Dimocarpus Longan Lour Research Articles

Physiological and biochemical changes in longan fruit (Dimocarpus longan Lour.) cultivated in Vietnam during growth and ripening

This paper presents research results on some physiological (pigments content) and biochemical indicators (reducing sugar content, starch, total organic acid, vitamin C, α-amylase enzyme, catalase enzyme, peroxidase enzyme) of longan fruit grown in Vietnam during growth and ripening, thereby determining the physiological ripening time of the fruit (the most appropriate time for fruit harvest). The results showed that significant changes occurred in pigments content, reducing sugar content, starch, total organic acid, vitamin C, protein, lipid, α-amylase enzyme, catalase enzyme, and peroxidase enzyme of longan from formation to fruit ripening. Through the research process, it was observed that the longan achieved the best quality to harvest when fruits were 19 weeks old. The results of this study provide important data for the harvesting and storage of longan fruit.

A comprehensive insight into the metabolic landscape of fruit pulp, peel, and seed in two longan (Dimocarpus longan Lour.) varieties

ABSTRACT Longan is an ancient and popular plant with highly nutritious fruit. The pulp is the main part of the fruit which is consumed. However, the potentials of other longan fruit parts such as the peel and the seed as reservoirs of important bioactive components have not yet fully been explored. This study aimed at exploring the diversity of primary and secondary metabolites in two commercial longan varieties, i.e., Shixia and Chuliang, concerning fruit, pulp, peel, and seed based on a widely targeted metabolomics approach. A total of 706 metabolites were identified grouped into eight diverse classes of metabolites, including flavonoids, amino acids and its derivatives, alkaloids, tannins, phenolic acids, organic acids, nucleotides and derivatives, lipids, and lignans. Chuliang peel showed a higher accumulation of metabolites viz. flavonoids, alkaloids, and tannins, while Shixia seeds showed abundance in amino acids, organic acid, nucleic acids and its derivatives. Chuliang pulp showed relatively higher accumulation of lipids when compared with other fruit parts. Differential metabolome profiling between fruit parts indicates the prevalence of key metabolites, i.e., O-Phosphocholine, betaine, piperidine, L-Arginine, and L-Phenylalanine, in seed and peel of the longan fruit. The findings in this research provide a new glance on the nutritional value and biochemical basis of longan fruit pharmaceutical value, with emphasis on valorization of longan peel and seed tissues for their pharmaceutical properties and nutritional values.

Phenolic content, antioxidant capacity, and α-amylase and α-glucosidase inhibitory activities of Dimocarpus longan Lour.

The aim of this study was to compare the phenolic compound profiles and antioxidant capacities of eight varieties of longan (Dimocarpus longan Lour.) planted in the middle and upper Yangtze River area. The total polyphenols content (TPC) and total flavonoids content (TFC) of dried longan pulp ranged from 1.07 ± 0.05 to 1.22 ± 0.05mg gallic acid equivalents/g and 0.25 ± 0.07 to 0.87 ± 0.14mg rutin equivalents/g. UHPLC-QqQ-MS/MS analysis revealed 12 individual polyphenol compounds in longan. The Fuwan8, Dongliang and FD97 varieties showed the strongest DPPH scavenging activity (IC50 of 1.03g/mL). The highest ABTS+ scavenging activity was found in the Dongliang. In the enzyme assays, the Fuwan8 and Dongliang varieties demonstrated maximum α-amylase and α-glucosidase inhibition activities, with values of 97.56 and 88.58%, respectively. The principal component analysis indicated that the Rongyu8 and Songfengben cultivars have nearly analogous polyphenol compounds.

Characterization and tissue-specific as well as heat-stress expression analysis ofCBL-interacting protein kinase genes in Dimocarpuslongan Lour

The CBL-interacting protein kinase (CIPK) gene family plays important roles in plant growth, development, and responses to abiotic stresses. To date, the CIPKs have been extensively identified and characterized in various plants. However, there have been few studies on CIPKs in Dimocarpus longan Lour (D. longan). In this study we identified eight putative CIPKs in D. longan (DlCIPKs) according to RNA-seq data. The physicochemical properties, subcellular localization, conserved motifs, phylogenetic relationships, glycosylation and phosphorylation sites, and gene ontology annotation were analyzed using bioinformatics tools. The tissue-specific and heat-stress-responsive expressions were systematically investigated as well. Ten motifs widely maintained by DlCIPKs were identified. All eight DlCIPKs identified from D. longan and the 50 CIPKs selected from Zea mays, Oryza sativa, Sorghum bicolor, Vitis vinifera, Populus trichocarpa, and Arabidopsis thaliana were categorized together into seven groups; group 7 was the largest and contained 20 CIPKs. Localizations of these eight DlCIPKs were predicted in the plasma membrane, cytoplasm, chloroplast thylakoid membrane, or nucleus and were predicted to differ. All eight DlCIPKs were predicted to be phosphorylated but with different numbers of phosphorylation sites. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that among the eight DlCIPKs, only DlCIPK1, DlCIPK5, and DlCIPK8 were differently expressed; notably, between root and leaf tissues. All eight DlCIPKs responded to heat treatments. The expressions of DlCIPK1, DlCIPK4, DlCIPK5, and DlCIPK6 in D. longan leaves were upregulated to the maximum level after 1 h of heat treatment. In contrast, the expression levels of DlCIPK2, DlCIPK3, DlCIPK7, and DlCIPK8 increased significantly after 4 h of heat treatment. The results of this study will enrich our knowledge of DlCIPKs and establish a foundation for enhancing tolerance to abiotic stresses through genetic engineering in D. longan.

Analyses of microRNA166 gene structure, expression, and function during the early stage of somatic embryogenesis in Dimocarpus longan Lour

MicroRNA166 (miR166) contributes to post-transcriptional regulation by binding the mRNAs of HD-ZIP III genes, which affects plant growth and development. The structural characteristics, expression, and functions of miR166 genes during the early somatic embryogenesis stage in Dimocarpus longan remain unknown. We isolated the transcripts of pri-miR166 S78 with two transcription initiation sites (TSSs) and pri-miR166 S338 with one TSS. These sequences contain potential smORFs and encode different miRNA peptides (miPEPs). Additionally, their promoters contain cis-acting elements responsive to diverse stimuli. The pre-miR166 S78 and pre-miR166 S338 expression levels were up-regulated in response to 2,4-D, abscisic acid, and ethylene. Although the expression patterns induced by hormones were similar, there were differences in the extent of the response, with pre-miR166 S338 more responsive than pre-miR166 S78. Thus, miRNA transcription and maturation are not simply linearly correlated. Moreover, pre-miR166 S78 and pre-miR166 S338 expression levels were down-regulated, whereas ATHB15 (target gene) expression was up-regulated, from the longan embryonic callus to the globular embryo stages. These results are indicative of a negative regulatory relationship between miR166 and ATHB15 during the early somatic embryogenesis stage in longan. At the same stages, miR166a.2-agomir, miR166a.2-antagomir, and miPEP166 S338 increased or decreased the expression of miR166a.2 and ATHB15, but with no consistent patterns or linear synchronization, from which we've found some reasons for it.

Occurrence of algal leaf spot on longan (Dimocarpus longan ) caused by Cephaleuros virescens in India

Longan (Dimocarpus longan Lour. ) is an evergreen subtropical fruit tree species of Sapindaceae family with a long cultivation tradition in South East Asia. Between July to September of 2014 and 2015, leaves of longan trees were found infected by green algae at experimental farm of National Research Centre on Litchi, Muzaffarpur, Bihar (India). The symptoms of the disease appeared on the upper leaf surface as dark gray to reddish-rust coloured lesions, slightly raised with a velvet-like appearance. The disease incidence among leaves was 28. 4-57. 3% while percent disease severity index was 13. 3 to 20. 2. The algal thalli were isolated and cultured successfully on potato dextrose agar and Bold's basal medium but there was no development of sporangiophores and sporangia in culture. In pathogenicity test, inoculums either from naturally infected leaves or from pure culture of algal filaments could not reproduce typical symptom of the disease even up to three months of inoculation. Based on the leaf symptom and morphological characteristics, the pathogen was identified as Cephaleuros virescens Kunze. To our knowledge, this is the first report of leaf spots caused by Cephaleuros virescens on longan trees in India.

DlICE1, a stress-responsive gene from Dimocarpus longan, enhances cold tolerance in transgenic Arabidopsis

ICE1 (inducer of CBF expression 1) encodes a typical MYC-like basic helix-loop- helix (bHLH) transcription factor that acts as a pivotal component in the cold signalling pathway. In this study, DlICE1, a novel ICE1-like gene, was isolated from the southern subtropical fruit tree longan (Dimocarpus longan Lour.). DlICE1 encodes a nuclear protein with a highly conserved bHLH domain. DlICE1 expression was slightly upregulated under cold stress. Overexpression of DlICE1 in Arabidopsis conferred enhanced cold tolerance via increased proline content, decreased ion leakage, and reduced malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation. Expression of the ICE1-CBF cold signalling pathway genes, including AtCBF1/2/3 and cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47 and AtKIN1), was also significantly higher in DlICE1-overexpressing lines than in wild-type (WT) plants under cold stress. In conclusion, these findings indicate that DlICE1 is a member of the bHLH gene family and positively regulates cold tolerance in D. longan.

Characterization and Tissue-specific Expression of bHLH Genes in Dimocarpus longan

In plants, the basic helix-loop-helix (bHLH) transcription factors (TFs) play pivotal roles in many biological processes including growth, stress response, and secondary metabolite synthesis. To date, many bHLH genes have been identified and characterized in diverse plant species. However, little is known regarding the bHLH genes in Dimocarpus longan Lour. (D. longan). Based on RNA-seq data, we identified 42 putative bHLH genes from D. longan and determined their putative functions using the NCBI Conserved Domain Search Tool and Pfam databases. The physicochemical properties, phylogenetic relationships, conserved motifs, gene ontology (GO) annotations, protein-protein interactions, and tissue-specific expression patterns of these bHLH genes were systematically explored. In total, ten motifs were found in DlbHLH proteins using MEME, among which two were highly conserved. Phylogenetic tree analysis found that DlbHLH proteins can be divided into nine groups, with group 2 being the largest. GO annotation results showed that the DlHLH genes were involved in various molecular functions. RNA-seq and qRT-PCR results revealed important differences in the expression patterns of 17 of the DlbHLH genes. In particular, DlbHLH-9, DlbHLH-19, DlbHLH-25, DlbHLH-26, and DlbHLH-35 were found to show significantly different expression patterns in root and leaf tissues. The results of this study will further enrich our knowledge regarding bHLH transcription factor genes and lay a foundation for enhancing the production of active secondary metabolites by genetic engineering in D. longan.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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Induced expression of NOX and SOD by gaseous sulfur dioxide and chlorine dioxide enhances antioxidant capacity and maintains fruit quality of ‘Daw’ longan fruit during storage through H2O2 signaling

Hydrogen peroxide (H2O2) is known to be a signaling molecule involved in the activation of plant defense against both biotic and abiotic stresses. The current study aimed to demonstrate that fumigation induces H2O2 production, which is believed to act as the upstream signaling molecule in the antioxidant defense responses. Longan (Dimocarpus longan Lour. cv. Daw) fruit were fumigated with either 1000 mg L−1 sulfur dioxide (SO2) or 10 mg L−1 chlorine dioxide (ClO2), or in combination, and stored for 8 d. Both types of fumigation reduced pericarp browning and maintained fruit quality for up to 3, 5 or 7 d, respectively, comparing with a 2 d shelf life for the non-fumigated control fruit. 2,2’-Azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazy (DPPH) assays indicated that antioxidant capacity was enhanced in treated fruit. H2O2 concentrations increased immediately after the fumigation in treated fruit, reaching a maximum within 6–12 h. Treatments increased expression of the plasma membrane nicotinamide adenine dinucleotide phosphate oxidase (RbohD) and superoxide dismutase (SOD). Subsequent nicotinamide adenine dinucleotide phosphate oxidase (NOX) and superoxide dismutase activity surges coincided with the rise of H2O2. Compared with the fumigated samples, H2O2 concentrations did not increase in the control until day 1, reaching concentrations that were about three times higher than those of the fumigated samples at the end of the experiment, while that of the fumigated fruit remained lower. These results suggested that SO2 and/or ClO2 fumigation triggers the NOX-dependent H2O2 generation, which could activate the antioxidant response in longan aimed to overcome the subsequent H2O2 production, thereby reducing the pericarp browning and maintaining fruit quality.

Effects of exogenous plant hormones on sugar accumulation and related enzyme activities during the development of longan (Dimocarpus Longan Lour.) fruits

ABSTRACTExogenous hormone treatment is a widely used and effective method to promote fruit ripening. To our knowledge, the effects of exogenous hormones on the sugar accumulation and related enzyme activities during the development of longan fruits have not yet been elucidated. In this study, the contents of sucrose, glucose and fructose, activities and transcriptional levels of sucrose phosphate synthase (SPS), sucrose synthase (SS), acid invertase (AI) and neutral invertase (NI) were detected during fruit development of exogenous hormone-treated and non-treated longan. The results indicated that exogenous hormones (IAA, ABA, GA3) could not alter the sugar contents when fruits were ripe but accelerate the sugar accumulation. IAA and ABA increased the gene transcriptional levels and enzyme activities of SS and SPS, and also showed the tendency of increasing the transcriptional levels and enzyme activity of AI. However, GA3 decreased the gene transcriptional levels of SS and SPS, and increased the gene transcriptional level of AI. Interestingly, GA3 also increased the enzyme activity of SPS which indicated GA3 may regulate the SPS activity at post-translational levels. Our results suggested that IAA, ABA and GA3 may regulate sugar accumulation during fruit development of longan.

Pericarp and seed of litchi and longan fruits: constituent, extraction, bioactive activity, and potential utilization.

Litchi (Litchi chinensis Sonn.) and longan (Dimocarpus longan Lour.) fruits have a succulent and white aril with a brown seed and are becoming popular worldwide. The two fruits have been used in traditional Chinese medicine as popular herbs in the treatment of neural pain, swelling, and cardiovascular disease. The pericarp and seed portions as the by-products of litchi and longan fruits are estimated to be approximately 30% of the dry weight of the whole fruit and are rich in bioactive constituents. In the recent years, many biological activities, such as tyrosinase inhibitory, antioxidant, anti-inflammatory, immunomodulatory, anti-glycated, and anti-cancer activities, as well as memory-increasing effects, have been reported for the litchi and longan pericarp and seed extracts, indicating a potentially significant contribution to human health. With the increasing production of litchi and longan fruits, enhanced utilization of the two fruit by-products for their inherent bioactive constituents in relation to pharmacological effects is urgently needed. This paper reviews the current advances in the extraction, processing, identification, and biological and pharmacological activities of constituents from litchi and longan by-products. Potential utilization of litchi and longan pericarps and seeds in relation to further research is also discussed.

Antiproliferative activity of longan (Dimocarpus longan Lour.) leaf extracts

Longan (Dimocarpus longan Lour.) belongs to the Sapindaceae family. We examined the antiproliferative activity of longan leaf extracts against cancer-derived cell lines in vitro. The tested samples were water extract, ethanol extract, n-hexane fraction, ethyl acetate fraction, and water fraction of longan leaf. Cytotoxicity test is against brine shrimps that were screened using Brine Shrimp Lethality Test. Antiproliferative activity assay on WEHI-164 cells (mouse fibrosarcoma cancer cell), THP-1 cells (human peripheral blood acute monocyte cell), and Vero cells (non-cancer or normal cell) that was conducted using a hemocytometer with Trypan Blue Dye exclusion. The 50% lethality concentration (LC50) value of water extract, ethanol extract, n-hexane fraction, ethyl acetate fraction, and water fraction were 854.64, 305.81, 446.55, 1313.44, and 1621.8 μg/ml. Ethanol extract exhibited significant cytotoxic due to the lowest LC50 value. The ethanol extract was then used for further examination. The highest antiproliferative activity was achieved 44.93% by 600 μg/ml ethanol extract on WEHI-164 and 57.45% by 500 μg/ml ethanol extract on THP-1. It was significantly equal to doxorubicin antiproliferative activity. Ethanol extract dose had a low effect on Vero cells. This present study confirmed that the longan leaf ethanol extract possesses marked antiproliferative activity on cancer-derived cell lines.

Comparison between 'Fuyan' and 'Dongbi' longans in aril breakdown and respiration metabolism

This study aimed to investigate the difference between ‘Fuyan’ longan (Dimocarpus longan Lour. cv. Fuyan) fruit and ‘Dongbi’ longan (Dimocarpus longan Lour. cv. Dongbi) fruit in term of their aril breakdown and respiratory metabolism. As compared to ‘Fuyan’ longans, the ‘Dongbi’ longans exhibited lower fruit respiration rate, lower aril breakdown index, higher NADK activity, higher total activities of G-6-PDH and 6-PGDH, higher contents of NADP and NADPH, lower activities of AAO, CCO, PPO, PGI, and SDH, and lower contents of NAD and NADH in aril. These findings suggest that better storability and lower aril breakdown index in ‘Dongbi’ longans than ‘Fuyan’ longans might be due to lower activities of respiratory terminal oxidases, and lower respiratory metabolic pathways of EMP-TCA cycle related-enzymes in ‘Dongbi’ longan aril, which decreased respiratory rate and reduced the consumption of substrates, and subsequently maintained the integrity of the aril of ‘Dongbi’ longans during storage.

Emergence Rate and Initial Growth of Longan (Dimocarpus longan Lour) in Relation to Seeds Sizes

The fruit plant ‘Longan’ is considered as being native to Asia and is at present commercially explored in some regions. The objective of this work was to study the influence of seed size on seed emergence and initial seedling growth. The experiment was carried out using a randomized block design (DBC), with three treatments, namely, the seed sizes at seedling emergence according to their longitudinal diameter: small, medium and large. Each plot was composed of six seeds and five replications per treatment. The following characteristics were evaluated: emergence speed index, average time, percentage and relative frequency of emergence, leaf number, stem diameter, plant height, shoot dry mass and root dry mass. Seeds of medium and large size are those that presented satisfactory results for the characteristics related to seed emergence. The same ones stood out in relation to the small seeds for the variables percentage, average time, average speed and emergence speed index. Small seeds are not recommended for the production of ‘Longan’ seedlings, given the long period of time to emerge and the low probability of the seedlings establishing satisfactorily in the field. The medium and large seeds were the most promising for the variables number of leaves, stem diameter, plant height, dry shoot mass and dry root mass.Therefore, according to the conditions in which the present work was conducted, the use of medium and large seeds for the production of ‘Longan’ seedlings is suggested.

Longan fruit increase bone mineral density in zebrafish and ovariectomized rat by suppressing RANKL-induced osteoclast differentiation

BackgroundThe receptor activator of nuclear factor-kappa B ligand (RANKL)-induced nuclear factor-kappa B (NF-κB) signaling pathway plays essential roles in osteoclast differentiation and may serve as an attractive target for the development of therapeutics for osteoporosis. PurposeThis study aimed to identify plant extracts that attenuated RANKL-induced NF-κB signaling pathway and examine their anti-osteoporotic effects in animal model systems. MethodsOsteoclast differentiation was determined by western blot analysis, RT-PCR, and tartrate-resistant acid phosphatase (TRAP) assay. The effect of Longan (Dimocarpus longan Lour.) fruit extract (LFE) on bone mineral density was evaluated by calcein staining in zebrafish and micro-CT analysis in ovariectomized (OVX) rat. ResultsLFE nullified RANKL-induced down-regulation of inhibitor of NF-κB, which keeps NF-κB sequestered in the cytosol, thereby inhibiting translocation of NF-κB to the nucleus, in RAW264.7 cells. In addition, LFE decreased the nuclear levels of c-Fos and nuclear factor of activated T-cells c1, which play crucial roles in RANKL-induced osteoclast differentiation, in RAW264.7 cells. LFE repressed RANKL-activated cathepsin K and TRAP expression in RAW264.7 cells, resulting in a reduction of the number of TRAP-positive multinucleated cells, without cytotoxicity. Furthermore, LFE increased bone mineralization in zebrafish and prevented bone loss in OVX rat. ConclusionCollectively, our findings suggest that LFE exerts its anti-osteoporotic activity through inhibition of osteoclast differentiation and may have potential as a herbal therapeutic or preventive agent for the treatment of osteoporosis.

Polyphenols and Alkaloids in Byproducts of Longan Fruits (Dimocarpus Longan Lour.) and Their Bioactivities.

The longan industry produces a large amount of byproducts such as pericarp and seed, resulting in environmental pollution and resource wastage. The present study was performed to systematically evaluate functional components, i.e., polyphenols (phenolics and flavonoids) and alkaloids, in longan byproducts and their bioactivities, including antioxidant activities, nitrite scavenging activities in simulated gastric fluid and anti-hyperglycemic activities in vitro. Total phenolic and total flavonoid contents in pericarp were slightly higher than those in seeds, but seeds possessed higher alkaloid content than pericarp. Four polyphenolic substances, i.e., gallic acid, ethyl gallate, corilagin and ellagic acid, were identified and quantified using high-performance liquid chromatography. Among these polyphenolic components, corilagin was the major one in both pericarp and seed. Alkaloid extract in seed showed the highest DPPH radical scavenging activity and oxygen radical absorbance capacity. Nitrite scavenging activities were improved with extract concentration and reaction time increasing. Flavonoids in seed and alkaloids in pericarp had potential to be developed as anti-hyperglycemic agents. The research result was a good reference for exploring longan byproducts into various valuable health-care products.

Efforts to improve the growth of longan plant grafting (Dimocarpus longan lour.) in Indonesia with the application of fertilizer

The purpose of this research was to study the response of longan grafting plant to the application of leaf and NPK fertilizer. The experimental design was randomized block design with three factors namely varieties, leaf fertilizers and NPK fertilizers. Varieties were Kristalin, Aroma Durian, Diamond River, and Itoh. Leaf fertilizer concentration was without fertilizer, 2 g/l, and 2.5 g/l. The dosage of NPK fertilizer were without fertilizer, 40 g/pot, and 60 g/pot. The observed variables were plant height, number of leaves, number of branches, leaf area and amount of chlorophyll. The results showed that Kristalin was the most responsive to NPK fertilizer at dosage of 60 g per plant. The 2.5 g of leaf fertilizer per plant was the optimal dosage to increase the height addition. The highest plant addition was found in Kristalin was 21.72 cm. Kristalin and Durian Aroma were have highest number of leaves at 102.75 while the largest leaf area is Krsitalin 3,861.54 cm2. The concentration of leaf fertilizer will increase the addition of plant height and number of leave, however it will reduce number of branches and leaf area. The more dosage of NPK fertilizer will reduce the number of leaves and leaf area.

HPLC Profile of Longan (cv. Shixia) Pericarp-Sourced Phenolics and Their Antioxidant and Cytotoxic Effects.

Longan (Dimocarpus longan Lour.) pericarp, the main by-product of aril and pulp processing, is abundant in phenolic compounds and worthy of further utilization. The present work firstly reported HPLC analysis and in vitro antioxidant evaluation of longan (cv. Shixia) pericarp-derived phenolics (LPPs), the purified longan pericarp extract (LPE), as well as their cytotoxic effect on lung cancer cell line, A549. The results indicated that the purified LPE had significant amounts of phenolics, with content of 57.8 ± 0.6 mg of gallic acid equivalents per gram of dry longan pericarp (mg GAE·g−1 DLP), which consisted of six phenolic compounds (A–F), including protocatechuic acid (A), isoscopoletin (B), quercetin (C), ellagic acid (D), corilagin (E), and proanthocyanidins C1 (F). Antioxidant assays showed that LPPs (10 μM) and LPE (1.0 mg·mL−1) had certain antioxidant activities, in which corilagin (E) possessed the best DPPH radical scavenging rate 71.8 ± 0.5% and •OH inhibition rate 75.9 ± 0.3%, and protocatechuic acid (A) exhibited the strongest Fe2+ chelating ability 36.4 ± 0.7%. In vitro cytotoxic tests suggested that LPPs had different effect on A549 cell line, in which corilagin (E) exhibited potent cytotoxicity with an IC50 value of 28.8 ± 1.2 μM. These findings were further confirmed by cell staining experiments.

Comprehensive analysis of the longan transcriptome reveals distinct regulatory programs during the floral transition

BackgroundLongan (Dimocarpus longan Lour.) is an important fruit tree in the subtropical regions of Southeast Asia and Australia. Among the factors affecting D. longan fruit yield, the difficulty and instability of blossoming is one of the most challenging issues. Perpetual flowering (PF) is a crucial trait for fruit trees and is directly linked to production potential. Therefore, studying the molecular regulatory mechanism of longan PF traits is crucial for understanding and solving problems related to flowering. In this study, comparative transcriptome analysis was performed using two longan cultivars that display opposite flowering phenotypes during floral induction.ResultsWe obtained 853.72 M clean reads comprising 125.08 Gb. After comparing these data with the longan genome, 27,266 known genes and 1913 new genes were detected. Significant differences in gene expression were observed between the two genotypes, with 6150 and 6202 differentially expressed genes (DEGs) for ‘SJ’ and ‘SX’, respectively. The transcriptional landscape of floral transition at the early stage was very different in these two longan genotypes with respect to key hormones, circadian rhythm, sugar metabolism, and transcription factors. Almost all flowering-related DEGs identified are involved in photoperiod and circadian clock pathways, such as CONSTANS-like (COL), two-component response regulator-like (APRRs), gigantea (GI), and early flowering (EFL). In addition, the leafy (LFY) gene, which is the central floral meristem identity gene, may inhibit PF formation in ‘SJ’.ConclusionThis study provides a platform for understanding the molecular mechanisms responsible for changes between PF and seasonal flowering (SF) longan genotypes and may benefit studies on PF trait mechanisms of evergreen fruit trees.

The Protein Extraction from Longan Pulp (<i>Dimocarpus longan</i> Lour. cv. Daw) for Proteomic Analysis Using One-Dimensional Electrophoresis

Three procedures for protein extraction in longan pulp had been applied to analyze protein pattern and quality of Longan pulp (Dimocarpus longan Lour. cv. Daw) during fruit growth to increase protein expression in proteomic analysis at Maejo university’s farm. There were data points to compare between normal and physiological disorder syndromes during fruit growth (5,10, 15, 20, 25 and 30 weeks, respectively) by one dimensional electrophoresis (1-D gel) technique in reducing condition. The first protein extraction, M1 (95% ethanol) showed obviously 15 protein bands which molecular weights were 14.97, 17.90, 18.30, 21.63, 28.54, 31, 33.96, 35.02, 42, 51.69, 65.69, 71.54, 88.02, 106.86 and 130 kDa, respectively. While M2 extraction (phenol-methanol/ammonium acetate) and M3 extraction (1.5 mM tris-HCl pH 8.0, 5 mM EDTA, 2% SDS) had low protein expression and no sharpness (13 and 12 protein bands, respectively). In different extraction conditions, therefore, M1 was a suitable method because of highest protein bands and obvious protein expression on longan pulp for proteomic analysis. Proteomic analysis of M1 extraction method was used in protein analysis by using LC-MS / MS techniques. It was found that the heat shock protein 83 (81.0 kDa), a family of proteins that was produced by cells in response to exposure on stressful conditions, the elongation factor 1-alpha (49.45 kDa), a selective regulator of translation, and the peroxidase 4 (39.74 kDa), a protein that is involved in the degeneration or aging of cells. These proteins exhibited a darker appearance of the protein bands at 30 weeks. Moreover, a partial glyceraldehyde-3-phosphate dehydrogenase (34.06 kDa), the protein involved in metabolic processes in glucose degradation, was also founded a darker appearance at 25 weeks and low appearance at 30 weeks of abnormal longan. However, higher proteomic techniques should be studied to confirm this biomarker protein in the further.