Kumquat Fruit Research Articles

Transient Expression Assay and Microscopic Observation in Kumquat Fruit.

Citrus fruits encompass a diverse family, including oranges, mandarins, grapefruits, limes, kumquats, lemons, and others. In citrus, Agrobacterium tumefaciens-mediated genetic transformation of Hongkong kumquat (Fortunella hindsii Swingle) has been widely employed for gene function analysis. However, the perennial nature of woody plants results in the generation of transgenic fruits taking several years. Here, we show the procedures of Agrobacterium-mediated transient transformation and live-cell imaging in kumquat (F. crassifolia Swingle) fruit, using the actin filament marker GFP-Lifeact as an example. Fluorescence detection, western blot analysis, and live-cell imaging with confocal microscopy demonstrate the high transformation efficiency and an extended expression window of this system. Overall, Agrobacterium-mediated transient transformation of kumquat fruits provides a rapid and effective method for studying gene function in fruit, enabling the effective observation of diverse cellular processes in fruit biology.

A natural mutant kumquat fruit with abnormal oil glands shows lower volatile production, better fruit flavor and higher resistance to postharvest disease

Oil glands of citrus peel are known sites for synthesis and deposition of volatile organic compounds (VOCs). However, it is unclear how oil glands and VOCs affect fruit flavor and postharvest disease resistance in vivo. Here, we report characterization of a natural mutant ‘Huapi’ (HP) kumquat (Fortunella crassifolia Swingle) compared with its wild progenitor ‘Rongan’ (RA). HP fruit decreased in both size and number of oil glands from the onset of fruit development when compared to RA. The total VOCs concentration and the number of individual VOCs in mature HP fruit were lower than that in RA. Limonene, α-pinene and β-myrcene concentrations showed the greatest reduction (30-, 21- and 20-fold). Sensory evaluation showed that flavor of HP fruit was more acceptable to consumers compared to that of RA. Sweeter, less acidic features of HP fruit were likely due to higher soluble sugars content and lower organic acid content, respectively. Changes in HP fruit VOCs likely contribute to its less pungent and better aroma features. HP fruit displayed stronger resistance to the fungal pathogens Penicillium italicum and Geotrichum candidum compared to RA in in vivo inoculation experiments. Transcriptomic analysis and qPCR validation indicated that FcERF096, FcCHI, FcCXE, FcPi21L1, FcPi21L2, FcPIP and FcXYLL potentially involve in enhanced disease resistance of HP fruit. Taken together, these results reveal the potential of oil glands and terpenes in affecting fruit sensory attributes and postharvest disease resistance in planta in kumquat, providing new insights into the technologies improving these important traits in citrus.

Determination, Quality, and Health Assessment of Pesticide Residues in Kumquat in China.

Pesticide residues in kumquat fruits from China, and the quality and chronic/acute intake risks in Chinese consumers, were assessed using the QuEChERS procedure and UHPLC-MS/MS and GC-MS/MS methods. Our 5-year monitoring and survey showed 90% of the 573 samples of kumquat fruits collected from two main production areas contained one or multiple residual pesticides. Overall, 30 pesticides were detected, including 16 insecticides, 7 fungicides, 5 acaricides, and 2 plant growth modulators, of which 2 pesticides were already banned. Two or more residual pesticides were discovered in 81% of the samples, and pesticide residues in 9.4% of the samples surpassed the MRLs, such as profenofos, bifenthrin, triazophos, avermectin, spirodiclofen, difenoconazole, and methidathion. The major risk factors on the safety of kumquat fruits before 2019 were profenofos, bifenthrin, and triazophos, but their over-standard frequencies significantly declined after 2019, which was credited to the stricter supervision and management policies by local governments. Despite the high detection rates and multi-residue occurrence of pesticides in kumquat fruits, about 81% of the samples were assessed as qualified. Moreover, the accumulative chronic diet risk determined from ADI is very low. To better protect the health of customers, we shall formulate stricter organic phosphorus pesticide control measures and stricter use guidelines, especially for methidathion, triazophos, chlorpyrifos, and profenofos. This study provides potential data for the design of kumquat fruit quality and safety control guidelines and for the reduction in health risks to humans.

Comparative analysis of the crystal morphology, chemical composition and key gene expression between two kumquat fruit cuticular waxes during postharvest cold storage

Waxes have an important protective role in the postharvest storage potential of fruit. However, there are few studies in which the waxes of fruit of kumquat cultivars have been analysed. In this work, the fruit of a kumquat mutant with a relatively thin skin ('Huapi' kumquat, HPK) was found to present lower fruit weight loss and decay during cold storage than the fruit of the control ('Rongan' kumquat, RAK) did. Scanning electron microscopy observations revealed the epicuticular wax crystals on the HPK fruit were more abundant and larger than those on the RAK fruit at harvest. Gas chromatography-mass spectrometry analysis showed the amounts of total wax, triterpenoids and most of the aliphatic wax fractions on the HPK fruit were much higher than those on the RAK fruit throughout the cold storage process. Correlation analysis showed that differences in amounts of fatty acids and aldehydes might be key factors responsible for the differences in the postharvest traits between the two kumquat cultivars. Additionally, the real-time quantitative RT-PCR analysis results indicated that 12 genes involved in wax synthesis, transport and transcription were considered to play important roles in regulating the wax formation of kumquat fruit during cold storage.

CsMYB15 positively regulates Cs4CL2-mediated lignin biosynthesis during juice sac granulation in navel orange.

'Lane Late', a late-maturing navel orange cultivar, is mainly distributed in the Three Gorges Reservoir area, which matures in the late March of the next year and needs overwintering cultivation. Citrus fruit granulation is a physiological disorder, which is characterized by lignification and dehydration of juice sac cells, seriously affecting the commercial value of citrus fruits. The pre-harvest granulation of late-maturing navel orange is main caused by low temperature in the winter, but its mechanism and regulation pattern remain unclear. In this study, a SG2-type R2R3-MYB transcription factor, CsMYB15, was identified from Citrus sinensis, which was significantly induced by both juice sac granulation and low temperature treatment. Subcellular localization analysis and transcriptional activation assay revealed that CsMYB15 protein was localized to the nucleus, and it exhibited transcriptional activation activity in yeast. Over-expression of CsMYB15 by stable transformation in navel orange calli and transient transformation in kumquat fruits and navel orange juice sacs significantly increased lignin content in the transgenic lines. Further, Yeast one hybrid, EMSA, and LUC assays demonstrated that CsMYB15 directly bound to the Cs4CL2 promoter and activated its expression, thereby causing a high accumulation of lignin in citrus. Taken together, these results elucidated the biological function of CsMYB15 in regulating Cs4CL2-mediated lignin biosynthesis, and provided novel insight into the transcriptional regulation mechanism underlying the juice sac granulation of late-maturing navel orange.

Flexible strain sensor with a hat-shaped structure for in situ measurement of 3D deformation

Flexible strain sensors that are currently available are mainly used in human motion recognition and medical health detection applications, and there is still an urgent need for sensors to realize real-time monitoring of the 3D deformation of industrial and agricultural products. In this work, a flexible strain sensor with a hat-shaped structure was fabricated using a molding technique to perform in situ measurement of 3D deformation. An algorithm for resistance change detection and linear calibration equations were proposed to enable analysis of the deformation data and calculation of local shape changes. The sensor was applied to monitor the growth deformation of a kumquat fruit, and the results were highly consistent with the algorithm. The proposed technique has great potential for application to 3D deformation detection of flexible objects.

Differential regulation of red light- and ethephon-induced degreening in postharvest kumquat fruit

Peel color is closely associated with the commercial value of citrus fruit. In early market or tropical regions, citrus fruit often show non-uniform coloration, which requires degreening practice at post-harvest stage. Here, we studied the degreening effect of red LED light, ethephon, and their combination treatment on kumquat fruit. Both red LED light and ethephon promoted fruit degreening, causing ultrastructural changes of chloroplasts accompanied by chlorophyll degradation. Transcriptome analysis revealed metabolic reprogramming in chloroplasts but the way how genes responded to red LED light and ethephon were remarkably different. Transient expression in Nicotiana benthamiana suggested that FcrCLH, FcrPPH and FcrSGR genes were potentially key factors in regulation of fruit degreening. Furthermore, red LED light promoted the catabolism of chloroplast components in vitro. This study provides novel insights into the molecular mechanism of fruit degreening and unravels an efficient practice for future post-harvest management of citrus fruit.

Physiochemical and nutritional evaluation of whole kumquat fruits powder and its protective effect on thyroid hormones and blood sugar levels in diabetic rats.

The present study was conducted to evaluate the chemical composition, antioxidant activity and hypoglycemic effects of whole kumquat (Ku) powder in diabetic rats fed a high-fat-high-cholesterol (HFHC) diet. The antioxidant activities were evaluated using stable 1,1-diphenyl 2-picrylhydrazyl (DPPH) free radical scavenging method, 2,2´-azinobis (3-ethyl benzo thiazoline-6-sulphonic acid) radical cation (ABTS) and Ferric reducing antioxidant power (FRAP). Total phenolic content was (51.85 mg GAE/g) and total flavonoid content was (0.24 mg Cateachin Equivalent, CE/g). DPPH and ABTS values were 3.32 and 3.98 mg Trolox equivalent (TE)/g where FRAP value was 3.00 mM Fe2+/kg dry material. A total of 90 albino rats were used in the present study. Rats group were as follows: normal diet; normal treated (2, 4, and 6% Ku.), diabetic rats (non-treated), diabetic + HFHC diet (non-treated), HFHC (non-treated), Diabetic (treated), HFHC (treated) and Diabetic + HFHC (treated). The diets were followed for 8 weeks. Blood samples were collected at the end of the experiment. Serum glucose was recorded and thyroid hormones (T4, Thyroxine and T3, Triiodothyronine) were conducted. Diet supplemented with Kumquat at different concentrations have a hypoglycemic effect and improve the thyroid hormones of both diabetic rats and HFHC diabetic rats.

Combining BN-PAGE and microscopy techniques to investigate pigment-protein complexes and plastid transitions in citrus fruit

BackgroundChlorophyll and carotenoids, the most widely distributed lipophilic pigments in plants, contribute to fruit coloration during development and ripening. These pigments are assembled with pigment-protein complexes localized at plastid membrane. Pigment-protein complexes are essential for multiple cellular processes, however, their identity and composition in fruit have yet to be characterized.ResultsBy using BN-PAGE technique in combination with microscopy, we studied pigment-protein complexes and plastid transformation in the purified plastids from the exocarp of citrus fruit. The discontinuous sucrose gradient centrifugation was used to isolate total plastids from kumquat fruit, and the purity of isolated plastids was assessed by microscopy observation and western blot analysis. The isolated plastids at different coloring stages were subjected to pigment autofluorescence observation, western blot, two-dimensional electrophoresis analysis and BN-PAGE assessment. Our results demonstrated that (i) chloroplasts differentiate into chromoplasts during fruit coloring, and this differentiation is accompanied with a decrease in the chlorophyll/carotenoid ratio; (ii) BN-PAGE analysis reveals the profiles of macromolecular protein complexes among different types of plastids in citrus fruit; and (iii) the degradation rate of chlorophyll-protein complexes varies during the transition from chloroplasts to chromoplasts, with the stability generally following the order of LHCII > PS II core > LHC I > PS I core.ConclusionsOur optimized methods for both plastid separation and BN-PAGE assessment provide an opportunity for developing a better understanding of pigment-protein complexes and plastid transitions in plant fruit. These attempts also have the potential for expanding our knowledge on the sub-cellular level synchronism of protein changes and pigment metabolism during the transition from chloroplasts to chromoplasts.

Effect of bifenthrin application at different maturity stages on its dissipation and residues in kumquat (Citrus japonica) and dietary intake risk assessment.

Bifenthrin is a pyrethroid pesticide widely used on kumquats, but the residues in the peel and pulp after bifenthrin application at different maturity stages of kumquats have not been evaluated. This study developed a simple and rapid high-performance liquid chromatography (HPLC) method for the quantitative analysis of bifenthrin residues in whole fruit, kumquat peel, kumquat pulp, and soil. The results showed that regardless of whether bifenthrin was applied one or three times during the near-mature period, the half-lives of the fruit peel and fruit pulp were longer than those in the immature period. Kumquat fruit residues decreased with time at both maturity levels. The residues of bifenthrin in near-mature fruit exceeded the MRL in Guangxi and Fujian 14days after the three applications of bifenthrin, suggesting that this issue should be focused on in kumquat production and supervision. However, for bifenthrin application in either the near-mature or the immature fruit period, the calculated risks for chronic dietary intake of kumquat were well below 100%. The data demonstrate that the chronic dietary intake risk of bifenthrin through kumquat consumption is low and within acceptable limits. These results provide a reference and risk assessment data for the safe and rational use of bifenthrin insecticides.

Functional Characterization of a Flavone Synthase That Participates in a Kumquat Flavone Metabolon.

Flavones predominantly accumulate as O- and C-glycosides in kumquat plants. Two catalytic mechanisms of flavone synthase II (FNSII) support the biosynthesis of glycosyl flavones, one involving flavanone 2-hydroxylase (which generates 2-hydroxyflavanones for C-glycosylation) and another involving the direct catalysis of flavanones to flavones for O-glycosylation. However, FNSII has not yet been characterized in kumquats. In this study, we identified two kumquat FNSII genes (FcFNSII-1 and FcFNSII-2), based on transcriptome and bioinformatics analysis. Data from in vivo and in vitro assays showed that FcFNSII-2 directly synthesized apigenin and acacetin from naringenin and isosakuranetin, respectively, whereas FcFNSII-1 showed no detectable catalytic activities with flavanones. In agreement, transient overexpression of FcFNSII-2 in kumquat peels significantly enhanced the transcription of structural genes of the flavonoid-biosynthesis pathway and the accumulation of several O-glycosyl flavones. Moreover, studying the subcellular localizations of FcFNSII-1 and FcFNSII-2 demonstrated that N-terminal membrane-spanning domains were necessary to ensure endoplasmic reticulum localization and anchoring. Protein–protein interaction analyses, using the split-ubiquitin yeast two-hybrid system and bimolecular fluorescence-complementation assays, revealed that FcFNSII-2 interacted with chalcone synthase 1, chalcone synthase 2, and chalcone isomerase-like proteins. The results provide strong evidence that FcFNSII-2 serves as a nucleation site for an O-glycosyl flavone metabolon that channels flavanones for O-glycosyl flavone biosynthesis in kumquat fruits. They have implications for guiding genetic engineering efforts aimed at enhancing the composition of bioactive flavonoids in kumquat fruits.

Two Dof transcription factors promote flavonoid synthesis in kumquat fruit by activating C-glucosyltransferase

Although DNA binding with one finger (Dof) constitutes a crucial plant-specific family of transcription factors (TFs) that plays important roles in a wide range of biological processes, the molecular mechanisms underlying Dof regulation of flavonoid biosynthesis in plants remain largely unknown. Here, we characterized 28 Dof genes (FhDof1-FhDof28) from the ‘Hongkong’ kumquat (Fortunella hindsii) cultivar genome. Promoter analysis and transcriptome profiling revealed that four FhDofs — FhDof4, FhDof9, FhDof15, and FhDof16 — may be involved in flavonoid biosynthesis through binding to the flavonoid C-glycosyltransferase (FhCGT) promoter. We cloned homologous genes of four FhDofs, designated as FcDof4, FcDof9, FcDof15, FcDof16, and a homologous gene of FhCGT, designated as FcCGT, from the widely cultivated ‘HuaPi’ kumquat (F. crassifolia). Quantitative reverse transcription-polymerase chain reaction analysis revealed that FcDof4 and FcDof16 were significantly correlated with FcCGT expression during development stages in the ‘HuaPi’ fruit (Pearson’s correlation coefficient > 0.7) and were localized to the nucleus. Results of yeast one-hybrid, electrophoretic mobility shift, and dual-luciferase assays indicated that the two FcDofs trigger FcCGT expression by specifically binding to its promoters. Moreover, transient overexpression of FcDof4 and FcDof16 enhances the transcription of structural genes in the flavonoid biosynthetic pathway and increases C-glycosylflavonoid content. Our results provide strong evidence that the TFs FcDof4 and FcDof16 promote flavonoid synthesis in kumquat fruit by activating FcCGT expression.

Kumquat fruit and leaves extracted with different solvents: phenolic content and antioxidant activity

Introduction. Kumquat is a good source of vitamin C, as well as phenolic and flavonoid substances. In this study, we used various solvents to obtain extracts from fresh and lyophilized dried fruits and leaves of kumquat plant, as well as six mutants, to compare their total phenolic and flavonoid contents and antioxidant activities.
 Study objects and methods. The total phenolic and flavonoid content was determined by the Folin-Ciocalteu method and the colorimetric method, respectively. The antioxidant capacities of the extracts were determined by commonly used antioxidant tests, such as the DPPH radical scavenging activity, reducing power, and metal chelating activity.
 Results and discussion. The total phenolic content of the extracts was in the range of 3705–86 329 mg GAE/g extract. The total amount of flavonoid substance ranged from 5556 to 632 222 mg QUE/g extract. The highest free radical scavenging activity was observed in the kumquat leaves. We also found that the activity of dried fruit was lower than that of fresh fruit. According to our results, the differences in the phenolic contents of the studied plants affected their antioxidant properties. We determined that the extracts with a high phenolic content showed high antioxidant activity. No significant difference was detected between the rootstock kumquat type and its mutants. Finally, we found no chelating activity in the extracts obtained from fresh and lyophilized dried fruits.
 Conclusion. Kumquat fruit and its leaves can be considered as functional foods due to phenolic compounds, which are able to neutralize free radicals.

Procjena nutritivnog potencijala i sadržaj specijaliziranih metabolita nekih vrsta agruma

The aim of this study was to assess the nutritional composition of fruits of some citrus species (sweet orange, grapefruit, clementine and kumquat) and to determine their basic physicochemical parameters, bioactive compounds content, and antioxidant capacity. According to the analyzed data, kumquat fruits had the highest dry matter content (18.71%) and total acid content (3.08%), while the highest values of total soluble solids (13.41%), pH value (3.92), vitamin C (53.69 mg/100 g FW), total phenols (162 mg GAE/100 g FW), β-carotene (1053.17 μg/100 g FW), and antioxidant capacity (1.70 mmol TE/kg) were determined in clementine fruits. Considering the nutritional composition of citrus fruits, it can be concluded that they are a rich source of various bioactive compounds, especially vitamin C, carotenoids, and polyphenols, and are characterized by their high antioxidant capacity, which is important for health. Moreover, the cultivation of citrus fruits is an important factor in the Croatian economy, which should be promoted in the future, and the potential of the southern part of Croatia for the cultivation of these citrus fruits should be exploited to the maximum.

Postharvest Treatment Comparison and Quality Analysis of Kumquat Fruit Under Cold Storage Transport Simulation Conditions

Postharvest Treatment Comparison and Quality Analysis of Kumquat Fruit Under Cold Storage Transport Simulation Conditions

Red light-induced kumquat fruit coloration is attributable to increased carotenoid metabolism regulated by FcrNAC22.

Carotenoids play vital roles in the coloration of plant tissues and organs, particularly fruits; however, the regulation of carotenoid metabolism in fruits during ripening is largely unknown. Here, we show that red light promotes fruit coloration by inducing accelerated degreening and carotenoid accumulation in kumquat fruits. Transcriptome profiling revealed that a NAC (NAM/ATAF/CUC2) family transcription factor, FcrNAC22, is specifically induced in red light-irradiated fruits. FcrNAC22 localizes to the nucleus, and its gene expression is up-regulated as fruits change color. Results from dual luciferase, yeast one-hybrid assays and electrophoretic mobility shift assays indicate that FcrNAC22 directly binds to, and activates the promoters of three genes encoding key enzymes in the carotenoid metabolic pathway. Moreover, FcrNAC22 overexpression in citrus and tomato fruits as well as in citrus callus enhances expression of most carotenoid biosynthetic genes, accelerates plastid conversion into chromoplasts, and promotes color change. Knock down of FcrNAC22 expression in transiently transformed citrus fruits attenuates fruit coloration induced by red light. Taken together, our results demonstrate that FcrNAC22 is an important transcription factor that mediates red light-induced fruit coloration via up-regulation of carotenoid metabolism.

Effect of dried kiwi and kumquat fruits against azathioprine induced liver toxicity in male albino rats

Effect of dried kiwi and kumquat fruits against azathioprine induced liver toxicity in male albino rats

Selection of Natural Fruit Ingredients for the Production of Wine Cocktails with High Organoleptic Properties

The aim of the research is to identify and select natural fruit ingredients for the production of wine cocktails with high organoleptic properties via investigating the chemical and organoleptic indices of the produced cocktails. Dried apricots and kumquat fruits have been selected as fruit ingredients. They have been mixed with the dry white wine materials with the doses of 10 g/dm3 and 20 g/dm3 respectively.

Drying Effects on The Volatile Compounds of Kumquat, Limequat and Mexican Lime Fruits

: Citrus fruits are cultivated and used as fresh fruits or for the production of juices Worldwide. These fruits are of great interest as raw materials for pharmaceutical, cosmetics and food industries due to their aromatic properties. Residues of the production of citrus juice, such as peels, membranes and seeds, possess a large variety of phytochemicals. In this study, it was aimed to prepare whole fruit powders of kumquat, limequat (a bigeneric hybrid) and Mexican lime excluding the seeds. The volatile compound profiles were determined by microdistillation. The cultivated mature fruits were harvested from Adana, Turkey in December 2017. Heat-treated or fresh mature fruits were freeze-dried. Then, each sample was pulverized in a blender and passed through a 100 μ sieve to obtain powders. Each sample was subjected to microdistillations. The volatile compounds were analyzed using GC-FID and GC-MS, simultaneously. Limonene was found to be the major component in all the samples.

Effects of pre-harvest gibberellic acid spray on endogenous hormones and fruit quality of kumquat (Citrus japonica) fruits

ABSTRACT Gibberellic acid (GA3) is important in plant growth, development, ripening, and senescence. In the present study, we evaluated the effect of pre-harvest GA3 application on the maintenance of postharvest fruit quality in kumquat (Citrus japonica). On-tree fruits were sprayed with 20 mg/L GA3. Unsprayed harvested fruit stored at 6 °C were used as the control. The contents of indoleacetic acid, GA3, and zeatin ribosides in the GA3-sprayed fruits were significantly higher than those in the control, while the contents of both abscisic acid and titratable acid in sprayed fruits were lower than those in the control. Regarding peel colour, GA3 treatment resulted in a lower decrease in hue angle value, with a slow increase in citrus colour index and browning index. Additionally, GA3 treatment inhibited the accumulation of malondialdehyde. In conclusion, pre-harvest application of GA3 may represent a novel strategy for the preservation of fruits on trees, by maintaining nutritional quality and prolonging the postharvest life of kumquat fruits.