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GIBBERELLIN PRODUCTION IN PEA SEEDS DEVELOPING IN EXCISED PODS: EFFECT OF GROWTH RETARDANT AMO-1618.

The gibberellin content of pea seeds developing in excised pea pods cultured on a medium containing the plant growth retardant AMO-1618 was reduced in comparison with pea seeds cultured on retardant-free medium. The reduction increased with increasing concentrations of AMO-1618. However, at the lowest concentration tested (5 milligrams per liter) the growth of the seeds was not affected whereas their gibberellin content was significantly reduced. In conjunction with earlier work on the effect of growth retardants on gibberellin biosynthesis in the fungus Fusarium moniliforme, these results indicate that AMO-1618 inhibits the biosynthesis of gibberellins in tissues of higher plants in much the same manner it does in Fusarium.

Gibberellins↗

Influence of ethylene produced by soil microorganisms on etiolated pea seedlings.

There is indirect evidence that soil microorganisms producing ethylene (C(2)H(4)) can influence plant growth and development, but unequivocal proof is lacking in the literature. A laboratory study was conducted to demonstrate the validity of this speculation. Four experiments were carried out to observe the characteristic "triple" response of etiolated pea seedlings to C(2)H(4) microbially derived from l-methionine as a substrate in the presence or absence of Ag(I), a potent inhibitor of C(2)H(4) action. In two experiments, the combination of l-methionine and Acremonium falciforme (as an inoculum) was used, while in another study the indigenous soil microflora was responsible for C(2)H(4) production. A standardized experiment was conducted with C(2)H(4) gas to compare the contribution of the microflora to plant growth. In all cases, etiolated pea seedlings exhibited the classical triple response, which includes reduction in elongation, swelling of the hypocotyl, and a change in the direction of growth (horizontal). The presence of Ag(I) afforded protection to the pea seedlings against the microbially derived C(2)H(4). This study demonstrates that microbially produced C(2)H(4) in soil can influence plant growth.

Journal Article↗

New Field Isolates of Rhizobium leguminosarum Biovar Viciae That Nodulate the Primitive Pea Cultivar Afghanistan in Addition to Modern Cultivars.

A collection of 13 field isolates of Rhizobium leguminosarum bv. viciae that have the ability to nodulate the roots of current North American cultivars of peas as well as a "primitive" cultivar, Afghanistan, was examined. These isolates originated in diverse geographical regions of the world, which indicates that this phenotype is not restricted to isolates from any one region. When subclones of the nodulation region from one plasmid were used to examine EcoRI-fragment-length polymorphisms in this collection of strains as well as in a collection comprising strains that do not nodulate the primitive cultivar, polymorphism was found in both collections. With one exception, RisphiA6, all strains that nodulated cv. Afghanistan pea contained a region called nodX as an extension to the nodA BCIJ operon that has been observed in all R. leguminosarum bv. viciae strains, including those that do not nodulate cv. Afghanistan pea. RisphiA6 was also the only strain in which nodulating ability could not be associated with a conjugative plasmid.

Journal Article↗

Procedure for Obtaining Efficient Root Nodulation of a Pea Cultivar by a Desired Rhizobium Strain and Preempting Nodulation by Other Strains.

The specificity between the sym-2 gene bred into certain cultivars of pea (Pisum sativum L.) and the nodX gene, present only rarely in isolates of Rhizobium leguminosarum, can be exploited to preempt competition or nodulation blocking by a Rhizobium strain indigenous to a soil environment. The principle is to isolate an R. leguminosarum strain prevalent in a locale, convert it into a strain that will nodulate a desirable pea cultivar carrying sym-2 by establishing nodX in it, and then use the resulting Rhizobium strain with the pea cultivar carrying sym-2. To accomplish this, we first constructed a transposon Tn5 derivative called Tn5nodX and an efficient delivery vehicle that is suicidal in R. leguminosarum. We tested the potential utility of the system in greenhouse experiments. The results are encouraging enough to warrant extensive experiments under field conditions.

Journal Article↗

Novel plant-microbe rhizosphere interaction involving Streptomyces lydicus WYEC108 and the pea plant (Pisum sativum).

A previously undescribed plant-microbe interaction between a root-colonizing Streptomyces species, S. lydicus WYEC108, and the legume Pisum sativum is described. The interaction is potentially of great importance to the health and growth in nature of this nodulating legume. The root-colonizing soil actinomycete S. lydicus WYEC108 influences pea root nodulation by increasing root nodulation frequency, possibly at the level of infection by Rhizobium spp. S. lydicus also colonizes and then sporulates within the surface cell layers of the nodules. Colonization leads to an increase in the average size of the nodules that form and improves the vigor of bacteroids within the nodules by enhancing nodular assimilation of iron and possibly other soil nutrients. Bacteroid accumulation of the carbon storage polymer, poly-beta-hydroxybutyrate, is reduced in colonized nodules. Root nodules of peas taken from agricultural fields in the Palouse hills of northern Idaho were also found to be colonized by actinomycete hyphae. We hypothesize that root and nodule colonization is one of several mechanisms by which Streptomyces acts as a naturally occurring plant growth-promoting bacterium in pea and possibly other leguminous plants.

Pisum sativum↗

Differential ability of genotypes of 2,4-diacetylphloroglucinol-producing Pseudomonas fluorescens strains to colonize the roots of pea plants.

Indigenous populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent Pseudomonas spp. that occur naturally in suppressive soils are an enormous resource for improving biological control of plant diseases. Over 300 isolates of 2,4-DAPG-producing fluorescent Pseudomonas spp. were isolated from the rhizosphere of pea plants grown in soils that had undergone pea or wheat monoculture and were suppressive to Fusarium wilt or take-all, respectively. Representatives of seven genotypes, A, D, E, L, O, P, and Q, were isolated from both soils and identified by whole-cell repetitive sequence-based PCR (rep-PCR) with the BOXA1R primer, increasing by three (O, P, and Q) the number of genotypes identified previously among a worldwide collection of 2,4-DAPG producers. Fourteen isolates representing eight different genotypes were tested for their ability to colonize the rhizosphere of pea plants. Population densities of strains belonging to genotypes D and P were significantly greater than the densities of other genotypes and remained above log 6.0 CFU (g of root)(-1) over the entire 15-week experiment. Genetic profiles generated by rep-PCR or restriction fragment length polymorphism analysis of the 2,4-DAPG biosynthetic gene phlD were predictive of the rhizosphere competence of the introduced 2,4-DAPG-producing strains.

Bacterial Proteins↗

Lectin-enhanced accumulation of manganese-limited Rhizobium leguminosarum cells on pea root hair tips.

The ability of Rhizobium leguminosarum 248 to attach to developing Pisum sativum root hairs was investigated during various phases of bacterial growth in yeast extract-mannitol medium. Direct cell counting revealed that growth of the rhizobia transiently stopped three successive times during batch culture in yeast extract-mannitol medium. These interruptions of growth, as well as the simultaneous autoagglutination of the bacteria, appeared to be caused by manganese limitation. Rhizobia harvested during the transient phases of growth inhibition appeared to have a better attachment ability than did exponentially growing rhizobia. The attachment characteristics of these manganese-limited rhizobia were compared with those of carbon-limited rhizobia (G. Smit, J. W. Kijne, and B. J. J. Lugtenberg, J. Bacteriol. 168:821-827, 1986, and J. Bacteriol. 169:4294-4301, 1987). In contrast to the attachment of carbon-limited cells, accumulation of manganese-limited rhizobia (cap formation) was already in full progress after 10 min of incubation; significantly delayed by 3-O-methyl-D-glucose, a pea lectin haptenic monosaccharide; partially resistant to sodium chloride; and partially resistant to pretreatment of the bacteria with cellulase. Binding of single bacteria to the root hair tips was not inhibited by 3-O-methyl-D-glucose. Whereas attachment of single R. leguminosarum cells to the surface of pea root hair tips seemed to be similar for both carbon- and manganese-limited cells, the subsequent accumulation of manganese-limited rhizobia at the root hair tips is apparently accelerated by pea lectin molecules. Moreover, spot inoculation tests with rhizobia grown under various culture conditions indicated that differences in attachment between manganese- and carbon-limited R. leguminosarum cells are correlated with a significant difference in infectivity in that manganese-limited rhizobia, in contrast to carbon-limited rhizobia, are infective. This growth-medium-dependent behavior offers and explanation for the seemingly conflicting data on the involvement of host plant lectins in attachment of rhizobia to root hairs of leguminous plants. Sym plasmid-borne genes do not play a role in manganese-limitation-induced attachment of R. leguminosarum.

Carbon↗

Regulation of L-alanine dehydrogenase in Rhizobium leguminosarum bv. viciae and its role in pea nodules.

Alanine dehydrogenase (AldA) is the principal enzyme with which pea bacteroids synthesize alanine de novo. In free-living culture, AldA activity is induced by carboxylic acids (succinate, malate, and pyruvate), although the best inducer is alanine. Measurement of the intracellular concentration of alanine showed that AldA contributes to net alanine synthesis in laboratory cultures. Divergently transcribed from aldA is an AsnC type regulator, aldR. Mutation of aldR prevents induction of AldA activity. Plasmid-borne gusA fusions showed that aldR is required for transcription of both aldA and aldR; hence, AldR is autoregulatory. However, plasmid fusions containing the aldA-aldR intergenic region could apparently titrate out AldR, sometimes resulting in a complete loss of AldA enzyme activity. Therefore, integrated aldR::gusA and aldA::gusA fusions, as well as Northern blotting, were used to confirm the induction of aldA activity. Both aldA and aldR were expressed in the II/III interzone and zone III of pea nodules. Overexpression of aldA in bacteroids did not alter the ability of pea plants to fix nitrogen, as measured by acetylene reduction, but caused a large reduction in the size and dry weight of plants. This suggests that overexpression of aldA impairs the ability of bacteroids to donate fixed nitrogen that the plant can productively assimilate. We propose that the role of AldA may be to balance the alanine level for optimal functioning of bacteroid metabolism rather than to synthesize alanine as the sole product of N(2) reduction.

Alanine↗

In vitro analysis of the pea chloroplast 16S rRNA gene promoter.

A cloned pea chloroplast 16S rRNA gene promoter has been characterized in detail by use of a homologous in vitro transcription system that contains a highly purified chloroplast RNA polymerase. The in vivo and in vitro 16S rRNA transcriptional start site has been identified to be a T on the plus strand, 158 bases upstream of the mature 5' end of the gene. BAL 31 deletions of the 16S rRNA leader region demonstrated that the bases between -66 to +30 relative to the transcriptional start site (+1) are necessary for specific 16S transcription. Disruption of canonical TTGACA or TATAAT elements within this region caused complete transcriptional inactivation and prevented protein binding. The topological requirement for 16S transcription was examined by using a construct that synthesized a transcript from the 16S promoter and released it from a pea plastid putative terminator sequence. This minigene was relaxed in vitro with a topoisomerase I from pea chloroplast. It was shown that the 16S promoter was most active when the minigene plasmid was supercoiled.

Base Sequence↗

Rhizobium population dynamics in the pea rhizosphere of rhizobial inoculant strain applied in different formulations.

The effect of inoculant formulation on the population dynamics of rhizobia in the pea rhizosphere was investigated using a streptomycin-resistant mutant of Rhizobium leguminosarum bv. viceae NITRAGIN128C56G (128C56G strR). The isolate was formulated into liquid, peat powder, and granular peat carriers, and was tested on pea at field sites near Saskatoon, Saskatchewan, and Beaverlodge, Alberta, in 1996 and 1997. The liquid and peat powder formulations were applied to seed while the granular inoculant was applied to soil. In three out of four site years, population dynamics were similar among formulations: an initial decline or lag period lasting 2-5 days followed by an increase to approximately 10(5) colony-forming units (CFU)/seedling by 14-28 days after planting (DAP) and, where sampled, a continuing increase from 10(7) to 10(8) CFU/plant at 63 DAP. In these same site years, nodule number (not determined at Beaverlodge in 1997) and nodule occupancy at 60 days were not significantly different among formulations. In contrast, soil populations of 128C56G strR from the liquid formulation declined to near zero by 28 DAP at Beaverlodge in 1996, when soil moisture was excessive in spring because of high rainfall. Populations increased in this treatment after this time, but remained significantly lower than the populations of the other two formulations throughout the sampling period. Pea seed yields were not significantly different among treatments in either year at Beaverlodge, but were significantly higher with granular inoculant than the noninoculated control in Saskatoon. Within inoculated treatments at Saskatoon, there were no significant differences in grain yield.

Colony Count, Microbial↗

Fate of dietary sucrose and neosynthesis of amino acids in the pea aphid, acyrthosiphon pisum, reared on different diets

The fate of sucrose, the major nutrient of an aphid's natural food, was explored by radiolabeling in the pea aphid Acyrthosiphon pisum. To investigate the influence of nitrogen quality of food on amino acid neosynthesis, pea aphids were reared on two artificial diets differing in their amino acid composition. The first (diet A) had an equilibrated amino acid balance, similar to that derived from analysis of aphid carcass, and the other (diet B) had an unbalanced amino acid composition similar to that of legume phloem sap. Aphids grown on either diet expired the same quantity of sucrose carbon as CO(2), amounting to 25-30 % of the ingested sucrose catabolized in oxidation pathways. On diet A, the aphids excreted through honeydew about twice as much sucrose carbon as on diet B (amounting to 12.6 % of the ingested sucrose for diet A and 8.4 % for diet B), while amounts of sucrose carbons incorporated into exuviae were almost identical (1.9 % of the ingested sucrose on diet A and 2.7 % on diet B). There was also no difference in the amounts of sucrose carbon incorporated into the aphid tissues, which represented close to 50 % of the ingested sucrose. Sucrose carbons in the aphid tissues were mainly incorporated into lipids and the quantities involved were the same in aphids reared on either diet. On diet B, we observed neosynthesis of all protein amino acids from sucrose carbons and, for the first time in an aphid, we directly demonstrated the synthesis of the essential amino acids leucine, valine and phenylalanine. Amino acid neosynthesis from sucrose was significantly higher on diet B (11.5 % of ingested sucrose carbons) than on diet A (5.4 %). On diet A, neosynthesis of most of the amino acids was significantly diminished, and synthesis of two of them (histidine and arginine) was completely suppressed. The origin of amino acids egested through honeydew was determined from the specific activity of the free amino acid pool in the aphid. Aphids are able to adjust to variation in dietary amino acids by independent egestion of each amino acid. While more than 80 % of excreted nitrogen was from food amino acids, different amino acids were excreted in honeydew of aphids reared on the two diets. The conversion yields of dietary sucrose into aphid amino acids determined in this study were combined with those obtained previously by studying the fate of amino acids in pea aphids reared on diet A. The origin of all the amino acid carbons in aphid tissues was thus computed, and the metabolic abilities of aphid are discussed from an adaptive point of view, with respect to their symbiotic status.

Journal Article↗

The impact of fermentation and in vitro digestion on the formation of angiotensin-I-converting enzyme inhibitory activity from pea and whey protein.

Pea and whey protein were fermented by Lactobacillus helveticus and Saccharomyces cerevisiae in monoculture and in combination at 28 and 37 degrees C in order to release angiotensin-I-converting enzyme (ACE) inhibitory peptides. The fermentation products were subjected to in vitro gastrointestinal digestion, and the digests of nonfermented samples served as controls. After fermentation, the ACE inhibitory activity (%) increased by 18 to 30% for all treatments, except for the fermentations of whey protein with Saccharomyces cerevisiae at 28 degrees C, where no significant change was observed. After digestion, however, both fermented and nonfermented samples reached maximum ACE inhibitory activity. The whey digests tended to have lower (50%) inhibitory concentrations (IC50; 0.14 to 0.07 mg/ml), hence, higher ACE inhibitory activity, than the pea digests (0.23 to 0.11 mg/ml). The nonfermented whey protein digest showed the highest ACE inhibitory activity of all. For pea protein, the nonfermented sample had the lowest IC50 value. These results suggest that in vitro gastrointestinal digestion was the predominant factor controlling the formation of ACE inhibitory activity, hence, indicating its importance in the bioavailability of ACE inhibitory peptides.

Angiotensin-Converting Enzyme Inhibitors↗

Reducing concentrate supplementation in dairy cow diets while maintaining milk production with pea-wheat intercrops.

In the first of 2 experiments, 40 dairy cows were used to evaluate the milk production potential and concentrate-sparing effect of feeding dairy cows a basal diet of pea-wheat intercrop silages instead of perennial rye-grass silage (GS). Dairy cows were offered GS or 2 intercrop silages prepared from wheat and either Magnus peas (MW, a tall-straw variety) or Setchey peas (SW, a short-straw variety) ad libitum. The respective intercrops were supplemented with 4 kg/d of a dairy concentrate (CP = 240 g/kg dry matter; MW4 and SW4), and the GS were supplemented with 4 (GS4) or 8 (GS8) kg/d of the same concentrate. The second experiment measured the forage DM intake, digestibility, rumen function, and microbial protein synthesis from the forages by offering them alone to 3, nonlactating cows (3 x 3 Latin square design with 21-d periods). Forage dry matter intake was greater in cows fed the intercrop silages than those fed GS. Milk production was greater in cows fed SW4 than those fed GS4 or MW4, but similar to cows fed GS8. Dietary treatment did not affect milk fat, protein, or lactose concentrations. The intercrops had greater N retention, and were more digestible than the GS, and these factors probably contributed to the greater forage DM intakes and greater milk production from the intercrop silages compared with the GS. Rumen volatile fatty acid concentrations were similar across forages, but urinary purine derivative excretion was greater in the cows fed the intercrop silages than the GS, suggesting that rumen microbial protein synthesis was enhanced by feeding the intercrops. In conclusion, similar milk yield and milk composition can be obtained by feeding SW and 4 kg of concentrates as that obtained with GS and 8 kg of concentrates. Feeding intercrop silages instead of GS with the same amount of concentrates increased forage intakes, N retention, and microbial protein synthesis.

Animal Feed↗

Nutritional homeostatic capacity of a three-breed cross in poultry and associated effects of genotypes at the pea comb and endogenous viral element 1 loci.

The effect of varying combinations of dietary CP, at 16, 18, and 20%, with ME, at 2,900 and 3,100 kcal ME/kg, on BW and feed conversion (FC) at 2 to 6 wk of age for a three-breed cross was evaluated. Additionally, effect of genotypes at the pea comb (P) and endogenous viral element 1 (ev1) loci on dietary treatments were evaluated. Average weekly feed intake per bird varied from 25.6 to 32.6 g for birds on 16% CP, 3,100 kcal ME/kg and 20% CP, 2,900 kcal ME/kg diets, respectively. Weekly BW and FC were highest for birds on a combination of 20% CP and 3,100 kcal ME/kg diet. On 18% CP and 3,100 kcal/ME diet, males with pea comb had significantly higher BW than those with a single comb. At the ev1 locus, differences among genotypes were significant only for BW of females on a diet consisting of 20% CP and 2,900 kcal ME/kg. Pooled data from the dietary treatments revealed that males with pea comb had significantly higher BW than males with single comb at 3 to 6 wk of age. Birds heterozygous at the ev1 locus had higher BW than those homozygous at this locus. Results of the current studies provide information necessary to develop the optimal protein and energy combination for BW and FC for a three-breed cross involving Araucona, White Leghorn, and Rhode Island Red. These studies also provide additional evidence of the possible effects of the P locus and a gene linked to it, ev1, on production traits in chickens.

Animals↗

Clones of pea aphid, Acyrthosiphon pisum (Hemiptera: aphididae) distinguished using genetic markers, differ in their damaging effect on a resistant alfalfa cultivar.

CUF 101, a resistant cultivar of alfalfa, was exposed to 15 clones of Acyrthosiphon pisum Harris collected from alfalfa fields in three regions of France (east, south, central west) to determine whether the level of resistance varied across the different clones. The survival of alfalfa seedlings infested at the cotyledon stage was assessed using a standardized method. Although no difference in seedling mortality was detected between clones grouped by region, there was a significant variation among the 15 pea aphid clones. In particular, two clones of southern origin were more aggressive. In addition, the different pea aphid clones were characterized using allozyme and RAPD-PCR markers. Among the 15 clones, seven allozyme genotypes (plus one when adding colour polymorphism) and 12 RAPD-PCR genotypes were distinguished. The two southern clones differing by their aggressiveness on the resistant alfalfa belonged to the same allozyme and RAPD genotype which was distinct from the other pea aphid clones. Our results reinforce the need to take into account aphid genetic diversity in breeding programmes for resistance in cultivated plants.

Agriculture↗

The effect of microgravity on proton permeability of thylakoid membranes and contribution of II and I photosystems in photosynthetic electron transport in pea chloroplasts.

According to a number investigations microgravity conditions affect membrane apparatus of photosynthesis in cells of higher plants and alga [for review, see Kordyum et al., 1994; Kordyum, 1997]. (see for review). Chloroplasts of space-grown pea plants showed disintegration of grana, shrinkage of the membrane constituting the grana stacks and other structural perturbance of the photosynthetic membranes. However there have been no studies on the effect of microgravity on proton permeability of thylakoid membranes and closely connected with this parameter their photochemical characteristics. The aim of the study is investigation of microgravity effects on protonic permeability of photosynthetic membrane and contribution of photosystem II (PSII) and photosystem I (PSI) in electron transfer from water to potassium ferrycianide (FeCy) in isolated pea chloroplasts. Pea.

Chloroplasts↗

Molecular and cytogenetic analysis of repetitive DNA in pea (pisum sativum L.).

A set of pea DNA sequences representing the most abundant genomic repeats was obtained by combining several approaches. Dispersed repeats were isolated by screening a short-insert genomic library using genomic DNA as a probe. Thirty-two clones ranging from 149 to 2961 bp in size and from 1,000 to 39,000/lC in their copy number were sequenced and further characterized. Fourteen clones were identified as retrotransposon-like sequences, based on their homologies to known elements. Fluorescence in situ hybridization using clones of reverse transcriptase and integrase coding sequences as probes revealed that corresponding retroelements were scattered along all pea chromosomes. Two novel families of tandem repeats, named PisTR-A and PisTR-B, were isolated by screening a genomic DNA library with Cot-1 DNA and by employing genomic self-priming PCR, respectively. PisTR-A repeats are 211-212 bp long, their abundance is 2 x 10(4) copies/lC, and they are partially clustered in a secondary constriction of one chromosome pair with the rest of their copies dispersed on all chromosomes. PisTR-B sequences are of similar abundance (10(4) copies/lC) but differ from the "A" family in their monomer length (50 bp), high A/T content, and chromosomal localization in a limited number of discrete bands. These bands are located mainly in (sub)telomeric and pericentromeric regions. and their patterns, together with chromosome morphology, allow discrimination of all chromosome types within the pea karyotype. Whereas both tandem repeat families are mostly specific to the genus Pisum, many of the dispersed repeats were detected in other legume species, mainly those in the genus Vicia.

Base Sequence↗

Identification of RAPD markers and their use for molecular mapping in pea (Pisum sativum L.).

The RAPD method (Random Amplified Polymorphic DNA) was used for identifying and mapping new molecular markers in pea. RAPD analysis of various cultivars and lines of pea was carried out using 10-mer random primers. The presence of multiple polymorphism between cultivars and lines was revealed; at least one fragment for any given primer was present in the DNA of one form of pea and absent in the DNA of another line or cultivar. To detect molecular markers linked to the genes of chi-15, xa-18 and also to the 12 morphological markers of the L-1238 line, the F2 populations (Chi-15 ? L-1238), (Vio ? L-1238), (Xa-18 ? L-1238), (L-111 ? Chi-15) and (L-84 ? Xa-18) were studied via bulked segregant analysis. DNA molecular analysis of F1 hybrids revealed the presence of parental polymorphic fragments in all of the populations. The study of the F2 plants showed that the obtained fragments are inherited as Mendelian factors. 13 RAPD-markers linked to genes of A/a (flower color), I/i (seed color), Gp/gp (pod color), R/r (seed form), S/s (seeds linkage), and also to genes of Chi-15/chi-15 (leaf color) and Xa-18/xa-18 (leaf color) were discovered. The study of individual plant DNA from the F2 populations allowed us to determine the genetic distances between genes and the RAPD markers linked to them.

Base Sequence↗