Longan Flower Research Articles

Effects of different fixation and drying methods on the quality of Dimocarpus longan scented tea

Scented tea has been demonstrated to possess favourable pharmacological properties and exert a range of beneficial effects on human health. Longan flowers (Dimocarpus longan) are rich in nutrients and have a strong aroma; however, to date, no studies have reported the production of scented tea from longan flowers. The present study sought to investigate the impact of varying fixation and drying methods on the nutritional and antioxidant components of longan flowers. The findings indicated that, with the exception of free amino acids, the contents of other components in longan flowers were not affected by the different drying methods. Longan flowers subjected to steam fixation had higher average content of polyphenols and flavonoids, resulting in higher antioxidant and reducing power capacity. Therefore, this study examined the quality of longan scented tea prepared using different fixation and drying methods, promoted further processing of longan scented tea, and provided a reference to comprehensively utilize longan scented tea for benefiting human health.

Identification and functional analysis of the LEAFY gene in longan flower induction

BackgroundFlowering at the right time is a very important factor affecting the stable annual yield of longan. However, a lack of knowledge of the regulatory mechanism and key genes of longan flowering restricts healthy development of the longan industry. Therefore, identifying relevant genes and analysing their regulatory mechanism are essential for scientific research and longan industry development.ResultsDlLFY (Dimocarpus longan LEAFY) contains a 1167 bp open reading frame and encodes 388 amino acids. The amino acid sequence has a typical LFY/FLO family domain. DlLFY was expressed in all tissues tested, except for the leaf, pericarp, and pulp, with the highest expression occurring in flower buds. Expression of DlLFY was significantly upregulated at the early flower induction stage in “SX” (“Shixia”). The results of subcellular localization and transactivation analysis showed that DlLFY is a typical transcription factor acting as a transcriptional activator. Moreover, overexpression of DlLFY in Arabidopsis promoted early flowering and restrained growth, resulting in reduced plant height and rosette leaf number and area in transgenic plants. DNA affinity purification sequencing (DAP-Seq) analysis showed that 13 flower-related genes corresponding to five homologous genes of Arabidopsis may have binding sites and be putative target genes. Among these five flower-related genes, only AtTFL1 (terminal flower 1) was strongly inhibited in transgenic lines.ConclusionTaken together, these results indicate that DlLFY plays a pivotal role in controlling longan flowering, possibly by interacting with TFL1.

Cloning and analysis of DlERF23 gene in flower induction

Irregular flowering is a serious problem in longan production. Identifying the flower induction-related genes and analyzing their regulation mechanism is the key to solve this problem. The APETALA2/ethylene responsive factor (AP2/ERF) superfamily members are transcription factors (TFs) that regulate diverse developmental processes, including flowering time, and stress responses in plants. However, there is still no research about AP2/ERF involved in the regulation of longan flower induction. In the present study, a AP2/ERF TF member DlERF23 was cloned from longan (Dimocarpus longan). It has a typical AP2 domain with the coding sequence (CDS) of DlERF23 is 552 bp in length and encodes 184 amino acids. The molecular weight of DlERF23 protein was 20.41 kda and the theoretical isoelectric point (PI) was 7.69. The amino acid sequence of DlERF23 protein had the highest similarity with CsERF23 (XP_006478313.1) of Citrus sinensis and CcERF23 (XP_006441807.2) of Citrus clementina. The results of qRT-PCR showed that the relative expression level of DlERF23 gene in pericarp was higher, followed by stem, leave, flower and flower bud. Meanwhile, DlERF23 gene significant down-regulated in the early stage of flower induction in ‘Sijimi’ (SJ) longan and up-regulated in the late stage of flower induction in ‘Shixia’ (SX). The results of transient expression of Arabidopsis protoplasts showed that the fluorescence signal was mainly concentrated in the nucleus. Moreover, overexpression of DlERF23 in Arabidopsis promoted early flowering. These results provide useful information for revealing the biological roles of DlERF23 in longan and increase our understanding of the AP2/ERF superfamily members in fruit trees.

Species-specific regulatory pathways of small RNAs play sophisticated roles in flower development in Dimocarpus longan Lour.

Flower development plays vital role in horticultural plants. Post-transcriptional regulation via small RNAs is important for plant flower development. To uncover post-transcriptional regulatory networks during the flower development in Dimocarpus longan Lour. ‘Shixia’, an economically important fruit crop in subtropical regions, we collected and analyzed sRNA deep-sequencing datasets and degradome libraries Apart from identifying miRNAs and phased siRNA generating loci (PHAS loci), 120 hairpin loci, producing abundant sRNAs, were identified by in-house protocols. Our results suggested that 56 miRNA-target pairs, 22 21-nt-PHAS loci, and 111 hairpin loci are involved in post-transcriptional gene silencing during longan reproductive development. Lineage-specific or species-specific post-transcriptional regulatory modules have been unveiled, including miR482-PHAS and miRN15. miR482-PHAS might be involved in longan flower development beyond their conserved roles in plant defense, and miRN15 is a novel miRNA likely associated with a hairpin locus (HPL-056) to regulate strigolactone receptor gene DWARF14 (D14) and the biogenesis of phasiRNAs from D14. These small RNAs are enriched in flower buds, suggesting they are likely involved in post-transcriptional regulatory networks essential for longan flower development via the strigolactone signaling pathway.

High-Throughput Sequencing Reveals Novel microRNAs Involved in the Continuous Flowering Trait of Longan (Dimocarpus longan Lour.).

A major determinant of fruit production in longan (Dimocarpus longan Lour.) is the difficulty of blossoming. In this study, high-throughput microRNA sequencing (miRNA-Seq) was carried out to compare differentially expressed miRNAs (DEmiRNAs) and their target genes between a continuous flowering cultivar 'Sijimi' (SJ), and a unique cultivar 'Lidongben' (LD), which blossoms only once in the season. Over the course of our study, 1662 known miRNAs and 235 novel miRNAs were identified and 13,334 genes were predicted to be the target of 1868 miRNAs. One conserved miRNA and 29 new novel miRNAs were identified as differently expressed; among them, 16 were upregulated and 14 were downregulated. Through the KEGG pathway and cluster analysis of DEmiRNA target genes, three critical regulatory pathways, plant-pathogen interaction, plant hormone signal transduction, and photosynthesis-antenna protein, were discovered to be strongly associated with the continuous flowering trait of the SJ. The integrated correlation analysis of DEmiRNAs and their target mRNAs revealed fourteen important flowering-related genes, including COP1-like, Casein kinase II, and TCP20. These fourteen flowering-related genes were targeted by five miRNAs, which were novel-miR137, novel-miR76, novel-miR101, novel-miR37, and csi-miR3954, suggesting these miRNAs might play vital regulatory roles in flower regulation in longan. Furthermore, novel-miR137 was cloned based on small RNA sequencing data analysis. The pSAK277-miR137 transgenic Arabidopsis plants showed delayed flowering phenotypes. This study provides new insight into molecular regulation mechanisms of longan flowering.

A comparative proteomic analysis provides insight into the molecular mechanism of bud break in longan

BackgroundThe timing of bud break is very important for the flowering and fruiting of longan. To obtain new insights into the underlying regulatory mechanism of bud break in longan, a comparative analysis was conducted in three flower induction stages of two longan varieties with opposite flowering phenotypes by using isobaric tags for relative and absolute quantification (iTRAQ).ResultsIn total, 3180 unique proteins were identified in 18 samples, and 1101 differentially abundant proteins (DAPs) were identified. “SX” (“Shixia”), a common longan cultivated variety that needs an appropriate period of low temperatures to accumulate energy and nutrients for flower induction, had a strong primary inflorescence, had a strong axillary inflorescence, and contained high contents of sugars, and most DAPs during the bud break process were enriched in assimilates and energy metabolism. Combined with our previous transcriptome data, it was observed that sucrose synthase 6 (SS6) and granule-bound starch synthase 1 (GBSSI) might be the key DAPs for “SX” bud break. Compared to those of “SX”, the primary inflorescence, axillary inflorescence, floral primordium, bract, and prophyll of “SJ” (“Sijimi”) were weaker. In addition, light, rather than a high sugar content or chilling duration, might act as the key signal for triggering bud break. In addition, catalase isozyme 1, an important enzyme in the redox cycle, and RuBisCO, a key enzyme in the Calvin cycle of photosynthetic carbon assimilation, might be the key DAPs for SJ bud break.ConclusionOur results present a dynamic picture of the bud break of longan, not only revealing the temporal specific expression of key candidate genes and proteins but also providing a scientific basis for the genetic improvement of this fruit tree species.

Transcriptome sequencing and DEG analysis in different developmental stages of floral buds induced by potassium chlorate in Dimocarpus longan.

Potassium chlorate can promote off-season flowering in longan, but the molecular mechanisms are poorly understood. In this study, four-year-old 'Shixia' longan trees were injected in the trunk with potassium chlorate, and terminal buds were sampled and analyzed using transcriptomics and bioinformatics tools. To generate a reference longan transcriptome, we obtained 207,734 paired-end reads covering a total of 58,514,149 bp, which we assembled into 114,445 unigenes. Using this resource, we identified 3,265 differentially expressed genes (DEGs) that were regulated in longan terminal buds in response to potassium chlorate treatment for 2, 6 or 30 days, including 179 transcription factor genes. By reference to the Arabidopsis literature, we then defined 38 longan genes involved in flowering, from which we constructed the longan flowering pathway. According to RNA-seq data, at least 24 of these genes, which participate in multiple signaling pathways, are involved in potassium chlorate-stimulated floral induction, and the differential regulation in terminal buds of ten floral pathway genes (GI, CO, GID1, GA4, GA5, FLC, AP1, LFY, FT and SOC1) was confirmed by qRT-PCR. These data will contribute to an improved understanding of the functions of key genes involved in longan floral induction by potassium chlorate.

Integrative mRNA and Long Noncoding RNA Analysis Reveals the Regulatory Network of Floral Bud Induction in Longan (Dimocarpus longan Lour.).

Longan (Dimocarpus longan Lour.) is a tropical/subtropical fruit tree of significant economic importance. Floral induction is an essential process for longan flowering and plays decisive effects on the longan yield. Due to the instability of flowering, it is necessary to understand the molecular mechanisms of floral induction in longan. In this study, mRNA and long noncoding RNA (lncRNA) transcriptome sequencing were performed using the apical buds of fruiting branches as materials. A total of 7,221 differential expressions of mRNAs (DEmRNAs) and 3,238 differential expressions of lncRNAs (DElncRNAs) were identified, respectively. KEGG enrichment analysis of DEmRNAs highlighted the importance of starch and sucrose metabolic, circadian rhythms, and plant hormone signal transduction pathways during floral induction. Combining the analysis of weighted gene co-expression network (WGCNA) and expression pattern of DEmRNAs in the three pathways, specific transcriptional characteristics at each stage during floral induction and regulatory network involving co-expressed genes were investigated. The results showed that sucrose metabolism and auxin signal transduction may be crucial for the growth and maturity of autumn shoots in September and October (B1-B2 stage); starch and sucrose metabolic, circadian rhythms, and plant hormone signal transduction pathways participated in the regulation of floral bud physiological differentiation together in November and December (B3-B4 stage) and the crosstalk among three pathways was also found. Hub genes in the co-expression network and key DEmRNAs in three pathways were identified. The circadian rhythm genes FKF1 and GI were found to activate SOC1gene through the photoperiod core factor COL genes, and they were co-expressed with auxin, gibberellin, abscisic acid, ethylene signaling genes, and sucrose biosynthesis genes at B4 stage. A total of 12 hub-DElncRNAs had potential for positively affecting their distant target genes in three putative key pathways, predominantly in a co-transcriptional manner. A hypothetical model of regulatory pathways and key genes and lncRNAs during floral bud induction in longan was proposed finally. Our studies will provide valuable clues and information to help elucidate the potential molecular mechanisms of floral initiation in longan and woody fruit trees.

Floral Induction of Longan (Dimocarpus longan) by Potassium Chlorate: Application, Mechanism, and Future Perspectives.

Longan (Dimocarpus longan L.) is one of the most important tropical and subtropical fruits in the world. Longan fruit has high nutritional and medical value, and is regarded as a treasure among fruits. Since it was first reported that potassium chlorate (KClO3) could be successfully applied to promote flowering in longan, this compound has been widely used in the production of on-season and off-season longan fruits. KClO3 has thus played a great role in promoting the development of the longan industry. In this review, we summarize the application methods, influencing factors, and physiological and molecular mechanisms associated with KClO3-mediated induction of longan flowering. It can be deduced that leaves may play a crucial role in the transport of and response to KClO3. Leaves supply carbon and nitrogen nutrition, and hormone and signaling molecules needed for the differentiation of apical buds. Moreover, cytokinins may be crucial for KClO3-mediated induction of longan flowering. More effort should be focused on studying the molecular mechanisms underlying this process. This will not only help us to better understand floral induction by KClO3 in longan but also enrich our understanding of flowering regulation mechanisms in woody plants.

Anti-apoptotic and pro-survival effects of longan flower extracts on rat hearts with fructose-induced metabolic syndrome.

The aim of this study was to investigate the effects of longan flower (LF) water extract on cardiac apoptotic and survival pathways in rat models of fructose-induced metabolic syndrome. The study findings revealed that the levels of glucose, insulin, triglyceride, and cholesterol and TUNEL-positive apoptotic cells were significantly increased in the HF group compared with the control group; whereas, the levels were decreased in the HFLF group. The expressions of Fas, FADD, and activated caspases 8 and 3, as well as the expressions of Bax, Bak, Bax/Bcl-2, Bak/Bcl-xL, cytosolic cytochrome c, and activated caspases 9 and 3 were increased in the HF group were significantly reversed in HFLF administrated group. Furthermore, LF extract increased IGF-1R, p-PI3K, p-Akt, Bcl-2, and Bcl-xL expression compared to HF group. Taken together, the present findings help identify LF as a potential cardioprotective agent that can be effectively used in treating fructose-induced metabolic syndrome.

Impacts of extraction methods on volatile constituents of longan flower

Impacts of extraction methods on volatile constituents of longan flower

Cytokinin accumulation and flowering gene expression are orchestrated for floral meristem development in longan (Dimocarpus longan Lour.) after chemical flower induction

Under non-inductive environmental conditions longan trees (Dimocarpus longan Lour.) were subjected to potassium chlorate (KClO3) applications, solely or in combination with shoot girdling or defoliation treatments, to induce flowering. Treated trees showed visible flower buds four weeks after treatment, while untreated reference trees remained vegetative. Trees treated with KClO3 solely and in combination with apical shoot defoliation flowered terminally at the shoot apex. KClO3 treatment in combination with girdling caused flowering exclusively at the lateral buds immediately below the girdle. Results from histological and hormone analyses are integrated with longan flowering gene expression data to build a comprehensive time course model for chemical flower induction in longan. The increased cytokinin concentration in shoot apex tissues, likely due to de novo biosynthesis and translocation, corresponds with transient up-regulation of the flower promoting gene Dimocarpus longan FLOWERING LOCUS 1 (DlFT1) in mature leaves after KClO3 treatment. Both occur during the presumed period of flower induction approximately at 10 days after treatment. Subsequently, and with some delay floral homeotic genes Dimocarpus longan APETALA 1 (DlAP1) are up-regulated in the buds indicating flower bud development, which coincides with visible floral meristems in histological specimen. The specific cytokinin accumulation and flowering gene expression pattern suggest a tight orchestration of hormonal and genetic pathways in chemically induced longan.

Synergistic Effect of Combined Treatment with Longan Flower Extract and 5-Fluorouracil on Colorectal Cancer Cells

To investigate the influence of longan flower extract (LFE) on the sensitization of colorectal cancer (CRC) cells to 5-fluorouracil (5-FU) treatment, HT-29, Colo 320DM and SW480 cells were treated with LFE and 5-FU alone and in combination, and the cell viability was then assessed by trypan blue exclusion, the cell cycle by propidium iodide staining, the mitochondria membrane potential by rhodamine 123 staining, and the expression levels of associated genes by immunoblotting and quantitative real-time polymerase chain reaction. LFE and 5-FU synergistically inhibited cell proliferation of HT-29 and Colo 320DM cells. Combined treatment also elevated the level of loss of mitochondria membrane potential of these two CRC cells and arrested HT-29 cells in the S phase of the cell cycle, in association with down-regulation of cyclin A mRNA expression. LFE synergistically potentiated chemosensitivity to 5-FU in at least two CRC cell lines. The results indicated that LFE has potential as a novel agent for the sensitization of CRC cells to 5-FU.

Longan flower proanthocyanidins induce apoptosis in HT-29 colorectal carcinoma spheroids.

Proanthocyanidin-rich longan flower extract (LFP) has been previously shown to inhibit the proliferation and anchorage-independent growth in soft agar of two colorectal carcinoma (CRC) cells in vitro. In this report, we further examined the effects of LFP in a CRC spheroid model. A liquid-overlay assay employing HT-29 spheroids was used to evaluate the effects of LFP on cancer cell tumorigenesis, viability, and apoptosis. Associated effects on signaling path ways (epidermal growth factor receptor [EGFR], Akt) and apoptotic regulators were measured using Western blot. Treatment with LFP up to 200 μg/ml inhibited tumor growth in a dose-dependent manner and induced prominent apoptosis as measured by annexin V staining. Cells treated with LFP showed decreased EGFR and Akt phosphorylation with decreased expression of B-cell lymphoma 2. The ability of LFP to induce apoptosis in CRC spheroids warrants further investigation of its composition and identification of tumor-active components.

Fruiting pattern in longan, Dimocarpus longan: from pollination to aril development

AbstractIn most fleshy fruits, the edible part of the fruit is formed either by the pericarp derived from the ovary wall or by an engrossed receptacle. However, in a number of fruit tree species the edible part is the aril, an outgrowth of the ovule that envelops the seed, and there is a paucity of information on fruit development and fruiting pattern in these crops. To fill this gap, in this work, we have characterised the progamic phase, fruit development and fruit/fruitlet drop in longan, Dimocarpus longan. The progamic phase from pollination to fertilisation took just 3 days; the pollen tubes arrived to the base of the style in 1 day, reached the locule 1 day later and penetrated the ovules 3 days after pollination. Only one of the two ovules present in each longan flower fertilised. However, this did not result in rapid fruitlet growth, since a very slow fruit development occurred up to 6 weeks after flowering. Pollination was required for fruiting and unpollinated flowers dropped 9 days after anthesis. Only 7% of the female flowers produced became fruits. There was a first flower/fruitlet drop 2–4 weeks after flowering that appeared to be related to lack of fertilisation followed by a second fruitlet drop 5–6 weeks after flowering, concomitantly with the rapid growth of the embryo and the aril, that appears to be related to competition for nutrients. These results set a frameline to understand fruiting in tree species in which the edible part of the fruit is a fleshy aril.

Evaluation of Xanthine Oxidase Inhibitory Potential and In vivo Hypouricemic Activity of Dimocarpus longan Lour. Extracts.

Background:Longan is a fruit tree known to contain many phenolic components, which are capable of protecting people from oxidative damage through an anti-inflammatory mechanism. It may be also worthwhile to study the effect on lowering uric acid activity.Materials and Methods:This study investigates the lowering of uric acid using longan extracts, including flowers, pericarps, seeds, leaves, and twigs, on potassium-oxonate-induced hyperuricemia mice and its inhibitory actions against xanthine oxidase (XO) activities.Results:The findings revealed that ethyl acetate fraction of longan extracts exhibited strong XO-inhibitory activity, and the flower extracts (IC50 = 115.8 μg/mL) revealed more potent XO-inhibitory activity to those of pericarps (118.9 μg/mL), twigs (125.3 μg/mL), seeds (262.5 μg/mL), and leaves (331.1 μg/mL) in vitro. In addition, different dosages of longan extract (50–100 mg/kg) were administered to hyperuricemic mice. The lowering effect of longan extracts on uric acid at 75 mg/kg markedly reduced plasma uric acid levels in decreasing order: Flowers (80%) > seeds (72%) > pericarps (64%) > twigs (59%) > leaves (41%), compared with allopurinol (89%). Finally, 10 isolated phytochemicals from longan flowers were then examined in vitro. The results indicated that proanthocyanidin A2 and acetonylgeraniin A significantly inhibited XO activity in vitro. This is the first report providing new insights into the urate-reducing effect of phenolic dimer and hydrolyzable tannin, which can be developed to potential hypouricemic agents.SUMMARY Longan flower extracts possess more potent XO-inhibitory activity than pericarps, twigs, seeds, and leaves in vitroThe lowering effect of longan flowers and seeds extracts markedly reduced plasma uric acid levels as compared to allopurinol in vivoThe extract proanthocyanidin A2 and acetonylgeraniin A were demonstrated potent XO inhibitory activity in vitro Abbreviations used: PO: Potassium-oxonate, XO: xanthine oxidase, HE: n-hexane, EA: ethyl acetate, i.p.: intraperitoneal, PBS: phosphate-buffered saline, AP: allopurinol, PUA: plasma uric acid.

Protective effects of the extract from longan flower against hepatic ischemia/reperfusion injury in rats

Ischemia/reperfusion (I/R) injury has a complex pathophysiology resulting from a number of contributing factors. The effect of longan flower ethyl acetate extract (LFEE) on hepatic I/R injury in rats was examined. Aspartate aminotransferase, alanine aminotransferase, hepatic thiobarbituric acid reactive substances (TBARS), interleukin-1β, interleukin-6, interleukin-10, tumor necrosis factor-α, inducible nitric oxide synthase, and cyclooxygenase-2 activities were significantly increased after I/R injury, but decreased in the groups with LFEE treatment. Significant decrease in hepatic glutathione levels after I/R injury was observed upon LFEE treatment. NADPH:quinone oxidoreductase 1 activity was significantly increased after I/R injury, and it was further increased in the groups with LFEE treatment. Histological results indicated that LFEE was effective in improving liver tissue morphology during I/R injury. Therefore, LFEE might offer a novel intervention for patients suffering from I/R of the liver especially in the process of hepatotomy and liver transplantation.

Alteration of antioxidative properties of longan flower-honey after high pressure, ultra-sonic and thermal processing

Abstract This work evaluated the effect of high hydrostatic pressure (300–500 MPa/25 °C/5–20 min), ultra-sonic (20–60% amplitude/20 kHz/5–20 min) and thermal (50–100 °C/1–5 min) processing on phenolic contents and antioxidant capacities of honey from the longan flower. Total phenolic compounds, total flavonoids and antioxidant capacity (DPPH and FRAP assays) were determined. It was found that high pressure, ultra-sonic and thermal treatments had a significant effect on antioxidative properties of honey sample. After pressurization, the quantities of total phenols, flavonoids and antioxidant capacity in honey significantly increased with the increasing pressure levels and processing times, in particular samples pressurized at 500 MPa for 20 min. Similarly, these bioactive compounds in honey samples processed by ultra-sonication were also enhanced when the amplitude levels and treatment times increased. For thermal treatments at 50 and 70 °C, all antioxidative constituents had no significant differences when compared to the control, while the sample heated at 100 °C contained the lowest levels of phenols and antioxidant capacity. Therefore, both high pressure and ultra-sonic processing are an alternative technique to preserve the antioxidative qualities of longan flower-honey, while also not affecting the nutritional values.

Activities of different types of Thai honey on pathogenic bacteria causing skin diseases, tyrosinase enzyme and generating free radicals.

BackgroundHoney is a natural product obtained from the nectar that is collected from flowers by bees. It has several properties, including those of being food and supplementary diet, and it can be used in cosmetic products. Honey imparts pharmaceutical properties since it has antibacterial and antioxidant activities. The antibacterial and antioxidant activities of Thai honey were investigated in this study.ResultsThe honey from longan flower (source No. 1) gave the highest activity on MRSA when compared to the other types of honey, with a minimum inhibitory concentration of 12.5% (v/v) and minimum bactericidal concentration of 25% (v/v).Moreover, it was found that MRSA isolate 49 and S. aureus were completely inhibited by the 50% (v/v) longan honey (source No. 1) at 8 and 20 hours of treatment, respectively. Furthermore, it was observed that the honey from coffee pollen (source No. 4) showed the highest phenolic and flavonoid compounds by 734.76 mg gallic/kg of honey and 178.31 mg quercetin/kg of honey, respectively. The antioxidant activity of the honey obtained from coffee pollen was also found to be the highest, when investigated using FRAP and DPPH assay, with 1781.77 mg FeSO4•7H2O/kg of honey and 86.20 mg gallic/kg of honey, respectively. Additionally, inhibition of tyrosinase enzyme was found that honey from coffee flower showed highest inhibition by 63.46%.ConclusionsHoney demonstrates tremendous potential as a useful source that provides anti-free radicals, anti-tyrosinase and anti-bacterial activity against pathogenic bacteria causing skin diseases.

Identification of regulatory genes implicated in continuous flowering of longan (Dimocarpus longan L.).

Longan (Dimocarpus longan L.) is a tropical/subtropical fruit tree of significant economic importance in Southeast Asia. However, a lack of transcriptomic and genomic information hinders research on longan traits, such as the control of flowering. In this study, high-throughput RNA sequencing (RNA-Seq) was used to investigate differentially expressed genes between a unique longan cultivar ‘Sijimi’(S) which flowers throughout the year and a more typical cultivar ‘Lidongben’(L) which flowers only once in the season, with the aim of identifying candidate genes associated with continuous flowering. 36,527 and 40,982 unigenes were obtained by de novo assembly of the clean reads from cDNA libraries of L and S cultivars. Additionally 40,513 unigenes were assembled from combined reads of these libraries. A total of 32,475 unigenes were annotated by BLAST search to NCBI non-redundant protein (NR), Swiss-Prot, Clusters of Orthologous Groups (COGs) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Of these, almost fifteen thousand unigenes were identified as significantly differentially expressed genes (DEGs) by using Reads Per kb per Million reads (RPKM) method. A total of 6,415 DEGs were mapped to 128 KEGG pathways, and 8,743 DEGs were assigned to 54 Gene Ontology categories. After blasting the DEGs to public sequence databases, 539 potential flowering-related DEGs were identified. In addition, 107 flowering-time genes were identified in longan, their expression levels between two longan samples were compared by RPKM method, of which the expression levels of 15 were confirmed by real-time quantitative PCR. Our results suggest longan homologues of SHORT VEGETATIVE PHASE (SVP), GIGANTEA (GI), F-BOX 1 (FKF1) and EARLY FLOWERING 4 (ELF4) may be involved this flowering trait and ELF4 may be a key gene. The identification of candidate genes related to continuous flowering will provide new insight into the molecular process of regulating flowering time in woody plants.