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PubMed1995

Binding of Galanthus nivalis lectin to Chlamydia trachomatis and inhibition of in vitro infection.

A glycoprotein present in Chlamydia trachomatis, serotype L1, elementary bodies (EBs) was earlier found to bind the lectin from Galanthus nivalis (GNA). In the present paper we investigate the interaction of GNA with chlamydial EBs and its effect on in vitro infectivity. The binding affinity was studied with 125I-GNA lectin. Within 15 min about 80% maximal binding was obtained. The chlamydia-GNA interaction was inhibited by alpha-methylmannoside, causing a decrease of about 50% at 1 mM. Curve fit analyses indicated two types of binding sites for GNA on the EBs. The affinity to these differed by a factor of 15. The influence of the lectin on the ability of C. trachomatis to infect McCoy cells was also investigated. There was a GNA-dependent inhibition with a 50% reduction in the number of intracellular inclusions at 0.2 microM of the lectin. The findings indicate the presence of terminal mannose structures on the chlamydial surface at or in the proximity of the cell-binding domains. Mannose-binding proteins of eukaryotic cells could be important for the initial uptake of EBs.

Animals↗
PubMed2003

Consumption of snowdrop lectin (Galanthus nivalisagglutinin) causes direct effects on adult parasitic wasps.

Honeydew is a common sugar-rich excretion of aphids and other phloem-feeding insects and represents the primary sugar in many agricultural systems. When honeydew-producing insects feed on genetically modified plants, the honeydew can contain amounts of the transgene product. Here we address whether this route of exposure poses a risk for non-target insects. Three species of parasitic wasps were selected: i.e. Aphidius colemani, Trichogramma brassicae and Cotesia glomerata, all of which are known to use honeydew as a carbohydrate source in the field. Wasps were fed sucrose solutions with varying concentrations of snowdrop lectin ( Galanthus nivalisagglutinin, GNA), a protein that has been engineered into crops to confer resistance against homopteran pests and that has been detected in honeydew. Parameters evaluated included gustatory response, longevity, fecundity, progeny emergence and sex ratio. While A. colemani and T. brassicae, but not C. glomerata, were able to detect GNA, this gustatory recognition had no effect on the acceptance of a GNA-sucrose solution. In all three species, GNA ingestion reduced parasitoid survival significantly. However, in respect to fecundity, negative effects were observed for T. brassicae but not for A. colemani. The results suggest that the effect of GNA consumption may depend on the specifics of a parasitoid's biology, especially its longevity and its mode of egg maturation.

Animals↗
PubMed2001

Direct and indirect sublethal effects of Galanthus nivalis agglutinin (GNA) on the development of a potato-aphid parasitoid, Aphelinus abdominalis (Hymenoptera: Aphelinidae).

Snowdrop lectin (Galanthus nivalis agglutinin, GNA), has been shown to confer partial resistance to two potato aphids Myzus persicae and Aulacorthum solani, when incorporated in artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess the potential effect of GNA on the aphid parasitoid Aphelinus abdominalis. GNA (0.1% w/v) was successfully delivered to Macrosiphum euphorbiae via artificial diet and induced a reduced growth rate and increased mortality compared to aphids fed a control diet. As aphid parasitoid larvae are endophagous, they may be exposed to GNA during their larval development and potential "chronic toxicity" on A. abdominalis was investigated. The amounts of GNA present in aphid and parasitoid tissues were estimated by western blotting. Results suggest that parasitoids excrete most of the GNA ingested. Sublethal effects of GNA on several parasitoid fitness parameters (parasitism success, parasitoid development and size, emergence success, progeny survival and sex ratio) were studied. No direct detrimental effect of GNA on A. abdominalis was observed. However, GNA had an indirect host-size-mediated effect on the sex ratio and the size of parasitoids developing in GNA-fed aphids. This work highlights the need to determine the exact "causes and effects" when assessing the ecological impact of transgenic plants on non-target beneficial insects. Such bioassays form the basis of a tiered risk assessment moving from laboratory studies assessing individuals towards field-scale experiments assessing populations.

Journal Article↗
PubMed2001

In vitro and in vivo binding of snowdrop (Galanthus nivalis agglutinin; GNA) and jackbean (Canavalia ensiformis; Con A) lectins within tomato moth (Lacanobia oleracea) larvae; mechanisms of insecticidal action.

When fed in semi-artificial diet the lectins from snowdrop (Galanthus nivalis: GNA: mannose-specific) and jackbean (Canavalia ensiformis: Con A: specific for glucose and mannose) were shown to accumulate in vivo in the guts, malpighian tubules and haemolymph of Lacanobia oleracea (tomato moth) larvae. Con A, but not GNA, also accumulated in the fat bodies of lectin-fed larvae. The presence of glycoproteins which bind to both lectins in vitro was confirmed using labelled lectins to probe blots of polypeptides extracted from larval tissues. Immunolocalisation studies revealed a similar pattern of GNA and Con A binding along the digestive tract with binding concentrated in midgut sections. Binding of lectins to microvilli appeared to lead to transport of the proteins into cells of the gut and malpighian tubules. These results suggested that both lectins are able to exert systemic effects via transport from the gut contents to the haemolymph across the gut epithelium. The delivery of GNA and Con A to the haemolymph was shown to be dependent on their functional integrity by feeding larvae diets containing denatured lectins. Con A, but not GNA, was shown to persist in gut and fat body tissue of lectin-fed larvae chased with control diet for three days. Con A also shows more extensive binding to larval tissues in vitro than GNA, and these two factors are suggested to contribute to the higher levels of toxicity shown by Con A, relative to GNA, in previous long term bioassays.

Journal Article↗
PubMed2000

Resistance to green leafhopper (Nephotettix virescens) and brown planthopper (Nilaparvata lugens) in transgenic rice expressing snowdrop lectin (Galanthus nivalis agglutinin; GNA).

Transgenic rice plants expressing snowdrop lectin (Galanthus nivalis agglutinin; GNA) were screened for resistance to green leafhopper (Nephotettix virescens; GLH), a major homopteran pest of rice. Survival was reduced by 29% and 53% (P<0.05) respectively, on plants where GNA expression was tissue-specific (phloem and epidermal layer) or constitutive. Similar levels of resistance in GNA-expressing transgenic rice were previously reported for rice brown planthopper (Nilaparvata lugens; BPH). GNA binding to glycoproteins in gut tissues showed that BPH contained more "receptors" than GLH, and that the binding affinity was stronger, particularly in the midgut. Subsequent toxicity of GNA is thus unlikely to be directly related to the amount of lectin bound. GNA was not detected in the honeydew of either insect species when they were fed on GNA-expressing plants, in contrast to results from artificial diet studies. This result suggests that GNA is not being delivered to the insect efficiently. When offered a free choice vs control plants, BPH nymphs tended to avoid plants expressing GNA; avoidance was less pronounced and took longer to develop on plants where GNA expression was tissue-specific, In contrast to BPH, GLH nymphs were attracted to plants expressing GNA, whether constitutively or in a tissue-specific manner.

Journal Article↗
PubMed2002

Binding of the Galanthus nivalis agglutinin to thymocytes reveals alterations in surface glycosylation during T-cell development.

Surface binding of the Galanthus nivalis agglutinin (GNA) to thymocyte subsets has been studied in pigs and rodents by multicolour flow cytometry. In all the species examined, analogous staining profiles have been recorded. Counter-staining with anti-CD3epsilon, anti-CD4 and anti-CD8 monoclonal antibodies (MoAb) revealed that a significant increase of the GNA targets on the cell surface occurred during early thymocyte differentiation and reached its maximum at the level of the CD3loCD4+CD8+ small cortical thymocyte. This was followed by a decrease in the GNA binding capacity upon terminal maturation to the single positive thymocytes. PAGE analysis has revealed a dominant GNA-binding glycoprotein (molar mass approx. 90 kDa) present on thymocyte plasma membranes and absent on the surface of splenic lymphocytes, although both the whole cell lysates from both organs contained GNA ligands of the same size. Our findings are in agreement with previous data showing that immature thymocytes differ from their mature counterparts and peripheral T lymphocytes in the surface glycosylation pattern, and support the hypothesis that lectin-glycoprotein interaction plays a significant role in the cell-to-cell crosstalk in the thymic cortex.

Animals↗
PubMed2006

Effects of Galanthus nivalis agglutinin (GNA) expressed in tomato leaves on larvae of the tomato moth Lacanobia oleracea (Lepidoptera: Noctuidae) and the effect of GNA on the development of the endoparasitoid Meteorus gyrator (Hymenoptera: Braconidae).

The effect of ingestion of transgenic tomato leaves expressing the plant lectin Galanthus nivalis agglutinin (GNA) on development of larvae of Lacanobia oleracea (Linnaeus) was studied under laboratory conditions. When L. oleracea larvae were fed on tomato line 14.1H, expressing approximately 2.0% GNA, significant increases in the mean larval weight and in the amount of food consumed were found. This resulted in an overall reduction in the mean development time to the pupal stage of approximately 7 days. A significant increase in the percentage survival to the adult moth was also recorded when newly hatched larvae were reared on transgenic tomato leaves (72%) compared to larvae reared on untransformed leaves (40%). The effects of ingestion of GNA by L. oleracea larvae, via artificial diet or the leaves of transgenic tomato or potato plants, on the subsequent development of its solitary endoparasitoid Meteorus gyrator (Thunberg) was also studied. No significant effects on the life cycle parameters of M. gyrator developing in L. oleracea fed on GNA-containing diets were observed. Experiments with transgenic potato plants indicated that the stadium of the host larvae at parasitism had a greater influence on M. gyrator development than the presence of GNA. Potential GNA-binding glycoproteins were detected in the gut and body tissues of larval M. gyrator. Despite detection in host tissues, GNA could not be detected in adult M. gyrator and therefore it is likely that at the time of pupation M. gyrator are able to void the GNA in the meconial pellet.

Animals↗
PubMed1988

Biosynthesis of the Snowdrop (Galanthus nivalis) Lectin in Ripening Ovaries.

The biosynthesis and processing of the Galanthus nivalis agglutinin were studied in vivo in ripening snowdrop ovaries. Using labeling and pulse chase labeling experiments it could be demonstrated that the snowdrop lectin is synthesized as a precursor of relative molecular weight (M(r)) 15,000 which is posttranslationally converted into the authentic lectin polypeptide of M(r) 13,000 with a half-life of about 6 hours. Gel filtration of an extract of [(3)H]leucine labeled ovaries on Sepharose 4B showed that a significant portion of the newly synthesized lectin is associated with the particulate fraction. When the organellar fraction was fractionated on isopycnic sucrose gradients this lectin banded in the same density region as the endoplasmic reticulum (ER) marker enzyme NADH cytochrome c reductase. Both radioactivity in lectin and in enzyme activity shifted towards a higher density in the presence of 2 millimolar Mg-acetate indicating that the labeled lectin was associated with the rough ER. Labeled lectin could be chased from the ER with a half-life of 4 hours and then accumulated in the soluble fraction. Whereas the ER-associated lectin contains exclusively polypeptides of M(r) 15,000 the soluble fraction contains both precursor molecules and mature lectin polypeptides. The snowdrop lectin in the ER is fully capable of binding immobilized mannose. It is associated into tetramers with an appropriate molecular weight of 60,000. These results indicate that newly synthesized snowdrop lectin is transiently associated with the ER before transport and processing.

Journal Article↗
PubMed2004

Seasonal dynamics of non-structural carbohydrates in bulbs and shoots of the geophyte Galanthus nivalis.

Seasonal dynamics of non-structural carbohydrates were studied in Galanthus nivalis L. over a 2-year period. The plants were collected in the field and separated into above- and below-ground biomass. The polysaccharide fraction of the bulbs consisted of fructans and starch. Seasonal variations suggest that the polysaccharides were utilized for carbon and energy supply for re-growth and flower development. With the re-sprouting of the bulbs in autumn the fructans within the bulbs were depolymerized and an increase of low degree of polymerization fructans as well as sucrose was observable. Within shoots the major polysaccharides were fructans, the starch content was much lower. Gas liquid chromatography and high-performance, anion-exchange chromatographyanalysis of the fructan fraction revealed that the fructans within the shoots were predominantly those with a low degree of polymerization. In addition to the two polysaccharides the other dominant sugar in shoots was sucrose. During the period of slow re-growth and flowering, fructan and starch pools were depleted to different degrees. Calculation of the difference between the carbohydrate content at the start of visible growth and at the time of lowest content revealed that the starch pool showed a higher depletion than the fructan pool. During the re-growth periods in 1996/97 and 1997/98 fructans were catabolized by 39 and 32% only, whereas the starch pool was depleted by 92% (1996/97) and 79% (1997/98), respectively. During rapid shoot growth and fruiting, the bulbs and above-ground organs appeared to be competing sinks for the photosynthetically fixed carbon. Refilling of the bulbs carbohydrate reserve started in February/March In shoots, the period of refilling the bulbs was characterized by a low content of oligosaccarides and a high content of hexoses.

Journal Article↗
PubMed2004

[Obtainment of transgenic wheat with the insecticidal lectin from snowdrop (Galanthus nivalis agglutinin; GNA) gene and analysis of resistance to aphid].

Snowdrop lectin (Galanthus nivalis agglutinin; GNA) is toxic to sap sucking injurious insects of Homopteran. A new gna gene has been transferred into common spring wheat Zhong60634 and winter wheat Yumai66 with high yield by using the biolistic transformation method. Transgenic wheat plants have been obtained in both of the two varieties. Two transgenic plants (T0) have been obtained from the bombarded 535 immature embryos of Zhong60634. Bioassay results show that the development of aphid could be slowed down and the survival rate of young aphid could be reduced by gna gene. Seventeen transgenic plants (T0) were obtained from the bombarded 4636 immature embryos of Yumai66. Twenty plantlets with good resistance to Rhopalosiphum padi and Macrosiphum avenae, which are mainly aphid in north wheat area, were identified from the transgenic plants of T1 generation that came from 8 T0 transgenic plants with good resistance to aphid. The anti-aphid bioassay shows that resistance to the different grain aphid is not the same in transgenic wheat plants. To Rhopalosiphum padi, the rate of survival aphid 8 days after exposing transgenic plants to aphids is significantly lower than that of nontransgenic plants. To Macrosiphum avenae, growth speed of aphids is slowed down but not killed. At the same time, the death rate of young aphids is increased. Anyway, feeding of the two kinds of aphids has been controlled in a certain degree by gna gene when aphids can free to move in plants.

Animals↗
PubMed1988

Binding properties of a mannose-specific lectin from the snowdrop (Galanthus nivalis) bulb.

Carbohydrate binding properties of a new plant lectin (GNA) isolated from snowdrop bulbs were studied using the technique of quantitative precipitation, hapten inhibition, and affinity chromatography on immobilized lectin. Purified GNA precipitated highly branched yeast mannans but did not react with most glucans. Hapten inhibition experiments showed that D-mannose is an inhibitor of GNA-mannan interaction but neither N-acetyl-D-mannosamine nor D-glucose is an inhibitor. Hapten inhibition with various sugars showed that GNA requires the presence of equatorial hydroxyl groups at the C-3 and C-4 positions and an axial group at the C-2 position of the D-pyranose ring. A nonreducing terminal D-mannose residue is necessary for the interaction of oligosaccharides, and oligosaccharides with terminal Man(alpha-1-3)Man units showed the highest inhibitory potency (10-30 times greater than D-mannose) among the manno-oligosaccharides tested. The presence of the hydrophobic p-nitrophenyl aglycone increased the affinity of D-mannose only slightly. Immobilized GNA bound yeast mannan but did not bind glycogen. The behavior of glycoproteins with high mannose type glycan chains depended on the density and the structure of their glycan chains. Glycopeptides which carry Man(alpha 1-3)Man units were retarded on the immobilized GNA column whereas those lacking this unit or with hybrid type glycan chains were not retarded on the column.

Animals↗