lengths ranged from a maximum of 7,779 bp to a minimum of 200 and 209 bp. We identified 14,822 putative coding DNA sequences (CDSs) averaging 1,063 bp, classified 1,007 transcription factors (TFs) into 84 families. Additionally, differential expression analysis of ripening fruit from both cultivars revealed 314 upregulated and 43 downregulated unigenes in TN1 compared to GH1. The top 10 significantly enriched Gene Ontology (GO) terms for the differentially expressed genes (DEGs) indicated that TN1's upregulated genes were primarily involved in nutrient transport, whereas GH1's up-regulated genes were associated with resistance mechanisms. Meanwhile, 17 PeTPS genes were identified in P. edulis and 13 of them were TPS-b members. A comparative analysis when compared PeTPS with AtTPS highlighted an expansion of the PeTPS-b subfamily in P. edulis, suggesting a role in its fruit flavor profile.

Conclusion

Our findings explain that the formation of fruit flavor is attributed to the upregulation of essential genes in synthetic pathway, in particular the expansion of TPS-b subfamily involved in terpenoid synthesis. This finding will also provide a foundational genetic basis for understanding the nuanced flavor differences in this species.

Genome-wide analysis of the passion fruit invertase gene family reveals involvement of PeCWINV5 in hexose accumulation

BACKGROUND

Invertases (INVs) are key enzymes in sugar metabolism, cleaving sucrose into glucose and fructose and playing an important role in plant development and the stress response, however, the INV gene family in passion fruit has not been systematically reported.

RESULTS

In this study, a total of 16 PeINV genes were identified from the passion fruit genome and named according to their subcellular location and chromosome position. These include six cell wall invertase (CWINV) genes, two vacuolar invertase (VINV) genes, and eight neutral/alkaline invertase (N/AINV) genes. The gene structures, phylogenetic tree, and cis-acting elements of PeINV gene family were predicted using bioinformatics methods. Results showed that the upstream promoter region of the PeINV genes contained various response elements; particularly, PeVINV2, PeN/AINV3, PeN/AINV5, PeN/AINV6, PeN/AINV7, and PeN/AINV8 had more response elements. Additionally, the expression profiles of PeINV genes under different abiotic stresses (drought, salt, cold temperature, and high temperature) indicated that PeCWINV5, PeCWINV6, PeVINV1, PeVINV2, PeN/AINV2, PeN/AINV3, PeN/AINV6, and PeN/AINV7 responded significantly to these abiotic stresses, which was consistent with cis-acting element prediction results. Sucrose, glucose, and fructose are main soluble components in passion fruit pulp. The contents of total soluble sugar, hexoses, and sweetness index increased significantly at early stages during fruit ripening. Transcriptome data showed that with an increase in fruit development and maturity, the expression levels of PeCWINV2, PeCWINV5, and PeN/AINV3 exhibited an up-regulated trend, especially for PeCWINV5 which showed highest abundance, this correlated with the accumulation of soluble sugar and sweetness index. Transient overexpression results demonstrated that the contents of fructose, glucose and sucrose increased in the pulp of PeCWINV5 overexpressing fruit. It is speculated that this cell wall invertase gene, PeCWINV5, may play an important role in sucrose unloading and hexose accumulation.

CONCLUSION

In this study, we systematically identified INV genes in passion fruit for the first time and further investigated their physicochemical properties, evolution, and expression patterns. Furthermore, we screened out a key candidate gene involved in hexose accumulation. This study lays a foundation for further study on INV genes and will be beneficial on the genetic improvement of passion fruit breeding.

The chromosome-level genome assembly of Cananga odorata provides insights into its evolution and terpenoid biosynthesis

Cananga odorata is known as a natural perfume tree of the Annonaceae family in Magnoliales. However, its phylogenetic position and the molecular mechanisms involved in the biosynthesis of the floral volatile organic compounds (VOCs) remain unclear. Here, by combining a variety of sequencing platforms, we present a telomere-to-telomere (T2T) genome of C. odorata with 735.83 Mb, which represents the highest integrity and assembly quality of genome in magnoliid plants reported to date. Phylogenetic analysis based on multiple datasets and approaches showed that C. odorata, as a member of magnoliids, is sister to eudicots, after their divergence from monocots. Metabolomic of VOCs in the essential oil and flowers scent showed that sesquiterpenes, especially β-caryophyllene, were the major compounds. Two CoTPS21 homologues derived from tandem duplication events were highly expressed during flower development and were identified as the key sesquiterpene synthases for the production of β-caryophyllene. In addition, CoSPL3 and CoSPL9 were considered as potential transcription factors for activating the expression of CoTPS21 homologues. Our results shed light on the molecular mechanisms underlying the biosynthesis of the unique floral fragrance in C. odorata and provide new insights into the phylogenetic position of magnoliids.

Passion fruit HD-ZIP genes: Characterization, expression variance, and overexpression PeHB31 enhanced drought tolerance via lignin pathway

The HD-ZIP (homeodomain-leucine zipper) genes hold significant importance in transcriptional regulation, especially in plant development and responses to abiotic stresses. However, a comprehensive study targeting HD-ZIP family members in passion fruit has been absent. In our current research, 34 HD-ZIP family members (PeHBs) were identified by bioinformatics analysis. Transcriptome analysis revealed that PeHBs exhibited distinct expression patterns when subjected to the four different abiotic stresses, and significant differential expression of PeHBs was also found among the three developmental stages of the fruit and between the purple and yellow genotype passion fruit leaves. An integrated metabolome and transcriptome analysis further revealed that the HD-ZIP III class gene PeHB31 (homologous to ATHB8), was co-upexpressed with lignans in yellow fruit P. edulis (commonly used as a resistance rootstock) when compared to purple fruit P. edulis. The transformation of Arabidopsis and yeast with the PeHB31 gene showed an enhancement in their capacity to withstand drought conditions. Notably, the transgenic Arabidopsis plants exhibited an increase in lignin content within the vascular tissues of their stems. This research lays the groundwork for future studies on the control mechanisms of lignin biosynthesis by HD-ZIP genes (especially HD-ZIP classes III and I) involved in drought tolerance.

Genome-wide identification and expression analysis of calmodulin and calmodulin-like genes in passion fruit (Passiflora edulis) and their involvement in flower and fruit development

BACKGROUND

The calmodulin (CaM) and calmodulin-like (CML) proteins play regulatory roles in plant growth and development, responses to biotic and abiotic stresses, and other biological processes. As a popular fruit and ornamental crop, it is important to explore the regulatory mechanism of flower and fruit development of passion fruit.

RESULTS

In this study, 32 PeCaM/PeCML genes were identified from passion fruit genome and were divided into 9 groups based on phylogenetic analysis. The structural analysis, including conserved motifs, gene structure and homologous modeling, illustrates that the PeCaM/PeCML in the same subgroup have relative conserved structural features. Collinearity analysis suggested that the expansion of the CaM/CML gene family likely took place mainly by segmental duplication, and the whole genome replication events were closely related with the rapid expansion of the gene group. PeCaM/PeCMLs were potentially required for different floral tissues development. Significantly, PeCML26 had extremely high expression levels during ovule and fruit development compared with other PeCML genes, suggesting that PeCML26 had potential functions involved in the development of passion fruit flowers and fruits. The co-presence of various cis-elements associated with growth and development, hormone responsiveness, and stress responsiveness in the promoter regions of these PeCaM/PeCMLs might contribute to their diverse regulatory roles. Furthermore, PeCaM/PeCMLs were also induced by various abiotic stresses. This work provides a comprehensive understanding of the CaM/CML gene family and valuable clues for future studies on the function and evolution of CaM/CML genes in passion fruit.

CONCLUSION

A total of 32 PeCaM/PeCML genes were divided into 9 groups. The PeCaM/PeCML genes showed differential expression patterns in floral tissues at different development stages. It is worth noting that PeCML26, which is highly homologous to AtCaM2, not only interacts with multiple BBR-BPC TFs, but also has high expression levels during ovule and fruit development, suggesting that PeCML26 had potential functions involved in the development of passion fruit flowers and fruits. This research lays the foundation for future investigations and validation of the potential function of PeCaM/PeCML genes in the growth and development of passion fruit.

Integrative multiomics profiling of passion fruit reveals the genetic basis for fruit color and aroma

Passion fruit (Passiflora edulis) possesses a complex aroma and is widely grown in tropical and subtropical areas. Here, we conducted the de novo assembly, annotation, and comparison of PPF (P. edulis Sims) and YPF (P. edulis f. flavicarpa) reference genomes using PacBio, Illumina, and Hi-C technologies. Notably, we discovered evidence of recent whole-genome duplication events in P. edulis genomes. Comparative analysis revealed 7.6∼8.1 million single nucleotide polymorphisms, 1 million insertions/deletions, and over 142 Mb presence/absence variations among different P. edulis genomes. During the ripening of yellow passion fruit, metabolites related to flavor, aroma, and color were substantially accumulated or changed. Through joint analysis of genomic variations, differentially expressed genes, and accumulated metabolites, we explored candidate genes associated with flavor, aroma, and color distinctions. Flavonoid biosynthesis pathways, anthocyanin biosynthesis pathways, and related metabolites are pivotal factors affecting the coloration of passion fruit, and terpenoid metabolites accumulated more in PPF. Finally, by heterologous expression in yeast (Saccharomyces cerevisiae), we functionally characterized 12 terpene synthases. Our findings revealed that certain TPS homologs in both YPF and PPF varieties produce identical terpene products, while others yield distinct compounds or even lose their functionality. These discoveries revealed the genetic and metabolic basis of unique characteristics in aroma and flavor between the 2 passion fruit varieties. This study provides resources for better understanding the genome architecture and accelerating genetic improvement of passion fruits.

Tissue-specific proteome profile analysis reveals regulatory and stress responsive networks in passion fruit during storage

Passiflora edulis, commonly known as passion fruit, is a crop with a fragrant aroma and refreshingly tropical flavor that is a valuable source of antioxidants. It offers a unique opportunity for growers because of its adaptability to tropical and subtropical climates. Passion fruit can be sold in the fresh market or used in value-added products, but its postharvest shelf life has not been well-researched, nor have superior cultivars been well-developed. Understanding the proteins expressed at the tissue level during the postharvest stage can help improve fruit quality and extend shelf life. In this study, we carried out comparative proteomics analysis on four passion fruit tissues, the epicarp, mesocarp, endocarp, and pulp, using multiplexed isobaric tandem mass tag (TMT) labeling quantitation. A total of 3352 proteins were identified, including 295 differentially expressed proteins (DEPs). Of these DEPs, 213 showed a fold increase greater than 1.45 (50 proteins) or a fold decrease less than 0.45 (163 proteins) with different patterns among tissue types. Among the DEPs, there were proteins expressed with functions in oxygen scavenging, lipid peroxidation, response to heat stress, and pathogen resistance. Thirty-six proteins were designated as hypothetical proteins were characterized for potential functions in immunity, cell structure, homeostasis, stress response, protein metabolism and miraculin biosynthesis. This research provides insight into tissue-specific pathways that can be further studied within fruit physiology and postharvest shelf life to aid in implementing effective plant breeding programs. Knowing the tissue-specific function of fruit is essential for improving fruit quality, developing new varieties, identifying health benefits, and optimizing processing techniques.

Passionfruit Genomic Database (PGD): a comprehensive resource for passionfruit genomics

Passionfruit (Passiflora edulis) is a significant fruit crop in the commercial sector, owing to its high nutritional and medicinal value. The advent of high-throughput genomics sequencing technology has led to the publication of a vast amount of passionfruit omics data, encompassing complete genome sequences and transcriptome data under diverse stress conditions. To facilitate the efficient integration, storage, and analysis of these large-scale datasets, and to enable researchers to effectively utilize these omics data, we developed the first passionfruit genome database (PGD). The PGD platform comprises a diverse range of functional modules, including a genome browser, search function, heatmap, gene expression patterns, various tools, sequence alignment, and batch download, thereby providing a user-friendly interface. Additionally, supplementary practical tools have been developed for the PGD, such as gene family analysis tools, gene ontology (GO) terms, a pathway enrichment analysis, and other data analysis and mining tools, which enhance the data's utilization value. By leveraging the database's robust scalability, the intention is to continue to collect and integrate passionfruit omics data in the PGD, providing comprehensive and in-depth support for passionfruit research. The PGD is freely accessible via http://passionfruit.com.cn .

PeHVA22 gene family in passion fruit (Passiflora edulis): initial characterization and expression profiling diversity

Passion fruit, an economically valuable fruit crop, is highly vulnerable to adverse climate conditions. The HVA22 genes, recognized as abscisic acid (ABA) and stress-inducible, play vital roles in stress response and growth regulation in diverse eukaryotic organisms. Here, six HVA22 genes were firstly identified in passion fruit genome and all predicted to be localized within the endoplasmic reticulum. Phylogenetic analyses showed that all PeHVA22s were divided into four subgroups. The gene structural features of PeHVA22 genes clustered in the same subgroup were relatively conserved, while the gene structure characteristics of PeHVA22s from different subgroups varied significantly. PeHVA22A and PeHVA22C closely clustered with barley HVA22 in Group II, were also induced by ABA and drought stress treatment, suggesting conserved roles similar to barley HVA22. Meanwhile, most PeHVA22s exhibited induced expression post-drought treatment but were suppressed under salt, low and high-temperature conditions, indicating a unique role in drought response. Additionally, PeHVA22s displayed tissue-specific expression patterns across diverse tissues, except for PeHVA22B which maybe a pseudogene. Notably, PeHVA22C, PeHVA22E, and PeHVA22F predominantly expressed in fruit, indicating their involvement in fruit development. Almost all PeHVA22s showed variable expression at different developmental stages of stamens or ovules, implying their roles in passion fruit's sexual reproduction. The intricate roles of PeHVA22s may result from diverse regulatory factors including transcription factors and CREs related to plant growth and development, hormone and stress responsiveness. These observations highlighted that PeHVA22s might play conserved roles in ABA response and drought stress tolerance, and also be participated in the regulation of passion fruit growth and floral development.

WRKY transcription factors in passion fruit analysis reveals key PeWRKYs involved in abiotic stress and flavonoid biosynthesis

WRKY transcription factors (TFs) are a superfamily of regulators involved in plant responses to pathogens and abiotic stress. Passion fruit is famous for its unique flavor and nutrient-rich juice, but its growth is limited by environmental factors and pathogens. In this study, 55 WRKY genes were identified from the Passiflora edulis genome. The structure and evolutionary characteristics of PeWRKYs were analyzed using a bioinformatics approach. PeWRKYs were classified into seven subgroups (I, IIa, IIb, IIc, IId, IIe, III) according to their homologs in Arabidopsis thaliana. Group IIa PeWRKY48 gene was highly up-regulated under cold stress by RNA expression analysis, and transgenic PeWRKY48 in yeast and Arabidopsis showed resistance exposure to cold, salt, and drought stress. Metabolome and transcriptome co-expression analysis of two different disease resistance genotypes of P. edulis identified PeWRKY30 as a key TF co-expressed with flavonoid accumulation in yellow fruit P. edulis, which may contribute to biotic or abiotic resistance. The qRT-PCR verified the expression of key genes in different tissues of P. edulis and in different species of Passiflora. This study provides a set of WRKY candidate genes that will facilitate the genetic improvement of disease and abiotic tolerance in passion fruit.

Volatile metabolomics reveals the characteristics of the unique flavor substances in oats

Oats is a cereal well known for its high nutritional value and unique flavor. This study investigated the metabolomics data from oats, wheat, and barley using broadly targeted GC-MS metabonomic techniques. A total of 437 volatile organic compounds (VOCs) were identified, of which 414 were shared metabolites, with three metabolites unique to oats. Three hundred and seven differentially accumulated metabolites (DAMs) were screened from all the comparison groups, of which 27 metabolites were shared by oats and barley, and 121 shared by oats and wheat. Terpenoids and esters were the key metabolites determining the differences in flavor. A KEGG analysis indicated that the alpha-linolenic acid and phenylalanine pathways were the most significant metabolic pathways. The 42 DAMs found may be the main substances leading to the flavor differences between the different varieties. Overall, this study reveals the main reasons for the unique flavor of oats through metabolomic evidence.

Multi-integrated genomic data for Passiflora foetida provides insights into genome size evolution and floral development in Passiflora

Passiflora is a plant genus known for its extremely distinctive and colorful flowers and a wide range of genome size variation. However, how genome characteristics are related to flower traits among Passiflora species remains poorly understood. Here, we assembled a chromosome-scale genome of P. foetida, which belongs to the same subgenus as the commercial passionfruit P. edulis. The genome of P. foetida is smaller (424.16 Mb) and contains fewer copies of long terminal repeat retrotransposons (LTR-RTs). The disparity in LTR-RTs is one of the main contributors to the differences in genome sizes between these two species and possibly in floral traits. Additionally, we observed variation in insertion times and copy numbers of LTR-RTs across different transposable element (TE) lineages. Then, by integrating transcriptomic data from 33 samples (eight floral organs and flower buds at three developmental stages) with phylogenomic and metabolomic data, we conducted an in-depth analysis of the expression, phylogeny, and copy number of MIKC-type MADS-box genes and identified essential biosynthetic genes responsible for flower color and scent from glandular bracts and other floral organs. Our study pinpoints LRT-RTs as an important player in genome size variation in Passiflora species and provides insights into future genetic improvement.

Insights into the Isolation, Identification, and Biological Characterization Analysis of and Novel Control Strategies for Diaporthe passiflorae in Postharvest Passion Fruit

Postharvest diseases seriously restrict developments in the passion fruit industry. In this study, we aimed to identify the postharvest pathogen affecting passion fruit, investigate its pathogenicity, and explore relevant control methods. The pathogen was isolated from rotting passion fruit and identified using morphological characteristics, ITS sequences, and phylogenetic tree analyses. Additionally, preliminary studies were conducted to assess the biological characteristics of the pathogen and evaluate the efficacy of various treatments for disease control. The fungus on the passion fruit called B4 was identified as Diaporthe passiflorae. Optimal conditions for mycelial growth were observed at 25-30 °C and pH 5-6, with starch as the carbon source and peptone as the nitrogen source. Infection by D. passiflorae accelerated fruit decay, reduced the h° value of the peel, and increased the peel cell membrane permeability when compared to the control. Notably, treatments with appropriate concentrations of ɛ-poly-l-lysine, salicylic acid, and melatonin showed inhibitory effects on the pathogen's growth in vitro and may thus be potential postharvest treatments for controlling brown rot caused by D. passiflorae in passion fruit. The results provide a scientific basis for the development of strategies to control postharvest decay and extend the storage period of passion fruit.

Integrated analysis of transcriptome, metabolome, and histochemistry reveals the response mechanisms of different ages Panax notoginseng to root-knot nematode infection

Panax notoginseng (P. notoginseng) is an invaluable perennial medicinal herb. However, the roots of P. notoginseng are frequently subjected to severe damage caused by root-knot nematode (RKN) infestation. Although we have observed that P. notoginseng possessed adult-plant resistance (APR) against RKN disease, the defense response mechanisms against RKN disease in different age groups of P. notoginseng remain unexplored. We aimed to elucidate the response mechanisms of P. notoginseng at different stages of development to RKN infection by employing transcriptome, metabolome, and histochemistry analyses. Our findings indicated that distinct age groups of P. notoginseng may activate the phenylpropanoid and flavonoid biosynthesis pathways in varying ways, leading to the synthesis of phenolics, flavonoids, lignin, and anthocyanin pigments as both the response and defense mechanism against RKN attacks. Specifically, one-year-old P. notoginseng exhibited resistance to RKN through the upregulation of 5-O-p-coumaroylquinic acid and key genes involved in monolignol biosynthesis, such as PAL, CCR, CYP73A, CYP98A, POD, and CAD. Moreover, two-year-old P. notoginseng enhanced the resistance by depleting chlorogenic acid and downregulating most genes associated with monolignol biosynthesis, while concurrently increasing cyanidin and ANR in flavonoid biosynthesis. Three-year-old P. notoginseng reinforced its resistance by significantly increasing five phenolic acids related to monolignol biosynthesis, namely p-coumaric acid, chlorogenic acid, 1-O-sinapoyl-D-glucose, coniferyl alcohol, and ferulic acid. Notably, P. notoginseng can establish a lignin barrier that restricted RKN to the infection site. In summary, P. notoginseng exhibited a potential ability to impede the further propagation of RKN through the accumulation or depletion of the compounds relevant to resistance within the phenylpropanoid and flavonoid pathways, as well as the induction of lignification in tissue cells.

Genome of Phyllanthus emblica: the medicinal plant Amla with super antioxidant properties

Phyllanthus emblica or Indian gooseberry, commonly known as amla, is an important medicinal horticultural plant used in traditional and modern medicines. It bears stone fruits with immense antioxidant properties due to being one of the richest natural sources of vitamin C and numerous flavonoids. This study presents the first genome sequencing of this species performed using 10x Genomics and Oxford Nanopore Technology. The draft genome assembly was 519 Mbp in size and consisted of 4,384 contigs, N50 of 597 Kbp, 98.4% BUSCO score, and 37,858 coding sequences. This study also reports the genome-wide phylogeny of this species with 26 other plant species that resolved the phylogenetic position of P. emblica. The presence of three ascorbate biosynthesis pathways including L-galactose, galacturonate, and myo-inositol pathways was confirmed in this genome. A comprehensive comparative evolutionary genomic analysis including gene family expansion/contraction and identification of multiple signatures of adaptive evolution provided evolutionary insights into ascorbate and flavonoid biosynthesis pathways and stone fruit formation through lignin biosynthesis. The availability of this genome will be beneficial for its horticultural, medicinal, dietary, and cosmetic applications and will also help in comparative genomics analysis studies.

Biotechnology of Passiflora edulis: role of Agrobacterium and endophytic microbes

Two forms of the genus Passiflora, belonging to the Passifloraceae family, are commonly called yellow and purple passion. These perennial woody climbers are found in the cooler regions at higher altitudes and in lowlands of tropical areas. The presence of alkaloids, terpenes, stilbenes, flavonoids, glycosides, carotenoids, etc. in different parts of the plant provides several pharmacological properties. Because of the various uses in foods and pharmaceuticals, in vitro propagation of this genus has been performed hugely and is of great interest to researchers. From different explants via direct organogenesis under controlled aseptic conditions, callus, root, shoot, and somatic embryos are induced successfully. Different PGRs are augmented in the media for the rapid multiplication or organogenesis, especially, the high ratio of cytokinin and auxin in the basal media efficiently regenerates the shoot and root respectively. The in vitro regenerated plantlets are then acclimatized and hardened properly before transferring to the field conditions. Thus, the present first of its kind review on P. edulis exclusively encompasses the wide applications of biotechnology for this species alongside its organogenesis, embryogenesis, cytology, and endophytic microbes with special emphasis on the role of genetic transformation studies mediated by Agrobacterium sp. KEY POINTS: • Critical assessment on in vitro biotechnology in P. edulis. • Agrobacterium-mediated transformation in P. edulis. • Role of endophytic microbes in P. edulis.

Cotyledon peeling method for passion fruit protoplasts: a versatile cell system for transient gene expression in passion fruit (Passiflora edulis)

Passion fruit (Passiflora edulis) is a perennial evergreen vine that grows mainly in tropical and subtropical regions due to its nutritional, medicinal and ornamental values. However, the molecular biology study of passion fruit is extremely hindered by the lack of an easy and efficient method for transformation. The protoplast transformation system plays a vital role in plant regeneration, gene function analysis and genome editing. Here, we present a new method ('Cotyledon Peeling Method') for simple and efficient passion fruit protoplast isolation using cotyledon as the source tissue. A high yield (2.3 × 107 protoplasts per gram of fresh tissues) and viability (76%) of protoplasts were obtained upon incubation in the enzyme solution [1% (w/v) cellulase R10, 0.25% (w/v) macerozyme R10, 0.4 M mannitol, 10 mM CaCl2, 20 mM KCl, 20 mM MES and 0.1% (w/v) BSA, pH 5.7] for 2 hours. In addition, we achieved high transfection efficiency of 83% via the polyethylene glycol (PEG)-mediated transformation with a green fluorescent protein (GFP)-tagged plasmid upon optimization. The crucial factors affecting transformation efficiency were optimized as follows: 3 μg of plasmid DNA, 5 min transfection time, PEG concentration at 40% and protoplast density of 100 × 104 cells/ml. Furthermore, the established protoplast system was successfully applied for subcellular localization analysis of multiple fluorescent organelle markers and protein-protein interaction study. Taken together, we report a simple and efficient passion fruit protoplast isolation and transformation system, and demonstrate its usage in transient gene expression for the first time in passion fruit. The protoplast system would provide essential support for various passion fruit biology studies, including genome editing, gene function analysis and whole plant regeneration.

5mC DNA methylation modification-mediated regulation in tissue functional differentiation and important flavor substance synthesis of tea plant (Camellia sinensis L.)

In plants, 5mC DNA methylation is an important and conserved epistatic mark involving genomic stability, gene transcriptional regulation, developmental regulation, abiotic stress response, metabolite synthesis, etc. However, the roles of 5mC DNA methylation modification (5mC methylation) in tea plant growth and development (in pre-harvest processing) and flavor substance synthesis in pre- and post-harvest processing are unknown. We therefore conducted a comprehensive methylation analysis of four key pre-harvest tissues (root, leaf, flower, and fruit) and two processed leaves during oolong tea post-harvest processing. We found that differential 5mC methylation among four key tissues is closely related to tissue functional differentiation and that genes expressed tissue-specifically, responsible for tissue-specific functions, maintain relatively low 5mC methylation levels relative to non-tissue-specifically expressed genes. Importantly, hypomethylation modifications of CsAlaDC and TS/GS genes in roots provided the molecular basis for the dominant synthesis of theanine in roots. In addition, integration of 5mC DNA methylationomics, metabolomics, and transcriptomics of post-harvest leaves revealed that content changes in flavor metabolites during oolong tea processing were closely associated with transcription level changes in corresponding metabolite synthesis genes, and changes in transcript levels of these important synthesis genes were strictly regulated by 5mC methylation. We further report that some key genes during processing are regulated by 5mC methylation, which can effectively explain the content changes of important aroma metabolites, including α-farnesene, nerolidol, lipids, and taste substances such as catechins. Our results not only highlight the key roles of 5mC methylation in important flavor substance synthesis in pre- and post-harvest processing, but also provide epimutation-related gene targets for future improvement of tea quality or breeding of whole-tissue high-theanine varieties.

Phytochemistry, nutritional composition, health benefits and future prospects of Passiflora: A review

Passiflora, also known as "passion fruit", is widely grown in tropical and subtropical regions. It is not only eaten raw but is also widely used in processed foods. Various extracts, juices and isolated compounds show a wide range of health effects and biological activities, such as antioxidant, anti-inflammatory, sedative, and neuroprotective effects. In this review, we not only review the phytochemical properties of Passiflora but also highlight the potential of Passiflora for food applications and the use of all parts as a source of ingredients for medicines and cosmetics that promote health and well-being. This will provide theoretical support for the integrated use of such natural products.

Identification of passion fruit HSF gene family and the functional analysis of PeHSF-C1a in response to heat and osmotic stress

Heat stress transcription factors (HSFs) are the major regulators of plant response to environmental stress, especially heat and drought stress. To gain a deeper understanding of the mechanisms underlying HSFs in the abiotic stress response of passion fruit, we conducted an in silico analysis of the HSF gene family. Through bioinformatics and phylogenetic analyses, we identified 18 PeHSF members and classified them into A, B, and C groups. Collinearity analysis results revealed that the expansion of the PeHSF gene family was due to the presence of segmental duplication. Furthermore, gene structure and protein domain analysis illustrated that PeHSFs in the same subgroup are relatively conserved. Conserved motif and function domain analysis suggested that PeHSF proteins possess typical conserved functional domains of the HSF family. A protein interaction network and 3D structure prediction were used to study the potential regulatory relationship of PeHSFs. Additionally, the subcellular localization results of PeHSF-A6a, PeHSF-B4b, and PeHSF-C1a were consistent with the predictions. RNA-seq and RT-qPCR analysis revealed the expression patterns of PeHSFs in different tissues of passion fruit floral organs. Promoter analysis and the expression patterns of the PeHSFs under different treatments demonstrated their involvement in various abiotic stress processes. Notably, overexpression of PeHSF-C1a consistently enhanced tolerance to drought and heat stress in Arabidopsis. Overall, our findings provide a scientific basis for further functional studies of PeHSFs that could contribute to improvement of passion fruit breeding.

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.

Analysis of Volatile Aroma Components and Regulatory Genes in Different Kinds and Development Stages of Pepper Fruits Based on Non-Targeted Metabolome Combined with Transcriptome

Aroma is a crucial attribute affecting the quality of pepper and its processed products, which has significant commercial value. However, little is known about the composition of volatile aroma compounds (VACs) in pepper fruits and their potential molecular regulatory mechanisms. In this study, HS-SPME-GC-MS combined with transcriptome sequencing is used to analyze the composition and formation mechanism of VACs in different kinds and development stages of pepper fruits. The results showed that 149 VACs, such as esters, alcohols, aldehydes, and terpenoids, were identified from 4 varieties and 3 development stages, and there were significant quantitative differences among different samples. Volatile esters were the most important aroma components in pepper fruits. PCA analysis showed that pepper fruits of different developmental stages had significantly different marker aroma compounds, which may be an important provider of pepper's characteristic aroma. Transcriptome analysis showed that many differential genes (DEGs) were enriched in the metabolic pathways related to the synthesis of VACs, such as fatty acids, amino acids, MVA, and MEP in pepper fruits. In addition, we identified a large number of differential transcription factors (TFs) that may regulate the synthesis of VACs. Combined analysis of differential aroma metabolites and DEGs identified two co-expression network modules highly correlated with the relative content of VACs in pepper fruit. This study confirmed the basic information on the changes of VACs in the fruits of several Chinese spicy peppers at different stages of development, screened out the characteristic aroma components of different varieties, and revealed the molecular mechanism of aroma formation, providing a valuable reference for the quality breeding of pepper.

A gap-free and haplotype-resolved lemon genome provides insights into flavor synthesis and huanglongbing (HLB) tolerance

The lemon (Citrus limon; family Rutaceae) is one of the most important and popular fruits worldwide. Lemon also tolerates huanglongbing (HLB) disease, which is a devastating citrus disease. Here we produced a gap-free and haplotype-resolved chromosome-scale genome assembly of the lemon by combining Pacific Biosciences circular consensus sequencing, Oxford Nanopore 50-kb ultra-long, and high-throughput chromatin conformation capture technologies. The assembly contained nine-pair chromosomes with a contig N50 of 35.6 Mb and zero gaps, while a total of 633.0 Mb genomic sequences were generated. The origination analysis identified 338.5 Mb genomic sequences originating from citron (53.5%), 147.4 Mb from mandarin (23.3%), and 147.1 Mb from pummelo (23.2%). The genome included 30 528 protein-coding genes, and most of the assembled sequences were found to be repetitive sequences. Several significantly expanded gene families were associated with plant-pathogen interactions, plant hormone signal transduction, and the biosynthesis of major active components, such as terpenoids and flavor compounds. Most HLB-tolerant genes were expanded in the lemon genome, such as 2-oxoglutarate (2OG)/Fe(II)-dependent oxygenase and constitutive disease resistance 1, cell wall-related genes, and lignin synthesis genes. Comparative transcriptomic analysis showed that phloem regeneration and lower levels of phloem plugging are the elements that contribute to HLB tolerance in lemon. Our results provide insight into lemon genome evolution, active component biosynthesis, and genes associated with HLB tolerance.

Plant and Trees Pathogens: Isolation, Characterization and Control Strategies (1.0)

Agricultural production is under constant threat from biotic and abiotic stresses [...]

Characterization of the NAC Transcription Factor in Passion Fruit (Passiflora edulis) and Functional Identification of PeNAC-19 in Cold Stress

The NAC (NAM, ATAF and CUC) gene family plays an important role in plant development and abiotic stress response. However, up to now, the identification and research of the NAC (PeNAC) family members of passion fruit are still lacking. In this study, 25 PeNACs were identified from the passion fruit genome, and their functions under abiotic stress and at different fruit-ripening stages were analyzed. Furthermore, we analyzed the transcriptome sequencing results of PeNACs under four various abiotic stresses (drought, salt, cold and high temperature) and three different fruit-ripening stages, and verified the expression results of some genes by qRT-PCR. Additionally, tissue-specific analysis showed that most PeNACs were mainly expressed in flowers. In particular, PeNAC-19 was induced by four various abiotic stresses. At present, low temperatures have seriously endangered the development of passion fruit cultivation. Therefore, PeNAC-19 was transformed into tobacco, yeast and Arabidopsis to study their function of resisting low temperature. The results show that PeNAC-19 responded to cold stress significantly in tobacco and Arabidopsis, and could improve the low temperature tolerance of yeast. This study not only improved the understanding of the PeNAC gene family characteristics and evolution, but also provided new insights into the regulation of the PeNAC gene at different stages of fruit maturation and abiotic stresses.

Optimization of strains for fermentation of kiwifruit juice and effects of mono- and mixed culture fermentation on its sensory and aroma profiles

In this study, a quality evaluation model of fermented kiwifruit juice (KJ) based on strain growth characteristics, sensory quality and functional characteristics was established by PCA, and the effects of mono- and mixed culture fermentation on the sensory and aroma profiles of KJ were comparatively studied. Experiments determined that L. brevis (LB) was the optimal strain for monoculture fermentation, and L. plantarum (LP2):LB = 1:2 was the optimum ratio for mixed fermentation. The results showed that lactic acid bacteria (LAB) fermentation significantly reduced the pH, soluble solid content and lightness, and improved its functional characteristics and viscosity. Mixed culture fermentation was superior to monoculture fermentation in terms of colony counts, sensory quality and viscosity. In general, after LAB fermentation, the concentrations of esters, ketones, alcohols and terpenoids in KJ increased significantly, while the concentrations of aldehydes decreased significantly. The production of esters and terpenoids was more strongly promoted by monoculture fermentation, while mixed culture fermentation promoted the production of more ketones and alcohols. 2,5-octanedione and 1-octen-3-ol could be the characteristic aroma compounds of mixed fermented KJ.

Differential gene expression analysis and physiological response characteristics of passion fruit (Passiflora edulis) buds under high-temperature stress

High temperature in summer is an unfavorable factor for passion fruit (Passiflora edulis), which can lead to restricted growth, short flowering period, few flower buds, low fruit setting rate, severe fruit drop, and more deformed fruit. To explore the molecular physiology mechanism of passion fruit responding to high-temperature stress, we use 'Zhuangxiang Mibao', a hybrid passion fruit cultivar, as the test material. Several physiological indicators were measured and compared between high-temperature (average temperature 38 °C) and normal temperature (average temperature 25 °C) conditions, including photosynthesis, chlorophyll fluorescence parameters, peroxidase activity (POD), superoxide dismutase activity (SOD) and malondialdehyde content. We performed RNA-seq analysis combined with biochemistry experiment to investigate the gene and molecular pathways that respond to high-temperature stress. The results showed that some physiological indicators in the high-temperature group, including the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, and the maximum chemical quantum yield of photosystemII (PSII), were significantly lower than those of the control group. Malondialdehyde content was substantially higher than the control group, while superoxide dismutase and superoxide dismutase activities decreased to different degrees. Transcriptome sequencing analysis showed that 140 genes were up-regulated and 75 genes were down-regulated under high-temperature stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis of differentially expressed genes revealed many metabolic pathways related to high-temperature stress. Further investigation revealed that 30 genes might be related to high-temperature stress, such as chlorophyllide a oxygenase (CAO), glutathione (GSH), WRKY transcription factors (WRKY), and heat shock protein (HSP), which have also been reported in other species. The results of real-time fluorescence quantitative PCR and RNA-seq of randomly selected ten genes are consistent, which suggests that the transcriptome sequencing results were reliable. Our study provides a theoretical basis for the mechanism of passion fruit response to high-temperature stress. Also, it gives a theoretical basis for the subsequent breeding of new heat-resistant passion fruit varieties.

Plant Growth Promotion and Biocontrol of Leaf Blight Caused by Nigrospora sphaerica on Passion Fruit by Endophytic Bacillus subtilis Strain GUCC4

Passion fruit (Passiflora edulis Sims) is widely cultivated in tropic and sub-tropic regions for the production of fruit, flowers, cosmetics, and for pharmacological applications. Its high economic, nutritional, and medical values elicit the market demand, and the growing areas are rapidly increasing. Leaf blight caused by Nigrospora sphaerica is a new and emerging disease of passion fruit in Guizhou, in southwest China, where the unique karst mountainous landscape and climate conditions are considered potential areas of expansion for passion fruit production. Bacillus species are the most common biocontrol and plant-growth-promotion bacteria (PGPB) resources in agricultural systems. However, little is known about the endophytic existence of Bacillus spp. in the passion fruit phyllosphere as well as their potential as biocontrol agents and PGPB. In this study, 44 endophytic strains were isolated from 15 healthy passion fruit leaves, obtained from Guangxi province, China. Through purification and molecular identification, 42 of the isolates were ascribed to Bacillus species. Their inhibitory activity against N. sphaerica was tested in vitro. Eleven endophytic Bacillus spp. strains inhibited the pathogen by >65%. All of them produced biocontrol- and plant-growth-promotion-related metabolites, including indole-3-acetic acid (IAA), protease, cellulase, phosphatase, and solubilized phosphate. Furthermore, the plant growth promotion traits of the above 11 endophytic Bacillus strains were tested on passion fruit seedlings. One isolate, coded B. subtilis GUCC4, significantly increased passion fruit stem diameter, plant height, leaf length, leaf surface, fresh weight, and dry weight. In addition, B. subtilis GUCC4 reduced the proline content, which indicated its potential to positively regulate passion fruit biochemical properties and resulted in plant growth promotion effects. Finally, the biocontrol efficiencies of B. subtilis GUCC4 against N. sphaerica were determined in vivo under greenhouse conditions. Similarly to the fungicide mancozeb and to a commercial B. subtilis-based biofungicide, B. subtilis GUCC4 significantly reduced disease severity. These results suggest that B. subtilis GUCC4 has great potential as a biological control agent and as PGPB on passion fruit.

Annotation of the Turnera subulata (Passifloraceae) Draft Genome Reveals the S-Locus Evolved after the Divergence of Turneroideae from Passifloroideae in a Stepwise Manner

A majority of Turnera species (Passifloraceae) exhibit distyly, a reproductive system involving both self-incompatibility and reciprocal herkogamy. This system differs from self-incompatibility in Passiflora species. The genetic basis of distyly in Turnera is a supergene, restricted to the S-morph, and containing three S-genes. How supergenes and distyly evolved in Turnera, and the other Angiosperm families exhibiting distyly remain largely unknown. Unraveling the evolutionary origins in Turnera requires the generation of genomic resources and extensive phylogenetic analyses. Here, we present the annotated draft genome of the S-morph of distylous Turnera subulata. Our annotation allowed for phylogenetic analyses of the three S-genes' families across 56 plant species ranging from non-seed plants to eudicots. In addition to the phylogenetic analysis, we identified the three S-genes' closest paralogs in two species of Passiflora. Our analyses suggest that the S-locus evolved after the divergence of Passiflora and Turnera. Finally, to provide insights into the neofunctionalization of the S-genes, we compared expression patterns of the S-genes with close paralogs in Arabidopsis and Populus trichocarpa. The annotation of the T. subulata genome will provide a useful resource for future comparative work. Additionally, this work has provided insights into the convergent nature of distyly and the origin of supergenes.

The Current Developments in Medicinal Plant Genomics Enabled the Diversification of Secondary Metabolites' Biosynthesis

Medicinal plants produce important substrates for their adaptation and defenses against environmental factors and, at the same time, are used for traditional medicine and industrial additives. Plants have relatively little in the way of secondary metabolites via biosynthesis. Recently, the whole-genome sequencing of medicinal plants and the identification of secondary metabolite production were revolutionized by the rapid development and cheap cost of sequencing technology. Advances in functional genomics, such as transcriptomics, proteomics, and metabolomics, pave the way for discoveries in secondary metabolites and related key genes. The multi-omics approaches can offer tremendous insight into the variety, distribution, and development of biosynthetic gene clusters (BGCs). Although many reviews have reported on the plant and medicinal plant genome, chemistry, and pharmacology, there is no review giving a comprehensive report about the medicinal plant genome and multi-omics approaches to study the biosynthesis pathway of secondary metabolites. Here, we introduce the medicinal plant genome and the application of multi-omics tools for identifying genes related to the biosynthesis pathway of secondary metabolites. Moreover, we explore comparative genomics and polyploidy for gene family analysis in medicinal plants. This study promotes medicinal plant genomics, which contributes to the biosynthesis and screening of plant substrates and plant-based drugs and prompts the research efficiency of traditional medicine.

Genome-Wide Identification and Characterization of the SBP Gene Family in Passion Fruit (Passiflora edulis Sims)

The SQUAMOSA promoter binding proteins (SBPs) gene family plays important roles in plant growth and development. The SBP gene family has been identified and reported in many species, but it has not been well studied in passion fruit. In this study, a total of 14 SBP genes were identified in passion fruit and named from PeSBP1 to PeSBP14 based on their chromosomal distribution. The phylogenetic tree, gene structure, conserved motifs, collinearity analysis, and expression patterns of the identified SBP members were analyzed. We classified the PeSBP genes into eight groups (I to VIII) according to the phylogenetic tree, gene structure, and conserved motifs. Synteny analysis found that 5 homologous gene pairs existed in PeSBP genes and 11 orthologous gene pairs existed between passion fruit and Arabidopsis. Synonymous nucleotide substitution analysis showed that the PeSBP genes were under strong negative selection. The expression pattern of PeSBP genes in seed, root, leaf, and flower showed that nine of the PeSBP genes displayed high expression in the leaf and the flower. The expression patterns of PeSBP3/6/8/9/10 were further detected by qRT-PCR. In addition, differences in the expression levels occurred for each gene in the different flower organs and at the different developmental stages. There were large differences among SBPs based on transcriptional levels under cold, heat, salt, and osmotic stress conditions. Altogether, this study provides an overview of SBP genes in passion fruit and lays the foundation for further functional analysis.

Natural products of medicinal plants: biosynthesis and bioengineering in post-genomic era

Globally, medicinal plant natural products (PNPs) are a major source of substances used in traditional and modern medicine. As we human race face the tremendous public health challenge posed by emerging infectious diseases, antibiotic resistance and surging drug prices etc., harnessing the healing power of medicinal plants gifted from mother nature is more urgent than ever in helping us survive future challenge in a sustainable way. PNP research efforts in the pre-genomic era focus on discovering bioactive molecules with pharmaceutical activities, and identifying individual genes responsible for biosynthesis. Critically, systemic biological, multi- and inter-disciplinary approaches integrating and interrogating all accessible data from genomics, metabolomics, structural biology, and chemical informatics are necessary to accelerate the full characterization of biosynthetic and regulatory circuitry for producing PNPs in medicinal plants. In this review, we attempt to provide a brief update on the current research of PNPs in medicinal plants by focusing on how different state-of-the-art biotechnologies facilitate their discovery, the molecular basis of their biosynthesis, as well as synthetic biology. Finally, we humbly provide a foresight of the research trend for understanding the biology of medicinal plants in the coming decades.

Genome Assembly and Analysis of the Flavonoid and Phenylpropanoid Biosynthetic Pathways in Fingerroot Ginger (Boesenbergia rotunda)

Boesenbergia rotunda (Zingiberaceae), is a high-value culinary and ethno-medicinal plant of Southeast Asia. The rhizomes of this herb have a high flavanone and chalcone content. Here we report the genome analysis of B. rotunda together with a complete genome sequence as a hybrid assembly. B. rotunda has an estimated genome size of 2.4 Gb which is assembled as 27,491 contigs with an N50 size of 12.386 Mb. The highly heterozygous genome encodes 71,072 protein-coding genes and has a 72% repeat content, with class I TEs occupying ~67% of the assembled genome. Fluorescence in situ hybridization of the 18 chromosome pairs at the metaphase showed six sites of 45S rDNA and two sites of 5S rDNA. An SSR analysis identified 238,441 gSSRs and 4604 EST-SSRs with 49 SSR markers common among related species. Genome-wide methylation percentages ranged from 73% CpG, 36% CHG and 34% CHH in the leaf to 53% CpG, 18% CHG and 25% CHH in the embryogenic callus. Panduratin A biosynthetic unigenes were most highly expressed in the watery callus. B rotunda has a relatively large genome with a high heterozygosity and TE content. This assembly and data (PRJNA71294) comprise a source for further research on the functional genomics of B. rotunda, the evolution of the ginger plant family and the potential genetic selection or improvement of gingers.