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Aphids and numerous other phloem-feeding insects primarily rely on sucrose in the phloem to locate their feeding sites. However, it is still unclear whether this sweet perception process could serve as a target for aphid control. In this study, we investigated the impact of the sweet taste inhibitor sodium salt of 2-(4-methoxyphenoxy)-propionic acid (lactisole), a widely used food additive that binds to sugar receptors, on the feeding behavior and performance of aphids. Our findings indicate that both the green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) and the English grain aphid Sitobion avenae (Fabricius) (Hemiptera: Aphididae) avoided settling on an artificial diet containing lactisole or on host plants treated with lactisole. In addition, these aphid species showed reduced weights when feeding on the artificial diet containing lactisole or on seedlings root drenched by lactisole. Furthermore, data from the electrical penetration graph revealed that S. avenae exhibited a greater number of phloem probes but significantly shorter mean and total phloem ingestion durations when feeding on wheat plants root-drenched by lactisole. It is worth noting, however, that root drenched by lactisole had a significant inhibitory effect on plant growth. These findings suggest that the sweet taste inhibitor lactisole may reduce aphid feeding preference and growth, offering a new avenue for aphid control strategies., (© The Author(s) 2025. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Phytochemicals derived from plants have been used as traditional medication owing to their potential therapeutic properties and gained recent attention due to their safe toxicological profiles contrary to synthetic drugs. Genistein (GEN) is a phytophenol reported to have an anticancer effect against various cancers including lung cancer, colorectal carcinoma, breast cancer, etc. However, its practical utilization is rendered by its limited aqueous solubility, slow dissolution, low oral bioavailability, poor stability, and non-specific biodistribution. Small bioactive molecules such as sugars are the most facile targeting ligands as almost all types of cancer cells are reported to exhibit the over-expression of sugar receptors in comparison to healthy cells. Sugar-based targeting of tumor sites is often mediated by surface-functionalized dendrimers which can simultaneously improve the efficacy of GEN and enable its site-specific delivery. In the present work, amine-terminated PAMAM dendrimers (DEND) have been used as a delivery carrier for improving the aqueous solubility and efficacy of GEN. Moreover, fucose (FUC) as a small sugar molecule, has been used for tumor-specific functionalization of DEND improving the lung cancer targeting of GEN. FUC conjugation also reduced the amine-terminal associated toxicity of DEND. The encapsulation of GEN in nanoscale FUC-DEND resulted 128 times enhancement in its water solubility, sustained release, improved physicochemical stability, and 22 times enhancement of anticancer activity. The greater cytotoxicity of GEN was attributed to higher cellular uptake and increased apoptosis in A549 human lung cancer cells. Hence, fucose-functionalized dendrimers could be an efficient carrier for the advanced and targeted delivery of phytochemicals. [ABSTRACT FROM AUTHOR]

The characterization of the binding of reducing carbohydrates present as mixtures of anomers in solution to a sugar recepor (lectin) poses severe difficulties. In this situation, NMR spectroscopy enables the observation of signals for each anomer in the mixture by applying approaches based on ligand observation. Saturation transfer difference (STD) NMR allows fast and efficient screening of compound mixtures for reactivity to a receptor. Owing to the exceptionally favorable properties of 19F in NMR spectroscopy and the often complex 1H spectra of carbohydrates, 19F-containing sugars have the potential to be turned into versatile sensors for recognition. Extending the recently established 1H → 1H STDre19F-NMR technique, we here demonstrate its applicability to measure anomeric selectivity of binding in a model system using the plant lectin concanavalin A (ConA) and 2-deoxy-2-fluoro-d-mannose. Indeed, it is also possible to account for the mutual inhibition between the anomers on binding to the lectin by means of a kinetic model. The monitoring of 19F-NMR signal perturbation disclosed the relative activities of the anomers in solution and thus enabled the calculation of their binding affinity towards ConA. The obtained data show a preference for the α anomer that increases with temperature. This experimental approach can be extended to others systems of biomedical interest by testing human lectins with suitably tailored glycan derivatives.

Abstract Olfaction and gustation play critical roles in the daily activities of insects by mediating important behaviors, such as locating host plants, mates and oviposition sites. These behaviors are mediated by a series of chemosensory receptor proteins, including odorant receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs). Holotrichia parallela is a worldwide pest on many crops and particularly on peanuts in China. In the present study, we produced Illumina-based transcriptomes from male and female antennae and ultimately identified 47 candidate ORs, 15 GRs and 27 IRs. Based on phylogenetic analyses, the relatedness with other species and possible functions of chemosensory genes were predicted and analyzed, such as the putative OR co-receptor (HparOR40), IR co-receptors (HparIR1 and HparIR27), carbon dioxide receptors (HparGR5 and HparGR14) and sugar receptors (HparGR8, HparGR11 and HparGR13). The differences in expression between genes and between sexes were analyzed using FPKM values and visualized in heat maps. Furthermore, the qRT-PCR results of 26 candidate genes were assessed to validate the differential expression analyses between sexes and between olfactory and non-olfactory tissues. Thirteen genes were more highly expressed in female than in male antennae, whereas four genes had higher expression in male than in female antennae. Twelve genes were predominantly expressed in the antennae as olfactory organs compared with expression in non-olfactory tissues. Our study was the first to annotate the chemosensory receptors of H. parallela , and it will provide a strong foundation for future work on physiology and ecology at the molecular level. [ABSTRACT FROM AUTHOR]

Honeybees ( Apis mellifera ) are well-known for their sophisticated division of labor with each bee performing sequentially a series of social tasks. Colony organization is largely based on age-dependent division of labor. While bees perform several tasks inside the hive such as caring for brood (“nursing”), cleaning or sealing brood cells or producing honey, older bees leave to colony to collect pollen (proteins) and nectar (carbohydrates) as foragers. The most pronounced behavioral transition occurs when nurse bees become foragers. For both social roles, the detection and evaluation of sugars is decisive for optimal task performance. Nurse bees rely on their gustatory senses to prepare brood food, while foragers evaluate a nectar source before starting to collect food from it. To test whether social organization is related to differential sensing of sugars we compared the taste of nurse bees and foragers for different sugars. Searching for molecular correlates for differences in sugar perception, we further quantified expression of gustatory receptor genes in both behavioral groups. Our results demonstrate that nurse bees and foragers perceive and evaluate different sugars differently. Both groups, however, prefer sucrose over fructose. At least part of the taste differences between social roles could be related to a differential expression of taste receptors in the antennae and brain. Our results suggest that differential expression of sugar receptor genes might be involved in regulating division of labor through nutrition-related signaling pathways. [ABSTRACT FROM AUTHOR]

Conventional array sensors mostly require the preparation of multiple sensing units and thus prevent miniaturization. This problem can be particularly solved by designing a sensing unit that acquires multidimensional information. In this study, with Mn-doped ZnS (Mn-ZnS) quantum dot (QD) two-dimensional (2D) optical properties (phosphorescence or fluorescence) as signals and boronic-acid-substituted viologens (BBV) as sugar receptors, we developed a single-material two-signal 2D sensor, and used it to discriminate the concentrations and types of six sugars (d-fructose, d-glucose, d-galactose, d-mannose, l-sorbose and sucrose). Its principle of detection is that BBV, through photoinduced electron-transfer (PIET), quenches the phosphorescence and fluorescence of Mn-ZnS QDs. After the sugars were added into the quenching system, since the sugar–BBV binding ability was decided by the type or concentration of sugar, this led to differences in the phosphorescence and fluorescence signals. Such differences could be differentiated using linear discriminant analysis. Based on this principle, a single-material 2D sensor for the six types of sugars and different concentrations was built. Our method expands the application of single-material multi-dimensional sensors and simplifies the preparation of conventional sugar array sensors. [ABSTRACT FROM AUTHOR]

Insects utilize sugars as their essential energy and nutrient sources; therefore, the sense of sugar detection plays a critical role in insect behaviours. Previously, using genomic and transcriptomic approaches, we identified eight putative sugar gustatory receptor (GR) genes from the cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Here, we further validated these annotated sugar receptor genes ( HarmGr4-HarmGr8 and HarmGr10-HarmGr12) and found HarmGr10 may be a pseudogene carrying a stop codon in the open reading frame. Sequence alignment revealed H. armigera sugar GR sequences are conserved at C-terminus and phylogenetic analysis showed that insect sugar GRs have evolved in a family-specific manner. Interestingly, all eight H. armigera sugar GRs are localized in a tandem array on the same scaffold of the genome. In silico gene expression and reverse transcription (RT)-PCR analysis showed that HarmGr10 is specifically expressed in male adult testes while HarmGr11 is specifically expressed in female adult ovaries, suggesting H. armigera sugar GRs may be involved in reproduction-related functions. This study improves our knowledge on insect sugar receptors and gustatory systems. [ABSTRACT FROM AUTHOR]

Carbohydrates establish the third alphabet of life. As part of cellular glycoconjugates, the glycans generate a multitude of signals in a minimum of space. The presence of distinct glycotopes and the glycome diversity are mapped by sugar receptors (antibodies and lectins). Endogenous (tissue) lectins can read the sugar-encoded information and translate it into functional aspects of cell sociology. Illustrated by instructive examples, each glycan has its own ligand properties. Lectins with different folds can converge to target the same epitope, while intrafamily diversification enables functional cooperation and antagonism. The emerging evidence for the concept of a network calls for a detailed fingerprinting. Due to the high degree of plasticity and dynamics of the display of genes for lectins the validity of extrapolations between different organisms of the phylogenetic tree yet is inevitably limited. [ABSTRACT FROM AUTHOR]

Recently, dRYamides-1 and -2 have been identified as ligands of the neuropeptide Y-like receptor CG5811 in Drosophila melanogaster. It has also been reported in brief that injection of dRYamide-1suppresses the early feeding behavior called proboscis extension reflex (PER) in the blowfly Phormia regina. Immunohistochemical analyses by our group using anti-dRYamide-1 antiserum indicated symmetrical localization of 32 immunoreactive cells in the brain of P. regina. In order to analyze the mechanism of feeding regulation, we further investigated the effects of dRYamide-1 and -2 on intake volume, PER exhibition, and activity of the sugar receptor neuron. After injection of dRYamide-1 or -2, flies showed little change in the intake volume of sucrose solution, but a significant depression of PER to sucrose. Injection of dRYamide-1 revealed a significant decrease in the responsiveness of the sugar receptor neuron, although the injection of dRYamide-2 did not. These results suggest that the dRYamide peptides decrease feeding motivation in flies, as evaluated by PER threshold, through a mechanism that partially involves desensitization of the sugar receptor neuron. [ABSTRACT FROM AUTHOR]

The characterization of the binding of reducing carbohydrates present as mixtures of anomers in solution to a sugar recepor (lectin) poses severe difficulties. In this situation, NMR spectroscopy enables the observation of signals for each anomer in the mixture by applying approaches based on ligand observation. Saturation transfer difference (STD) NMR allows fast and efficient screening of compound mixtures for reactivity to a receptor. Owing to the exceptionally favorable properties of 19F in NMR spectroscopy and the often complex 1H spectra of carbohydrates, 19F-containing sugars have the potential to be turned into versatile sensors for recognition. Extending the recently established 1H → 1H STDre 19F-NMR technique, we here demonstrate its applicability to measure anomeric selectivity of binding in a model system using the plant lectin concanavalin A (ConA) and 2-deoxy-2-fluoro-D-mannose. Indeed, it is also possible to account for the mutual inhibition between the anomers on binding to the lectin by means of a kinetic model. The monitoring of 19F-NMR signal perturbation disclosed the relative activities of the anomers in solution and thus enabled the calculation of their binding affinity towards ConA. The obtained data show a preference for the α anomer that increases with temperature. This experimental approach can be extended to others systems of biomedical interest by testing human lectins with suitably tailored glycan derivatives. [ABSTRACT FROM AUTHOR]

The order of Lepidoptera has historically been crucial for chemosensory research, with many important advances coming from the analysis of species like Bombyx mori or the tobacco hornworm, Manduca sexta . Specifically M. sexta has long been a major model species in the field, especially regarding the importance of olfaction in an ecological context, mainly the interaction with its host plants. In recent years transcriptomic data has led to the discovery of members of all major chemosensory receptor families in the species, but the data was fragmentary and incomplete. Here we present the analysis of the newly available high-quality genome data for the species, supplemented by additional transcriptome data to generate a high quality reference gene set for the three major chemosensory receptor gene families, the gustatory (GR), olfactory (OR) and antennal ionotropic receptors (IR). Coupled with gene expression analysis our approach allows association of specific receptor types and behaviors, like pheromone and host detection. The dataset will provide valuable support for future analysis of these essential chemosensory modalities in this species and in Lepidoptera in general. [ABSTRACT FROM AUTHOR]

Oogenesis in most adult insects is a nutrient-dependent process involving ingestion of both proteins and carbohydrates that ultimately depends on peripheral input from chemoreceptors. The main goal of this study was to characterize, in the female blowfly Phormia regina , the responsive changes of the labellar chemoreceptors to carbohydrates and proteins in relation to four different stages along the ovarian cycle: (1) immature ovaries, (2) mid-mature ovaries, (3) mature ovaries and ready for egg-laying and (4) post egg-laying ovaries. Then, the possible effects exerted by exogenous serotonin on the chemoreceptor sensitivity profiles were investigated. Our results show that ovary length, width and contraction rate progressively increase from stage 1 to 3, when all these parameters reach their maximum values, before declining in the next stage 4. The sensitivity of the labellar “sugar” chemoreceptors to both sucrose and proteins varies during the ovarian maturation stages, reaching a minimum for sucrose in stage 3, while that to proteins begins. Exogenous 5-HT supply specifically increases the chemoreceptor sensitivity to sugar at the stages 3 and 4, while it does not affect that to proteins. In conclusion, our results provide evidence that in female blowflies the cyclic variations in the sensitivity of the labellar chemosensilla to sugars and proteins are time-related to ovarian development and that during the stages 3 and 4 the responsiveness of the sugar cell to sucrose is under serotonergic control. [ABSTRACT FROM AUTHOR]

The emerging physiological significance of carbohydrate (glycan)–protein (lectin) recognition engenders the interest to design synthetic inhibitors with a high level of selectivity among natural sugar receptors. Plant agglutinins are common models to determine structure–activity relationships. Focussing on the contribution of valency towards selectivity, copper-catalysed azide (sugar derivative)–alkyne (scaffold) cycloaddition yielded a panel of 10 bi- to tetravalent glycoclusters with N -acetylglucosamine as the bioactive headgroup. They were introduced into assays using (neo)glycoproteins and cell surfaces as platforms to study carbohydrate-dependent lectin binding. The ability of the bivalent compounds, which exhibit a distance profile of the sugar headgroups of about 16–21 Å, for intramolecular bridging of two contact sites from the eight hevein domains of wheat germ agglutinin led to comparatively high enhancements of inhibitory potency relative to a tetrameric leguminous lectin (distance profile of 50–70 Å between sugar-specific sites), especially for a β-S-glycoside. The extent of inhibition at fixed concentrations of the sugar depended on the type of matrix used for the assay. Increases to tri- and tetravalency played a less important role than the anomeric position to keep cross-reactivity low, these tested topologies enabling cross-linking for both lectins. The potential for cis-interactions (intramolecular interactions), with glycoclusters serving as molecular rulers, is suggested to help designing selective blocking reagents. [ABSTRACT FROM AUTHOR]

Summary Identification of nutritious compounds is dependent on expression of specific taste receptors in appropriate taste-cell types [ 1 ]. In contrast to mammals, which rely on a single, broadly tuned heterodimeric sugar receptor [ 2 ], the Drosophila genome harbors a small subfamily of eight, closely related gustatory receptor ( Gr ) genes, Gr5a , Gr61a , and Gr64a – Gr64f , of which three have been proposed to mediate sweet taste [ 3–6 ]. However, expression and function of several of these putative sugar Gr genes are not known. Here, we present a comprehensive expression and functional analysis using Gr LEXA/GAL4 alleles that were generated through homologous recombination. We show that sugar Gr genes are expressed in a combinatorial manner to yield at least eight sets of sweet-sensing neurons. Behavioral investigations show that most sugar Gr mutations affect taste responses to only a small number of sugars and that effective detection of most sugars is dependent on more than one Gr gene. Surprisingly, Gr64a , one of three Gr genes previously proposed to play a major role in sweet taste [ 3, 4 ], is not expressed in labellar taste neurons, and Gr64a mutant flies exhibit normal sugar responses elicited from the labellum. Our analysis provides a molecular rationale for distinct tuning profiles of sweet taste neurons, and it favors a model whereby all sugar Grs contribute to sweet taste. Furthermore, expression in olfactory organs and the brain implies novel roles for sugar Gr genes in olfaction and internal nutrient sensing, respectively. Thus, sugar receptors may contribute to feeding behavior via multiple sensory systems. [ABSTRACT FROM AUTHOR]

The pKas as well as apparent binding constants of several 3-amino-substituted benzoxaboroles with alizarin red S (ARS) and some biologically important sugars have been evaluated and compared with that of the parent aminomethylphenylboronic acids. The investigated benzoxaboroles reveal lower acidity than the corresponding boronic acids. All the studied boronic compounds display the usual order of apparent binding constant values with glucose, galactose and fructose. The X-ray structure of the model catechol ester of the morpholinylmethylphenylboronic acid has been determined. The molecules are monomeric zwitterions with a tetracoordinated boron atom. The intermolecular interactions have been described with the aid of the Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

Abstract: Glycodendrimeric porphyrins seem promising photosensitizers usable in photodynamic therapy. Evidence of their ability to interact with an artificial supported bilayer membrane exhibiting a model sugar receptor has been previously shown. In the present work, the interaction of the glycodendrimeric porphyrins with retinoblastoma cells bearing the actual sugar receptor has been assessed by both classical cell cultures and an original approach using the quartz crystal microbalance (QCM-D). Our results showed that unlike cell cultures, QCM-D allowed analyzing the mechanism of interaction of the glycodendrimeric porphyrins with the sugar receptor. Not only was molecular recognition demonstrated, but our methodology also proved efficient to discriminate between the studied compounds, depending on the presence of carbohydrate, and the spacer length. [Copyright &y& Elsevier]

Animals have to perform adequate behavioral actions dependent on internal states and environmental situations, and adjust their behavior according to positive or negative consequences. The fruit fly Drosophila melanogaster represents a key model organism for the investigation of neuronal mechanisms underlying adaptive behavior. The authors are using a behavioral paradigm in which fruit flies attached to a manipulator can walk on a Styrofoam ball whose movements are recorded such that intended left or right turns of the flies can be registered and used to operantly control heat stimuli or optogenetic activation of distinct subsets of neurons. As proof of principle, the authors find that flies in this situation avoid heat stimuli but prefer optogenetic self-stimulation of sugar receptors. Using this setup it now should be possible to study the neuronal network underlying positive and negative value assessment of adult Drosophila in an operant setting. [ABSTRACT FROM AUTHOR]

The gustatory system is essential for almost all animals. However, the signal transduction mechanisms have not yet been fully elucidated. We isolated labellar chemosensilla from blowfly, Phormia regina, and purified calcium binding proteins from the water soluble fraction. The most abundant calcium-binding protein was calmodulin. To investigate the role of calmodulin in taste transduction, electrophysiological responses were recorded with the calmodulin inhibitor, W-7. When we stimulated the labellar chemosensillum with sucrose plus W-7, a dose-dependent decrease of impulse frequency was observed when the concentration was <50 μM. In addition, when W-7 at 50 μM or higher concentration was added, an initial short-term impulse generation from the sugar receptor cell was observed, but this was followed by a silent period. When the sensillum was stimulated with W-7 plus a membrane-permeable cGMP analog, dibtyryl-cGMP or 8-bromo-cGMP, impulses of the sugar receptor cell were induced but the frequency was decreased. By the sidewall-recording method, we observed that the receptor potential induced by sucrose stimulation was decreased by W-7 in the sugar receptor cell, and corresponded with a disappearance of impulses. These data strongly suggest that the cGMP-gated channel generating receptor potential in the sugar receptor cell requires calmodulin for its gating. [ABSTRACT FROM AUTHOR]

Generalization of a conditioned taste aversion (CTA) is based on similarities in taste qualities shared by the aversive substance and another taste substance. CTA experiments with rats have found that an aversion to a variety of sweet stimuli will cross-generalize with monosodium glutamate (MSG) when amiloride, a sodium channel blocker, is added to all solutions to reduce the taste of sodium. These findings suggest that the glutamate anion elicits a sweet taste sensation in rats. CTA experiments, however, generally do not indicate whether two substances have different taste qualities. In this study, discrimination methods in which rats focused on perceptual differences were used to determine if they could distinguish between the tastes of MSG and four sweet substances. As expected, rats readily discriminated between two natural sugars (sucrose, glucose) and two artificial sweeteners (saccharin, SC45647). Rats also easily discriminated between MSG and glucose, saccharin and, to a lesser extent, SC45647 when the taste of the sodium ion of MSG was reduced by the addition of amiloride to all solutions, or the addition of amiloride to all solutions and NaCl to each sweet stimulus to match the concentration of Na+ in the MSG solutions. In contrast, reducing the cue function of the Na+ ion significantly decreased their ability to discriminate between sucrose and MSG. These results suggest that the sweet qualities of glutamate taste is not as dominate a component of glutamate taste as CTA experiments suggest and these qualities are most closely related to the taste qualities of sucrose. The findings of this study, in conjunction with other research, suggest that sweet and umami afferent signaling may converge through a taste receptor with a high affinity for glutamate and sucrose or a downstream transduction mechanism. These data also suggest that rats do not necessarily perceive the tastes of these sweet stimuli as similar and that these sweet stimuli are detected by multiple sweet receptors. [ABSTRACT FROM AUTHOR]

Glycerol, a linear triol, is a sweet tastant for mammals but it has not previously been recognized to stimulate the sense of taste in insects. Here we show by electrophysiological experimentation that it effectively stimulates the labellar sugar receptor cell of Drosophila. We also show that in accord with the electrophysiological observations, the behavioral feeding response to glycerol is dose dependent. 3-Amino-1,2-propanediol inhibited the response of the sugar receptor cell to glycerol, specifically and competitively, while it had almost no effect on responses to sucrose, d-glucose, d-fructose and trehalose. In the null Drosophila mutant for the trehalose receptor (ΔEP19), the response to glycerol showed no change, in sharp contrast with a characteristic drastic decrease in the response to trehalose. The glycerol concentration–response curves for I-type and L-type labellar hairs were statistically indistinguishable, while those for sucrose, d-glucose, d-fructose and trehalose were clearly different. These all indicate the presence of a specific receptor site for glycerol. The glycerol site was characterized by comparing the effectiveness of various derivatives of glycerol. Based on this structure–taste relationship of glycerol, a model is proposed for the glycerol site including three subsites and two steric barriers, which cannot accommodate carbon-ring containing sugars such as d-glucose. [ABSTRACT FROM AUTHOR]

The taste organ in insects is a hair-shaped taste sensory unit having four functionally differentiated contact chemoreceptor cells. In the blowfly, Phormia regina, cGMP has been suggested to be a second messenger for the sugar receptor cell. Generally, cGMP is produced by membranous or soluble guanylyl cyclase (sGC), which can be activated by nitric oxide (NO). In the present paper, we electrophysiologically showed that an NO scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (PTIO), an NO donor, 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC 7) or an NO synthase (NOS) inhibitor, NG-nitro-l-arginine methyl ester (l-NAME) specifically affected the response in the sugar receptor cell, but not in other receptor cells. PTIO, when introduced into the receptor cells in a sensillum aided by sodium deoxycholate (DOC, pH 7.2), depressed the response of sugar receptor cells to sucrose but did not affect those of the salt or water receptor cells. NOC 7, given extracellularly, latently induced the response of sugar receptor cells; and l-NAME, when introduced into the receptor cells, depressed the response of sugar receptor cells. The results clearly suggest that NO, which may be produced by intrinsic NOS in sugar receptor cells, participates in the transduction cascade of these cells in blowfly. [ABSTRACT FROM AUTHOR]

The lycaenid butterfly, Niphanda fusca, has a parasitic relationship with its host ant, Camponotus japonicus: the caterpillars may use chemical mimicry to enter the ant nest where they are fed mouth-to-mouth by the adult ants until pupation. Nevertheless, larvae offer their host ants a nutritious secretion that contains 160 mM glucose and 43 mM glycine. Using glucose and glycine mixture as artificial secretions, we investigated the gustatory effect of glucose and/or glycine on the ants. Glycine induced neither feeding behavior nor gustatory response in the ants if its concentration was <500 mM. In the presence of glycine at the concentration in the secretion, however, the ants improved their preference to glucose, and the sugar receptor cell exhibited electrophysiological enhancement of response to glucose in a glycine-concentration-dependent manner. By adding glycine to glucose in their secretions, therefore, the butterfly larvae can manipulate the gustatory sense of the ants. The alluring taste of `glycine-flavored glucose' could motivate the host ants to feed the larvae and thereby receive the secretions as a reward. The taste enhancement created by the combination of sugar and amino acid may play a role in the evolution of the parasitic relationships of these insects. The taste-enhancing effect appears to be analogous to taste enhancement by `umami' substances in humans. [ABSTRACT FROM AUTHOR]

The characteristics of the recognition system involved in the receptor mediated endocytosis of the neoglycoprotein, fucose human serum albumin (HSA) were studied. It was found that (i) fucose-HSA showed strong affinity binding and uptake by various macrophages; (ii) binding was specific for L-fucose and D-mannose; (iii) binding was found to be inhibited by oxidant like HO and swainsonine whereas it was elevated by dexamethasone; (iv) clearance ofI-fucose-HSA was rapid and strongly inhibited by unlabelled fucose-HSA. Greater than 70% of fucose-HSA was found in liver and more than 60% of this was found in liver lysosomes; (v) uptake of fucose-HSA was thirty-fold more efficient in liver macrophages (Kupffer cells) than in hepatocytes; (vi) moreover, mannose-HSA and ovalbumin which are potent inhibitors of mannose/N-acetylglucosamine receptors inhibited clearance and uptake of fucose-HSA by liver as well as by isolated Kupffer cells suggesting the involvement of both fucose and mannose receptors or a single type of receptor having greater affinity for fucose-HSA than for mannose-HSA. These results emphasize the important role of fucose-terminated glycoproteins in site-specific drug targeting. [ABSTRACT FROM AUTHOR]

In this article the authors discuss a report within the issue regarding research by M. W. Baldwin et al. describing the evolution of an amino acid taste receptor in sweet nectar-eating hummingbirds to sense sugar and other sweeteners, which allowed them to adapt their diet and occupy a novel avian niche. Topics include the T1R2-T1R3 sweet taste receptor and the T1R1-T1R3 amino acid taste receptor, the loss of the sweet taste receptor gene Tas1r2 in birds, and behavioral taste testing results.

The article discusses research study that examined the ammonioacetohydrazones of formylphenylboronic acids as an ionic prospectuve sugar receptors through synthesis and nuclear magnetic resonance (NMR) and mass spectrometry. Topics discussed include the presence of ammonioacetohydrazones of formylphenylboronic acids in dimethylsulfoxide (DMS) solution and matrix-assisted laser desorption/ionization (MALDI) in the positive-ion mode analysis.

A correction to the article "Intrinsic Nitric Oxide Regulates the Taste Response of the Sugar Receptor Cell in the Blowfly, Phormia regina," by Yoshihiro Murata and colleagues is presented.

Arthropods employ a large family of up to 100 putative taste or gustatory receptors (Grs) for the recognition of a wide range of non-volatile chemicals. In Drosophila melanogaster, a small subfamily of 8 Gr genes is thought to mediate the detection of sugars, the fly's major nutritional source. However, the specific roles for most sugar Gr genes are not known. Here, we report the generation of a series of mutant sugar Gr knock-in alleles and several composite sugar Gr mutant strains, including a sugar blind strain, which will facilitate the characterization of this gene family. Using Ca(2+) imaging experiments, we show that most gustatory receptor neurons (GRNs) of sugar blind flies (lacking all 8 sugar Gr genes) fail to respond to any sugar tested. Moreover, expression of single sugar Gr genes in most sweet GRNs of sugar-blind flies does not restore sugar responses. However, when pair-wise combinations of sugar Gr genes are introduced to sweet GRNs, responses to select sugars are restored. We also examined the cellular phenotype of flies homozygous mutant for Gr64a, a Gr gene previously reported to be a major contributor for the detection of many sugars. In contrast to these claims, we find that sweet GRNs of Gr64a homozygous mutant flies show normal responses to most sugars, and only modestly reduced responses to maltose and maltotriose. Thus, the precisely engineered genetic mutations of single Gr genes and construction of a sugar-blind strain provide powerful analytical tools for examining the roles of Drosophila and other insect sugar Gr genes in sweet taste.