Comprehensive genomic exploration of class III peroxidase genes in guava unravels physiology, evolution, and postharvest storage responses.

Peroxidases (PRXs) play multifaceted roles in plant growth, development, and stress responses. Here, we present a comprehensive analysis of the PRX gene family in guava, a globally significant fruit. In the guava genome, we identified 37 PRX genes, a number lower than that of Arabidopsis, suggesting a distinctive gene family expansion pattern. Phylogenetic analysis unveiled close relationships with Arabidopsis PRXs, with 12 PgPRX genes forming ortholog pairs, indicating a specific expansion pattern. Predictions placed most PRX proteins in the chloroplast and extracellular regions. Structural analysis of PgPRX proteins revealed commonalities in domain structures and motif organization. Synteny analysis underscored the dynamic role of segmental duplication in the evolution of guava's PRX genes. We explored the dynamic expression of PgPRX genes across guava tissues, exposing functional diversity. Furthermore, we examined changes in peroxidase levels and gene expressions during postharvest fruit storage, providing insights for preserving fruit quality. This study offers an initial genome-wide identification and characterization of Class III peroxidases in guava, laying the foundation for future functional analyses.

RNAi-Mediated Suppression of OsBBTI5 Promotes Salt Stress Tolerance in Rice.

This study explores the impact of RNAi in terms of selectively inhibiting the expression of the OsBBTI5 gene, with the primary objective of uncovering its involvement in the molecular mechanisms associated with salt tolerance in rice. OsBBTI5, belonging to the Bowman-Birk inhibitor (BBI) family gene, is known for its involvement in plant stress responses. The gene was successfully cloned from rice, exhibiting transcriptional self-activation in yeast. A yeast two-hybrid assay confirmed its specific binding to OsAPX2 (an ascorbate peroxidase gene). Transgenic OsBBTI5-RNAi plants displayed insensitivity to varying concentrations of 24-epibrassinolide in the brassinosteroid sensitivity assay. However, they showed reduced root and plant height at high concentrations (10 and 100 µM) of GA3 immersion. Enzyme activity assays revealed increased peroxidase (POD) and superoxide dismutase (SOD) activities and decreased malondialdehyde (MDA) content under 40-60 mM NaCl. Transcriptomic analysis indicated a significant upregulation of photosynthesis-related genes in transgenic plants under salt stress compared to the wild type. Notably, this study provides novel insights, suggesting that the BBI gene is part of the BR signaling pathway, and that OsBBTI5 potentially enhances stress tolerance in transgenic plants through interaction with the salt stress-related gene OsAPX2.

Unlocking the Potential of Carbon Quantum Dots for Cell Imaging, Intracellular Localization, and Gene Expression Control in Arabidopsis thaliana (L.) Heynh.

Utilizing carbon quantum dots (CQDs) as biomaterials for delivering small substances has gained significant attention in recent research. However, the interactions and mechanisms of action of CQDs on plants have received relatively little focus. Herein, we investigated the transportation of CQDs into various organs of Arabidopsis thaliana (L.) Heynh. via the vessel system, leading to the epigenetic inheritance of Argonaute family genes. Our findings reveal that CQDs may interact with microRNAs (miRNAs), leading to the repression of post-transcriptional regulation of target genes in the cytoplasm. Transcriptome and quantitative PCR analyses demonstrated consistent gene expression levels in offspring. Moreover, microscopic observations illustrated rapid CQD localization on cell membranes and nuclei, with increased nuclear entry at higher concentrations. Notably, our study identified an alternative regulatory microRNA, microRNA172D, for the Argonaute family genes through methylation analysis, shedding light on the connection between CQDs and microRNAs.

Transcriptome Insights into Candidate Genes of the SWEET Family and Carotenoid Biosynthesis during Fruit Growth and Development in Prunus salicina 'Huangguan'.

The Chinese plum (Prunus salicina L.) is a fruit tree belonging to the Rosaceae family, native to south-eastern China and widely cultivated throughout the world. Fruit sugar metabolism and color change is an important physiological behavior that directly determines flavor and aroma. Our study analyzed six stages of fruit growth and development using RNA-seq, yielding a total of 14,973 DEGs, and further evaluation of key DEGs revealed a focus on sugar metabolism, flavonoid biosynthesis, carotenoid biosynthesis, and photosynthesis. Using GO and KEGG to enrich differential genes in the pathway, we selected 107 differential genes and obtained 49 significant differential genes related to glucose metabolism. The results of the correlation analyses indicated that two genes of the SWEET family, evm.TU.Chr1.3663 (PsSWEET9) and evm.TU.Chr4.676 (PsSWEET2), could be closely related to the composition of soluble sugars, which was also confirmed in the ethylene treatment experiments. In addition, analysis of the TOP 20 pathways between different growth stages and the green stage, as well as transient overexpression in chili, suggested that capsanthin/capsorubin synthase (PsCCS) of the carotenoid biosynthetic pathway contributed to the color change of plum fruit. These findings provide an insight into the molecular mechanisms involved in the ripening and color change of plum fruit.

Exogenously applied zinc improves sugar-acid profile of loquat (Eriobotrya japonica Lindl.) by regulating enzymatic activities and expression of their metabolism-related genes.

Soluble sugars and organic acids are the most abundant components in ripe fruits, and they play critical roles in the development of fruit flavor and taste. In this study, loquat trees were sprayed with 0.1, 0.2 and 0.3% zinc sulphate. The contents of soluble sugars and organic acids were determined using HPLC-RID and UPLC-MS, respectively. The activities of key enzymes involved in sugar-acid metabolism were measured and expression profiling of related genes was done using RT-qPCR. The results revealed that 0.1% zinc sulphate was a promising treatment among other Zn applications with respect to the increased levels of soluble sugars and decreased acid contents in loquats. Correlation analysis showed that the enzymes i.e., SPS, SS, FK, and HK were may be involved in the regulation of fructose and glucose metabolism in the fruit pulp of loquat. While, the activity of NADP-ME showed negative and NAD-MDH showed a positive correlation with malic acid content. Meanwhile, EjSPS1-4, EjSS2-4, EjHK1-3, and EjFK1-6 may play an important role in soluble sugar metabolism in the pulp of loquat fruits. Similarly, EjPEPC2, EjPEPC3, EjNAD-MDH1, EjNAD-MDH3-5, EjNAD-MDH6 and EjNAD-MDH13 may have a vital contribution to malic acid biosynthesis in loquat fruits. This study provides new insights for future elucidation of key mechanisms regulating soluble sugars and malic acid biosynthesis in loquats.

LhANS-rr1, LhDFR, and LhMYB114 Regulate Anthocyanin Biosynthesis in Flower Buds of Lilium 'Siberia'.

The bulb formation of Lilium is affected by many physiological and biochemical phenomena, including flower bud differentiation, starch and sucrose accumulation, photoperiod, carbon fixation, plant hormone transduction, etc. The transcriptome analysis of flower buds of Lilium hybrid 'Siberia' at different maturity stages showed that floral bud formation is associated with the accumulation of anthocyanins. The results of HPLC-MS showed that cyanidin is the major anthocyanin found in Lilium 'Siberia'. Transcriptome KEGG enrichment analysis and qRT-PCR validation showed that two genes related to flavonoid biosynthesis (LhANS-rr1 and LhDFR) were significantly up-regulated. The functional analysis of differential genes revealed that LhMYB114 was directly related to anthocyanin accumulation among 19 MYB transcription factors. Furthermore, the qRT-PCR results suggested that their expression patterns were very similar at different developmental stages of the lily bulbs. Virus-induced gene silencing (VIGS) revealed that down-regulation of LhANS-rr1, LhDFR, and LhMYB114 could directly lead to a decrease in anthocyanin accumulation, turning the purple phenotype into a white color. Moreover, this is the first report to reveal that LhMYB114 can regulate anthocyanin accumulation at the mature stage of lily bulbs. The accumulation of anthocyanins is an important sign of lily maturity. Therefore, these findings have laid a solid theoretical foundation for further discussion on lily bulb development in the future.

Transcriptome Analysis Reveals the Molecular Regularity Mechanism Underlying Stem Bulblet Formation in Oriental Lily 'Siberia'; Functional Characterization of the LoLOB18 Gene.

The formation of underground stem bulblets in lilies is a complex biological process which is key in their micropropagation. Generally, it involves a stem-to-bulblet transition; however, the underlying mechanism remains elusive. It is important to understand the regulatory mechanism of bulblet formation for the reproductive efficiency of Lilium. In this study, we investigated the regulatory mechanism of underground stem bulblet formation under different conditions regarding the gravity point angle of the stem, i.e., vertical (control), horizontal, and slanting. The horizontal and slanting group displayed better formation of bulblets in terms of quality and quantity compared with the control group. A transcriptome analysis revealed that sucrose and starch were key energy sources for bulblet formation, auxin and cytokinin likely promoted bulblet formation, and gibberellin inhibited bulblet formation. Based on transcriptome analysis, we identified the LoLOB18 gene, a homolog to AtLOB18, which has been proven to be related to embryogenic development. We established the stem bud growth tissue culture system of Lilium and silenced the LoLOb18 gene using the VIGS system. The results showed that the bulblet induction was reduced with down-regulation of LoLOb18, indicating the involvement of LoLOb18 in stem bulblet formation in lilies. Our research lays a solid foundation for further molecular studies on stem bulblet formation of lilies.

Sugar and acid profile of loquat (Eriobotrya japonica Lindl.), enzymes assay and expression profiling of their metabolism-related genes as influenced by exogenously applied boron.

Soluble sugars and organic acids are the most abundant components in ripe fruits, and they play critical roles in the development of fruit flavor and taste. Some loquat cultivars have high acid content which seriously affect the quality of fruit and reduce the value of commodity. Consequently, studying the physiological mechanism of sugar-acid metabolism in loquat can clarify the mechanism of their formation, accumulation and degradation in the fruit. Minerals application has been reported as a promising way to improve sugar-acid balance of the fruits. In this study, loquat trees were foliar sprayed with 0.1, 0.2 and 0.3% borax, and changes in soluble sugars and organic acids were recorded. The contents of soluble sugars and organic acids were determined using HPLC-RID and UPLC-MS, respectively. The activities of enzymes responsible for the metabolism of sugars and acids were quantified and expressions of related genes were determined using quantitative real-time PCR. The results revealed that 0.2% borax was a promising treatment among other B applications for the increased levels of soluble sugars and decreased acid contents in loquats. Correlation analysis showed that the enzymes i.e., SPS, SS, FK, and HK were may be involved in the regulation of fructose and glucose metabolism in the fruit pulp of loquat. While the activity of NADP-ME showed negative and NAD-MDH showed a positive correlation with malic acid content. Meanwhile, EjSPS1, EjSPS3, EjSS3, EjHK1, EjHK3, EjFK1, EjFK2, EjFK5, and EjFK6 may play an important role in soluble sugars metabolism in fruit pulp of loquat. Similarly, EjPEPC2, EjPEPC3, EjNAD-ME1, EjNAD-MDH1, EjNAD-MDH5-8, EjNAD-MDH10, and EjNAD-MDH13 may have a vital contribution to malic acid biosynthesis in loquat fruits. This study provides new insights for future elucidation of key mechanisms regulating soluble sugars and malic acid biosynthesis in loquats.

Genome-wide identification and comprehensive analyses of NAC transcription factor gene family and expression analysis under Fusarium kyushuense and drought stress conditions in Passiflora edulis.

The NAC gene family is one of the largest plant transcription factors (TFs) families and plays important roles in plant growth, development, metabolism, and biotic and abiotic stresses. However, NAC gene family has not been reported in passion fruit (Passiflora edulis). In this study, a total of 105 NAC genes were identified in the passion fruit genome and were unevenly distributed across all nine-passion fruit chromomere, with a maximum of 48 PeNAC genes on chromosome one. The physicochemical features of all 105 PeNAC genes varied including 120 to 3,052 amino acids, 3 to 8 conserved motifs, and 1 to 3 introns. The PeNAC genes were named (PeNAC001-PeNAC105) according to their chromosomal locations and phylogenetically grouped into 15 clades (NAC-a to NAC-o). Most PeNAC proteins were predicted to be localized in the nucleus. The cis-element analysis indicated the possible roles of PeNAC genes in plant growth, development, light, hormones, and stress responsiveness. Moreover, the PeNAC gene duplications including tandem (11 gene pairs) and segmental (12 gene pairs) were identified and subjected to purifying selection. All PeNAC proteins exhibited similar 3D structures, and a protein-protein interaction network analysis with known Arabidopsis proteins was predicted. Furthermore, 17 putative ped-miRNAs were identified to target 25 PeNAC genes. Potential TFs including ERF, BBR-BPC, Dof, and bZIP were identified in promoter region of all 105 PeNAC genes and visualized in a TF regulatory network. GO and KEGG annotation analysis exposed that PeNAC genes were related to different biological, molecular, and cellular terms. The qRT-PCR expression analysis discovered that most of the PeNAC genes including PeNAC001, PeNAC003, PeNAC008, PeNAC028, PeNAC033, PeNAC058, PeNAC063, and PeNAC077 were significantly upregulated under Fusarium kyushuense and drought stress conditions compared to controls. In conclusion, these findings lay the foundation for further functional studies of PeNAC genes to facilitate the genetic improvement of plants to stress resistance.

Isolation and Functional Characterization of a Green-Tissue Promoter in Japonica Rice (Oryza sativa subsp. Japonica).

Plant promoters play a vital role in the initiation and regulation of gene transcription. In this study, a rice protein/gene of unknown expression, named Os8GSX7, was gained from a rice T-DNA capture line. The semi-quantitative RT-PCR analysis showed that the gene was only expressed in root, glume, and flower, but not in stem, leaf, embryo, and endosperm of japonica rice. The GUS activity analysis of the GSX7R promoter showed that it was a reverse green tissue expression promoter, except in endosperm. The forward promoter of GSX7 cannot normally drive the expression of the foreign GUS gene, while the reverse promoter of GSX7 is a green tissue-specific expression promoter, which can drive the expression of the foreign GUS gene. The region from -2097 to -1543 bp was the key region for controlling the green tissue-specific expression. The regulatory sequences with different lengths from the 2097 bp reverse sequence from the upstream region of the Os8GSX7 were fused with the GUS reporter gene and stably expressed in rice. Furthermore, transgenic rice plants carrying Cry1Ab encoding Bacillus thuringiensis endotoxin, regulated by GSX7R, were resistant to yellow stem borer. The analysis suggested that 10 light responsive elements of tissue-specific expression were found, including ACE, Box4, CAT-box, G-Box, G-box, GATA motif, GC motif, I-box, Sp1, and chs-unit1 M1. In addition, the results of 5' and 3' deletions further speculated that ACE and I-box may be the key elements for determining the green tissue-specific expression of GSX7R promoter.

Comprehensive Genome-Wide Identification and Expression Profiling of Eceriferum (CER) Gene Family in Passion Fruit (Passiflora edulis) Under Fusarium kyushuense and Drought Stress Conditions.

Plant surfaces are covered with cuticle wax and are the first barrier between a plant and environmental stresses. Eceriferum (CER) is an important gene family involved in wax biosynthesis and stress resistance. In this study, for the first time, 34 CER genes were identified in the passion fruit (Passiflora edulis) genome, and PeCER proteins varied in physicochemical properties. A phylogenetic tree was constructed and divided into seven clades to identify the evolutionary relationship with other plant species. Gene structure analyses revealed that conserved motifs ranged from 1 to 24, and that exons ranged from 1 to 29. The cis-element analysis provides insight into possible roles of PeCER genes in plant growth, development and stress responses. The syntenic analysis revealed that segmental (six gene pairs) and tandem (six gene pairs) gene duplication played an important role in the expansion of PeCER genes and underwent a strong purifying selection. In addition, 12 putative ped-miRNAs were identified to be targeting 16 PeCER genes, and PeCER6 was the most targeted by four miRNAs including ped-miR157a-5p, ped-miR164b-5p, ped-miR319b, and ped-miR319l. Potential transcription factors (TFs) such as ERF, AP2, MYB, and bZIP were predicted and visualized in a TF regulatory network interacting with PeCER genes. GO and KEGG annotation analysis revealed that PeCER genes were highly related to fatty acid, cutin, and wax biosynthesis, plant-pathogen interactions, and stress response pathways. The hypothesis that most PeCER proteins were predicted to localize to the plasma membrane was validated by transient expression assays of PeCER32 protein in onion epidermal cells. qRT-PCR expression results showed that most of the PeCER genes including PeCER1, PeCER11, PeCER15, PeCER17, and PeCER32 were upregulated under drought and Fusarium kyushuense stress conditions compared to controls. These findings provide a foundation for further studies on functions of PeCER genes to further facilitate the genetic modification of passion fruit wax biosynthesis and stress resistance.

Genome-Wide Identification and Expression Profiling of KCS Gene Family in Passion Fruit (Passiflora edulis) Under Fusarium kyushuense and Drought Stress Conditions.

Plant and fruit surfaces are covered with cuticle wax and provide a protective barrier against biotic and abiotic stresses. Cuticle wax consists of very-long-chain fatty acids (VLCFAs) and their derivatives. ß-Ketoacyl-CoA synthase (KCS) is a key enzyme in the synthesis of VLCFAs and provides a precursor for the synthesis of cuticle wax, but the KCS gene family was yet to be reported in the passion fruit (Passiflora edulis). In this study, thirty-two KCS genes were identified in the passion fruit genome and phylogenetically grouped as KCS1-like, FAE1-like, FDH-like, and CER6-like. Furthermore, thirty-one PeKCS genes were positioned on seven chromosomes, while one PeKCS was localized to the unassembled genomic scaffold. The cis-element analysis provides insight into the possible role of PeKCS genes in phytohormones and stress responses. Syntenic analysis revealed that gene duplication played a crucial role in the expansion of the PeKCS gene family and underwent a strong purifying selection. All PeKCS proteins shared similar 3D structures, and a protein-protein interaction network was predicted with known Arabidopsis proteins. There were twenty putative ped-miRNAs which were also predicted that belong to nine families targeting thirteen PeKCS genes. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation results were highly associated with fatty acid synthase and elongase activity, lipid metabolism, stress responses, and plant-pathogen interaction. The highly enriched transcription factors (TFs) including ERF, MYB, Dof, C2H2, TCP, LBD, NAC, and bHLH were predicted in PeKCS genes. qRT-PCR expression analysis revealed that most PeKCS genes were highly upregulated in leaves including PeKCS2, PeKCS4, PeKCS8, PeKCS13, and PeKCS9 but not in stem and roots tissues under drought stress conditions compared with controls. Notably, most PeKCS genes were upregulated at 9th dpi under Fusarium kyushuense biotic stress condition compared to controls. This study provides a basis for further understanding the functions of KCS genes, improving wax and VLCFA biosynthesis, and improvement of passion fruit resistance.

Effect of Paper and Aluminum Bagging on Fruit Quality of Loquat (Eriobotrya japonica Lindl.).

Bagging regulates the fruit microenvironment and improves the quality and market value of fruits. It is a safe and ecofriendly technique to protect fruits from insect/pest infestation and multiple biotic and abiotic stresses. In the current study, the influence of fruit bagging was evaluated on the development and quality of loquat fruits. Fruits from a healthy loquat orchard (Cv. Zaozhong No.6), located in Fujian, China, were enveloped in paper (T1), aluminum (T2), and aluminum-polyethylene bags (T3), while unbagged fruits were maintained as control (T0). In general, fruit bagging improved fruit quality in terms of fruit physiological and biochemical attributes and protected fruits from physical damage. In particular, aluminum-polyethylene bagging enhanced fruit weight, length, and width by 1.37-, 1.18-, and 1.13-fold, respectively. Loquat fruits bagged with paper bags exhibited the maximum soluble sugar and lowest titratable acid content. Fruits treated with paper and aluminum-ethylene bags showed twofold higher sugar-acid ratio as compared to control. Aluminum-polyethylene bagging caused 66.67%, 55.56%, and 33.33% reductions in skin burn, fruit rotting, and black spot of loquat. The fruits bagged in aluminum and aluminum-polyethylene did not show insect or bird damage, while unbagged fruits had 14.70% and 17.65% insect and bird damage, respectively. Overall, the results suggest that paper, aluminum, and aluminum-polyethylene bagging improved fruit health by 75%, 131%, and 144%, respectively, as compared to control. To delineate bagging type-dependent effects, principal component analysis was performed. Paper bagging was positively correlated with fruit firmness, rotting, soluble sugars, sugar-acid ratio, and proline content. Aluminum bagging was highly associated with improvements in titratable acids, cystine, and methionine. Aluminum-polyethylene bags were correlated with fruit weight, size, peel thickness, edible rate, and certain amino acids.

Flavonoids Accumulation in Fruit Peel and Expression Profiling of Related Genes in Purple (Passiflora edulis f. edulis) and Yellow (Passiflora edulis f. flavicarpa) Passion Fruits.

Flavonoids play a key role as a secondary antioxidant defense system against different biotic and abiotic stresses, and also act as coloring compounds in various fruiting plants. In this study, fruit samples of purple (Passiflora edulis f. edulis) and yellow (Passiflora edulis f. flavicarpa) passion fruit were collected at five developmental stages (i.e., fruitlet, green, veraison, maturation, and ripening stage) from an orchard located at Nanping, Fujian, China. The contents of flavonoid, anthocyanin, proanthocyanin, and their metabolites were determined using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS), activities of key enzymes involved in flavonoid metabolism were measured, and expression profiling of related genes was done using quantitative real-time PCR (qRT-PCR). The results revealed that total flavonoids, anthocyanins, and procyanidins were found to be increased in the fruit peel of both cultivars with fruit maturity. Total flavonoids, anthocyanins, procyanidins, flavonoid metabolites (i.e., rutin, luteolin, and quercetin), and anthocyanin metabolites (i.e., cyanidin-3-O-glucoside chloride, peonidin-3-O-glucoside, and pelargonidin-3-O-glucoside) were found abundant in the peel of purple passion fruit, as compared to yellow passion fruit. Principle component analysis showed that the enzymes, i.e., C4H, 4CL, UFGT, and GST were maybe involved in the regulation of flavonoids metabolism in the peel of passion fruit cultivars. Meanwhile, PePAL4, Pe4CL2,3, PeCHS2, and PeGST7 may play an important role in flavonoid metabolism in fruit peel of the passion fruit. This study provides new insights for future elucidation of key mechanisms regulating flavonoids biosynthesis in passion fruit.

Establishment of a Novel and Efficient Agrobacterium-Mediated in Planta Transformation System for Passion Fruit (Passiflora edulis).

Passion fruit (Passiflora edulis) is an important fruit crop with high economic value. Genetic engineering plays an important role in crop improvement with desired traits and gene functional studies. The lack of a simple, efficient, and stable transformation system for passion fruit has greatly limited gene functional studies. In this study, a simple and efficient Agrobacterium-mediated in planta transformation system for passion fruit was established, using Agrobacterium virulent strain EHA105 harboring the binary vectors pCAMBIA1301 and pCAMBIA1302 with GUS and GFP reporter genes. The system requires less time and labor costs than conventional transformation systems, and no additional phytohormones and sterile conditions are required. Regeneration efficiency of 86% and transformation efficiency of 29% were achieved, when the wounds were wrapped with Parafilm and the plants were kept in darkness for 15 days. Approximately 75% of the regenerated plants had a single shoot and 26% multiple shoots. The transformation was confirmed at the DNA and RNA levels as well as by GUS staining and GFP fluorescent measurements. The developed protocol will contribute to the genetic improvement of passion fruit breeding.

Increasing the performance of Passion fruit (Passiflora edulis) seedlings by LED light regimes.

Due to progress in the industrial development of light-emitting diodes (LEDs), much work has been dedicated to understanding the reaction of plants to these light sources in recent years. In this study, the effect of different LED-based light regimes on growth and performance of passion fruit (Passiflora edulis) seedlings was investigated. Combinations of different light irradiances (50, 100, and 200 µmol m-2 s-1), quality (red, green, and blue light-emitting LEDs), and photoperiods (10 h/14 h, 12 h/12 h and 14 h/10 h light/dark cycles) were used to investigate the photosynthetic pigment contents, antioxidants and growth traits of passion fruit seedlings in comparison to the same treatment white fluorescent light. Light irradiance of 100 µmol m-2 s-1 of a 30% red/70% blue LED light combination and 12 h/12 h light/dark cycles showed the best results for plant height, stem diameter, number of leaves, internode distance, and fresh/dry shoot/root weights. 14 h/10 h light/dark cycles with the same LED light combination promoted antioxidant enzyme activities and the accumulation of phenols and flavonoids. In contrast, lower light irradiance (50 µmol m-2 s-1) had negative effects on most of the parameters. We conclude that passion fruit seedlings' optimal performance and biomass production requires long and high light irradiances with a high blue light portion.

Identification of Fungal Pathogens to Control Postharvest Passion Fruit (Passiflora edulis) Decays and Multi-Omics Comparative Pathway Analysis Reveals Purple Is More Resistant to Pathogens than a Yellow Cultivar.

Production of passion fruit (Passiflora edulis) is restricted by postharvest decay, which limits the storage period. We isolated, identified, and characterized fungal pathogens causing decay in two passion fruit cultivars during two fruit seasons in China. Morphological characteristics and nucleotide sequences of ITS-rDNA regions identified eighteen isolates, which were pathogenic on yellow and purple fruit. Fusarium kyushuense, Fusarium concentricum, Colletotrichum truncatum, and Alternaria alternata were the most aggressive species. Visible inspections and comparative analysis of the disease incidences demonstrated that wounded and non-wounded yellow fruit were more susceptible to the pathogens than the purple fruit. Purple cultivar showed higher expression levels of defense-related genes through expression and metabolic profiling, as well as significantly higher levels of their biosynthesis pathways. We also found fungi with potential beneficial features for the quality of fruits. Our transcriptomic and metabolomics data provide a basis to identify potential targets to improve the pathogen resistance of the susceptible yellow cultivar. The identified fungi and affected features of the fruit of both cultivars provide important information for the control of pathogens in passion fruit industry and postharvest storage.

Transcriptome data-based identification of candidate genes involved in metabolism and accumulation of soluble sugars during fruit development in 'Huangguan' plum.

Fruit sweetness being an important factor of organoleptic quality directly affects the consumers' preferences for fresh fruit consumption, and is influenced by the composition and quantity of sugars. In this study, four soluble sugars (sucrose, fructose, glucose, and sorbitol) were identified and quantified in plum fruits cv. 'Huangguan' at four different maturity stages (fruitlet, green, veraison, and mature stage). The results revealed that sucrose and glucose are major soluble sugar components at the fruitlet and mature stages, respectively. RNA-Seq analysis was carried out and 6,778 differentially expressed genes (DEGs) were identified, including 121 genes involved in sugar metabolism. Furthermore, a total of 39 transcripts of 8 gene families encoding key enzymes related to the metabolism and accumulation of soluble sugars were separately identified. ERD6L (gene 103322904) was involved in keeping a balance of glucose between the inside and outside of vacuole. SS (gene 103333990) and SDH (gene 103335104) regulated the accumulation of fructose at the green stage. SDH (gene 103335104) controlled the degradation of sorbitol at the green stage. SS (gene 103333990) and PFK (gene 103333391) regulated the degradation of sucrose at the early stages of fruit development. Moreover, NINV (gene 103331108) regulated the accumulation of total sugar in plum. Genes 103321334 and 103335689 were important bZIP transcription factors that regulate the accumulation of glucose and fructose in fruits. Twelve DEGs were selected and validated to observe the relative accuracy of transcriptome sequencing data using qRT-PCR. Gene expression patterns were consistent between qRT-PCR and RNA-Seq data, indicating the reliability of RNA-Seq data. PRACTICAL APPLICATIONS: The results of this study provided new insights into comprehensive understanding of the genetic control of sugar metabolism and accumulation in plum fruits.

Free Amino Acids Profile and Expression Analysis of Core Genes Involved in Branched-Chain Amino Acids Metabolism during Fruit Development of Longan (Dimocarpus longan Lour.) Cultivars with Different Aroma Types.

Amino acids are important component of fruit nutrition and quality. In this study, three longan cultivars, including non-aroma types 'Shixia' (SX), 'Lidongben' (LDB), and strong aroma type 'Xiangcui' (XC), were selected to analyze free amino acids (FAAs) variations at six distinct growth stages (S1-S6). The genome-wide identification and expression analysis of genes related to the branched-chain amino acids (BCAA) synthesis pathway were carried out. Results showed that 36 FAAs were identified, and the total FAAs content ranged from 2601.0 to 9073.5 mg/kg, which increased drastically with fruit development until ripening. L-glutamic acid (Glu), L-alanine (Ala), L-arginine (Arg), γ-Aminobutyric acid (GABA), L-aspartic acid (Asp), L-leucine (Leu), hydroxyl-proline (Hypro), and L-serine (Ser) were the predominant FAAs (1619.9-7213.9 mg/kg) in pulp, accounting for 62.28-92.05% of the total amino acids. During the period of rapid fruit expansion (S2-S4), the aroma of XC changed from light to strong, and the contents of L-alanine (Ala) and L-leucine (Leu) were significantly higher than those of SX and LDB. Furthermore, a total of two 2-isopropyl malate synthase (IPMS), two 3-isopropyl malate dehydrogenase (IPMD), and 16 BCAA transferase (BCAT) genes were identified. The expression levels of DilBCAT1, -6, and -9 genes in XC were significantly higher than those in SX and LDB, while DilBCAT16 in XC was lower. The content of Leu was negatively correlated with the expression of DilBCAT1, -6, and -9 in three varieties, but positively correlated with DilBCAT16, indicating that these four genes may be responsible for the different synthesis and degradation of Leu among cultivars.

Changes in the Content of Organic Acids and Expression Analysis of Citric Acid Accumulation-Related Genes during Fruit Development of Yellow (Passiflora edulis f. flavicarpa) and Purple (Passiflora edulis f. edulis) Passion Fruits.

Organic acids are key components that determine the taste and flavor of fruits and play a vital role in maintaining fruit quality and nutritive value. In this study, the fruits of two cultivars of passion fruit Yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis f. edulis) were harvested at five different developmental stages (i.e., fruitlet, green, veraison, near-mature and mature stage) from an orchard located in subtropical region of Fujian Province, China. The contents of six organic acids were quantified using ultra-performance liquid chromatography (UPLC), activities of citric acid related enzymes were determined, and expression levels of genes involved in citric acid metabolism were measured by quantitative real-time PCR (qRT-PCR). The results revealed that citric acid was the predominant organic acid in both cultivars during fruit development. The highest citric acid contents were observed in both cultivars at green stage, which were reduced with fruit maturity. Correlation analysis showed that citrate synthase (CS), cytosolic aconitase (Cyt-ACO) and cytosolic isocitrate dehydrogenase (Cyt-IDH) may be involved in regulating citric acid biosynthesis. Meanwhile, the PeCS2, PeACO4, PeACO5 and PeIDH1 genes may play an important role in regulating the accumulation of citric acid. This study provides new insights for future elucidation of key mechanisms regulating organic acid biosynthesis in passion fruit.