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Involvement of both cellulose fibrils and a Ca2+-dependent adhesin in the attachment of Rhizobium leguminosarum to pea root hair tips.

We have previously described an assay for the attachment of Rhizobium bacteria to pea root hair tips (cap formation) which was used as a model to study the attachment step in the nodulation process. Under all conditions tested, a positive correlation was observed between the percentage of fibrillated cells and the ability of these bacteria to form caps and to adhere to glass, suggesting that fibrils play a role in the attachment of Rhizobium leguminosarum to pea root hair tips and to glass (G. Smit, J. W. Kijne, and B. J. J. Lugtenberg, J. Bacteriol. 168:821-827, 1986). In the present paper the chemical and functional characterization of the fibrils of R. leguminosarum is described. Characterization of purified fibrils by infrared spectroscopy and cellulase treatment followed by thin-layer chromatography showed that the fibrils are composed of cellulose. Purified cellulose fibrils, as well as commercial cellulose, inhibited cap formation when present during the attachment assay. Incubation of the bacteria with purified cellulase just before the attachment assay strongly inhibited cap formation, indicating that the fibrils are directly involved in the attachment process. Tn5-induced fibril-overproducing mutants showed a greatly increased ability to form caps, whereas Tn5-induced fibril-negative mutants lost this ability. None of these Tn5 insertions appeared to be located on the Sym plasmid. Both types of mutants showed normal nodulation properties, indicating that cellulose fibrils are not a prerequisite for successful nodulation under the conditions used. The ability of the fibril-negative mutants to attach to glass was not affected by the mutations, indicating that attachment to pea root hair tips and attachment to glass are (partly) based on different mechanisms. However, growth of the rhizobia under low Ca2+ conditions strongly reduced attachment to glass and also prevented cap formation, although it had no negative effect on fibril synthesis. This phenomenon was found for several Rhizobium spp. It was concluded that both cellulose fibrils and a Ca2+ -dependent adhesin(s) are involved in the attachment of R. leguminosarum to pea root hair tips. A model cap formation as a two-step process is discussed.

Adhesins, Bacterial↗

Lipopolysaccharide epitope expression of Rhizobium bacteroids as revealed by in situ immunolabelling of pea root nodule sections.

To investigate the in situ expression of lipopolysaccharide (LPS) epitopes on nodule bacteria of Rhizobium leguminosarum, monoclonal antibodies recognizing LPS macromolecules were used for immunocytochemical staining of pea nodule tissue. Many LPS epitopes were constitutively expressed, and the corresponding antibodies reacted in nodule sections with bacteria at all stages of tissue infection and cell invasion. Some antibodies, however, recognized epitopes that were only expressed in particular regions of the nodule. Two general patterns of regulated LPS epitope expression could be distinguished on longitudinal sections of nodules. A radial pattern probably reflected the local physiological conditions experienced by endosymbiotic bacteria as a result of oxygen diffusion into the nodule tissue. The other pattern of expression, which followed a linear axis of symmetry along a longitudinal section of the pea nodule, was apparently associated with the differentiation of nodule bacteria and the development of the nitrogen-fixing capacity in bacteroids. Basically similar patterns of LPS epitope expression were observed for pea nodules harboring either of two immunologically distinct strains of R. leguminosarum bv. viciae, although these epitopes were recognized by different sets of strain-specific monoclonal antibodies. Furthermore, LPS epitope expression of rhizobia in pea nodules was compared with that of equivalent strains in nodules of French bean (Phaseolus vulgaris). From these observations, it is suggested that structural modifications of Rhizobium LPS may play an important role in the adaptation of endosymbiotic rhizobia to the surrounding microenvironment.

Antibodies, Bacterial↗

Characterization of Stowaway MITEs in pea (Pisum sativum L.) and identification of their potential master elements.

We have investigated miniature inverted-repeat transposable elements (MITEs) of the Stowaway family and corresponding Mariner-like master elements that could potentially facilitate their mobilization in the genome of the garden pea (Pisum sativum L.). The population of pea Stowaway MITEs consists of 103-104 copies dispersed in the genome. Judging from a sequence analysis of 17 isolated Stowaway elements and their flanking genomic regions, the elements are relatively uniform in size and sequence and occur in the vicinity of genes as well as within repetitive sequences. Insertional polymorphism of several elements was detected among various Pisum accessions, suggesting they were still transpositionally active during diversification of these taxa. The identification of several Mariner-like elements (MLEs) harboring intact open reading frames, capable of encoding a transposase, further supports a recent mobilization of the Stowaway elements. Using transposase-coding sequences as a hybridization probe, we estimated that there are about 50 MLE sequences in the pea genome. Among the 5 elements sequenced, 3 distinct subfamilies showing mutual similarities within their transposase-coding regions, but otherwise diverged in sequence, were distinguished and designated as Psmar-1 to Psmar-3. The terminal inverted repeats (TIRs) of these MLE subfamilies differed in their homology to the TIRs of Stowaway MITEs. The homlogy ranged from 9 bp in Psmar-3 to 30 bp in Psmar-1, which corresponds to the complete Stowaway TIR sequence. Based on this feature, the Psmar-1 elements are believed to be the most likely candidates for the master elements of the Stowaway MITEs in pea.

Amino Acid Sequence↗

Molecular evidence against phylogenetically distinct host races of the pea aphid (Acyrthosiphon pisum).

Pea aphid (Acyrthosiphon pisum) clones have been shown to be adapted to particular host plant species but it is unknown whether there are host races. A 1101 base pair region of the mitochondrial cytochrome oxidase I gene (COI) was sequenced for 21 pea aphid clones that had been collected from different host plants in Canada and the U.S.A. Only five closely related mitochondrial haplotypes were found. A maximum likelihood phylogeny was estimated for these five haplotypes and four related aphid species: Acyrthosiphon macrosiphum, A. kondoi, Fimbriaphis fimbriata, and Macrosiphum creelii. Pea aphids from the same host plant species were no more likely to have the same mitochondrial haplotype than aphids from different host plant species. In addition, aphids from the same geographical regions were no more likely to have the same mitochondrial haplotype than aphids from different geographic regions. I therefore reject the hypothesis that there are monophyletic host races of the pea aphid.

Animals↗

Biological control of fusarial wilt of pigeon pea by Bacillus brevis.

A virulent strain of pigeon pea wilt pathogen was isolated from wilted pigeon pea plants and was identified as Fusarium oxysporum f. sp. udum. Many bacterial cultures showing antagonism to the pathogen were isolated from various ecological niches. When tested under pot and field conditions, development of fusarial wilt symptoms was prevented in pigeon pea seeds treated with one such antagonist, Bacillus brevis. A formulation of B. brevis with vermiculite as a carrier had a shelf life of at least 6 months. Bacillus brevis produced an extracellular antagonistic substance which induced swelling of the pathogen's hyphal tips, and cells were bulbous and swollen with shrunken and granulated cytoplasm. The antagonistic substance also inhibited germination of conidia, and was fungicidal to the vegetative mycelia of the pathogen. Comparison of the properties of our antagonistic substance with that of known antibiotics produced by B. brevis suggests that our antagonistic substance is a novel compound. The observations reported here indicate that this strain of B. brevis may have potential as a biocontrol agent against fusarial wilt in pigeon pea.

Bacillus↗

Physiological effects of a pea protein isolate in gnotobiotic rats: comparison with a soybean isolate and meat.

Pea proteins have been considered for the introduction into the human diet only recently. This protein source was tested on nutritional and digestive parameters in heteroxenic male Fischer rats inoculated with a human faecal microflora from a methane producer. Compared to soybean proteins, pea proteins have similar effects on the rat's endogenous and bacterial digestive patterns. Compared to the pea proteins, a diet containing a standard meat meal enhanced the pH and the production of ammonia, while a lyophilized beef meat enhanced that of urea. The diet containing the standard meat decreases short-chain fatty acids and modifies the ratio of caecal short-chain fatty acids. Both animal diets decreased the specific activities of pancreatic proteases such as chymotrypsin (EC 3.4.21.1), trypsin (EC 3.4.21.4), and carboxypeptidase A (EC 3.4.17.1) when compared to the diet containing the pea isolate. In conclusion, the whole composition of the diet, more than the origin of the dietary protein, influences the rat's digestive pattern.

Animal Nutritional Physiological Phenomena↗

Growth stimulation of dwarf peas (Pisum sativum L.) through homeopathic potencies of plant growth substances.

BACKGROUND: Efficacy of higher homeopathic potencies is controversial. Universally accepted specific detection assays for homeopathic dilutions do not exist. Basic research has to develop a spectrum of standardized tools to investigate the mode of action and nature of homeopathic potencies. OBJECTIVE: Can the shoot growth reaction of dwarf peas (gibberellin- deficient mutants) be regarded as evidence of treatment with homeopathic potencies of plant growth substances? MATERIALS AND METHODS: Pea seed (Pisum sativum L. cv. Fruher Zwerg) is immersed for 24 hours in homeopathic potency or control solutions for soaking. Plants germinate and grow in a standard cultivation substrate under controlled environmental conditions. Shoot length is measured 14 days after planting. RESULTS: A screening of homeopathic potencies (12x-30x) of four different plant growth substances revealed biological activity of certain potency levels of gibberellin and kinetin (p < 0.05). Growth stimulation through gibberellin 17x (5 x 10(-18 M)) was assessed in six independent replications; results confirmed those of the screening (p < 0.05). The effect of gibberellin 17x seemed to weaken during the course of the experiments. CONCLUSION: The results back the hypothesis that homeopathic potencies of plant growth substances affect pea shoot growth. Dwarf peas might thus be an interesting system model for studying the action of homeopathic potencies. Further work is required to identify all boundary conditions modulating the reactivity of this system.

Adenine↗

An actin-related protein inside pea chloroplasts.

A pea chloroplast protein resembles vertebrate and algal actins by several chemical and immunological criteria. On two-dimensional polyacrylamide gels it migrated with a slightly lower relative molecular mass (Mr = 41,000) and slightly more basic isoelectric point than rabbit skeletal muscle actin. A monoclonal antibody to chicken gizzard actin reacted on immunoblots with rabbit skeletal actin, with Chara actin and with a 41,000 Mr band from pea chloroplasts. Pea and Chara bands of approximately 58,000 Mr were also stained. A DNase I-affinity column that bound muscle actin also bound 41,000 and 58,000 Mr chloroplast polypeptides. Similarities existed between enzymically and chemically generated fragments of the 41,000 Mr chloroplast polypeptide and rabbit muscle actin. The 41,000 Mr protein was protected from degradation by thermolysin only in preparations of intact, but not ruptured, isolated chloroplasts, indicating that this protein resides within the outer envelope membrane of these organelles. It is concluded that a 41,000 Mr protein with major similarities to actin occurs inside pea chloroplasts, and that a 58,000 Mr protein with some similarities to actin also probably exists within chloroplasts.

Actins↗

A homologue of EGL1 encoding endo-1,4-beta-glucanase in elongating pea stems.

A gene (EGL2) encoding an endo-1,4-beta-glucanase in peas has been cloned as a homologue of EGL1. EGL2 encodes a polypeptide of 506 amino acids, including a 24-mer putative signal polypeptide. The gene product contains a domain conserved in endo-1,4-beta-glucanase (family 9) showing 60% amino acid identity to EGL1. EGL2 mRNA was accumulated only in the elongating regions of pea stems, although EGL1 mRNA was abundant in both elongating and non-elongating tissues. However, the level of EGL2 mRNA was not increased by the treatment with sucrose and auxin in pea segments. These results suggest that the expression of EGL2 either requires the presence of other factors related to the auxin effect or occurs independent of auxin in the elongating pea stems.

Amino Acid Sequence↗

Peas (Pisum sativum L.).

In this chapter we describe a robust method for transformation of peas that has been successfully used in our laboratory since 1992. Using immature pea seed collected from field- or greenhouse-grown plants, we have produced transgenic lines for over 30 genotypes including named pea cultivars and advanced breeding lines. This method uses immature cotyledons as the explant, and the transformation efficiency is in the range 0.2 to 13.5% of cotyledons producing at least one independently transformed line. Agrobacterium tumefaciens strains AGL1 and KYRT1 are the most successful in our procedure, and kanamycin, phosphinothricin, and hygromycin are reliable selectable markers. Potentially useful genes have been introduced for pest and disease resistance, altering quality traits, and investigating metabolic pathways and are being studied in transgenic pea lines.

Agrobacterium tumefaciens↗

Purification and characterisation of pyruvate decarboxylase from pea seeds (Pisum sativum cv. Miko).

Pyruvate decarboxylase (PDC) was purified from pea seeds. The catalytically active holoenzyme is an oligomer of two types of subunits with molecular masses of about 65 kDa and 68 kDa, respectively. The active enzyme is a mixture of tetramers, octamers and even higher oligomers. These differences in the quaternary structure compared with PDC from yeast (tetramer) do not result in a different kinetic behaviour. The activity of pea PDC as well as that of yeast PDC is regulated by its substrate pyruvate resulting in a sigmoid shape of the v/S-plot. At the optimum pH of 6.0 a S0.5-value of 1 mM pyruvate is found that increases with rising pH and increasing concentrations of phosphate. The substrate analogue activator pyruvamide activates the enzyme resulting in a hyperbolic v/S-plot. The stability of PDC from pea seeds in solution is about one order of magnitude higher than that of yeast PDC. Despite the described similarities of the two enzymes no significant cross reactivity of the anti-pea PDC antibody with the enzyme from yeast occurs.

Blotting, Western↗

Purification and thermal characterization of a novel peroxidase from a local chick pea cultivar.

A novel peroxidase isolated from a local chick pea (Cicer arietinum L.) cultivar (Balksar 2000) was purified by means of ammonium sulfate precipitation, DEAE-cellulose chromatography and two runs on gel filtration. The purified enzyme has a specific activity of 2045 U/mg with 17 % activity recovery. The molecular mass of the enzyme was estimated to be 39 kDa by SDS-polyacrylamide gel electrophoresis. Optimum pH and temperature of the enzyme were 5.5 and 45 degrees C respectively. The thermal denaturation of local chick pea peroxidase was studied in aqueous solution at temperatures ranging from 45 degrees C to 65 degrees C. The temperature of 50% inactivation of the enzyme was found to be 68 degrees C. The enthalpy (DeltaH*) and free energy (DeltaG*) of thermal denaturation of chick pea peroxidase were 101.4 and 103.4 k J/mol respectively at 65 degrees C. Metals like Zn2+, Mn2+, Hg2+, Co2+ and Al3+ slightly inhibited the peroxidase activity while Ca2+, Mg2+ and Ba2+ have no effect on enzyme activity. The high specific activity and thermal stability make chick pea peroxidase an alternative to horseradish peroxidase (HRP) in various applications.

Ammonium Sulfate↗

X-ray crystal structure of a pea lectin-trimannoside complex at 2.6 A resolution.

The x-ray crystal structure of pea lectin, in complex with a methyl glycoside of the N-linked-type oligosaccharide trimannosyl core, methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside, has been solved by molecular replacement and refined at 2.6-A resolution. The R factor is 0.183 for all data in the 8.0 to 2.6 A resolution range with an average atomic temperature factor of 26.1 A2. Strong electron density for a single mannose residue is found in the monosaccharide-binding site suggesting that the trisaccharide binds primarily through one of the terminal alpha-linked mannose residues. The complex is stabilized by hydrogen bonds involving the protein residues Asp-81, Gly-99, Asn-125, Ala-217, and Glu-218, and the carbohydrate oxygen atoms O3, O4, O5, and O6. In addition, the carbohydrate makes van der Waals contacts with the protein, involving Phe-123 in particular. These interactions are very similar to those found in the monosaccharide complexes with concanavalin A and isolectin 1 of Lathyrus ochrus, confirming the structural relatedness of this family of proteins. Comparison of the pea lectin complex with the unliganded pea lectin and concanavalin A structures indicates differences in the conformation and water structure of the unliganded binding sites of these two proteins. Furthermore, a correlation between the position of the carbohydrate oxygen atoms in the complex and the bound water molecules in the unliganded binding sites is found. Binding of the trimannose core through a single terminal monosaccharide residue strongly argues that an additional fucose-binding site is responsible for the high affinity pea lectin-oligosaccharide interactions.

Amino Acid Sequence↗

Effects of cultivars on ensiling characteristics, chemical composition, and ruminal degradability of pea silage.

A study was conducted to determine the effects of cultivar on ensiling characteristics, chemical composition and ruminal nutrient degradability of pea (Pisum sativum L.) silage. The cultivars evaluated were Lenca (L), Carneval (C), and Delta (D). Peas were field-grown and forage was harvested and ensiled in mini-silos for 0, 2, 4, 8, 16, and 70 d. The ensiled forage of all cultivars went through a rapid fermentation with a sharp reduction in pH during the first 2 days of ensiling. Extensive proteolysis took place between 0 and 2 d as indicated by a reduction in true protein and neutral detergent insoluble protein (NDICP) and an increase in nonprotein nitrogen. Chemical analysis of the 70 d silage showed that cultivar L contained higher neutral detergent fiber (NDF) and acid detergent fiber and lower starch levels than C and D. Crude protein was highest for C (20.5% DM), intermediate for D (19.0% DM) and lowest for L (17.9% DM). Distribution of protein fractions showed that L contains lower soluble protein and higher NDICP levels than the other two pea cultivars. However, no difference in acid detergent insoluble protein levels was observed between the three cultivars. Results of the in situ incubation experiment indicated that L had lower ruminal DM (69.2 vs 74.0%) and CP (84.1 vs 90.6%) degradabilities than C or D. However, ruminal degradability of NDF was similar among the three cultivars (average of 32.9%). It was concluded that chemical composition and ruminal nutrient degradability of pea silage are significantly influenced by cultivars.

Acetic Acid↗

Effect of cooling on Clostridium perfringens in pea soup.

Foods associated with Clostridium perfringens outbreaks are usually abused after cooking. Because of their short generation times, C. perfringens spores and cells can grow out to high levels during improper cooling. Therefore, the potential of C. perfringens to multiply in Dutch pea soup during different cooling times was investigated. Tubes of preheated pea soup (50 degrees C) were inoculated with cocktails of cells or heat-activated spores of this pathogen. The tubes were linearly cooled to 15 degrees C in time spans of 3, 5, 7.5, and 10 h and were subsequently stored in a refrigerator at 3 or 7 degrees C for up to 84 h. Cell numbers increased by 1-log cycle during the 3-h cooling period and reached their maximum after 10 h of cooling. Subsequent refrigeration hardly reduced cell numbers. Cooling of 3.75 liters of pea soup in an open pan showed that this amount of pea soup cooled from 50 to 15 degrees C in 5 h, which will allow a more than 10-fold increase in cell numbers. These findings emphasize the need of good hygienic practices and quick cooling of heated foods after preparation.

Clostridium perfringens↗

Expression of thioredoxins f and m, and of their targets fructose-1,6-bisphosphatase and NADP-malate dehydrogenase, in pea plants grown under normal and light/temperature stress conditions.

Thioredoxins (Trxs) f and m, as well as their targets chloroplast fructose-1,6-bisphosphatase (FBPase) and NADP+-malate dehydrogenase (NADP-MDH), displayed transcriptional expression in both photosynthetic and non-photosynthetic organs of pea plants (Pisum sativum L. cv. Lincoln) grown for 50 d under normal irradiance. However, whereas Trx m and both target enzymes were poorly expressed in non-photosynthetic tissues, the content of the precursor form of the Trx f-specific mRNA was high in pea roots. In contrast, the translational expression of Trx f was low in this organ. The high FBPase activity in immature seeds, and the low activity of leaves, must be related to high starch synthesis in the first, and with high sucrose formation in the second. The transcriptional expression of FBPase and NADP+-MDH, and to a lesser extent that of Trxs f and m, was inhibited under low irradiance in plants grown under both normal and high temperatures. Pea plants grown at low temperature displayed a high level of mRNAs for Trxs and their targets, especially when the growth was carried out at low light. To a lesser extent, similar behaviour was observed at the protein level. Chloroplasts of mesophyll leaf cells of pea plants grown under saturating light, or under sub-saturating continuous irradiance, showed broken envelopes, distorted structural elements and disorganized starch grains, as a consequence of a photobleaching process and high starch accumulation.

Blotting, Western↗

Effect of temperature and cultivar on pea aphid, Acyrthosiphon pisum (Hemiptera: Aphididae) life history.

Life history parameters of the pea aphid, Acyrthosiphon pisum were studied at five constant temperatures on two cultivars of peas, Scout and Sancho. The development and mortality of juveniles and the life-span, age-specific fecundity and survivorship of adult aphids were recorded and used to construct life tables. The juvenile development period (from birth to adulthood) was longest at 11.9 degrees C (16.8 days on cv. Scout and 16.2 days on cv. Sancho) and shortest at 26.7 degrees C (8.5 days on cv. Scout and 8.8 days on cv. Sancho). At all temperatures, except 26.7 degrees C, juveniles developed faster on cv. Sancho than on cv. Scout. On both pea varieties juvenile mortality was highest at temperatures above 19.6 degrees C and lowest at 19.6 degrees C. Highest cumulative juvenile mortality was recorded on cv. Scout at 26.7 degrees C when only 9% of aphids survived from birth to reproductively mature adults. Fecundity rates were unaffected by temperature in the range tested on cv. Sancho but increased with increasing temperatures between 11.9 and 19.6 degrees C on cv. Scout. These differences in life history parameters were reflected in the population growth (rm) of aphids on both pea cultivars which increased with increasing temperatures between 11.9 and 23.1 degrees C on cv. Sancho and 11.9 and 19.6 degrees C on cv. Scout, declining thereafter. Population growth was consistently greater at all temperatures for aphids reared on cv. Sancho than those reared on cv. Scout.

Animals↗

Characterization of cDNAs encoding two isoforms of granule-bound starch synthase which show differential expression in developing storage organs of pea and potato.

We have isolated cDNA clones to two isoforms of granule-bound starch synthase (GBSS) from pea embryos and potato tubers. The sequences of both isoforms are related to that of glycogen synthase from E. coli and one, GBSSI, is very similar to the waxy protein of maize and other species. In pea, GBSSII carries a novel 203-amino-acid domain at its N-terminus. Genes encoding both proteins are expressed during pea embryo development, but GBSSII is most highly expressed earlier in development than GBSSI. Similarly, GBSSI and GBSSII are differentially expressed in developing potato tubers. Expression of both isoforms is much lower in other organs of pea than in embryos. GBSSII is expressed in every organ tested while GBSSI is not expressed in roots, stipules or flowers. The possible consequences of this differential use of GBSS isoforms are discussed.

Amino Acid Sequence↗