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PubMed1999

One type of chalcone synthase gene expressed during embryogenesis regulates the flavonoid accumulation in citrus cell cultures.

To elucidate the relationship between the expression of chalcone synthase (CHS) genes and the production of flavonoid in citrus cell cultures, two cDNA clones encoding CHS were isolated (CitCHS1 and CitCHS2) from the citrus. The accumulation of CitCHS2 mRNA was notably induced by embryogenesis but CitCHS1 mRNA was not. There was no detectable accumulation of flavonoid in the undifferentiated calli, but flavonoid accumulated after the morphological changes to embryoids. These results indicate that two CHS genes differentially expressed during citrus somatic embryogenesis and CitCHS2 may regulate the accumulation of flavonoid in citrus cell cultures.

Acyltransferases↗

PubMed2003

Improvement in growth and salt resistance of lemon (Citrus limon) trees by an interstock-induced mechanism.

Interstocks can reduce toxic ion accumulations in leaves of budded citrus trees, but the mechanism is not understood. We grew sour orange (Citrus aurantium L.; SO) seedlings, budded trees of 'Salustiano' orange (Citrus sinensis L. Osbeck; SAO) on SO, 'Verna' lemon (Citrus limon L. Burm. f; VL/SO) and interstock trees (VL/SAO/SO) in pots of sand watered with nutrient solution containing 5 (control) or 50 mM NaCl (saline treatment) for 12 weeks. Plants were harvested in six successive harvests and time trends in relative growth rate (RGR) and its components were estimated by fitting a Richards function regression to the harvest data. The VL/SAO/SO trees in saline conditions had higher mean RGR than VL/SO trees in control conditions. Increases in both net assimilation rate on a leaf mass basis (NARw) and leaf mass fraction (LMF) contributed equally to a twofold increase in RGR of VL/SAO/SO trees in saline conditions. In control conditions, the increase in RGR caused by the interstock had growth response coefficients of GRC(NARw) = 0.20 and GRC(LMF) = 0.80. Structural modifications-specific leaf area, leaf area ratio and LMF-had a slight influence on the salt-induced changes in RGR, whereas NARw had a large influence. Salinity decreased root mass fraction (RMF) and increased stem mass fraction (SMF). In contrast, the interstock decreased SMF and increased LMF and RMF. The VL/SAO/SO trees had the highest RMF and proportionally higher Cl- and Na+ allocations in roots than the other plant types. In saline conditions, reductions in leaf ion transport rate and dilution of imported ions by foliar growth nearly halved ion accumulations in leaves of VL/SAO/SO trees.

Agriculture↗

PubMed2003

Factors influencing Agrobacterium-mediated embryogenic callus transformation of Valencia sweet orange (Citrus sinensis) containing the pTA29-barnase gene.

Valencia sweet orange (Citrus sinensis (L.) Osbeck) calluses were used as explants to develop a new transformation system for citrus mediated by Agrobacterium tumefaciens. Factors affecting Agrobacterium-mediated transformation efficiency included mode of pre-cultivation, temperature of cocultivation and presence of acetosyringone (AS). The highest transformation efficiency was obtained with a 4-day pre-cultivation period in liquid medium. Transformation efficiency was higher when cocultivation was performed for 3 days at 19 degrees C than at 23 or 28 degrees C. Almost no resistant callus was obtained if the cocultivation medium lacked AS. The transformation procedure yielded transgenic Valencia plants containing the pTA29-barnase gene, as verified by PCR amplification and confirmed by Southern blotting. Because male sterility is a common factor leading to seedlessness in citrus cultivars with parthenocarpic characteristics, production of seedless citrus genotypes by Agrobacterium-mediated genetic transformation is a promising alternative to conventional breeding methods.

Acetophenones↗

PubMed1995

A putative vacuolar processing protease is regulated by ethylene and also during fruit ripening in Citrus fruit.

A putative citrus vacuolar processing thiolprotease cDNA (Cit-vac) was isolated from a cDNA library of Citrus fruits (Citrus sinensis L. Osbeck var Washington navel). The cDNA is 58 and 57% identical with vacuolar processing seed proteases from castor bean and soybean, respectively. The Citvac sequence shows a typical signal peptide for entering into the endoplasmic reticulum and two glycosylation signals. Using an in vitro transcription-translation system, we show that the Citvac precursor is able to enter a microsomal fraction and to undergo proteolytic processing and glycosylation. Transcript levels for the Citvac are developmentally regulated in the flavedo (outer colored part of the fruit peel) and increase during fruit ripening and in the flower during opening. Exogenous treatment with ethylene induces Citvac mRNA expression in both fruits and leaves. Citvac is encoded by one or two genes in the Citrus genome. The possible role of the Citvac gene product during fruit ripening and other ethylene-mediated processes is discussed.

Amino Acid Sequence↗

PubMed1996

Polyembryony in Citrus. Accumulation of seed storage proteins in seeds and in embryos cultured in vitro.

Citrus exhibits polyembryonic seed development, an apomictic process in which many maternally derived embryos arise from the nucellus surrounding the developing zygotic embryo. Citrus seed storage proteins were used as markers to compare embryogenesis in developing seeds and somatic embryogenesis in vitro. The salt-soluble, globulin protein fraction (designated citrin) was purified from Citrus sinensis cv Valencia seeds. Citrins separated into two subunits averaging 22 and 33 kD under denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A cDNA clone was isolated representing a citrin gene expressed in seeds when the majority of embryos were at the early globular stage of embryo development. The predicted protein sequence was most related to the globulin seed storage proteins of pumpkin and cotton. Accumulation of 33-kD polypeptides was first detected in polyembryonic Valencia seeds when the majority of embryos were at the globular stage of development. Somatic Citrus embryos cultured in vivo were observed to initiate 33-kD polypeptide accumulation later in embryo development but accumulated these peptides at only 10 to 20% of the level observed in polyembryonic seeds. Therefore, factors within the seed environment must influence the higher quantitative levels of citrin accumulation in nucellar embryos developing in vivo, even though nucellar embryos, like somatic embryos, are not derived from fertilization events.

Amino Acid Sequence↗

PubMed2006

Impact of citrus soft drinks relative to grapefruit juice on ciclosporin disposition.

AIMS: A recent case report had suggested a citrus soft drink (Sun Drop) may have caused clinically relevant elevations in ciclosporin levels through a grapefruit juice-like mechanism via inactivation of intestinal cytochrome P450 3A4 (CYP3A4). This study was conducted to investigate the effect of grapefruit juice and citrus sodas Sun Drop and Fresca, the latter soda containing 83-fold higher concentration of the proposed CYP3A4 inhibitor bergamottin than Sun Drop, relative to water on oral ciclosporin pharmacokinetics. METHODS: In a randomized four-way crossover study with a washout of at least 1 week, 12 healthy volunteers received a single oral dose of ciclosporin (Neoral) with Sun Drop, Fresca, grapefruit juice and water (control). Each drink (591 ml) was consumed twice on the prior day and three times on the study day. Whole blood concentrations of ciclosporin were measured up to 24 h with a fluorescence polarization immunoassay. RESULTS: Grapefruit juice increased area under the concentration-time curve by 186% (P < 0.0001; 95% confidence interval of mean difference 3302-6240 ng ml h(-1)) and peak concentration by 150% (P < 0.0001) of ciclosporin with a significant decrease in oral clearance of 43% (P < 0.0001) when compared with water. Neither citrus soda altered significantly ciclosporin pharmacokinetic variables; changes in mean values ranged from +/- 3 to 11% of the corresponding water value. CONCLUSION: Although our results do not support a clinically relevant grapefruit juice-like interaction between oral ciclosporin and citrus constituent containing sodas Sun Drop or Fresca, an effect in the setting of chronic ciclosporin therapy cannot be ruled out.

Adult↗

PubMed2006

Primers based on the rpf gene region provide improved detection of Xanthomonas axonopodis pv. citri in naturally and artificially infected citrus plants.

AIMS: To have a PCR-based detection method for Xanthomonas axonopodis pv. citri (Xac) using primers designed in a specific region of its genome. METHODS AND RESULTS: A Xac-specific region was identified inside the rpf gene cluster of strain IAPAR 306 in an analysis of its complete genomic sequence. Two primers were designed, Xac01 and Xac02, which, when used in a standard PCR assay, direct the amplification of a 581 bp fragment from DNA of strains belonging to Xac from different regions around the world including unusual American and Asian strains. This product was not observed when DNA from strains of the closely related X. a. aurantifolli and X. a. citrumelo were used as templates. Extracts prepared from 28 xanthomonads of other species, and epiphytic bacteria isolated from citrus also failed to produce products with these primers. Amplification was obtained from cells grown in vitro, from extracts of both fresh and dried citrus canker lesions and from washes of inoculated but asymptomatic leaf surfaces. In sensitivity tests, this PCR technique detected as few as 100 cells. CONCLUSIONS: Primers Xac01 and Xac02 provide specific and sensitive detection of Xac in all citrus tissues where the pathogen is found. SIGNIFICANCE AND IMPACT OF THE STUDY: This PCR-based diagnostic test is suitable for monitoring asymptomatic plants in areas where the bacteria is endemic, in plant quarantine and regulatory situations, and also for obtaining an accurate diagnosis in a very short time. These are important characteristics for any assay to be used for the management of citrus canker disease.

Bacterial Infections↗

PubMed1995

An evaluation of sequence tagged microsatellite site markers for genetic analysis within Citrus and related species.

Microsatellites, also called sequence tagged microsatellite sites (STMSs), have become important markers for genome analysis but are currently little studied in plants. To assess the value of STMSs for analysis within the Citrus plant species, two example STMSs were isolated from an intergeneric cross between rangpur lime (Citrus x limonia Osbeck) and trifoliate orange (Poncirus trifoliata (L.) Raf.). Unique flanking primers were constructed for polymerase chain reaction amplification both within the test cross and across a broad range of citrus and related species. Both loci showed length variation between test cross parents with alleles segregating in a Mendelian fashion to progeny. Amplification across species showed the STMS flanking primers to be conserved in every genome tested. The traits of polymorphism, inheritance, and conservation across species mean that STMS markers are ideal for genome mapping within Citrus, which contains high levels of genetic variability.

Alleles↗

PubMedDate not supplied

Effects of citrus fragrance on immune function and depressive states.

In our previous experiments on animals evidence was found that citrus fragrance can restore the stress-induced immunosuppression, suggesting that citrus fragrance may have an effect on restoring the homeostatic balance. Since a dysregulation of the neuroendocrine and immune function is thought to be associated with psychosomatic or psychiatric disorders an attempt was made to restore their mental health by stimulation of one of the sensory systems. Fragrance (citrus was our choice) which comforts through stimulation of the olfactory system was applied to depressive patients. It was given to 12 depressive subjects and the results indicated that the doses of antidepressants necessary for the treatment of depression could be markedly reduced. The treatment with citrus fragrance normalized neuroendocrine hormone levels and immune function and was rather more effective than antidepressants.

Adult↗

PubMed2001

Isotope ratio by HRGC-MS of citrus Junos tanaka (yuzu) essential oils: m/z 137/136 of terpene hydrocarbons.

The isotope ratios of monoterpene hydrocarbons in Citrus junos Tanaka (yuzu) essential oils from different origins were determined by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). Both intensities of the molecular mass peaks (m/z 136) and of the isotope peaks (m/z 137) of monoterpene hydrocarbons were measured by single-ion monitoring with an MS analysis. The isotope ratios (m/z 137/136) of the ten monoterpene hydrocarbons commonly contained in citrus essential oils, alpha-pinene, beta-pinene, sabinene, myrcene, alpha-phellandrene, alpha-terpinene, limonene, gamma-terpinene, beta-phellandrene and terpinolene, were determined in yuzu samples of the highest commercial quality from 42 different production districts. Statistical treatment of these data by the t-test and sign test revealed significant differences of the isotope effects in each yuzu sample. It is suggested that this technique will be applicable for evaluating the quality, genuineness and origin of citrus fruits and their products. The isotope fingerprints were also demonstrated in several citrus fruits other than the yuzu samples.

Citrus↗

PubMed2003

Isotope ratio analysis by HRGC-MS of monoterpene hydrocarbons from citrus essential oils.

The isotope ratio of monoterpene hydrocarbons in citrus essential oils of different origins was measured by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). The isotope ratio (Ir) was determined by the ratio of the isotope peak intensity (m/z 137) to the molecular mass peak intensity (m/z 136) of the monoterpene hydrocarbons. The accuracy of Ir was examined by measuring monoterpene hydrocarbon standards and 13C-labeled compounds. The isotope fingerprints based on the values of monoterpene hydrocarbons from lemon, lime and yuzu essential oils were determined. These citrus essential oils were also discriminated by a principal component analysis of their Ir data. The characteristic vectors showed that alpha-terpinene, beta-pinene and beta-phellandrene were important components for distinguishing between the citrus species. It is suggested that this technique will be applicable to evaluate the quality, genuineness and origin of citrus fruits and their products.

Citrus↗

PubMed2004

MS fragment isotope ratio analysis for evaluation of citrus essential oils by HRGC-MS.

To evaluate the origin of citrus essential oils, the isotope ratio of fragment peaks on HRGC-MS of the volatile compounds from various citrus oils was measured. The MS fragment ratio was found by the ratio of fragment peak intensity, m+1/m (m/z). This ratio reflects the isotope effect of volatile compounds, that is, it provides information about locality, quality, and species for essential oils. Multivariate analysis based on the MS fragment ratio of monoterpene hydrocarbons clearly distinguished three citrus species, yuzu, lemon, and lime. The carbonyl fractions were also extracted from citrus essential oils by the sodium hydrogensulfite method. The isotope ratio of MS fragments of octanal, nonanal, and decanal was also examined. The results suggest that there was no significant difference in the individual fragment isotope ratios of the three aldehydes.

Aldehydes↗

PubMed2000

Citrus leafminer (Lepidoptera: Gracillariidae) density: effect on yield of 'Tahiti' lime.

The relationship between damage by citrus leafminer, Phyllocnistis citrella Stainton, and 'Tahiti' lime yield were investigated in a 15-yr-old and a 5-yr-old lime orchard. Citrus leafminer population densities were controlled by insecticide applications of abamectin plus FC 435 oil, abamectin plus FC435 oil plus imidacloprid, and methomyl. The control was not treated. To ensure adequate citrus leafminer densities, adult citrus leafminer were periodically released in the experimental plots during fall and winter. For the 15-yr-old trees, the least amount of leaf area damage occurred in the abamectin plus FC 435 oil plus imidacloprid (1.9%) and the abamectin plus FC435 oil (2.3%) treatments compared with the control treatment (10-21%). In the 5-yr-old orchard, the least amount of leaf area damaged occurred in the abamectin plus FC 435 oil plus imidacloprid (0.4%) and the imidacloprid (0.1%) treatments compared with the control (20.85%). The percentage of leaf area damaged was linearly correlated with the average number of mines per leaf, average mine days, and cumulative mine days in both orchards. In both orchards, the percentage of leaf area damaged and cumulative mine days was linearly correlated with the number of fruit per tree and total fruit weight per tree. Calculating the economic injury levels indicated that 16-23% and 18-85% of leaf area damaged caused significant yield reductions in 15-yr-old and 5-yr-old trees, respectively.

Animals↗

PubMed2005

Nontarget impact of spinosad GF-120 bait sprays for control of the Mexican fruit fly (Diptera: Tephritidae) in Texas citrus.

Bait sprays containing the toxicant spinosad (GF-120) were applied to citrus groves in the Rio Grande Valley of Texas where Mexican fruit flies were detected in surveillance traps. The sprays were applied as a supplement to a continuous sterile insect release program. Sterile fly captures were 47-63% lower in the treated groves compared with control groves. Eight of 10 secondary pest populations declined in the test groves subsequent to spray applications, but they also declined in the control groves, suggesting that the decline was a seasonal phenomenon rather than a result of the bait sprays. Citrus whitefly, Dialeurodes citri (Ashmead), populations increased modestly and citrus blackfly, Aleurocanthus woglumi (Ashby), populations remained unchanged compared with pretreatment levels. Thus, no outbreaks of secondary pests occurred as a result of the spinosad bait sprays in this instance, as has been reported for malathion bait sprays in citrus. The bait sprays had no detectable effect on populations of specific indicator species of parasitoids (including Aphytis spp. and Comperiella bifasciata Howard), or on numbers of beneficial insects in general, in the treated groves.

Animals↗

PubMed2001

Biological properties of citrus flavonoids pertaining to cancer and inflammation.

Citrus flavonoids encompass a diverse set of structures, including numerous flavanone and flavone O- and C-glycosides and methoxylated flavones. Each of these groups of compounds exhibits a number of in vitro and in vivo anti-inflammatory and anticancer actions. These biological properties are consistent with their effects on the microvascular endothelial tissue. Evidence suggests that the biological actions of the citrus flavonoids are possibly linked to their interactions with key regulatory enzymes involved in cell activation and receptor binding. The citrus flavonoids show little effect on normal, healthy cells, and thus typically exhibit remarkably low toxicity in animals. The citrus flavonoids extend their influence in vivo through their induction of hepatic phase I and II enzymes, and through the biological actions of their metabolites. Evidence clearly indicates to the potential health promoting properties of these dietary compounds.

Animals↗

PubMed2003

Quantitative determination of sugars and myo-inositol in citrus fruits grown in Japan using high-performance anion-exchange chromatography.

Fifteen commercial samples of citrus fruits grown in Japan were analyzed for their sugar contents by high-performance anion-exchange chromatography (HPAEC) and electrochemical detection (ED) coupled with a stationary phase D10 column prepared using chloromethylated styrene-divinylbenzene copolymer and N,N,N',N'-tetramethyldiaminodecane. Myo-inositol, glucose, fructose, and sucrose in all of these various citrus fruits could be successfully separated within 25 min using 0.5 M NaOH eluent at a flow-rate of 0.4 mL/min. Myo-inositol, as a better nutritional source, was found in all the citrus fruits grown in Japan (0.7 +/- 0.04-2.1 +/- 0.2 g/L). The sugar contents of twelve citrus fruits grown in other countries were also determined.

Carbohydrates↗

PubMedDate not supplied

Effects of citrus phytochemicals on liver and lung cytochrome P450 activity and on the in vitro metabolism of the tobacco-specific nitrosamine NNK.

NNK is a potent environmental carcinogen to which both smokers and nonsmokers are exposed. The response to NNK may be affected by factors including nutrition. We investigated the effects of five citrus phytochemicals on the in vitro metabolism of the tobacco-specific nitrosamine NNK and on the dealkylation of methoxyresorufin (MROD) and pentoxyresorufin (PROD) in liver and lung microsomes of the Syrian golden hamster. In the NNK metabolism experiments in vitro incubations contained 3 microCi [5-H3] NNK, 0.5 mg microsomal protein and 0.5 mumole of the citrus phytochemical diosmin, naringin, naringenin, quercetin or rutin. In the dealkylation studies incubations contained 0.5 microM methoxyresorufin or pentoxyresorufin, 0.5 mg microsomal protein and 0.5 mumole of citrus phytochemical. The major NNK metabolism pathway in hamster liver microsomes was NNK-reduction while in lung microsomes it was alpha-hydroxylation. The alpha-hydroxylation pathway produces metabolic products that methylate and pyridyloxobutylate DNA. Naringenin, a metabolite of naringin, and quercetin were the most potent inhibitors of alpha-hydroxylation of NNK in both liver and lung microsomes. This inhibition correlated with a potent inhibition of MROD and PROD activity in liver but not in lung microsomes. The metabolic activation of NNK is associated with cytochrome P450 isoforms 1A1, 1A2, 2B1, 2D6 and 2E1. Our results suggest that naringenin and quercetin from citrus fruits inhibit the activity of cytochrome P450 (CYP) isoforms that activate NNK and may afford protection against NNK-induced carcinogenesis.

Animals↗

PubMed2002

Analysis of sucrose synthase genes in citrus suggests different roles and phylogenetic relationships.

The purpose of this work was 2-fold; first, a molecular/evolutionary characterization of three sucrose synthase genes from citrus, and second, an analysis of their differential expression related to potential physiological function. Three non-allelic genes (CitSUS1, CitSUSA and CitSUS2) encoding sucrose synthase were isolated from citrus fruit (Citrus unshiu Marc.). Phylogenetic analysis from the deduced amino acid sequences showed that CitSUS1 and CitSUS2 could be classified into a dicot group. However, CitSUSA, together with Arabidopsis SSA, sugar beet SS and pea SusA defined another dicot group designated SUSA. Unlike other dicot sucrose synthases, these show a distinctive, monocot-like arrangement of introns and exons. The CitSUS1 and CitSUSA were also differentially expressed in leaf, flower and fruit tissues. Contrasting expression patterns were observed for CitSUS1 and CitSUSA in edible tissue (juice sacs/segment epidermis) and peel tissue (albedo/flavedo) of fruit: CitSUS1 mRNA levels decreased throughout fruit development, whereas those of CitSUSA increased. Various sugars also influenced the transcript levels of the CitSUS1 and CITSUSA: These results indicate that the CitSUS1 and CitSUSA genes for sucrose synthase in citrus differ markedly in their molecular structure and potential physiological roles. Sucrose synthase activity in edible tissue was high in the early stages and decreased until mid-develoment, then rapidly increased during maturation. The increase in activity during maturation paralleled that of sucrose accumulation. This result suggests that sucrose synthase has important roles on sugar metabolism when sucrose is accumulated in fruit.

Citrus↗