Exogenous melatonin delays oxidative browning in litchi during cold storage by regulating biochemical attributes and gene expression.

Oxidative damage leading to loss of nutritional quality and pericarp discoloration of harvested litchi fruits drastically limits consumer acceptance and marketability. In the present investigation, the impact of postharvest melatonin application at different concentrations, i.e., 0.1 mM, 0.25 mM, and 0.5 mM, on fruit quality and shelf life of litchi fruits under cold storage conditions was studied. The results revealed the positive effect of melatonin application at all concentrations on fruit quality and shelf life. However, treatment with 0.5 mM concentration of melatonin resulted in minimum weight loss, decay loss, pericarp discoloration, and also retained higher levels of TSS, acidity, total sugar, ascorbic acid, anthocyanin, antioxidant, and phenolics content during cold storage. Melatonin administration also restricted the enzymatic activity of the polyphenol oxidase (PPO) and peroxidase (POD) enzymes in the fruit pericarp and maintained freshness of the fruits up to 30 days in cold storage. At the molecular level, a similar reduction in the expression of browning-associated genes, LcPPO, LcPOD, and Laccase, was detected in preserved litchi fruits treated with melatonin. Anthocyanin biosynthetic genes, LcUFGT and LcDFR, on the other hand showed enhanced expression in melatonin treated fruits compared to untreated fruits. Melatonin, owing to its antioxidant properties, when applied to harvested litchi fruits retained taste, nutritional quality and red color pericarp up till 30 days in cold storage.

Advancements in Litchi chinensis Peel Processing: A Scientific Review of Drying, Extraction, and Isolation of Its Bioactive Compounds.

This article systematically reviews the advancements in processing litchi peel (Litchi chinensis), emphasizing drying, extraction, purification methods, and the potential of bioactive compounds obtained from litchi peel. This work also highlights the impact of various drying techniques on phytochemical profiles, focusing on how methods such as hot air and freeze-drying affect the preservation of bioactive compounds. The study delves into extraction methods, detailing how different solvents and techniques influence the efficiency of extracting bioactive compounds from litchi peel. Furthermore, the purification and characterization of active compounds, showcasing the role of chromatographic techniques in isolating specific bioactive molecules, is discussed. Biological properties and mechanisms of action, such as antioxidant, antihyperglycemic, cardioprotective, hepatoprotective, anti-atherosclerotic, and anticancer activities, are reviewed, providing insight into the potential health benefits of litchi peel compounds. This review highlights the importance of optimizing and selecting accurate drying and extraction methods to maximize the therapeutic effects of litchi peel and its bioactive compounds. This review also reveals the broad pharmacological potential of the isolated compounds, underscoring the need for further research to discover their specific actions and health benefits.

Corrigendum: The LcKNAT1-LcEIL2/3 regulatory module is involved in fruitlet abscission in litchi.

[This corrects the article DOI: 10.3389/fpls.2021.802016.].

[Identification and expression analysis of the HSP70 gene family under abiotic stresses in Litchi chinensis].

HSP70 protein, as an important member of the heat shock protein (HSP) family, plays an important role in plant growth, development, and response to biotic and abiotic stresses. In order to explore the role of HSP70 gene family members in Litchi chinensis under low temperature, high temperature, drought, and salt stress, bioinformatics methods were used to identify the HSP70 gene family members within the entire L. chinensis genome. The expression of these genes under various abiotic stresses was then detected using quantitative real-time PCR (qRT-PCR). The results showed that the LcHSP70 gene family consisted of 18 members, which were unevenly distributed across ten L. chinensis chromosomes. The LcHSP70 protein contained 479-851 amino acids, with isoelectric points ranging from 5.07 to 6.95, and molecular weights from 52.44 kDa to 94.07 kDa. The predicted subcellular localization showed that LcHSP70 protein was present in the nucleus, cytoplasm, endoplasmic reticulum, mitochondria, and chloroplast. Phylogenetic analysis divided the LcHSP70 proteins into five subgroups, namely Ⅰ, Ⅱ, Ⅲ, Ⅳ, and Ⅵ. The promoter regions of the LcHSP70 genes contained various cis-acting elements related to plant growth, development, hormone response, and stress response. Moreover, the expression of LcHSP70 genes displayed distint tissue-specific expression level, categorized into universal expression and specific expression. From the selected 6 LcHSP70 genes (i.e., LcHSP70-1, LcHSP70-5, LcHSP70-10, LcHSP70-14, LcHSP70-16, and LcHSP70-18), their relative expression levels were assessed under different abiotic stresses using qRT-PCR. The results indicated that the gene family members exhibited diverse responses to low temperature, high temperature, drought, and salt stress, with significant variations in their expression levels across different time periods. These results provide a foundation for further exploration of the function of the LcHSP70 gene family.

Diet with different concentrations of lychee peel flour modulates oxidative stress parameters and antioxidant activity in zebrafish.

The agri-food industry generates substantial waste, leading to significant environmental impacts. Lychee (Litchi chinensis Sonnerat), which is rich in bioactive compounds in its peel, pulp, and seeds, offers an opportunity for waste use. This study aimed to evaluate the effects of supplementing a high-carbohydrate diet with varying levels of lychee peel flour on lipid metabolism biomarkers and oxidative stress in a zebrafish (Danio rerio) model. A total of 225 zebrafish, approximately four months old, were divided into five groups: control, high-carbohydrate (HC), HC2%, HC4%, and HC6%. The study did not find significant differences in the growth performance of zebrafish in any group. However, the HC6% group exhibited a significant decrease in glucose and triglyceride levels compared with the HC group. Furthermore, this group showed enhanced activities of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), along with reduced levels of malondialdehyde (MDA). Increased antioxidant activity was also evidenced by DPPH-, ABTS+, and ß-carotene/Linoleic acid assays in the HC6% group. A positive correlation was identified between SOD/CAT activity and in vitro antioxidant assays. These findings suggest that dietary supplementation with 6% lychee peel flour can significantly modulate glucose homeostasis, lipid metabolism, and antioxidant activity in zebrafish.

Increased DNA methylation of the splicing regulator SR45 suppresses seed abortion in litchi.

The gene regulatory networks that govern seed development are complex, yet very little is known about the genes and processes that are controlled by DNA methylation. Here, we performed single-base resolution DNA methylome analysis and found that CHH methylation increased significantly throughout seed development in litchi. Based on the association analysis of differentially methylated regions and weighted gene co-expression network analysis (WGCNA), 46 genes were identified as essential DNA methylation-regulated candidate genes involved in litchi seed development, including LcSR45, a homolog of the serine/arginine-rich (SR) splicing regulator SR45. LcSR45 is predominately expressed in the funicle, embryo, and seed integument, and displayed increased CHH methylation in the promoter during seed development. Notably, silencing of LcSR45 in a seed-aborted litchi cultivar significantly improved normal seed development, whereas the ectopic expression of LcSR45 in Arabidopsis caused seed abortion. Furthermore, LcSR45-dependent alternative splicing events were found to regulate genes involved in seed development. Together, our findings demonstrate that LcSR45 is hypermethylated, and plays a detrimental role in litchi seed development, indicating a global increase in DNA methylation at this stage.

Tocotrienol monomers and dimers from the roots of Litchi chinensis with tyrosinase inhibition activity.

Four undescribed modified tocotrienols, including two monomers, litchinols A (1) and B (2), and two walsurol dimers, δ,δ-walsurol (3) and γ,δ-bi-O-walsurol (4), as well as seven known compounds (5-11) were isolated from the roots of Litchi chinensis. The structures of the undescribed compounds were elucidated based on analyses of spectroscopic data and ECD spectra. All tocotrienol derivatives (1-6) were evaluated for their tyrosinase inhibition activity. Only monomers 1-2 and 5-6 displayed potent inhibitory activity and greater than kojic acid. Kinetic analysis revealed that the representative compound 2 was uncompetitive inhibitor with the inhibition constant value of 5.70 µM.

LcERF10 functions as a positive regulator of litchi fruitlet abscission.

Phytohormone ethylene is well-known in positive modulation of plant organ abscission. However, the molecular mechanism underlying ethylene-induced abscission remains largely unknown. Here, we identified an ethylene-responsive factor, LcERF10, as a key regulatory gene in litchi fruitlet abscission. LcERF10 was strongly induced in the fruitlet abscission zone (FAZ) during the ethylene-activated abscission. Silencing of LcERF10 in litchi weakened the cytosolic alkalization of the FAZ and reduced fruitlet abscission. Moreover, LcERF10 directly bound the promoter and repressed the expression of LcNHX7, a Na+/H+ exchanger that was down-regulated in FAZ following the ethylene-activated abscission and up-regulated after LcERF10 silencing. Additionally, ectopic expression of LcERF10 in Arabidopsis promoted the cytosolic alkalization of the floral organ AZ and accelerated the floral organ abscission. Collectively, our results suggest that the transcription factor LcERF10 plays a positive role in litchi fruitlet abscission.

Genome-Wide Identification, Characterization, and Expression Analysis of the NAC Gene Family in Litchi chinensis.

NAC proteins play an essential role in the growth and development of litchi, especially during reproductive development. However, a comprehensive analysis of the litchi NAC gene family is currently absent. Based on information from the litchi genome, we found that the 112 NAC genes of litchi show an uneven distribution on the chromosomes. Phylogenetic and conserved structural domain analyses indicated that different types of variability were exhibited in the family of litchi NACs (LcNACs). Gene covariance analysis showed that the LcNACs showed better similarity in the same genus than with Arabidopsis. We further investigated the differential expression patterns of LcNACs in buds and rudimentary leaves of litchi. qRT-PCR results implied that they were involved in the process. Profiling of LcNAC promoter elements in litchi showed that they were extensively involved in light response, phytohormone regulation, abiotic stress response, and plant growth and development processes. This study provides new insights into the identification, structural characterization, tissue-specific expression analysis, and promoter response elements of LcNACs. It reveals the characteristics of the LcNACs and lays the foundation for the subsequent understanding of its biological functions and molecular regulatory mechanisms.

Metabolome and transcriptome analyses reveal the molecular mechanisms of LcMYB1 regulating anthocyanin accumulation in litchi hairy roots.

Agrobacterium rhizogenes-mediated hairy root culture offer a promising approach for gene function analysis and production of plant secondary metabolites. Here, we obtained red litchi hairy roots using A. rhizogenes-mediated LcMYB1 transformation. Using high performance liquid chromatography, the main anthocyanins in the red hairy roots were determined to be cyanidin 3-rutinoside and cyanidin 3-glucoside. A total of 164 metabolites were significantly upregulated or downregulated in the red hairy roots, which were mostly involved in flavone and flavonol pathway, and flavonoid pathway. The transcriptome analysis revealed 472 differentially expressed genes (DEGs). Up-regulated genes were considerably enriched in anthocyanin, flavone and flavonol biosynthesis. Integrative metabolite profiling and transcriptome analyses showed that LcF3'H, LcUFGT1, and LcGST4 were key structural genes in anthocyanin biosynthesis. However, the expression of Cinnamyl-alcohol dehydrogenase (CAD) and Peroxidase (POD) leading to the production of lignin were significantly down-regulated, suggesting flavonoids and lignin compete with each other in the phenylpropanoid pathway. A total of 52 DEGs were identified as transcription factors. Correlation analysis showed that 8 transcription factors were positively correlated with LcUFGT1, and LcGST4, involving in anthocyanin biosynthesis. These findings clarify the molecular mechanisms of LcMYB1 regulating anthocyanin accumulation in litchi hairy roots.

Single-nucleus RNA sequencing and mRNA hybridization indicate key bud events and LcFT1 and LcTFL1-2 mRNA transportability during floral transition in litchi.

In flowering plants, floral induction signals intersect at the shoot apex to modulate meristem determinacy and growth form. Here, we report a single-nucleus RNA sequence analysis of litchi apical buds at different developmental stages. A total of 41 641 nuclei expressing 21 402 genes were analyzed, revealing 35 cell clusters corresponding to 12 broad populations. We identify genes associated with floral transition and propose a model that profiles the key events associated with litchi floral meristem identity by analyzing 567 identified floral meristem cells at single cell resolution. Interestingly, single-nucleus RNA-sequencing data indicated that all putative FT and TFL1 genes were not expressed in bud nuclei, but significant expression was detected in bud samples by RT-PCR. Based on the expression patterns and gene silencing results, we highlight the critical role of LcTFL1-2 in inhibiting flowering and propose that the LcFT1/LcTFL1-2 expression ratio may determine the success of floral transition. In addition, the transport of LcFT1 and LcTFL1-2 mRNA from the leaf to the shoot apical meristem is proposed based on in situ and dot-blot hybridization results. These findings allow a more comprehensive understanding of the molecular events during the litchi floral transition, as well as the identification of new regulators.

A LcDOF5.6-LcRbohD regulatory module controls the reactive oxygen species-mediated fruitlet abscission in litchi.

Reactive oxygen species (ROS) have been emerging as a key regulator in plant organ abscission. However, the mechanism underlying the regulation of ROS homeostasis in the abscission zone (AZ) is not completely established. Here, we report that a DOF (DNA binding with one finger) transcription factor LcDOF5.6 can suppress the litchi fruitlet abscission through repressing the ROS accumulation in fruitlet AZ (FAZ). The expression of LcRbohD, a homolog of the Arabidopsis RBOHs that are critical for ROS production, was significantly increased during the litchi fruitlet abscission, in parallel with an increased accumulation of ROS in FAZ. In contrast, silencing of LcRbohD reduced the ROS accumulation in FAZ and decreased the fruitlet abscission in litchi. Using in vitro and in vivo assays, we revealed that LcDOF5.6 was shown to inhibit the expression of LcRbohD via direct binding to its promoter. Consistently, silencing of LcDOF5.6 increased the expression of LcRbohD, concurrently with higher ROS accumulation in FAZ and increased fruitlet abscission. Furthermore, the expression of key genes (LcIDL1, LcHSL2, LcACO2, LcACS1, and LcEIL3) in INFLORESCENCE DEFICIENT IN ABSCISSION signaling and ethylene pathways were altered in LcRbohD-silenced and LcDOF5.6-silenced FAZ cells. Taken together, our results demonstrate an important role of the LcDOF5.6-LcRbohD module during litchi fruitlet abscission. Our findings provide new insights into the molecular regulatory network of organ abscission.

Degradation of water-soluble polysaccharides in pulp of litchi during storage.

Water-soluble polysaccharides (WSP) were extracted from the pulp of litchi. Its main component was identified as arabinogalactan. The dominant monosaccharide constituents were arabinose and galactose. Galactose and mannose accumulated at the end of storage. ATP, ADP and AMP levels declined with increasing pulp breakdown index. WSP depolymerized which was characterized by a decrease in its content and molecular weight, while its structure remained stable during storage. Polygalacturonase and pectate lyase (PL) were active at the early storage time, and ß-galactosidase (GAL) and α-l-arabinofuranosidase followed thereafter. Except for some pectin methylesterase (LcPME), LcPL, LcGAL and LcPME gene expression was downregulated. It was deduced that depolymerization of polysaccharides was mainly caused by the rupture of the branched side chain and glacturonic acid backbone to smaller repeating units, and both cell wall-degrading enzymes and nonenzymatic factors, such as energy level, participated in the degradation of polysaccharides, and consequently pulp breakdown of litchi.

Function of a non-enzymatic hexokinase LcHXK1 as glucose sensor in regulating litchi fruit abscission.

Fruit abscission is a severe hindrance to commercial crop production, and a lack of carbohydrates causes fruit abscission to intensify in a variety of plant species. However, the precise mechanism by which carbohydrates affect fruit setting potential has yet to be determined. In the current study, we noticed negative correlation between hexose level and fruit setting by comparing different cultivars, bearing shoots of varying diameters, and girdling and defoliation treatments. The cumulative fruit-dropping rate was significantly reduced in response to exogenous glucose dipping. These results suggested that hexose, especially glucose, is the key player in lowering litchi fruit abscission. Moreover, five putative litchi hexokinase genes (LcHXKs) were isolated and the subcellular localization as well as activity of their expressed proteins in catalyzing hexose phosphorylation were investigated. LcHXK2 was only found in mitochondria and expressed catalytic protein, whereas the other four HXKs were found in both mitochondria and nuclei and had no activity in catalyzing hexose phosphorylation. LcHXK1 and LcHXK4 were found in the same cluster as previously reported hexose sensors AtHXK1 and MdHXK1. Furthermore, VIGS-mediated silencing assay confirms that LcHXK1 suppression increases fruit abscission. These findings revealed that LcHXK1 functions as hexose sensor, negatively regulating litchi fruit abscission.

Antimicrobial activity of comfort related properties of silk treated with herbal extracts in making of reusable masks

The study was aimed at divulging an eco-friendly antimicrobial finish on 100 % silk woven fabric. The leaves' extract of Azadirachata indica, Butea monosperma and Litche chinensis were used as the development of eco-friendly antimicrobial finish. The antimicrobial property and comfort related property were checked before and after applying antimicrobial finish. In comfort related property absorbency & air permeability were checked. The ASTEM E2149 Shake Flask method was used to check antimicrobial finish and AATCC method was used for checking fabric property. One way ANOVA statistical test was applied for analysis of results. The FTIR and SEM results showed the presences of finish on fabrics. In comfort related property, absorbency and air permeability was increased. The results showed that antimicrobial finish made 100% reduction against microorganism up to 25 washes which can be used in making reusable masks fight against COVID- 19.

Arthropods associated with the lychee erinose mite, Aceria litchii (Acari: Eriophyidae) on lychee trees in Minas Gerais, Brazil.

Lychee fruit production (Litchi chinensis) has been threatened in many regions of the world where the presence has been reported of the litchii erinose mite, Aceria litchii (Keifer). This study aims to identify the arthropod community associated with A. litchii on lychee plants in Minas Gerais, Brazil, and to seek for potential natural enemies associated with this mite pest in this region. We sampled lychee leaves infested with A. litchii in commercial and non-commercial lychee orchards during seven consecutive months, covering the dry and wet seasons of the year. Arthropods found in association with A. litchii on lychee leaves were collected and identified. The results indicate that a great diversity and abundance of mites and hexapods are associated with A. litchii. A total of 985 and 1872 specimens of mites were identified in commercial and non-commercial areas, respectively, belonging to the families Cheyletidae, Cunaxidae, Eupodidae, Iolinidae, Stigmaeidae, Phytoseiidae, Tarsonemidae, Tenuipalpidae, Tetranychidae, Tryophtydeidae, Tuckerellidae, Tydeidae, Winterschmidtiidae and Xenocaligonellidae and the suborder Oribatida. Among them, Phytoseiidae was the most abundant and diverse family with a total of 11 species identified, in which Phytoseius intermedius was the most abundant predatory mite species collected. Minor specimens of hexapods were also been, belonging to the orders Collembola, Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, Psocoptera and Thysanoptera. The presence of a high community of predatory mites in association with A. litchii deserves attention and our results indicate that studies to test the potential of these species and the adoption of management practices that enhance this ecological service must be carried out to achieve satisfactory control of the lychee erinose mite in lychee plants.

Exogenous methyl jasmonate modulates antioxidant activities and delays pericarp browning in litchi.

Pericarp browning (PB) is a serious problem in harvested litchi and drastically affects consumer acceptability and marketability. Postharvest PB and subsequent decay in fruit are linked to reactive oxygen species (ROS) accumulation in tissues. Antioxidants neutralize or scavenge ROS and maintain the shelf-life of fruit, especially in non-climacteric ones such as litchi. This work was aimed to assess the effect of vacuum infiltrated methyl jasmonate (MeJA; 1 and 2 mM) on the quality of harvested litchi fruit (cv. Purbi) during ambient storage (28 °C, RH 70-75%). The exogenous MeJA infiltration (2 mM) significantly retained quality attributes of litchi fruit as evident by lowered PB, weight loss, disease occurrence, quinone, and ROS (H2O2 and O2 -) accumulation. Moreover, MeJA infiltrated fruit suppressed the activity of polyphenol oxidase and peroxidase resulting in higher anthocyanin, phenolics, antioxidant potential, phenylalanine ammonia lyase activity as well as membrane integrity throughout the storage. Control fruit showed an early quality deterioration marked by prominent PB and other biochemical degradative changes. Thus, exogenous MeJA infiltration (2 mM) could be suggested to increase the shelf life of litchi by four days under ambient conditions.

Protective Effect of Litchi chinensis Peel Extract-Prepared Nanoparticles on Rabbits Experimentally Infected with Eimeria stiedae.

The present study used Litchi chinensis peel extract to synthesize silver nanoparticles (AgNPs). This technique is eco-friendly and can be performed in a single step; thus, it has attracted great attention for NPs biosynthesis. Herein, we biosynthesized AgNPs with L. chinensis peel extract and examined their anticoccidial activity in rabbit hepatic coccidiosis induced by E. stiedae infection. Thirty-five rabbits were allocated into seven groups: a healthy group (G1), an infected control group (G2), four groups infected before treatment with 10 mg/kg L. chinensis peel extract-biosynthesized AgNPs (G3, G5) or 50 mg/kg amprolium (G4, G6), and rabbits infected after two weeks of pretreatment with 10 mg/kg L. chinensis eel extract-biosynthesized AgNPs (G7). In this study, both pre-and post-treatment with AgNPs produced a substantial reduction in fecal oocyst output, liver enzyme levels, and histopathological hepatic lesions relative to the infected group. In conclusion, L. chinensis peel extract-prepared AgNPs should be considered harmless and efficient in the cure of hepatic coccidiosis in rabbits.

"Hong Long" Lychee (Litchi chinensis Sonn.) Is the Optimal Pollinizer for the Main Lychee Cultivars in Israel.

The lychee fruit is in high demand worldwide. However, the yields of many cultivars are low, including the high-quality cultivars "Nuomici" (NMC) and "Fei Zi Xiao" (FZX), which are very tasty and produce large fruit with a small seed, but tend to shed their fruitlets. In a previous work, we found that cross-hand pollination of "Mauritius" (MA) with pollen of another cultivar increased fruit set and reduced fruit-drop in comparison to self-hand pollination. In the current research, we aimed to identify the optimal pollen donor for three of the main cultivars grown in Israel: MA, FZX, and "Tamuz" (TA). We compared the effect of different pollinizers and found that the Vietnamese cultivar "Hong Long" (HL), which is becoming an important cultivar in Israel, was the optimal pollinizer for the three cultivars. In addition, we found that FZX and TA were not self-fertile under the Israeli environmental conditions since they tend to shed fruitlets that originated from self-fertilization. In contrast, MA is able to fertilize itself, although cross-pollination greatly increased its fruit number and size. We also identified a new PCR marker for lychee, M3, that enabled us to distinguish between self- and cross-fertilized FZX fruits pollinated by HL. Our results indicate that cross-pollination, particularly by HL, has beneficial effects on the production of lychee and it is especially important for cultivars that generate small seeds and tend to shed their fruitlets.

Litchi-Derived Polyphenol Alleviates Liver Steatosis and Gut Dysbiosis in Patients with Non-Alcoholic Fatty Liver Disease: A Randomized Double-Blinded, Placebo-Controlled Study.

Preclinical data suggest the role of litchi extract in alleviating non-alcoholic fatty liver disease (NAFLD) by modulating gut microbiota. We aimed at investigating whether oligonol, a litchi-derived polyphenol, could improve liver steatosis and gut dysbiosis in patients with NAFLD. Adults with grade ≥2 steatosis, defined by an MRI proton density fat fraction (MRI-PDFF) of ≥11%, were randomly assigned to receive either oligonol or placebo for 24 weeks. The alteration in the MRI-PDFF and gut microbiota composition assessed by 16S ribosomal RNA sequencing were examined. There were 38 patients enrolled (n = 19 in each group). A significant reduction in the MRI-PDFF between week 0 and week 24 was observed in the oligonol group, while there was a non-significant decrease in the placebo group. A significant improvement in alpha-diversity was demonstrated in both of the groups. The oligonol-induced microbiota changes were characterized by reduced abundance of pathogenic bacteria, including Dorea, Romboutsia, Erysipelotrichaceae UCG-003 and Agathobacter, as well as increased abundance of short-chain fatty acids (SCFAs)-producing bacteria, such as Akkermansia, Lachnospira, Dialister and Faecalibacterium. In summary, this study is the first to provide evidence that supports that oligonol improves steatosis through the modulation of gut bacterial composition. Our results also support the beneficial and complementary role of oligonol in treating NAFLD.