Substantially altered bacterial diversity associated with developmental stages of litchi stink bug, Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae).

The mutualistic symbiotic relationship between insects and bacteria greatly influences the growth and development of host insects. Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae), also referred to as the litchi stink bug, has recently been established as an important insect pest of Litchi chinensis Sonn. and causes substantial yield loss in India. To design effective and environmentally safe management strategies, an understanding of the diversity and functions of microbiota harbored across the development stages is very important. The assessment of the diversity of development-associated bacteria in T. javanica and their predicted functions was conducted using 16S rRNA gene sequences obtained by the Illumina MiSeq technology. The result showed that taxonomic analysis of associated bacteria in different developmental stages includes a total of 46 phyla, encompassing 139 classes, 271 orders, 474 families, and 893 genera of bacteria. All developmental stages of T. javanica shared a total of 42.82 percent of operational taxonomic units (OTUs), with a 97 % similarity threshold. Alpha diversity indices showed maximum species richness in the egg and adult stages. The phyla Proteobacteria followed by Firmicutes, Bacteriodetes, and Actinobacteria, exhibited the highest levels of abundance across all the developmental stages of T. javanica. Microbiota were most different between the egg and the 4th nymphal stage (χ2 = 711.67) and least different between the 2nd and 4th nymphal instars (χ2 = 44.45). The predicted functions of the microbiota associated with T. javanica are mainly involved in amino acid metabolism, cell motility, cellular processes and signaling, glycan biosynthesis and metabolism, lipid metabolism, and membrane transport. The present study documentation and information on symbiotic bacteria across T. javanica life stages will prompt the development of novel biological management strategies.

Spectrum-effect relationship between HPLC fingerprint and hypoglycemic of litchi leaves (Litchi chinensis Sonn) in vitro.

Litchi chinensis Sonn (Litchi) has been listed in the Chinese Pharmacopeia, and is an economically and medicinally valuable species within the family Sapindaceae. However, the material basis of its pharmacological action and the pharmacodynamic substances associated with its hypoglycemic effect are still unclear. The predominant objective of this study was to establish the fingerprint profile of litchi leaves and to evaluate the relationship between the components of the high-performance liquid chromatography (HPLC) fingerprint of litchi leaves, assess its hypoglycemic effect by measuring α-glucosidase and α-amylase inhibition, and find the spectrum-effect relationship of litchi leaves by bivariate correlation analysis, Grey relational analysis and partial least squares regression analysis. In this study, the fingerprint of litchi leaves was established by HPLC, and a total of 15 common peaks were identified that clearly calibrated eight components, with P1 being gallic acid, P2 being protocatechuic acid, P3 being catechin, P6 being epicatechin, P12 being rutin, P13 being astragalin, P14 being quercetin and P15 being kaempferol. The similarities between the fingerprints of 11 batches of litchi leaves were 0.766-0.979. Simultaneously, the results of the spectrum-effect relationship showed that the chemical constituents represented by peaks P8, P3, P12, P14, P2, P13, and P11 were relevant to the hypoglycemic effect.

Mechanisms of Litchi Response to Postharvest Energy Deficiency via Energy and Sugar Metabolisms.

In the post-harvest phase, fruit is inexorably subjected to extrinsic stressors that expedite energy expenditure and truncate the storage lifespan. The present study endeavors to elucidate the response strategies of litchi to the alterations of energy state caused by 2,4-Dinitrophenol (DNP) treatment through energy metabolism and sugar metabolism. It was observed that the DNP treatment reduced the energy state of the fruit, exacerbated membrane damage and triggered rapid browning in the pericarp after 24 h of storage. Furthermore, the expression of genes germane to energy metabolism (LcAtpB, LcAOX1, LcUCP1, LcAAC1, and, LcSnRK2) reached their peak within the initial 24 h of storage, accompanied by an elevation in the respiratory rate, which effectively suppressed the rise in browning index of litchi pericarp. The study also posits that, to cope with the decrease of energy levels and membrane damage, litchi may augment the concentrations of fructose, glucose, inositol, galactose, and sorbose, thus safeguarding the canonical metabolic functions of the fruit. Collectively, these findings suggest that litchi can modulate energy and sugar metabolism to cope with fruit senescence under conditions of energy deficiency. This study significantly advances the understanding of the physiological responses exhibited by litchi fruit to post-harvest external stressors.

Diversification of FT-like genes in the PEBP family contributes to the variation of flowering traits in Sapindaceae species.

Many species of Sapindaceae, such as lychee, longan, and rambutan, provide nutritious and delicious fruit. Understanding the molecular genetic mechanisms that underlie the regulation of flowering is essential for securing flower and fruit productivity. Most endogenous and exogenous flowering cues are integrated into the florigen encoded by FLOWERING LOCUS T. However, the regulatory mechanisms of flowering remain poorly understood in Sapindaceae. Here, we identified 60 phosphatidylethanolamine-binding protein-coding genes from six Sapindaceae plants. Gene duplication events led to the emergence of two or more paralogs of the FT gene that have evolved antagonistic functions in Sapindaceae. Among them, the FT1-like genes are functionally conserved and promote flowering, while the FT2-like genes likely serve as repressors that delay flowering. Importantly, we show here that the natural variation at nucleotide position - 1437 of the lychee FT1 promoter determined the binding affinity of the SVP protein (LcSVP9), which was a negative regulator of flowering, resulting in the differential expression of LcFT1, which in turn affected flowering time in lychee. This finding provides a potential molecular marker for breeding lychee. Taken together, our results reveal some crucial aspects of FT gene family genetics that underlie the regulation of flowering in Sapindaceae.

Methanolic extracts of litchi (Litchi chinensis Sonn.): A novel approach of targeting glucose-6-phosphate dehydrogenase for liver cancer therapy.

Cancer metabolism has emerged as a potential target for innovative therapeutic approaches in the treatment of cancer. Cancer metabolism has received much attention, particularly in relation to glucose metabolism. It has been observed that human malignancies have high levels of glucose-6-phosphate dehydrogenase (G6PD) activity which is an important enzyme of glucose metabolism. This overactivity is associated with the cell death and angiogenesis, highlighting its potential as a viable target for cancer treatment. This study was conducted to examine the methanolic extracts from the seeds, bark and leaves of litchi (Litchi chinensis Sonn.) in order to discover effective compounds targeting G6PD and potentially active entities against liver cancer. Plant extract screening for the target protein was carried out through enzymatic activity assay. The recombinant plasmid pET-24a-HmG6PD was expressed in E. coli (BL21-DE3) strain, then purified and assessed using metal affinity chromatography with Ni-NTA columns and SDS-PAGE. The cytotoxicity of plant extracts against liver cancer HepG2 cells was assessed using the MTT assay. All three extracts demonstrated significant inhibitory effects (> 80% inhibition) against G6PD. They were then subjected to testing at various concentrations, and their IC50 values were subsequently determined. The extracts of litchi (leaf, IC50: 1.199µg/ml; bark, IC50: 2.350 µg/ml; seeds, IC50: 1.238 µg/ml) displayed significant inhibition of G6PD activity at lower concentrations. Subsequently, the leaf extract of litchi was further assessed for its impact on HepG2 cell lines in a dose-dependent manner and exhibited strong potential as an inhibitor of cancer cell progression. Moreover, the results of acute toxicity study in mice revealed nontoxic effects of litchi leaf extract on hepatocytes. The results imply that Litchi chinensis leaf extract could be considered as a promising candidate for safer drug development in the treatment of liver cancer.

Genome-Wide Identification and Expression Analysis of the Class III Peroxidase Gene Family under Abiotic Stresses in Litchi (Litchi chinensis Sonn.).

Class III peroxidases (CIII PRXs) are plant-specific enzymes with high activity that play key roles in the catalysis of oxidation-reduction reactions. In plants, CIII PRXs can reduce hydrogen peroxide to catalyze oxidation-reduction reactions, thereby affecting plant growth, development, and stress responses. To date, no systematic analysis of the CIII PRX gene family in litchi (Litchi chinensis Sonn.) has been documented, although the genome has been reported. In this study, a total of 77 CIII PRX (designated LcPRX) gene family members were predicted in the litchi genome to provide a reference for candidate genes in the responses to abiotic stresses during litchi growth and development. All of these LcPRX genes had different numbers of highly conserved PRX domains and were unevenly distributed across fifteen chromosomes. They were further clustered into eight clades using a phylogenetic tree, and almost every clade had its own unique gene structure and motif distribution. Collinearity analysis confirmed that there were eleven pairs of duplicate genes among the LcPRX members, and segmental duplication (SD) was the main driving force behind the LcPRX gene expansion. Tissue-specific expression profiles indicated that the expression levels of all the LcPRX family members in different tissues of the litchi tree were significantly divergent. After different abiotic stress treatments, quantitative real-time PCR (qRT-PCR) analysis revealed that the LcPRX genes responded to various stresses and displayed differential expression patterns. Physicochemical properties, transmembrane domains, subcellular localization, secondary structures, and cis-acting elements were also analyzed. These findings provide insights into the characteristics of the LcPRX gene family and give valuable information for further elucidating its molecular function and then enhancing abiotic stress tolerance in litchi through molecular breeding.

Litchi (Litchi chinensis Sonn.): A comprehensive and critical review on cancer prevention and intervention.

Litchi (Litchi chinensis Sonn.) is a tropical fruit with various health benefits. The objective of this study is to present a thorough analysis of the cancer preventive and anticancer therapeutic properties of litchi constituents and phytocompounds. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis criteria were followed in this work. Various litchi extracts and constituents were studied for their anticancer effects. In vitro studies showed that litchi-derived components reduced cell proliferation, induced cytotoxicity, and promoted autophagy via increased cell cycle arrest and apoptosis. Based on in vivo studies, litchi flavonoids and other extracted constituents significantly reduced tumor size, number, volume, and metastasis. Major signaling pathways impacted by litchi constituents were shown to stimulate proapoptotic, antiproliferative, and antimetastatic activities. Despite promising antineoplastic activities, additional research, especially in vivo and clinical studies, is necessary before litchi-derived products and phytochemicals can be used for human cancer prevention and intervention.

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.

A crosslinked and percolation network alginate coating for litchi prevention.

The short shelf life of Litchi is due to its rapid metabolism after being harvested. Refrigeration is not a suitable method for preserving litchi, as the browning process of litchi that has been cryogenic will accelerate when it is brought to room temperature. This study introduces an alginate-based coating as a solution to control the post-harvest metabolism of litchi. The coating achieves this by simultaneously establishing crosslink and percolation networks, both of which act as barriers. The percolation network is created using rod-like cellulose nanocrystals, which possess excellent percolation properties. This network effectively reduces moisture loss. Compared to the control group, the coated litchi exhibited a 38.1 % lower browning index and a 62.5 % lower decay rate. Additionally, the soluble solid content increased by 107.1 %. The inclusion of cellulose nanocrystals and the crosslinking of calcium ions enhanced the mechanical properties of the composite membrane. Specifically, the tensile strength and elongation at break increased by 70 % and 366 % respectively. As all the components in the coating are edible, it is environmentally friendly and safe for human consumption.

Sinomonas terricola sp. nov., a plant-beneficial bacterium isolated from litchi rhizosphere soil in Guangdong, China.

A novel plant-beneficial bacterium strain, designated as JGH33T, which inhibited Peronophythora litchii sporangia germination, was isolated on Reasoner's 2A medium from a litchi rhizosphere soil sample collected in Gaozhou City, Guangdong Province, PR China. Cells of strain JGH33T were Gram-stain-positive, aerobic, non-motile, bent rods. The strain grew optimally at 30-37 °C and pH 6.0-8.0. Sequence similarity analysis based on 16S rRNA genes indicated that strain JGH33T exhibited highest sequence similarity to Sinomonas albida LC13T (99.2 %). The genomic DNA G+C content of the isolate was 69.1 mol%. The genome of JGH33T was 4.7 Mbp in size with the average nucleotide identity value of 83.45 % to the most related reference strains, which is lower than the species delineation threshold of 95 %. The digital DNA-DNA hybridization of the isolate resulted in a relatedness value of 24.9 % with its closest neighbour. The predominant respiratory quinone of JGH33T was MK-9(H2). The major fatty acids were C15 : 0 anteiso (43.4 %), C16 : 0 iso (19.1 %) and C17 : 0 anteiso (19.3 %), and the featured component was C18 : 3 ω6c (1.01 %). The polar lipid composition of strain JGH33T included diphosphatidylglycerol, phosphatidylglycerol, dimannosylglyceride, phosphatidylinositol and glycolipids. On the basis of polyphasic taxonomy analyses data, strain JGH33T represents a novel species of the genus Sinomonas, for which the name Sinomonas terricola sp. nov. is proposed, with JGH33T (=JCM 35868T=GDMCC 1.3730T) as the type strain.

Olfactory preference of the litchi fruit borer for oviposition on two litchi varieties.

BACKGROUND: The litchi fruit borer Conopomorpha sinensis Bradley is a major destructive pest of litchi and longan plants in China, India and South East Asia. Given its strong olfactory-based oviposition behaviour, interfering with the chemical communication between this insect pest and its host plant may serve as a potential control strategy. However, the chemical compounds associated with its egg-laying behaviour remain poorly understood. RESULTS: In this study, we investigated the olfactory preference of female C. sinensis for oviposition on intact mature fruits of the Feizixiao (FZX) and Guiwei (GW) varieties. Results showed that female C. sinensis preferred to lay eggs on FZX compared with GW fruits, and this preference was olfactory-induced. In addition, we identified differences in the chemical composition of the volatile blend and proportions between FZX and GW fruits, with terpenes being the main volatile components contributing to this divergence. Compounds that induced electrophysiological activity in female borers were subsequently screened from FZX. d-Limonene exhibited the strongest oviposition attraction among four candidates. Furthermore, this compound served as a volatile olfactory cue for recognition and orientation in female C. sinensis. CONCLUSION: The results of this study provide a deeper understanding of the olfactory preferences of female C. sinensis for oviposition on specific litchi varieties. © 2024 Society of Chemical Industry.

Environmental fate and safety analysis of methoxyfenozide application to control litchi and longan pests.

Litchi and longan pests significantly affect crop yield and quality. Chemical prevention and control are very effective for production; therefore, it is crucial to study fate assessment and appropriate field efficacy before pesticide application on crops to appropriately assess the health and ecological risks linked with these agents. This study conducted Good Agricultural Practice (GAP) field trials and laboratory experiments to elucidate the dissipation, terminal residues, and efficacy of methoxyfenozide on litchi and longan in six locations throughout China. To detect methoxyfenozide residues on litchi and longan, a QuEChERS/UPLC-MS/MS-based method was designed. The initial methoxyfenozide levels in litchi and longan ranged from 2.21-2.86 to 0.83-0.95 mg kg-1 and indicated half-lives of 5.1-5.3 and 5.3-5.7 days, respectively. After 7 days of foliage treatment, the concentrations of terminal methoxyfenozide residue were 0.78-2.61 and 0.02-1.01 mg kg-1, which were less than the established maximum residue limit for methoxyfenozide in litchi and longan. The chronic (acceptable daily intake = 0.0055-0.0331%) dietary intake risk analysis for methoxyfenozide in longan and litchi indicated acceptable concentrations of terminal residue for the general population. Methoxyfenozide in litchi and longan was readily degraded in first-order kinetics models, the degradation rate on longan was higher than that on litchi, and their dietary risks were negligible to consumers. Two hundred forty grams per liter of methoxyfenozide suspension concentrate (SC) represents a highly efficacious insecticidal dose to control litchi and longan pests and indicates a significant application potential as it is rapidly degraded and linked with reduced post-treatment residue levels.

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

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

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.

[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.

Litchi Pericarp Extract Treats Type 2 Diabetes Mellitus by Regulating Oxidative Stress, Inflammatory Response, and Energy Metabolism.

Litchi pericarp is rich in polyphenols, and demonstrates significant biological activity. This study assessed the therapeutic effects of litchi pericarp extract (LPE) on type 2 diabetes mellitus in db/db mice. The results showed that LPE ameliorated symptoms of glucose metabolism disorder, oxidative stress, inflammatory response, and insulin resistance in db/db mice. The mechanistic studies indicated that LPE activates adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and suppresses the protein expression of phosphoenolpyruvate carboxykinase (PEPCK), thereby reducing hepatic gluconeogenesis. Additionally, LPE facilitates the translocation of nuclear factor erythroid2-related factor 2 (Nrf2) into the cell nucleus, initiating the transcription of antioxidant factors superoxide dismutase (SOD) and NAD(P)H: quinone oxidoreductase 1 (NQO1), which alleviate oxidative stress and reduce oxidative damage. Furthermore, LPE blocks nuclear factor kappa-B (NF-κB) nuclear translocation and subsequent inflammatory response initiation, thereby reducing inflammation. These findings indicate that LPE addresses type 2 diabetes mellitus by activating the AMPK energy metabolic pathway and regulating the Nrf2 oxidative stress and NF-κB inflammatory signaling pathways.

Physiological, Metabolic, and Transcriptomic Analyses Reveal Mechanisms of Proliferation and Somatic Embryogenesis of Litchi (Litchi chinensis Sonn.) Embryogenic Callus Promoted by D-Arginine Treatment.

D-arginine (D-Arg) can promote embryogenic callus (EC) proliferation and increase the rate of somatic embryo induction of litchi (Litchi chinensis Sonn.), yet the mechanism underlying the processes is incompletely understood. To investigate the mechanism, physiological responses of polyamines (PAs) [putrescine (Put), spermidine (Spd), and spermine (Spm)] were investigated for D-Arg-treated litchi EC and enzyme activity related to polyamine metabolism, plant endogenous hormones, and polyamine- and embryogenic-related genes were explored. Results showed that the exogenous addition of D-Arg reduces the activity of diamine oxidase (DAO) and polyamine oxidase (PAO) in EC, reduces the production of H2O2, promotes EC proliferation, and increases the (Spd + Spm)/Put ratio to promote somatic embryo induction. Exogenous D-Arg application promoted somatic embryogenesis (SE) by increasing indole-3-acetyl glycine (IAA-Gly), kinetin-9-glucoside (K9G), and dihydrozeatin-7-glucoside (DHZ7G) levels and decreasing trans-zeatin riboside (tZR), N-[(-)-jasmonoyl]-(L)-valine (JA-Val), jasmonic acid (JA), and jasmonoyl-L-isoleucine (Ja-ILE) levels on 18 d, as well as promoting cell division and differentiation. The application of exogenous D-Arg regulated EC proliferation and somatic embryo induction by altering gene expression levels of the WRKY family, AP2/ERF family, C3H family, and C2H2 family. These results indicate that exogenous D-Arg could regulate the proliferation of EC and the SE induction of litchi by changing the biosynthesis of PAs through the alteration of gene expression pattern and endogenous hormone metabolism.

Water Supply via Pedicel Reduces Postharvest Pericarp Browning of Litchi (Litchi chinensis) Fruit.

Pericarp browning is the key factor for the extension of shelf life and the maintenance of the commercial value of harvested litchi fruit. Water loss is considered a leading factor of pericarp browning in litchi fruit. In this study, based on the distinct structure of litchi fruit, which is a special type of dry fruit with the aril as the edible part, the effects of water supply via pedicel (WSP) treatment on pericarp browning and the fruit quality of litchi were investigated. Compared with the packaging of the control fruit at 25 °C or 4 °C, the WSP treatment was found to significantly reduce pericarp browning and the decay of litchi fruit. The WSP-treated fruit had a higher L* value, total anthocyanin content, and pericarp water content, and the pericarp was thicker. The WSP treatment significantly suppressed the increase in the electrolyte leakage of the pericarp and maintained higher ascorbic acid (AA) contents in the aril. In addition, the WSP treatment was effective in reducing the activity and gene expression of browning-related genes Laccase (ADE/LAC) and Peroxidase (POD) during the storage period. In conclusion, the WSP treatment could be an effective method to delay pericarp browning and maintain the quality of harvested litchi fruit, and this further supports that litchi fruit has dry fruit characteristics.

Comparative transcriptome and metabolome profiles of the leaf and fruits of a Xianjinfeng litchi budding mutant and its mother plant.

Background: Litchi (Litchi chinensis) is an important sub-tropical fruit in the horticulture market in China. Breeding for improved fruit characteristics is needed for satisfying consumer demands. Budding is a sustainable method for its propagation. During our ongoing breeding program, we observed a litchi mutant with flat leaves and sharp fruit peel cracking in comparison to the curled leaves and blunt fruit peel cracking fruits of the mother plant. Methods: To understand the possible molecular pathways involved, we performed a combined metabolome and transcriptome analysis. Results: We identified 1,060 metabolites in litchi leaves and fruits, of which 106 and 101 were differentially accumulated between the leaves and fruits, respectively. The mutant leaves were richer in carbohydrates, nucleotides, and phenolic acids, while the mother plant was rich in most of the amino acids and derivatives, flavonoids, lipids and organic acids and derivatives, and vitamins. Contrastingly, mutant fruits had higher levels of amino acids and derivatives, carbohydrates and derivatives, and organic acids and derivatives. However, the mother plant's fruits contained higher levels of flavonoids, scopoletin, amines, some amino acids and derivatives, benzamidine, carbohydrates and derivatives, and some organic acids and derivatives. The number of differentially expressed genes was consistent with the metabolome profiles. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway-enriched gene expressions showed consistent profiles as of metabolome analysis. Conclusion: These results provide the groundwork for breeding litchi for fruit and leaf traits that are useful for its taste and yield.

The transcriptional control of LcIDL1-LcHSL2 complex by LcARF5 integrates auxin and ethylene signaling for litchi fruitlet abscission.

At the physiological level, the interplay between auxin and ethylene has long been recognized as crucial for the regulation of organ abscission in plants. However, the underlying molecular mechanisms remain unknown. Here, we identified transcription factors involved in indoleacetic acid (IAA) and ethylene (ET) signaling that directly regulate the expression of INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) and its receptor HAESA (HAE), which are key components initiating abscission. Specifically, litchi IDA-like 1 (LcIDL1) interacts with the receptor HAESA-like 2 (LcHSL2). Through in vitro and in vivo experiments, we determined that the auxin response factor LcARF5 directly binds and activates both LcIDL1 and LcHSL2. Furthermore, we found that the ETHYLENE INSENSITIVE 3-like transcription factor LcEIL3 directly binds and activates LcIDL1. The expression of IDA and HSL2 homologs was enhanced in LcARF5 and LcEIL3 transgenic Arabidopsis plants, but reduced in ein3 eil1 mutants. Consistently, the expressions of LcIDL1 and LcHSL2 were significantly decreased in LcARF5- and LcEIL3-silenced fruitlet abscission zones (FAZ), which correlated with a lower rate of fruitlet abscission. Depletion of auxin led to an increase in 1-aminocyclopropane-1-carboxylic acid (the precursor of ethylene) levels in the litchi FAZ, followed by abscission activation. Throughout this process, LcARF5 and LcEIL3 were induced in the FAZ. Collectively, our findings suggest that the molecular interactions between litchi AUXIN RESPONSE FACTOR 5 (LcARF5)-LcIDL1/LcHSL2 and LcEIL3-LcIDL1 signaling modules play a role in regulating fruitlet abscission in litchi and provide a long-sought mechanistic explanation for how the interplay between auxin and ethylene is translated into the molecular events that initiate abscission.