Properties of the lectin from the hog peanut (Amphicarpaea bracteata)

An N-acetyl-D-galactosamine-specific lectin has been isolated from the two seed forms of the hog peanut (Amphicarpaea bracteata) using an affinity support containing the synthetic type A blood group trisaccharide alpha-D-GalNAc-(1,3)-[alpha-L-Fuc-(1,2)]-beta-D-Gal (Synsorb A). The affinity-purified lectin appears to be identical in both seed types. Gel filtration on Sephadex G-200 gives a single symmetrical peak corresponding to Mr 135,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows four subunit forms, each of which contains carbohydrate. Limited amino terminal sequencing indicates heterogeneity in two of the first 10 residues. The lectin contains no cysteine. There are four equivalent, noninteracting GalNAc binding sites per 135,000-Da molecule, having an association constant for methyl N-acetyl-alpha-D-galactosaminide of 4.0 X 10(4) M-1. Precipitin and hapten inhibition studies show the lectin to be specific for terminal, nonreducing D-GalNAc units, with a preference for the alpha-anomer and enhanced specificity for the disaccharide, GalNAc alpha 1,3GalNAc. There is also a single adenine binding site per Mr 135,000 lectin molecule with an association constant of 1.3 X 10(6) M-1.     

Evolution in natural and experimental populations of Amphicarpaea bracteata

Genetically divergent lineages (biotypes) often coexist within local populations of the selfing annual Amphicarpaea bracteata (Leguminosae). At one site, a rapid change in lineage frequency was observed, with one biotype decreasing from 41% to 16% of the population over a 2 year period. During 6 additional years of censuses, this lineage showed no tendency to recover to its former abundance. An experimental population was constructed with approximately equal numbers of individuals from the two dominant biotypes in this population, and plants were allowed to grow and reproduce without interference for 3 generations. The same lineage that declined in the natural habitat was also strongly selected against in this experimental population, with a selection coefficient (0.57 per generation) comparable to that inferred from the initial decline in frequency of this lineage in nature (0.47). A greenhouse experiment suggested that differential adaptation to high vs. low light environments could be one factor affecting relative success of these lineages. Differences in reproductive allocation and disease resistance to local pathogens are also key factors likely to affect relative fitness. Overall, these results show that the genetic structure of selfing plant populations can be highly dynamic, with intense selection and sudden shifts in relative abundance of different lineages.     

Divergence and isolation of cryptic sympatric taxa within the annual legume Amphicarpaea bracteata

The amphicarpic annual legume Amphicarpaea bracteata is unusual in producing aerial and subterranean cleistogamous flowers that always self‐fertilize and, less commonly, aerial chasmogamous flowers that outcross. Although both morphologic and genetic variants are known in this highly selfing species, debate continues over whether this variation is continuous, reflecting the segregation of standing genetic variation, or discontinuous, reflecting distinct taxa that rarely intercross. We characterized SNP variation in 128 individuals in southern Wisconsin to assess within‐ and among‐population variation at 3928 SNPs. We also assessed genotype and leaf morphology in an additional 76 individuals to connect phenotypic variation with genetic variation. Genetic variation maps onto three strongly divergent and highly inbred genetic groups showing little relation to site location. Each group has a distinct phenotype, but the divergence of these groups differs from the varietal divisions previously identified based on morphological characters. Like previous authors, we argue that the taxonomy of this species should be revised. Despite extensive sympatry, estimates of among‐group migration rates are low, and hybrid individuals were at low frequency (<2%) in our dataset. Restricted gene flow likely results from high selfing rates and partial reproductive incompatibility as evidenced by the U‐shaped distribution of pairwise F_ST values reflecting “islands” of genomic divergence. These islands may be associated with hybrid incompatibility loci that arose in allopatry. The coexistence of lineages within sites may reflect density‐dependent attack by species‐specific strains of pathogenic fungi and/or root‐nodulating bacteria specializing on distinct genotypes.     

Individual variation in pathogen attack and differential reproductive success in the annual legume,Amphicarpaea bracteata

Summary Demographic analyses in two natural populations of the annual legume Amphicarpaea bracteate examined whether variation in attack by the host-specific fungal pathogen Synchytrium decipiens was associated with variation in the reproductive success of individual plants. In both populations, fungal infection early in life was significantly associated with reduced seedling growth rates. Laboratory inoculation experiments confirmed that S. decipiens infection had a negative impact on plant growth. The laboratory experiments further indicated that there was significant variation among the progenies of different plant genotypes in the degree of growth reduction caused by pathogen attack. Prereproductive mortality rates in natural environments were significantly higher for plants with infection intensities above the median; for the two populations studied, heavily infected plants had 3.8 and 12 gimes higher death rates compared with low infection plants. Among surviving plants, fungal infection intensity was significantly negatively correlated with total seed biomass in both populations. As a result of these associations between plant survivorship, fecundity, and fungal infection, lifetime relative fitness within both plant populations was strongly negatively correlated with the intensity of S. decipiens infection. These results demonstrate the existence of consistent natural selection for increased resistance to pathogen attack in this plant species.     

Consequences of a mixed reproductive system in the hog peanut,Amphicarpaea bracteata, (Fabaceae)

Summary The forest annual, Amphicarpaea bracteata L. can reproduce via aerial chasmogamous, aerial cleistogamous, and subterranean cleistogamous flowers. Both plant size and light intensity influenced the utilization of the three modes of reproduction. chasmogamous and aerial cleistogamous flower number and the ratio of chasmogamous flowers to the total number of aerial flowers increased with plant size. The latter demonstrated a shift to xenogamy and outbreeding in larger plants. Light intensity indirectly influenced reproductive modes through its infuence on plant size. Seed set by both types of aerial flowers was low and unrelated to plant size. Subterranean seed number and the total dry weight of subterranean seeds per plant increased with size. The subterranean seeds of Amphicarpaea bracteata are thirty-four times larger than the aerial seeds (fresh weight). Under field conditions, subterranean seeds had greater germination after one year than acrial seeds. The plants arising from subterranean seeds were significantly larger and more fecund than those from aerial seeds. Seeds produced by aerial cleistogamous, hand selfpollinated chasmogamous, and naturally pollinated chasmogamous flowers had equivalent germination rates and produced plants of equal size and fecundity. This suggests that the outbred progeny from chasmogamous flowers have no advantage over the inbred progeny from aerial cleistogamous flowers.     

An N-acetyl-d-glucosamine binding lectin from Bandeiraea Simplicifolia seeds

A second lectin with a high activity for nonreducing 2-acetamido-2-deoxy-α-d-glucopyranosyl residues has been isolated from the seed extracts of Bandeiraea simplicifolia by affinity chromatography on chitin. The lectin is a glycoprotein of subunit molecular weight 30,000. Some properties of the new lectin are reported.     

Diversity and relationships of Bradyrhizobia from Amphicarpaea bracteata based on partial nod and ribosomal sequences.

Partial sequences of three nod genes (nodC, nodD1, and nodA 5' flanking region) and of 16S and 23S rDNA were obtained from isolates of Bradyrhizobium sp. associated with the native North American legume Amphicarpaea bracteata. Isolates from Amphicarpaea had identical sequences in the three nod gene regions, but differed from all other Bradyrhizobium taxa at > 10% of nucleotide sites. Parsimony analysis of all nod gene segments indicated a phylogenetic relationship of these bacteria to B. elkanii, with B. japonicum diverging prior to the diversification of these taxa. All Bradyrhizobium isolates from Amphicarpaea were also identical to B. elkanii in the size of the intervening sequence (IVS) in the 5' region of the 23S rRNA gene, while B. japonicum had an IVS length variant with 29 additional nucleotides. Parsimony analysis of both 16S and 23S partial rDNA sequences grouped Bradyrhizobium sp. isolates from Amphicarpaea into a clade together with B. elkanii, consistent with the relationships inferred from nod sequences.     

A new anti-H lectin from the seeds ofGalactia tenuiflora

A new anti-blood group H lectin was isolated from the seeds ofGalactia tenuiflora. This lectin is mostly specific for the H type 2 trisaccharide but it shows some cross-reactivity with the H type 4 and H type 3 trisaccharides. Differences between this lectin and lectin 1 fromUlex europaeus are described. These differences concern the respective abilities of the lectins to recognize erythrocytes from some H deficient phenotypes, the inhibitions by salivas and the tissue distribution of the antigens recognized by the two lectins. The most important differences were noted in the surface epithelium of the stomach. This area is known to express ABH antigens under the control of theSe gene as defined by theUlex europaeus lectin 1, yet it is always strongly labelled by theGalactia tenuiflora lectin irrespective of the secretor status of the tissue donor.     

Characterization of a lectin from the seeds of Erythrina vespertilio

A lectin was isolated from the seeds of Erythrina vespertilio by affinity chromatography on lactose-Sepharose 6B. The lectin has an M, of 59 000 and consists of two non-covalently associated subunits (M, ∼ 30 000). The lectin is devoid of cysteine but has six methionine residues/mol and a neutral sugar content of 9.7% The carbohydrate composition was mannose, N-acetylglucosamine, fucose, xylose and galactose in amounts of 15.0, 4.0, 1.0, 5.0 and 25 mol/59 000 g, respectively. Alkaline gel electrophoresis and isoelectric focusing showed that the affinity purified lectin consists of a family ofisolectins. Valine was the only N-terminal amino acid found and the N-terminal sequence was homologous with that found for other legume lectins. The lectin was inhibited by galactosyl containing carbohydrates; p-nitrophenyl-β-galactoside was the best inhibitor and the lectin showed a slight preference for β-galactosides. Comparison of its properties with those of other Erythrina lectins shows that most of the lectins of this genus are closely related.     

Use and nutritive value of talet beans,Amphicarpaea bracteata (Fabaceae: Phaseoleae) as human food in Puebla, México

Species of the genus Amphicarpaea have been reported as edible (for human consumption or as fodder) in Asia and North America. In northern Puebla, México, talet, A. bracteata, grows as a weed in multiple cropping systems, and its subterranean fruits are used as food by Nahuas, Totonacs, and Mestizos. This study documents how the seed is harvested during agricultural practices, the way in which the pleasant-tasting seeds are prepared for consumption, and how the plants are integrated in the management of the maizebean agroecosystem. We provide data on the chemical composition of talet beans, which is similar to that reported for other food legumes. Talet beans are recommended for development as a casually eaten protein supplement to the human diet in northern Puebla.     

Carbohydrate binding studies on the lectin from Datura stramonium seeds

The carbohydrate-binding properties of the Datura stramonium seed lectin were studied by equilibrium dialysis, quantitative precipitation of natural and synthetic glycoproteins, and hapten inhibition of precipitation. The dimeric lectin (M_r = 86,000) possesses two carbohydrate-binding sites for N,N′,N′',N?-tetraacetylchitotetritol/mol protein, with an apparent K_a = 8.7 × 10³M^?1 at 4 °C. Whereas fetuin and orosomucoid reacted poorly with the Datura lectin, the asialo derivatives of these glycoproteins gave strong precipitation with the lectin. Carcinoembryonic antigen, type 14 pneumococcal capsular polysaccharide, and bovine serum albumin, highly substituted with N,N′- diacetylchitobiose units, also precipitated the lectin. Of the homologous series of chitin oligosaccharides tested, N,N′,N?-triacetylchitotriose was over 6-fold more potent than the disaccharide (N′,N′-diacetylchitobiose) which, in turn, was 90 times more reactive than N-acetyl-d-glucosamine.N-Acetyllactosamine [β-d-Gal-(1 → 4)-d-GlcNAc] was also a potent inhibitor of Datura lectin being equivalent to N,N′-diacetylchitobiose. The requirement for an N-acetyl-d-glucosaminyl unit linked at the C-4 position was established. The biantennary pentasaccharide (penta-2,6) was a 500-fold more potent inhibitor than N-acetyllactosamine, suggesting that it might interact with both saccharide-binding sites of the Datura lectin simultaneously.     

Properties of a lectin purified from the seeds of Cicer arietinum

A lectin was isolated from seed extracts of Cicer arietinum by (NH4)2SO4 precipitation and subsequent ion exchange chromatography and gel filtration. Affinity chromatography on desialylated human IgM coupled to AH-Sepharose was also performed, but the amount bound was very low. The lectin has a molecular mass of about 44000 Da, as determined by ultracentrifugation and gel filtration. Dodecyl sulphate polyacrylamide-gel electrophoresis showed one band corresponding to a molecular mass of 26000 Da. N-Terminal amino acid sequence analyses indicate only one type of chain, suggesting that the lectin is probably dimeric. The amino acid composition is given. Papainized human erythrocytes of the different ABO groups were agglutinated equally well by the Cicer lectin, whereas untreated cells reacted weakly and only in the presence of bovine serum albumin. Simple sugars did not inhibit the agglutination, but some glycoproteins did inhibit. The lectin is probably nonmitogenic against human lymphocytes. Antigenic analyses in an enzyme-linked immunosorbent assay (ELISA) showed only a weak cross-reaction between Cicer and the lectins in the Vicieae tribe. Thus, our physicochemical and antigenic studies of the Cicer lectin support the botanical reasons recently given for removing the genus Cicer from the Vicieae tribe.     

Biochemical characterization of a lectin from Delonix regia seeds

A lectin from Delonix regia (DRL) seeds was purified by gel filtration on Sephadex G-100 followed by ion-exchange chromatography on diethylaminoethyl-Sepharose and reverse-phase high-performance liquid chromatography on a C18 column. Hemagglutinating activity was monitored using rat erythrocytes. DRL showed no specificity for human erythrocytes of ABO blood groups. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a single protein in the presence of 0.1 M of dithiothreitol (DTT) and in nonreducing conditions. Native-PAGE showed that DRL is a monomer with a molecular mass of about 12 kDa, as determined by denaturing gel electrophoresis and gel filtration chromatography. An amino acid composition revealed the absence of cysteine residues, the presence of 1 mol methionine/mol protein and a high proportion of acidic amino acids and glycine. The N-terminal sequence of DRL was determined by Edman degradation, and up to 16 amino acid residues showed more than 90% homology with other lectins from the Leguminosae family. The optimal pH range for lectin activity was between pH 8.0 and 9.0, and the lectin was active up to 60°C. The lectin required Mn²⁺ for hemagglutinating activity and remained active after reduction with 0.1 M of DTT, but lost activity in the presence of 8 M of urea. Sodium metaperiodate had no effect on the activity of DRL.     

An unusual sample of irregular anti-A1, probably causing an early delayed transfusion reaction

An unusual case of a 37 degrees C-active irregular anti-A1 is reported. Apparently consisting mainly of IgG, the antibody appeared in an A2B recipient only two days after massive transfusion of A1-cells in absence of previous transfusion. It was associated with severe hemolysis and renal failure which was reversed after exchange transfusion.     

A blood group A specific lectin from the seeds of Crotalaria striata

A lectin, monospecific for human blood group A red blood cells was extracted from seeds of Crotalaria striata and purified by molecular sieving on Sephadex G-100 and ion-exchange on DEAE-cellulose. A molecular mass of 30 kDa was determined by SDS-polyacrylamide gel electrophoresis under non-reducing and reducing conditions. Molecular sieving on a Superose 12 column indicated a molecular mass of 110 kDa, suggesting the tetrameric nature of the native protein. Amino-acid composition showed the presence of aminated carbohydrate residues on the lectin. N-terminal amino-acid sequencing showed a striking similarity with the N-terminal sequence of the lectin from Crotalaria juncea, which is blood-group non-specific. The potency order of agglutination inhibition with galactose containing monosaccharides was N-acetyl-D-galactosamine greater than D-galactose greater than D-galactosamine as found for blood-group-A-specific lectins from other species.     

Purification and some properties of a lectin from the seeds ofTrichosanthes anguina

A galactose-binding lectin was isolated in electrophoretically pure form from the seeds of the snake gourd,Trichosanthes anguina, by affinity chromatography on an immobilised lactose column, as well as on a cross-linkedGuar Gum column. The lectin agglutinates native erythrocytes of human A, B and 0 phenotypes and of rabbit, rat and mouse. The molecular mass of the lectin, as estimated bySephadex G-200 gel chromatography, is 49 kDa. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis, after reduction with β-mercaptoethanol, revealed two polypeptide chains linked by disulphide bonds in the lectin molecule. It contains no covalently linked sugars. Amino acid analysis of the lectin revealed a high content of acidic amino acids, relatively lower proportion of basic amino acids and traces of cysteine and methionine. The lectin has good thermal stability, and is inactivated when oxidised by metaperiodate.     

Purification and characterization of a lectin from Annona coriacea seeds

A novel lectin, denominated ACLEC, was isolated from Annona coriacea seeds, belonging to the Annonaceae family. The lectin presented one protein band in SDS-PAGE of 14 kDa. Of the sugars tested, Dglucose and D-mannose were the best inhibitors. A search sequence database showed that ACLEC had homology with other plant lectins, belonging to leguminous lectin family.