Detection of lectins in nodulated peanut and soybean plants

The direct double-antibody enzymelinked immunosorbent assay system was used in the detection and measurement of seed lectins from peanut (Arachis hypogaea L.) and soybean (Glycine max L.) plants (PSL and SBL, respectively) that had been inoculated with their respective rhizobia. Concentrations of PSL dropped to undetectable levels in peanut roots at 9 d and stems and leaves at 27 d after planting; SBL could no longer be detected in soybean roots at 9 d and in stems and leaves at 12 d. A lectin antigenically similar to PSL was first detected in root nodules of peanuts at 21 d reaching a maximum of 8 g/g at 29 d then decreasing to 2.5 g/g at 60 d. There was no evidence of a corresponding lectin in soybean nodules.Sugar haemagglutination inhibition tests with neuraminidase-treated human blood cells established that PSL and the peanut nodule lectin were both galactose/lactose-specific. Further tests with rabbit blood cells demonstrated a second mannosespecific lectin in peanut nodule extracts that was not detected in root extracts of four-week-old inoculated plants or six-week-old uninoculated plants, although six-week-old root extracts from inoculated plants showed weak lectin activity. The root extracts from both nodulated and uninoculated plants contained another peanut lectin that agglutinated rabbit but not human blood cells. Haemagglutination by this lectin was, however, not inhibited by simple sugars but a glycoprotein, asialothyroglobulin, was effective in this respect.Abbreviations DAS double antibody sandwich - ELISA enzyme-linked immunosorbent assay - PBS phosphate-buffered saline - PSL peanut seed lectin - SBL soybean lectin     

Localization of mannose- and galactose-binding lectins in an effective peanut nodule

Summary Mannose/glucose- and galactose-binding lectins (ML and GL respectively, were located by immunogold labelling in tissues of a peanut (Arachis hypogaea) nodule induced by an effectiveBradyrhizobium sp. strain. Light and electron microscopic examination of silver-enhanced semithin and ultrathin sections, respectively, revealed that both lectins were widely distributed throughout the cortex and bacteroidal zones although ML was more abundant. The lectins were predominantly in the vacuoles of cortical cells but GL was absent from, or at low concentration in, a two-cell-thick layer of cortical cells surrounding the bacteroidal region. Only ML was detected in cells of the vascular bundle endodermis and in central vascular bundle cells; neither lectin was found in pericycle cells. Bacteroidal cells contained abundant ML in the nuclei and cytoplasm surrounding bacteroids while GL was mainly located in the central vacuoles of these cells. Neither lectin was associated with bacteroid surfaces, peribacteroid membranes, plant cell walls or cell organelles and membranes. The above observations indicate that the nodule lectins are not symbiotic cell recognition determinants and suggest that they have protein storage functions.Abbreviations BSA bovine serum albumin - GL galactose-binding lectin - ML mannose-binding lectin - PBS phosphate-buffered saline - PBST phosphate-buffered saline plus Tween     

A new lectin from tulip (Tulipa) bulbs

A lectin was isolated from tulip (Tulipa) bulbs by affinity chromatography on fetuin-agarose and partially characterized. The tulip lectin is a tetrameric protein composed of four identical subunits of M_r 28 000, which are not held together by disulphide bonds. It is not glycosylated and has an amino-acid composition typified by a high content of asparagine-aspartic acid, leucine, glycine and serine. Tulip lectin agglutinates human red blood cells, but has a much higher specific activity with rabbit erythrocytes. In hapten-inhibition assays with the latter type of red blood cell the lectin exhibits a complex specificity, whereas its agglutination with human erythrocytes is readily inhibited by N-acetylgalactosamine, lactose, fucose and galactose.Abbreviations DEAE diethylaminoethyl - PBS phosphate-buffered saline - TL Tulipa lectin - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

Purification of lectins from the stems of peanut plants

The stem of the peanut plant contains two lectins, a methyl -mannoside specific lectin (SL-I) and a lactose/cellobiose specific lectin (SL-II). These lectins are found to be developmentally regulated and maximum activites are observed in 3–4-weeks-old plants. The two lectins SL-I and SL-II have been purified from 3-week-old stem by affinity chromatography on Sephadex G-50 and guar gum matrices respectively. Both are glycosylated lectins and have the identical subunit molecular weight of 31 kDa.     

Distribution of glucose/mannose-specific isolectins in pea (Pisum sativum L.) seedlings

We report on the distribution and initial characterization of glucose/mannose-specific isolectins of 4- and 7-d-old pea (Pisum sativum L.) seedlings grown with or without nitrate supply. Particular attention was payed to root lectin, which probably functions as a determinant of host-plant specificity during the infection of pea roots by Rhizobium leguminosarum bv. viciae. A pair of seedling cotyledons yielded 545±49 g of affinity-purified lectin, approx. 25% more lectin than did dry seeds. Shoots and roots of 4-d-old seedlings contained 100-fold less lectin than cotyledons, whereas only traces of lectin could be found in shoots and roots from 7-d-old seedlings. Polypeptides with a subunit structure similar to the precursor of the pea seed lectin could be demonstrated in cotyledons, shoots and roots. Chromatofocusing and isoelectric focusing showed that seed and non-seed isolectin differ in composition. An isolectin with an isoelectric point at pH 7.2 appeared to be a typical pea seed isolectin, whereas an isolectin focusing at pH 6.1 was the major non-seed lectin. The latter isolectin was also found in root cell-wall extracts, detached root hairs and root-surface washings. All non-seed isolectins were cross-reactive with rabbit antiserum raised against the seed isolectin with an isolectric point at pH 6.1. A protein similar to this acidic glucose/mannose-specific seed isolectin possibly represents the major lectin to be encountered by Rhizobium leguminosarum bv. viciae in the pea rhizosphere and at the root surface. Growth of pea seedlings in a nitrate-rich medium neither affected the distribution of isolectins nor their hemagglutination activity; however, the yield of affinity-purified root lectin was significantly reduced whereas shoot lectin yield slightly increased. Agglutination-inhibition tests demonstrated an overall similar sugar-binding specificity for pea seed and non-seed lectin. However root lectin from seedlings grown with or without nitrate supplement, and shoot lectin from nitrate-supplied seedlings showed a slightly different spectrum of sugar binding. The absorption spectra obtained by circular dichroism of seed and root lectin in the presence of a hapten also differed. These data indicate that nutritional conditions may affect the sugar-binding activity of non-seed isolectin, and that despite their similarities, seed and non-seed isolectins have different properties that may reflect tissue-specialization.Abbreviations IEF isoelectric focusing - MW molecular weight - pI isoelectric point - Psl1, Psl2 and Psl3 pea isolectins - SDSPAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis The authors wish to thank Professors L. Kanarek and M. van Poucke for helpful discussions.     

Isolation and characterization of glycoprotein lectins from the bark of three species of elder,Sambucus ebulus,S. nigra and S. racemosa

Lectins have been isolated from the bark of three members of the family Caprifoliaceae, Sambucus nigra (elder), S. racemosa (red-berried elder) and S. ebulus (dwarf elder), by affinity chromatography on fetuin-agarose, ion-exchange and gel-filtration chromatography. They are all glycoproteins of M _r 140 000 made up of at least four subunits. The lectin have similar but not identical amino-acid compositions and the carbohydrate content varies between 12% and 19% (w/w), the main sugars being (N-acetyl)glucosamine, mannose, fucose and xylose. Inhibition studies of hemagglutination with various mono- and oligosaccharides have shown that N-acetylgalactosamine and galactose together with galactose-containing oligosaccharides are the most effective inhibitors. There are some differences in specificity, in particular S. ebulus agglutinin is inhibited to the same degree by galactosamine, N-acetylgalactosamine and by galactose.Abbreviations PBS phosphate-buffered saline - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - SEA S. ebulus agglutinin - SNA S. nigra agglutinin - SRA S. racemosa agglutinin     

Predicted sequence and structure of a vegetative lectin in Pisum sativum

We report the predicted sequence of four vegetative homologues (Blec1,2,3 and 4) of the pea seed lectin. This study indicates that, in contrast to the single-copy pea seed lectin (Kaminski et al., Plant Mol Biol 9: 497–507, 1987), the pea vegetative lectin is transcribed by at least four members of a highly conserved multigene family whose members are only distantly related to the pea seed lectin at the primary amino-acid sequence level. For example, Blec1 shares only 38% amino-acid identity with the pea seed lectin. However, molecular homology modelling predicts that Blec1 probably forms a similar tertiary structure to the pea seed lectin.     

Isolation and partial characterization of a lectin from ground elder (Aegopodium podagraria) rhizomes

A lectin has been isolated from rhizomes of ground elder (Aegopodium podagraria) using a combination of affinity chromatography on erythrocyte membrane proteins immobilized on cross-linked agarose and hydroxyapatite, and ion-exchange chromatography. The molecular structure of the lectin was determined by gelfiltration, sucrose density-gradient centrifugation and gel electrophoresis under denaturing conditions. It has an unusually high M_r (about 480000) and is most probably an octamer composed of two distinct types of subunits with slightly different M_r (about 60000). Hapten inhibition assays indicated that the Aegopodium lectin is preferentially inhibited by N-acetylgalactosamine. Nevertheless, it does not agglutinate preferentially blood-group-A erythrocytes. The ground-elder lectin is a typical non-seed lectin, which occurs virtually exclusively in the underground rhizomes. In this organ it is an abundant protein as it represents up to 5% of the total protein content. The lectin content of the rhizome tissue varies strongly according to its particular location along the organ. In addition, the lectin content changes dramatically as a function of the seasons. The ground-elder lectin differs from all other plant lectins by its unusually high molecular weight. In addition, it is the first lectin to be isolated from a species of the family Apiaceae.Abbreviations APA Aegopodium podagraria agglutinin - PBS phosphate-buffered saline - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis     

Determination of pea (Pisum sativum L.) root lectin using an enzyme-linked immunoassay

Root lectins are believed to participate in the recognition between Rhizobium and its leguminous host plant. Among other factors, testing this hypothesis is difficult because of the very low amounts in which root lectins are produced. A double-antibody-sandwich enzyme-linked immunoassay, was used to determine nanogram quantities of pea lectin in root slime and salt extracts of root cell-wall material when pea seedlings were 4 and 7 d old. In addition, a critical NO ₃ ^- concentration (20 mM) which inhibited nodulation was found, and the lectin present in root slime and salt extracts of root cell walls of 4- and 7-d-old peas supplied with 20 mM NO ₃ ^- was comparatively determined. With the enzyme-linked immunoassay, lectin quantities ranging between 20 and 100 nanograms could be determined. The assay is not affected by monomeric mannose and glucose (pealectin haptens). The slime of the 4-d-old roots contained more lectin than the slime of the 7-d-old roots. Salt-extractable, cell-wall-associated lectin accumulated in the older roots. Nitrate affected slime and cell-wall production, and the extractability of cell-wall material in both age groups. The presence of NO ₃ ^- increased lectin in the slime, most notably in the younger roots; the relative amount of lectin in the slime was almost doubled. The cell-wall-associated, salt-extractable lectin decreased two- to threefold compared with the control group.Abbreviations ELISA enzyme-linked immunoassay - PTN 0.01 M phosphate buffer (pH 7.4), containing 0.15 M NaCl, 0.05% Tween-20 and 0.02% NaN₃ Dedicated to Professor A. Quispel on the occasion of his retirement     

Electron-microscopic analysis of ground elder (Aegopodium podagraria L.) lectin: evidence for a new type of supra-molecular protein structure

The lectin of ground elder (Aegopodium podagraria L.) was investigated electron-microscopically after negative staining with uranyl salts. Affinity-purified preparations of this glycoprotein were highly heteromorphous as they contained small particles approximately 4.6 nm in diameter and very large particles of different shapes. Among the latter, circular and helicoidal structures were the most regular in appearance. The circles were 9.3 nm in diameter, whereas the helices were 9 nm or 20 nm in diameter and up to 60 nm in length. After photographic enhancement, pictures of the molecules indicated that both the larger structures and the small particles could be obtained in pure forms by gel filtration of the lectin on Sepharose 4B. Since the former were the only constituents of the excluded fraction (M_r>5000000), whereas they were totally absent in the fraction eluting with an apparent molecular weight of about 500000, these supra-molecular structures revealed by the electron microscope cannot be artefacts generated during preparation of the lectin for electron-microscopic observation.Abbreviations APA Aegopodium podagraria agglutinin - EM electron microscopy - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis     

Identification of a cDNA clone encoding for a galactose-binding lectin from peanut (Arachis hypogaea) seedling roots

A cDNA clone obtained from developing peanut (Arachis hypogaea) seedling roots, when expressed in Escherichia coli and insect cells (Sf9) gave a 29 kDa subunit protein. The native recombinant protein agglutinates neuraminidase treated human erythrocytes and the agglutination is inhibited by galactose. Nucleotide sequence and predicted amino acid sequence analyses indicate that it is different from peanut seed (PNA and SGL) and nodule (NGLa and NGLb) galactose-binding lectins.     

Distribution of lectins in membranes of soybean and peanut plants

The distribution of lectin activity in soybean and peanut plants has been investigated. In both plants activity is found in all tissues examined (roots, shoots and leaves) at all stages of development from seedling to maturity (7 weeks). The cellular location of the lectins differs between soybean and peanut: in soybean the lectins are generally membrane-associated, whereas in peanut plants lectin activity is present also in the soluble cytoplasmic fraction. The membrane-associated lectins appear to differ from the seed lectins of the respective plants. The function of membrane-associated lectins is discussed.Abbreviations RCA lectin of castor bean - SBA soybean agglutinin - PNA peanut agglutinin - HEPES 2-[4-(2-Hydroxyethyl)-piperazinyl-(1)]ethanesulphonic acid - MES morpholinoethane sulphonic acid - PBS phosphate-buffered saline     

Utility of pentose colorimetric assay for the purification of potato lectin, an arabinose-rich glycoprotein

Potato lectin (Solanum tuberosum agglutinin, STA) is an unusual glycoprotein containing approximately 50% carbohydrates by weight. Of the total carbohydrates, 92% is contributed by L-arabinose, which are O-linked to hydroxyproline residues. The ferric chloride-orcinol assay (Bial’s test), which is specific for pentoses has so far been used only for the determination of free pentoses in biological samples. However, this colorimetric assay has not been used for the detection of pentoses in bound form as it occurs in Solanaceae lectins (potato, tomato, and Datura lectins). Utilizing the pentose colorimetric assay for monitoring the presence of potato lectin, a simpler and shorter procedure for the purification of this lectin from potato tubers has been developed. The yield of potato lectin (1.73 mg per 100 g potato tuber) is twice compared to the yields reported in earlier procedures. Although potato lectin is well known for its specificity to free trimers and tetramers of N-acetyl-D-glucosamine (GlcNAc), it possesses a similar specificity to the core (GlcNAc)₂ of N-linked glycoproteins. The utilization of the pentose assay in the purification of arabinose-rich lectins/agglutinins obviates the necessity for the use of agglutination assay in the various purification steps. The pentose assay appears to be a simple and convenient colorimetric assay for detecting any pentose-rich glycoprotein in plant extracts. The utility of the pentose assay appears to have a significant potential in the detection of hydroxyproline-rich glycoproteins (HRGPs), which are generally O-arabinosylated.     

A putative carbohydrate-binding domain of the lactosebindingCytisus sessilifolius anti-H(O) lectin has a similar amino acid sequence to that of thel-fucose-bindingUlex europaeus anti-H(O) lectin

The complete amino acid sequence of a lactose-bindingCytisus sessilifolius anti-H(O) lectin II (CSA-II) was determined using a protein sequencer. After digestion of CSA-II with endoproteinase Lys-C or Asp-N, the resulting peptides were purified by reversed-phase high performance liquid chromatography (HPLC) and then subjected to sequence analysis. Comparison of the complete amino acid sequence of CSA-II with the sequences of other leguminous seed lectins revealed regions of extensive homology. The amino acid sequence of a putative carbohydrate-binding domain of CSA-II was found to be similar to those of several anti-H(O) leguminous lectins, especially to that of thel-fucose-bindingUlex europaeus lectin I (UEA-I).Abbreviations BPA Bauhinia purpurea lectin - Con A concanavalin A - CMA-I Cytisus multiflorus lectin I - CMA-II Cytisus multiflorus lectin II - CSA-I Cytisus sessilifolius lectin I - CSA-II Cytisus sessilifolius lectin II - CSII Cytisus scoparius lectin II - ECorL Erythrina corallodendron lectin - GSIV Griffonia simplicifolia lectin IV - HPLC high performance liquid chromatography - LAA-I Laburnum alpinum lectin I - LAA-II Laburnum alpinum lectin II - LOL Lathyrus ochrus lectin - LTA Lotus tetragonolobus lectin - MAH Maackia amurensis haemagglutinin - PSA Pisum sativum lectin - SDS sodium dodecyl sulfate - TFA trifluoroacetic acid - UEA-I Ulex europaeus lectin I - UEA-II Ulex europaeus lectin II - VFA Vicia faba lectin     

Studies on growth inhibition by lectins of penicillia and aspergilli

It has previously been shown in our laboratory that wheat germ agglutinin (WGA) binds to Trichoderma viride and inhibits growth of this fungus. Here we report on the effect of WGA, soybean agglutinin (SBA) and peanut agglutinin (PNA) on Penicillia and Aspergilli. Binding of the lectins to the fungi was examined with the aid of their fluorescein isothiocyanate (FITC) conjugated derivatives. FITC-WGA bound to young hyphal walls of all species, in particular to the hyphal tips and septa, in agreement with the chitinous composition of the cell walls of the two genera. Hyphae of all species examined were labelled, though in different patterns, by FITC-SBA and FITC-PNA, suggesting the presence of galactose residues on their surfaces. Young conidiophores, metulae (of the Penicillia), vesicles (of the Aspergilli), sterigmata and young spores, were also labelled. The three lectins inhibited incorporation of [³H]acetate, N-acetyl-D-[³H]glucosamine and D-[¹⁴C]galactose into young hyphae of Aspergillus ochraceus, indicating interference with fungal growth. Inhibition of spore germination by the three lectins was also observed. Preincubation of the lectins with their specific saccharide inhibitors prevented binding and the inhibitory effects. We conclude that lectins are useful tools for the study of fungal cell surfaces, and may also serve as an important aid in fungal classification. The present findings also support the suggestion that one role of lectins in plants is protection against fungal pathogens.Abbreviations Con A concanavalin A - PNA peanut agglutinin - SBA soybean agglutinin - WGA wheat germ agglutinin - FITC fluorescein isothiocyanate - GlcNAc N-acetyl-D-glucosamine - GalNAc N-acetyl-D-galactosamine     

A Peanut Nodule Lectin in Infected Cells and in Vacuoles and the Extracellular Matrix of Nodule Parenchyma

Root nodules on peanut (Arachis hypogaea L.) accumulate a galactose/lactose-binding lectin that is similar, but not identical, to the major seed lectin in peanut. The function of the peanut nodule lectin (PNL) is not known. In the current study, we have investigated the location of lectin in the nodule using immunogold labeling and enzyme-linked immunosorbant assays (ELISA). Lectin was most abundant in the nodule parenchyma, where it accumulated in vacuoles, suggesting a possible role as a vegetative storage protein. Lectin was also detected in the extracellular matrix in the nodule parenchyma, a location that corresponds to the tissue layer forming a barrier to oxygen diffusion. The potential for interactions between PNL and other cell wall components, including a previously described high-molecular weight glycoprotein that co-localizes with PNL, is discussed. Within infected cells, lectin was not detectable by immunogold labeling within the cytoplasm, but light labeling was suggestive of lectin localization within the symbiosome lumen. Analysis of fractionated symbiosomes by the more sensitive ELISA technique confirmed that lectin was present within the symbiosome, but was not bound to bacteroids. Our results indicate that PNL probably plays several roles in this nitrogen-fixing symbiosis.     

An isolectin complex from Trichosanthes anguina seeds

Sepharose 4B affinity chromatography of Trichosanthes anguina seed extract and subsequent elution with galactose resulted in the isolation of an apparently single lectin with molecular weight of 45,000 +/- 700. However, major amount of the hemagglutinating activity was recovered as unadsorbed protein fraction. High affinity matrix Lactamyl Seralose could retain most of the galactose specific lectin activity from fraction 'A' which was eluted with lactose. It is evident from PAGE and SDS-PAGE analysis of the purified protein that T. anguina seeds contains a mixture of isolectins ranging in molecular weight from 30,000 to 50,000 +/- 1300. Periodic Acid Schiff's staining of the gels revealed this lectin complex to be a combination of glycosylated and non-glycosylated lectins. Two Isolectins SLc and IEL from within this complex have been isolated by affinity and ion exchange chromatography respectively. Apparent homology of these two lectins is indicated by their identical molecular weight (45 kDa), sub unit composition, non glycoprotein nature and immunological identity. However, these two lectins show minor differences in their biological and physicochemical properties. The peptide maps of the two lectins obtained after digestion with Trypsin and Pronase E also indicate minor changes in the primary structure.     

The seed lectins of black locust (robinia pseudoacacia) are encoded by two genes which differ from the bark lectin genes

Two lectins were isolated from Robinia pseudoacacia (black locust) seeds using affinity chromatography on fetuin-agarose, and ion exchange chromatography on a Neobar CS column. The first lectin, R. pseudoacacia seed agglutinin I, referred to as RPsAI, is a homotetramer of four 34 kDa subunits whereas the second lectin, referred to as RPsAII, is composed of four 29 kDa polypeptides. cDNA clones encoding the polypeptides of RPsAI and RPsAII were isolated and their sequences were determined. Both polypeptides are translated from mRNAs of ca. 1.2 kb encoding a precursor carrying a signal peptide. Alignment of the deduced amino acid sequences of the different clones indicates that the 34 and 29 kDa seed lectin polypeptides show 95% sequence identity. In spite of this striking homology, the 29 kDa polypeptide has only one putative glycosylation site whereas the 34 kDa subunit has four of these sites. Carbohydrate analysis revealed that the 34 kDa possesses three carbohydrate chains whereas the 29 kDa polypeptide is only partially glycosylated at one site. A comparison of the deduced amino acid sequences of the two seed and three bark lectin polypeptides demonstrated unambiguously that they are encoded by different genes. This implies that five different genes are involved in the control of the expression of the lectins in black locust.Abbreviations LECRPAs cDNA clone encoding Robinia pseudoacacia seed lectin - LoLI Lathyrus ochrus isolectin I - PsA Pisum sativum agglutinin - RPbAI Robinia pseudoacacia bark agglutinin I - RPbAII Robinia pseudoacacia bark agglutinin II - RPsAI Robinia pseudoacacia seed agglutinin I - RPsAII Robinia pseudoacacia seed agglutinin II     

Molecular cloning,expression, and cytokinin (6-benzylaminopurine) antagonist activity of peanut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis>) lectin SL-I

Isolation and purification of a α-methyl-mannoside specific lectin (SL-I) of peanut was reported earlier [Singh and Das (1994) Glycoconj J 11:282–285]. Native SL-I is a glycoprotein having ∼31 kDa subunit molecular mass and forms dimer. The gene encoding this lectin is identified from a 6-day old peanut root cDNA library by anti-SL-I antibody and N-terminal amino acid sequence homology to the native lectin. Nucleotide sequence derived amino acid sequence of the re-SL-I shows amino acid sequence homology with the N-terminal and tryptic digests’ amino acid sequence of the native SL-I (nSL-I). Presence of a putative glycosylation (QNPS) site and a hydrophobic adenine-binding (VLVSYDANS) site is also identified in SL-I. Homology modeling of the lectin suggests it to be an archetype of legume lectins. It is expressed as a ~30 kDa apoprotein in E. coli and has the carbohydrate specificity and secondary structure identical to its natural counterpart. The lectin SL-I inhibits cytokinin 6-benzylaminopurine (BA)-induced “delayed leaf senescence” and “cotyledon expansion”. Equilibrium dialysis revealed a single high-affinity binding site for adenine (7.6 × 10⁻⁶ M) and BA (1.09 × 10⁻⁵ M) in the SL-I dimer and thus suggesting that the cytokinin antagonist effect of SL-I is mediated by the direct interaction of SL-I with BA.The nucleotide sequence data reported here are available in the DDBJ/EMBL/GenBank databases under the Accession No. AJ585523     

Detection and characterization of a lectin from non-seed tissue ofPhaseolus vulgaris

The distribution of lectin in various tissues ofPhaseolus vulgaris L. (cv. red) has been investigated using a sensitive solid-phase enzyme immunoassay. Roots, leaves and stems from 3- to 4-week-old plants were screened for their lectin content; low levels could be detected in all organs, with a relative distribution of 37% in roots, 20% in leaves and 43% in stems. The lectin from stemsleaves and roots was then isolated from 5- to 6-week-old plants using extraction, salt fractionation and affinity chromatography on immobilized porcine thyroglobulin. A comparative study of the seed lectin and the lectin isolated from 5- to 6-week-old plants was made using hemagglutination, inhibition of hemagglutination, immunodiffusion, polyacrylamide and agarose electrophoresis. The results showed that lectin isolated from the different tissues was immunologically identical and exhibited the same subunit structure and similar isolectin composition as the seed lectin.Abbreviations EDTA ethylenediaminetetraacetic acid - PHA phytohemagglutinin - SDS sodium dodecyl sulfate