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PubMed2002

Determination of the pesticide napropamide in soil, pepper, and tomato by micelle-stabilized room-temperature phosphorescence.

A selective and sensitive method for determining napropamide by room-temperature phosphorescence in SDS micelles is proposed and applied to the determination of this substance in a technical formulation and in spiked soil, pepper, and tomato samples. The use of phosphorescence enhancers such as sodium dodecyl sulfate (micellar agent), thallium (I) nitrate (external heavy atom), and sodium sulfite (deoxygenation agent) was studied and optimized to obtain maximum sensitivity. The determination was performed in 66 mM SDS, 30 mM thallium (I) nitrate, and 8 mM sodium sulfite. Taking into account both maximum phosphorescence intensity and the time required to reach that, a pH value of 7.2 was selected. After the samples were left standing at room temperature for 10 min, the phosphorescence was totally developed. The intensity was then measured at lambda(ex) = 282 nm and lambda(em) = 528 nm. The calibration graph was linear for 50-600 ng mL(-1) napropamide. The detection limit, according to the error propagation theory, was 16 ng mL(-1). The method has been demonstrated for the analysis of soils, peppers, and tomatoes, but, because of matrix interference, the method of standard additions was applied to determine napropamide in the vegetable samples. Recoveries from all these matrixes of added napropamide were near 100%.

Calibration↗

PubMed2004

Differences in the volatile components and their odor characteristics of green and ripe fruits and dried pericarp of Japanese pepper (Xanthoxylum piperitum DC.).

The essential oils of green and ripe fruits and dried pericarp of Japanese pepper (Xanthoxylum piperitum DC.), which are commonly used in Japanese dishes as spices, were extracted with methanol, followed by adsorption to Porapak Q resin. Their aroma profiles were characterized by a sensory evaluation, and their chemical constituents were investigated by using gas chromatography (GC), gas chromatography-mass spectrometry, and aroma extract dilution analysis. Geraniol, citronellal, linalool, and methyl cinnamate were perceived to be important to the basic flavor of the three samples of Japanese pepper by GC-sniffing at high flavor dilution (FD) factors. Monoterpene hydrocarbons constituting almost 76% of the essential oil are the major flavor compounds in the green fruit, and the stronger green and pine leaf notes in the green fruit were considered to be imparted mainly by the large amount of d-limonene, beta-phellandrene, and myrcene due to their high FD factors. On the other hand, the oxygenated terpenes including citronellal, geraniol, and geranial are predominant for the potent odorant in the ripe fruit. The marked citrus-like note in the ripe fruit was thought to be due to the amounts of geranial and citronellal, being 20% of the essential oil. In the dried pericarp, the ratio of oxygenated terpenoids was almost equal to that of monoterpene hydrocarbons. These seemed to induce the flavor character of the dried pericarp to be milder than that of the ripe fruit.

Chromatography, Gas↗

PubMed2004

Identification and synthesis of 2-heptanethiol, a new flavor compound found in bell peppers.

2-Heptanethiol was identified for the first time as a constituent of red and green bell pepper extracts. The chemical structure of this new aroma compound was proposed on the basis of mass spectra and retention indices and confirmed by chemical synthesis and nuclear magnetic resonance spectroscopy measurements. Its aroma properties were described as sulfury, onion-like, and vegetable-like, reminiscent of bell pepper at lower concentrations, with an orthonasal detection threshold of 10 microg/L of water. No differences in odor note and threshold value were observed for the enantiomeric forms, which were prepared from enantiopure 2-heptanol by tosylation, followed by thioacetylation and reduction, giving the target thiol enantiomers.

Capsicum↗

PubMed2005

Electron beam ionization induced oxidative enzymatic activities in pepper (Capsicum annuum L.), associated with ultrastructure cellular damages.

Mature green pepper fruits (Capsicum annuum L.) were subjected to ionizing radiation, in the range of 1-7 kGy, with accelerated electrons. Ultrastructural changes by electron microscopy, and the activity of several oxidative metabolism-related enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaicol peroxidase (POX), and lipoxygenase (LOX), were determined in pericarp tissue just after the ionization treatment and during postionization storage at 7 degrees C followed by 3 days at 20 degrees C. Changes in oxidative stress during the ionization treatment was assessed by the accumulation of malondyaldehide (MDA), a lipid peroxidation product. The ionization induced modifications in the cell ultrastructure, a moderate separation of the plasma membrane from the cell wall being observed for all doses. At 5 and 7 kGy, peroxisomes were not detected and the structures of the chloroplast and vacuoles were seriously damaged. Lipid peroxidation and lipoxygenase activity increased with the ionization dose, staying constant and decreasing, respectively, during the storage period. Conversely, catalase, ascorbate peroxidase, and superoxide dismutase had lower values than in nonionized fruits and, in general, their values did not change or diminished slightly from the seventh day of storage. Peroxidase exhibited an increase in activity with the ionization dose, although these was not a linear relationship, with higher values at 3kGy. Ionization of pepper, especially at doses of 5 and 7 kGy, caused a significant oxidative damage in the fruit, since it increased oxidation and decreased the antioxidant enzymatic defense systems causing ultrastructural changes at cell level.

Ascorbate Peroxidases↗

PubMed2006

Pressurized liquid extraction of capsaicinoids from peppers.

A method has been developed for the extraction of capsaicinoids from peppers by pressurized liquid extraction (PLE); these compounds are determined by reverse phase high-performance liquid chromatography (HPLC), with detection by fluorescence spectrophotometry and mass spectrometry (MS). The stability of capsaicin and dihydrocapsaicin has been studied at different temperatures (50-200 degrees C), and several extraction variables have been assayed: solvent (methanol, ethanol, and water), different percentages of water in the methanol (0-20%) and in the ethanol (0-20%), and the number of extraction cycles. The study has evaluated the repeatability (RSD < 7%) and the reproducibility (RSD < 7%) of the method. Finally, the PLE method developed has been applied to quantify the capsaicinoids present in three varieties of hot peppers cultivated in Spain, quantifying five capsaicinoids: nordihydrocapsaicin, capsaicin, dihydrocapsaicin, an isomer of dihydrocapsaicin, and homodihydrocapsaicin.

Capsaicin↗

PubMed2006

Three-year comparison of the content of antioxidant microconstituents and several quality characteristics in organic and conventionally managed tomatoes and bell peppers.

Understanding how the environment and production and cultivation practices influence the composition and quality of food crops is fundamental to the production of high-quality nutritious foods. In this 3-year study, total phenolics, percent soluble solids, ascorbic acid, and the flavonoid aglycones quercetin, kaempferol, and luteolin were measured in two varieties of tomato (Lycopersicon esculentum L. cv. Ropreco and Burbank) and two varieties of bell peppers (Capsicum annuum L. cv. California Wonder and Excalibur) grown by certified organic and conventional practices in a model system. Significantly higher levels of percent soluble solids (17%), quercetin (30%), kaempferol (17%), and ascorbic acid (26%) were found in Burbank tomatoes (fresh weight basis; FWB), whereas only levels of percent soluble solids (10%) and kaempferol (20%) were significantly higher in organic Ropreco tomatoes (FWB). Year-to-year variability was significant, and high values from 2003 influenced the 3-year average value of quercetin reported for organic Burbank tomatoes. Burbank tomatoes generally had higher levels of quercetin, kaempferol, total phenolics, and ascorbic acid as compared to Ropreco tomatoes. Bell peppers were influenced less by environment and did not display cropping system differences.

Antioxidants↗

PubMed1999

Change in the carotenoid and antioxidant content of spice red pepper (paprika) as a function of ripening and some technological factors.

A study was conducted to investigate the change in quality attributes of red pepper (paprika) (Capsicum annuum L. var. Km-622) as a function of ripening and some technological factors. Of quality attributes, carotenoids and bioantioxidants (ascorbic acid and tocopherols) have been studied. It was found that the dynamics of fruit ripening with regard to carotenoids and bioantioxidants was influenced to a considerable extent by weather conditions of the production season. A rainy and cool season yielded fruits with more beta-carotene but less diesters of red xanthophylls as compared to those produced in a relatively dry and warm season. The ripening stage at harvest was found to affect the quality of paprika. Harvest at unripe stages (color break or faint red) resulted in a high accumulation of dehydroascorbic acid in the overripe fruits, whereas de novo biosynthesis of carotenoids and tocopherols was partially retarded. Application of pre-drying centrifugation resulted in a marked loss of ascorbic acid, and as a consequence, carotenoid stability was impaired during the storage of ground paprika. Sugar caramelization caused dry pods and ground paprika to retain more pigments and tocopherol as compared to those from control or centrifuged red pepper samples. During the storage of ground paprika, color stability was improved by grinding the seeds with the pericarp.

Antioxidants↗

PubMed1998

The capsanthin-capsorubin synthase gene: a candidate gene for the y locus controlling the red fruit colour in pepper.

The red colour of pepper fruits is determined by the y+ dominant allele and the yellow colour by the y recessive allele. The capsanthin-capsorubin synthase (CCS) gene is activated specifically during the final stages of pepper fruit ripening. RFLP and specific-PCR polymorphisms derived from the CCS gene were analysed in a F2 progeny of a red by yellow-fruited cross. They cosegregated completely with fruit colour. Our results support the hypothesis that the yellow phenotype might result from a deletion of the CCS gene. These specific markers were integrated into the genetic map and will be useful for marker assisted plant breeding.

Alleles↗

PubMed2003

Ferredoxin from sweet pepper (Capsicum annuum L.) intensifying harpin(pss)-mediated hypersensitive response shows an enhanced production of active oxygen species (AOS).

The hypersensitive response (HR) is a form of cell death associated with plant resistance to pathogen infection. Harpin(pss), an elicitor from the bacterium Pseudomonas syringae pv. syringae, induces a HR in non-host plants. Previously, we reported an amphipathic protein from sweet pepper interfering with harpin(pss)-mediated HR. In this report, we isolated and characterized a cDNA clone encoded that amphipathic protein from sweet pepper. This protein is designated as PFLP (plant ferredoxin-like protein) by virtue of its high homology with plant ferredoxin protein containing an N-terminal signal peptide responsible for chloroplast targeting and a putative 2Fe-2S domain responsible for redox activity. Recombinant PFLP obtained from Escherichia coli was able to significantly increase active oxygen species (AOS) generation when mixed with harpin(pss) in tobacco suspension cells. It also showed enhanced HR when co-infiltrated with harpin(pss) in tobacco leaves. We used a transgenic tobacco suspension cells system that constitutively expresses the Pflp gene driven by the CaMV 35S promoter to study the function of PFLP in enhancing harpin(pss)-mediated hypersensitive cell death in vivo. In response to harpin(pss), suspension cells derived from Pflp transgenic tobacco showed a significant increase both in the generation of AOS and in cell death as compared to the wild type. AOS inhibitors diphenylene iodonium chloride (DPI) and lanthanum chlorate (LaCl3) were used to study the involvement of AOS in harpin(pss)-induced cell death. Our results demonstrate enhanced generation of AOS is necessary to cause enhanced hypersensitive cell death in Pflp transgenic tobacco cells and it is plasma membrane-bound NADPH-oxidase-dependent. Sub-cellular localization studies showed that PFLP is present in the cytoplasm and chloroplast of Pflp transgenic tobacco cells, but only in the chloroplast, not in the cytoplasm, of wild-type tobacco cells. It is possible that PFLP can change the redox state of the cell upon harpin(pss) inoculation to increase AOS generation and hypersensitive cell death. Overall, this study will provide a new insight in the functional properties of ferredoxin in hypersensitive cell death.

Amino Acid Sequence↗

PubMed2003

The sweet pepper ferredoxin-like protein (pflp) conferred resistance against soft rot disease in Oncidium orchid.

Genetic engineering to date has not been used to introduce disease resistance genes into the orchid gene pool. The ferredoxin-like protein gene originally isolated from sweet pepper is thought to function as a natural defense against infection due to its antimicrobial properties. Hence it was reasoned that introduction of this gene might produce Oncidium plants resistant to Erwinia carotovora, the causal agent for the soft rot disease. An expression vector containing sweet pepper ferredoxin-like protein (pflp) cDNA, hph and gusA coding sequence was successfully transformed into protocorm-like bodies (PLBs) of Oncidium orchid, using Agrobacterium tumefaciens strain EHA105. A total of 17 independent transgenic orchid lines was obtained, out of which six transgenic lines (beta-glucuronidase (GUS) positive) were randomly selected and confirmed by Southern, northern and western blot analyses. A bioassay was conducted on the transgenic lines. Transgenic plants showed enhanced resistance to E. carotovora, even when the entire plant was challenged with the pathogen. Our results suggest that pflp may be an extremely useful gene for genetic engineering strategies in orchids to confer resistance against soft rot disease.

Capsicum↗

PubMed2001

The effect of high temperature and high atmospheric CO2 on carbohydrate changes in bell pepper (Capsicum annuum) pollen in relation to its germination.

Pollen viability and germination are known to be sensitive to high temperature (HT). However, the mode by which high temperature impairs pollen functioning is not yet clear. In the present study, we investigated the effect of high temperature on changes occurring in carbohydrate of bell pepper (Capsicum annuum L. cv. Mazurka) pollen in order to find possible relations between these changes and pollen germination under heat stress. When pepper plants were maintained under a moderate HT regime (32/26 degrees C, day/night) for 8 days before flowers have reached anthesis, pollen count at anthesis was similar to that found in plants grown under normal temperatures (NT 28/22 degrees C). However, the in vitro germination, carried out at 25 degrees C, of pollen from HT plants was greatly reduced. This effect matched the marked reduction in the number of seeds per fruit in the HT plants. Maintaining the plants at high air CO2 concentration (800 &mgr;mol mol-1 air) in both temperature treatments did not affect the in vitro germination of pollen from NT plants, but restored germination to near the normal level in pollen from HT plants. Under NT conditions, starch, which was negligible in pollen at meiosis (8 days before anthesis, A-8) started to accumulate at A-4 and continued to accumulate until A-2. From that stage until anthesis, starch was rapidly degraded. On the other hand, sucrose concentration rose from stage A-4 until anthesis. Acid invertase (EC 3.2.1.26) activity rose parallel with the increase of sucrose. In pollen from HT plants, sucrose and starch concentrations were significantly higher at A-1 pollen than in that of NT plants. Under high CO2 conditions, the sucrose concentration in the pollen of HT plants was reduced to levels similar to those in NT pollen. In accordance with the higher sucrose concentration in HT pollen, the acid invertase activity in these pollen grains was lower than in NT pollen. The results suggest that the higher concentrations of sucrose and starch in the pollen grains of HT plants may result from reduction in their metabolism under heat stress. Elevated CO2 concentration, presumably by increasing assimilate availability to the pollen grain, may alleviate the inhibition of sucrose and starch metabolism, thereby increasing their utilization for pollen germination under the HT stress. Acid invertase may have a regulatory role in this system.

Journal Article↗

PubMed1979

Reversal of innate aversions: attempts to induce a preference for chili peppers in rats.

Although humans frequently develop preferences for innately unpalatable bitter or irritant substances, such preferences are extremely rare in animals. An attempt was made to understand the nature of this difference by systematic experiments with laboratory rats, with chili pepper as the unpalatable substance. In parallel with major aspects of the human experience with chili pepper, rats were exposed to it as a flavoring in all their food for periods up to 11 mo from birth, without significant preference enhancement. Gradual introduction of chili into the diet also had no effect, nor did a series of poisoning and safety experiences designed to teach the rats that only chili-flavored foods were safe to eat. A sequence of seven pairings of chili-flavored diet with prompt recovery from thiamine deficiency did significantly attenuate the innate aversion and may have induced a chili preference in at least one case. Extensive experience with chili did not reliably make rats much less sensitive to its oral effects. The only reliable way to eliminate chili aversion in rats is to destroy their chemical irritant sense, which was accomplished in one group of rats. It is concluded that in contrast to humans, it is extremely difficult to reverse innate aversions in rats.

Animals↗

PubMed2005

Microspore-derived embryogenesis in pepper (Capsicum annuum L.): subcellular rearrangements through development.

Background information. In vitro-cultured microspores, after an appropriate stress treatment, can switch towards an embryogenic pathway. This process, known as microspore embryogenesis, is an important tool in plant breeding. Basic studies on this process in economically interesting crops, especially in recalcitrant plants, are very limited and the sequence of events is poorly understood. In situ studies are very convenient for an appropriate dissection of microspore embryogenesis, a process in which a mixture of different cell populations (induced and non-induced) develop asynchronically.Results. In the present study, the occurrence of defined subcellular rearrangements has been investigated during early microspore embryogenesis in pepper, an horticultural crop of agronomic interest, in relation to proliferation and differentiation events. Haploid plants of Capsicum annuum L. (var. Yolo Wonder B) have been regenerated from in vitro anther cultures by a heat treatment at 35 degrees C for 8 days. Morphogenesis of microspore-derived embryos has been analysed, at both light and electron microscopy levels, using low-temperature-processed, well-preserved specimens. The comparison with the normal gametophytic development revealed changes in cell organization after embryogenesis induction, and permitted the characterization of the time sequence of a set of structural events, not previously defined in pepper, related to the activation of proliferative activity and differentiation. These changes mainly affected the plastids, the vacuolar compartment, the cell wall and the nucleus. Further differentiation processes mimicked that of the zygotic development.Conclusions. The reported changes can be considered as markers of the microspore embryogenesis. They have increased the understanding of the mechanisms controlling the switch and progression of the microspore embryogenesis, which could help to improve its efficiency and to direct strategies, especially in agronomically interesting crops.

Capsicum↗

PubMed1998

Tocopherol synthesis from homogentisate in Capsicum anuum L. (yellow pepper) chromoplast membranes: evidence for tocopherol cyclase.

The present study shows for the first time appreciable tocopherol cyclase activities in plastidial membrane preparations of Capsicum annuum L. (yellow pepper) fruits. When chromoplast membranes from yellow peppers were incubated with [3H]homogentisate and phytyl pyrophosphate under strictly reducing conditions, all biosynthesis precursors were labelled. The main labelling was found in gamma-tocopherol. These observations contradict the hypothesis that assigns a rate-limiting function to tocopherol cyclase in plastidial alpha-tocopherol biosynthesis. The stoichiometry of alpha-tocopherol, 2,3-dimethylphytylquinol and gamma-tocopherol formation and the inhibition of alpha-tocopherol synthesis by increasing gamma-tocopherol concentrations suggests the regulation of this pathway by its precursors.

Capsicum↗

PubMed1989

Analysis of language-speech samples with salt and pepper.

Microcomputer-aided analysis of spontaneous language-speech samples offers researchers an efficient means of analyzing large amounts of data. It may be necessary, however, to format samples for more than one software program in order to obtain comprehensive morpho-syntactic and phonetic/phonologic analyses. This paper suggests a procedure for the combined use of SALT (Systematic Analysis of Language Transcripts, Miller & Chapman, 1985) and PEPPER (Programs to Examine Phonetic and Phonologic Evaluation Records, Shriberg, 1986) that is designed to minimize the duplication of effort involved in following two different formatting procedures. Results of a study undertaken to explore methodological issues in the combined use of SALT and PEPPER generally support the validity, reliability, and efficiency of the procedure. Results also raise some issues concerning the use of narrow phonetic transcription as opposed to standard orthographic transcription of continuous language-speech samples.

Data Collection↗

PubMed2001

Eukaryotic features of the Xanthomonas type III effector AvrBs3: protein domains involved in transcriptional activation and the interaction with nuclear import receptors from pepper.

The AvrBs3 protein of the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria is targeted to host-plant cells by the bacterial Hrp type III secretion system. In pepper plants containing the Bs3 resistance gene, AvrBs3 induces the hypersensitive response (HR). AvrBs3 recognition is thought to occur in the plant cell nucleus as HR induction is dependent on nuclear localization signals (NLSs) and an acidic transcription activation domain (AAD). In a search for AvrBs3-interacting pepper proteins using the yeast two-hybrid system, we have isolated eight different classes of cDNA inserts including two genes for importin alpha proteins. Importin alpha is part of the nuclear import machinery and interacts with AvrBs3 through an NLS in the carboxy-terminus of the protein, both in yeast and in vitro. The mechanism of AvrBs3 recognition was further studied by analysis of the C-terminal AAD. This putative transcription-activation domain was shown to be required for AvrBs3 HR-inducing activity, and could be functionally replaced with the VP16 AAD from the Herpes simplex virus. Our data support the model in which the AvrBs3 effector localizes to the nucleus, where the Bs3-mediated surveillance system of resistant plants detects AvrBs3 through its interference with host gene transcription.

Active Transport, Cell Nucleus↗

PubMed2004

A genetic screen to isolate type III effectors translocated into pepper cells during Xanthomonas infection.

The bacterial pathogen Xanthomonas campestris pv. vesicatoria (Xcv) uses a type III secretion system (TTSS) to translocate effector proteins into host plant cells. The TTSS is required for Xcv colonization, yet the identity of many proteins translocated through this apparatus is not known. We used a genetic screen to functionally identify Xcv TTSS effectors. A transposon 5 (Tn5)-based transposon construct including the coding sequence for the Xcv AvrBs2 effector devoid of its TTSS signal was randomly inserted into the Xcv genome. Insertion of the avrBs2 reporter gene into Xcv genes coding for proteins containing a functional TTSS signal peptide resulted in the creation of chimeric TTSS effector::AvrBs2 fusion proteins. Xcv strains containing these fusions translocated the AvrBs2 reporter in a TTSS-dependent manner into resistant BS2 pepper cells during infection, activating the avrBs2-dependent hypersensitive response (HR). We isolated seven chimeric fusion proteins and designated the identified TTSS effectors as Xanthomonas outer proteins (Xops). Translocation of each Xop was confirmed by using the calmodulin-dependent adenylate cydase reporter assay. Three xop genes are Xanthomonas spp.-specific, whereas homologs for the rest are found in other phytopathogenic bacteria. XopF1 and XopF2 define an effector gene family in Xcv. XopN contains a eukaryotic protein fold repeat and is required for full Xcv pathogenicity in pepper and tomato. The translocated effectors identified in this work expand our knowledge of the diversity of proteins that Xcv uses to manipulate its hosts.

Bacterial Proteins↗

PubMed2000

Molecular signals required for type III secretion and translocation of the Xanthomonas campestris AvrBs2 protein to pepper plants.

Strains of Xanthomonas campestris pv. vesicatoria (Xcv) carrying avrBs2 are specifically recognized by Bs2 pepper plants, resulting in localized cell death and plant resistance. Agrobacterium-mediated transient expression of the Xcv avrBs2 gene in plant cells results in Bs2-dependent cell death, indicating that the AvrBs2 protein alone is sufficient for the activation of disease resistance-mediated cell death in planta. We now provide evidence that AvrBs2 is secreted from Xcv and that secretion is type III (hrp) dependent. N- and C-terminal deletion analysis of AvrBs2 has identified the effector domain of AvrBs2 recognized by Bs2 pepper plants. By using a truncated Pseudomonas syringae AvrRpt2 effector reporter devoid of type III signal sequences, we have localized the minimal region of AvrBs2 required for type III secretion in Xcv. Furthermore, we have identified the region of AvrBs2 required for both type III secretion and translocation to host plants. The mapping of AvrBs2 sequences sufficient for type III delivery also revealed the presence of a potential mRNA secretion signal.

Agrobacterium tumefaciens↗