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1.
In cold extracts of senescent leaves of the Lime tree (Tilia cordata), two colorless nonfluorescent chlorophyll catabolites (NCCs) were identified, named Tc‐NCC‐1 and Tc‐NCC‐2, as well as a polar yellow chlorophyll catabolite (YCC), named Tc‐YCC. The constitution of the two NCCs was determined by spectroscopic means. In addition, a tentative structure was derived for Tc‐YCC. The three chlorophyll degradation products exhibited tetrapyrrolic structures, as are typical of NCCs or YCCs, and turned out to be rather polar, due to a glucopyranosyl group at their 82‐position. At their 3‐positions, the more polar Tc‐NCC‐1 carried a 1,2‐dihydroxyethyl group and the less polar Tc‐NCC‐2 a vinyl group. Tc‐YCC was identified as the product of an oxidation of Tc‐NCC‐1.  相似文献   

2.
In extracts of senescent leaves of the tobacco plant Nicotiana rustica, two colorless compounds with UV/VIS characteristics of nonfluorescent chlorophyll catabolites (NCCs) were detected and tentatively identified as Nr-NCCs. These two polar NCCs were found in similar amounts in the fresh extracts, and their constitutions could be determined by spectroscopic analysis. The data showed both of the two Nr-NCCs to have the same tetrapyrrolic core structure, as reported previously for all other NCCs from senescent higher plants. In the less polar catabolite, named Nr-NCC-2, this core structure was conjugated with a glucopyranose unit, as similarly discovered earlier in Bn-NCC-2, an NCC from oilseed rape (Brassica napus). The more polar NCC from tobacco leaves, Nr-NCC-1, carried an additional malonyl substituent at the 6'-OH group of the glucopyranosyl moiety. Partial (enzyme-catalyzed) hydrolysis of Nr-NCC-1 gave Nr-NCC-2, while enzyme-catalyzed malonylation of Nr-NCC-2 gave Nr-NCC-1, establishing the identity of their basic tetrapyrrole structure. In earlier work (on the polar NCCs from oilseed rape), only separate glucopyranosyl and malonyl functionalities were detected. Nr-NCC-1, thus, represents a further variant of the structures of NCCs from senescent higher plants and exhibits an unprecedented peripheral refunctionalization in chlorophyll catabolites.  相似文献   

3.
In extracts of senescent leaves of spinach (Spinacia oleracea), five colourless compounds with UV/Vis-characteristics of nonfluorescent chlorophyll catabolites (NCCs) were detected and tentatively named So-NCCs. The most abundant polar NCC in the leaves of this vegetable, So-NCC-2, had been isolated earlier and its constitution was determined by spectroscopic means. The catabolite So-NCC-2 was found to be an epimer of a polar NCC from barley (Hordeum vulgare), the first non-green chlorophyll catabolite from a higher plant to be structurally analyzed. Here, we report on the isolation of four additional So-NCCs from the extracts of senescent leaves of Sp. oleracea by two- (or multi-)stage chromatographic purification and on their structural characterization. The constitution of So-NCC-3 could be determined by spectroscopic analysis in combination with chemical correlation with a known NCC from Cercidiphyllum japonicum (Cj-NCC): So-NCC-3 was identified as the hydrolysis product of the methyl ester function of Cj-NCC. The less polar catabolite So-NCC-4 could be directly identified with Cj-NCC. Two further So-NCCs, So-NCC-1 and So-NCC-5, were detected only in trace amounts. Five structurally related nonfluorescent chlorophyll catabolites (So-NCCs) are thus present in senescent leaves of spinach. The structures of this set of So-NCCs indicate several peripheral refunctionalization reactions and inform on the late catabolic transformations during leaf senescence. The transformation of the tetrapyrrolic skeleton in chlorophyll catabolism in spinach and in C. japonicum is revealed to exhibit a common stereochemical pattern. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

4.
The typical main products of chlorophyll (Chl) breakdown in higher plants are non‐fluorescent, colorless phyllobilins, named phylloleucobilins. These long elusive Chl‐catabolites are linear tetrapyrroles, whose structure elucidation has required thorough spectroscopic analyses. Interestingly, in recent LC/MS studies of leaf extracts, isomeric forms of phylloleucobilins were detected. The existence of isomeric phyllobilins may suggest incomplete stereo‐selectivity of catabolic processes, or isomerization processes in plant cells or in the analytes. Here we report a study with the phylloleucobilin NCC‐1, a basic Chl‐catabolite in extracts of leaves and fruit. NCC‐1 and its main isomerization product in aqueous solution were identified as 82‐epimers. Formation of 82‐epi‐NCC‐1 from NCC‐1 implies an unstable enol(ate)‐intermediate, which reverts to NCC‐1 or converts to 82‐epi‐NCC‐1. Such reversible epimerization reactions are a non‐biological in vitro feature of typical phylloleucobilins, and probably also take place in vivo.  相似文献   

5.
Analyzing the optical properties of fruits represents a powerful approach for non‐destructive observations of fruit development. With classical spectroscopy in the visible and near‐infrared wavelength ranges, the apparent attenuation of light results from its absorption or scattering. In horticultural applications, frequently, the normalized difference vegetation index (NDVI) is employed to reduce the effects of varying scattering properties on the apparent signal. However, this simple approach appears to be limited. In the laboratory, with time‐resolved reflectance spectroscopy, the absorption coefficient, μa, and the reduced scattering coefficient, μs′, can be analyzed separately. In this study, these differentiated optical properties were recorded (540–940 nm), probing fruit tissue from the skin up to 2 cm depth in apple (Malus × domestica ‘Elstar’) and plum (Prunus domestica ‘Tophit plus’) harvested four times (65–145 days after full bloom). The μa spectra showed typical peak at 670 nm of the chlorophyll absorption. The μs′ at 670 nm in apple changed by 14.7% (18.2–15.5 cm?1), while in plum differences of 41.5% (8.5–5.0 cm?1) were found. The scattering power, the relative change of μs′, was zero in apple, but enhanced in plum over the fruit development period. This mirrors more isotropic and constant structures in apple compared with plum. For horticultural applications, the larger variability in scattering properties of plum explains the discrepancy between commercially assessed NDVI values or similar indices and the absolute μa values in plum (R < 0.05), while the NDVI approach appeared reasonable in apple (R ≥ 0.80).  相似文献   

6.
Melanocytes are pigment‐producing cells generated from neural crest cells (NCCs) that delaminate from the dorsal neural tube. The widely accepted premise that NCCs migrating along the dorsolateral pathway are the main source of melanocytes in the skin was recently challenged by the finding that Schwann cell precursors are the major cellular source of melanocytes in the skin. Still, in a wide variety of vertebrate embryos, melanocytes are exclusively derived from NCCs. In this study, we show that a NCC population that is not derived from Sox1+ dorsal neuroepithelial cells but are derived from Sox1? cells differentiate into a significant population of melanocytes in the skin of mice. Later, these Sox1? cells clearly segregate from cells that originated from Sox1+ dorsal neuroepithelial cell‐derived NCCs. The possible derivation of Sox1? cells from epidermal cells also strengthens their non‐neuroepithelial origin.  相似文献   

7.
During leaf senescence, chlorophyll (Chl) is broken down to nonfluorescent chlorophyll catabolites (NCCs). These arise from intermediary fluorescent chlorophyll catabolites (FCCs) by an acid-catalyzed isomerization inside the vacuole. The chemical structures of NCCs from Arabidopsis (Arabidopsis thaliana) indicate the presence of an enzyme activity that demethylates the C13(2)-carboxymethyl group present at the isocyclic ring of Chl. Here, we identified this activity as methylesterase family member 16 (MES16; At4g16690). During senescence, mes16 leaves exhibited a strong ultraviolet-excitable fluorescence, which resulted from large amounts of different FCCs accumulating in the mutants. As confirmed by mass spectrometry, these FCCs had an intact carboxymethyl group, which slowed down their isomerization to respective NCCs. Like a homologous protein cloned from radish (Raphanus sativus) and named pheophorbidase, MES16 catalyzed the demethylation of pheophorbide, an early intermediate of Chl breakdown, in vitro, but MES16 also demethylated an FCC. To determine the in vivo substrate of MES16, we analyzed pheophorbide a oxygenase1 (pao1), which is deficient in pheophorbide catabolism and accumulates pheophorbide in the chloroplast, and a mes16pao1 double mutant. In the pao1 background, we additionally mistargeted MES16 to the chloroplast. Normally, MES16 localizes to the cytosol, as shown by analysis of a MES16-green fluorescent protein fusion. Analysis of the accumulating pigments in these lines revealed that pheophorbide is only accessible for demethylation when MES16 is targeted to the chloroplast. Together, these data demonstrate that MES16 is an integral component of Chl breakdown in Arabidopsis and specifically demethylates Chl catabolites at the level of FCCs in the cytosol.  相似文献   

8.
Neural crest cells (NCCs) are a remarkable, dynamic group of cells that travel long distances in the embryo to reach their target sites. They are responsible for the formation of craniofacial bones and cartilage, neurons and glia in the peripheral nervous system and pigment cells. Live imaging of NCCs as they traverse the embryo has been critical to increasing our knowledge of their biology. NCCs exhibit multiple behaviors and communicate with each other and their environment along each step of their journey. Imaging combined with molecular manipulations has led to insights into the mechanisms controlling these behaviors. In this Review, we highlight studies that have used live imaging to provide novel insight into NCC migration and discuss how continued use of such techniques can advance our understanding of NCC biology.Key words: live imaging, neural crest, EMT, Rho GTPase, ephrin, PCP signaling, cadherin, VEGFNeural crest cells (NCCs) are a pluripotent population of cells that migrate from the dorsal neuroepithelium and give rise to multiple cell types including neurons and glia of the peripheral nervous system, pigment cells and craniofacial bone and cartilage.1 An important hallmark of NCCs is their remarkable ability to migrate over long distances and along specific pathways through the embryo. NCC migration begins with an epithelial to mesenchymal transition (EMT), in which NCCs lose adhesions with their neighbors and segregate from the neuroepithelium.2,3 Following EMT, NCCs acquire a polarized morphology and initiate directed migration away from the neural tube. While migrating along their pathways to their target tissues, NCCs are guided by extensive communication with one another and by other cues from the extracellular environment. Each of these aspects of NCC migration requires precise regulation of cell motile behaviors, although the mechanisms controlling them are still not well understood. A critical step toward understanding the molecular control of NCC motility is characterization of NCC behaviors as they migrate in their native environment. In the past 15 years, multiple studies have analyzed specific behaviors associated with NCCs along the various stages of their journey and have begun to identify molecules controlling these behaviors. In this review we will focus specifically on these studies that employ live imaging and will highlight the strength of live imaging to reveal mechanisms regulating NCC motility and migration pathways.  相似文献   

9.
During senescence, chlorophyll (chl) is metabolized to colorless nonfluorescent chl catabolites (NCCs). A central reaction of the breakdown pathway is the ring cleavage of pheophorbide (pheide) a to a primary fluorescent chl catabolite. Two enzymes catalyze this reaction, pheide a oxygenase (PAO) and red chl catabolite reductase. Five NCCs and three fluorescent chl catabolites (FCCs) accumulated during dark-induced chl breakdown in Arabidopsis (Arabidopsis thaliana). Three of these NCCs and one FCC (primary fluorescent chl catabolite-1) were identical to known catabolites from canola (Brassica napus). The presence in Arabidopsis of two modified FCCs supports the hypothesis that modifications, as present in NCCs, occur at the level of FCC. Chl degradation in Arabidopsis correlated with the accumulation of FCCs and NCCs, as well as with an increase in PAO activity. This increase was due to an up-regulation of Pao gene expression. In contrast, red chl catabolite reductase is not regulated during leaf development and senescence. A pao1 knockout mutant was identified and analyzed. The mutant showed an age- and light-dependent cell death phenotype on leaves and in flowers caused by the accumulation of photoreactive pheide a. In the dark, pao1 exhibited a stay-green phenotype. The key role of PAO in chl breakdown is discussed.  相似文献   

10.
Neural crest cells (NCCs) are a transient population of cells present in vertebrate development that emigrate from the dorsal neural tube (NT) after undergoing an epithelial-mesenchymal transition 1,2. Following EMT, NCCs migrate large distances along stereotypic pathways until they reach their targets. NCCs differentiate into a vast array of cell types including neurons, glia, melanocytes, and chromaffin cells 1-3. The ability of NCCs to reach and recognize their proper target locations is foundational for the appropriate formation of all structures containing trunk NCC-derived components 3. Elucidating the mechanisms of guidance for trunk NCC migration has therefore been a matter of great significance. Numerous molecules have been demonstrated to guide NCC migration 4. For instance, trunk NCCs are known to be repelled by negative guidance cues such as Semaphorin, Ephrin, and Slit ligands 5-8. However, not until recently have any chemoattractants of trunk NCCs been identified 9. Conventional in vitro approaches to studying the chemotactic behavior of adherent cells work best with immortalized, homogenously distributed cells, but are more challenging to apply to certain primary stem cell cultures that initially lack a homogenous distribution and rapidly differentiate (such as NCCs). One approach to homogenize the distribution of trunk NCCs for chemotaxis studies is to isolate trunk NCCs from primary NT explant cultures, then lift and replate them to be almost 100% confluent. However, this plating approach requires substantial amounts of time and effort to explant enough cells, is harsh, and distributes trunk NCCs in a dissimilar manner to that found in in vivo conditions. Here, we report an in vitro approach that is able to evaluate chemotaxis and other migratory responses of trunk NCCs without requiring a homogenous cell distribution. This technique utilizes time-lapse imaging of primary, unperturbed trunk NCCs inside a modified Zigmond chamber (a standard Zigmond chamber is described elsewhere10). By exposing trunk NCCs at the periphery of the culture to a chemotactant gradient that is perpendicular to their predicted natural directionality, alterations in migratory polarity induced by the applied chemotactant gradient can be detected. This technique is inexpensive, requires the culturing of only two NT explants per replicate treatment, avoids harsh cell lifting (such as trypsinization), leaves trunk NCCs in a more similar distribution to in vivo conditions, cuts down the amount of time between explantation and experimentation (which likely reduces the risk of differentiation), and allows time-lapse evaluation of numerous migratory characteristics.  相似文献   

11.
Congenital diseases caused by abnormal development of the cranial neural crest usually present craniofacial malformations and heart defects while the precise mechanism is not fully understood. Here, we show that the zebrafish eif3ba mutant caused by pseudo-typed retrovirus insertion exhibited a similar phenotype due to the hypogenesis of cranial neural crest cells (NCCs). The derivatives of cranial NCCs, including the NCC-derived cell population of pharyngeal arches, craniofacial cartilage, pigment cells and the myocardium derived from cardiac NCCs, were affected in this mutant. The expression of several neural crest marker genes, including crestin, dlx2a and nrp2b, was specifically reduced in the cranial regions of the eif3ba mutant. Through fluorescence-tracing of the cranial NCC migration marker nrp2b, we observed reduced intensity of NCC-derived cells in the heart. In addition, p53 was markedly up-regulated in the eif3ba mutant embryos, which correlated with pronounced apoptosis in the cranial area as shown by TUNEL staining. These findings suggest a novel function of eif3ba during embryonic development and a novel level of regulation in the process of cranial NCC development, in addition to providing a potential animal model to mimic congenital diseases due to cranial NCC defects. Furthermore, we report the identification of a novel transgenic fish line Et(gata2a:EGFP)pku418 to trace the migration of cranial NCCs (including cardiac NCCs); this may serve as an invaluable tool for investigating the development and dynamics of cranial NCCs during zebrafish embryogenesis.  相似文献   

12.
Abstract: The relationship between abundance of rose‐grain aphid Metopolophium dirhodum (Walker) and leaf chlorophyll content of spring wheat, spring oats and winter barley was investigated. Within production stands of each crop 18–25 plots were established, located at places with different plant quality where aphids were counted on particular leaves of 50–100 tillers, and the leaf chlorophyll content and area were determined. In all stands aphid numbers × tiller?1 increased exponentially with chlorophyll content (r2 = 0.783–0.933). This parallel variation may be explained by increased nitrogen content and assimilate production of vigorous chlorophyll‐rich plants. The aphid numbers on leaves of particular order (within‐plant distribution) were also correlated with leaf chlorophyll content (r2 = 0.373–0.827). However, in oats and barley the analysis of variance of residuals of log aphids × leaf?1 versus leaf chlorophyll regression revealed a significant effect of leaf position (the order of the leaf from the top of the plant). The magnitude of residuals was positively related to leaf size and may be related to the intensity of phloem transport from the source leaves to sink organs.  相似文献   

13.
Plum decline was associated with Pseudomonas syringae pathovars syringae and morsprunorum in Baden‐Württemberg. The trunks of affected plum trees (Prunus domestica) were girdled by bacterial cankers resulting in sudden death of infected trees. Copper compounds that were applied extensively during leaf fall and bud burst, were not effective. A minority of P. syringae strains isolated from cankers on plum trees were moderately resistant, while most strains were sensitive to cupric ions. Invasions through blossoms, leaves and wounds during the vegetation period were limited to the infection sites and plum trees coped effectively with both P. syringae pathovars eliminating them eventually. Infections after dormancy including very rare leaf scar infections did not induce cankers on the trunk. However, infections of dormant trees through frost injuries, (pruning) wounds or non‐injurious ingress by freezing and thawing were serious, because they led to cankers girdling the trunk. Control strategies to manage plum decline have to be adapted to the disease cycle. They should concentrate on the dormant period beginning with early frosts in autumn and ending with bud burst.  相似文献   

14.
A central reaction of chlorophyll breakdown, porphyrin ring opening of pheophorbide a to the primary fluorescent chlorophyll catabolite (pFCC), requires pheophorbide a oxygenase (PAO) and red chlorophyll catabolite reductase (RCCR), with red chlorophyll catabolite (RCC) as a presumably PAO-bound intermediate. In subsequent steps, pFCC is converted to different fluorescent chlorophyll catabolites (FCCs) and nonfluorescent chlorophyll catabolites (NCCs). Here, we show that RCCR-deficient Arabidopsis thaliana accumulates RCC and three RCC-like pigments during senescence, as well as FCCs and NCCs. We also show that the stereospecificity of Arabidopsis RCCR is defined by a small protein domain and can be reversed by a single Phe-to-Val exchange. Exploiting this feature, we prove the in vivo participation of RCCR in chlorophyll breakdown. After complementation of RCCR mutants with RCCRs exhibiting alternative specificities, patterns of chlorophyll catabolites followed the specificity of complementing RCCRs. Light-dependent leaf cell death observed in different RCCR-deficient lines strictly correlated with the accumulation of RCCs and the release of singlet oxygen, and PAO induction preceded lesion formation. These findings suggest that RCCR absence causes leaf cell death as a result of the accumulation of photodynamic RCC. We conclude that RCCR (together with PAO) is required for the detoxification of chlorophyll catabolites and discuss the biochemical role(s) for this enzyme.  相似文献   

15.
16.
Host preference of the plum curculio   总被引:1,自引:0,他引:1  
We assessed host preference of adult plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), based on the total number of mark‐released and wild adults recovered and the total distance moved by mark‐released adults in an orchard whose layout was designed to specifically allow foraging plum curculios to choose among host tree species. Host trees included apple, Malus domestica Borkh.; pear, Pyrus communis (L.); peach, Prunus persica (L.) Batsch; apricot, Prunus armeniaca L.; tart cherry, Prunus cerasus L.; sweet cherry, Prunus avium (L.); European plum, Prunus domestica L.; and Japanese plum, Prunus salicina Lindl. (all Rosaceae). We released 2900 marked adults and recovered 17.7%. We used screen traps to provide a measure of the number of adults that arrived at and climbed up particular host trees and found that significantly greater numbers of marked adults and the greatest number of wild adults were recovered from screen traps attached to Japanese plum. We sampled host tree canopies by tapping limbs to provide a measure of the number of adults within a tree canopy at a particular moment. Again, significantly greater numbers of marked and wild adults were recovered from plum species, with no difference between Japanese and European plum cultivars for marked individuals, but with significantly greater numbers of wild individuals recovered from Japanese plum. The preference index (PI) for Japanese plum based on total distances moved by all marked adults recovered on Japanese plum divided by the total distance moved by marked adults recovered on other host trees indicated that Japanese plum was the most highly preferred host, followed by European plum, peach, sweet cherry, tart cherry, apricot, apple, and pear, respectively.  相似文献   

17.
Neural crest cells (NCCs) are a multipotent embryonic cell population that contributes to the formation of various craniofacial structures including teeth. It has been generally believed that dental enamel is an ectodermal derivative, whereas the dentin–pulp complex and the surrounding supporting tissues originate from NCC-derived mesenchyme. These traditional concepts stem mainly from several early studies of fishes and amphibians. Recently, Wnt1-Cre/R26R mice, a mouse model for NCC lineage analysis, revealed the contribution of NCCs to mammalian tooth development. However, the discrepancy of expression patterns between different NCC-specific transgenic mouse lines makes it compulsory to revisit the cell lineage in mammalian tooth development. Here, we reevaluated the NCC lineage during mouse tooth development by using P0-Cre/R26R mice, another NCC-specific transgenic mouse line. Inconsistent with the traditional concepts, we observed the potential contribution of NCCs to developing enamel organ and enamel formation. We also demonstrated that the P0-Cre transgene was specifically expressed in migrating NCC in the hindbrain region, where NCC contributes to tooth, validating their applicability for NCC lineage analysis. Our unanticipated finding may change the general understanding of tooth development and provide new insights into dental stem cell biology.  相似文献   

18.
19.
Transgenic plants of tobacco (Nicotiana tabacum L) and European plum (Prunus domestica L) were produced by transforming with the apple class 1 KNOX genes (MdKN1 and MdKN2) or corn KNOX1 gene. Transgenic tobacco plants were regenerated in vitro from transformed leaf discs cultured in a medium lacking cytokinin. Ectopic expression of KNOX genes retarded shoot growth by suppressing elongation of internodes in transgenic tobacco plants. Expression of each of the three KNOX1 genes induced malformation and extensive lobbing in tobacco leaves. In situ regeneration of adventitious shoots was observed from leaves and roots of transgenic tobacco plants expressing each of the three KNOX genes. In vitro culture of leaf explants and internode sections excised from in vitro grown MdKN1 expressing tobacco shoots regenerated adventitious shoots on MS (Murashige and Skoog 1962) basal medium in the absence of exogenous cytokinin. Transgenic plum plants that expressed the MdKN2 or corn KNOX1 gene grew normally but MdKN1 caused a significant reduction in plant height, leaf shape and size and produced malformed curly leaves. A high frequency of adventitious shoot regeneration (96%) was observed in cultures of leaf explants excised from corn KNOX1-expressing transgenic plum shoots. In contrast to KNOX1-expressing tobacco, leaf and internode explants of corn KNOX1-expressing plum required synthetic cytokinin (thidiazuron) in the culture medium to induce adventitious shoot regeneration. The induction of high-frequency regeneration of adventitious shoots in vitro from leaves and stem internodal sections of plum through the ectopic expression of a KNOX1 gene is the first such report for a woody perennial fruit trees.  相似文献   

20.
Colorless, non-fluorescent Chl-catabolites (NCCs) are the typical, ubiquitous products of chlorophyll (Chl)-breakdown in senescent leaves. However, a fluorescent Chl-catabolite (FCC) accumulated in de-greened leaves of Spathiphyllum wallisii (Peace Lily), which showed a weak blue luminescence. The FCC, named Sw-FCC-62, was ‘hypermodified’ with an unprecedented 6-(2-[3,4-dihydroxy-phenyl]-ethyl)-β-glucopyranosidyl ester at the propionyl group. Such esters stabilize FCCs against their typical and rapid, spontaneous isomerization to NCCs. Chl-breakdown in Sp. wallisii thus branches off from the ‘common’ path in leaves, and furnishes unique and ‘persistent’ FCCs. Our findings on ‘hypermodified’ FCCs also call for attention as to possible physiological roles of Chl-catabolites in plants.  相似文献   

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