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[Nutritional quality of pigeon pea protein, immature and ripe, and its supplementary value for cereals].

The purpose of the present research was to determine the differences which could exist between immature and mature pigeon pea in gross chemical composition and protein quality, raw and cooked, as well as their respective supplementary value to rice, and to mature and immature corn and sorghum. The chemical composition data showed only small differences in proximate composition between the mature and immature grain. The cooking process did not affect chemical composition. Based on the FAO/WHO amino acid reference pattern, immature pigeon pea was more deficient in threonine than mature pigeon pea, which was limiting in valine. Both grains were limiting in sulfur amino acids. The protein quality of the immature grain was higher than that of the mature grain, and both responded positively to cooking, suggesting the presence of antiphysiological substances in both. Amino acid supplementation studies demonstrated that both the immature and mature grain responded to methionine addition, the first limiting amino acid, and to tryptophan, the second limiting amino acid. The effects were more marked when samples were cooked. Both types of grains were good supplements to rice, when added in amounts of 10-20%. Mature pigeon peas supplemented relatively well the proteins of sorghum, immature and mature corn, at the 20, 30 and 20% levels, respectively. The differences found could be explained on the basis of the amino acids limiting cereal grains and pigeon peas protein.

Amino Acids, Essential↗

[Effect of gibberellic acid on RNA synthesis in dwarf peas].

The effect of gibberellic acid (GA) on total RNA and polysomal poly-[A]+-RNA synthesis in epicotylia and embryos of dwarf pea of two varieties differing in their physiological sensitivity to GA was studied. It was found that incubation with GA increases the accumulation of total RNA in pea epicotylia, var. "Pioner" and "Polzunok". The maximal stimulation of RNA accumulation makes up to 40% for the low sensitivity variety "Polzunok" and 150% for the highly sensitive variety "Pioner". GA increases the synthesis of polysomal poly (A)+-mRNA in 5-year-old pea sprouts and that of newly synthesized poly (A)+-mRNA in epicotylian polysomes of both varieties 5, 24, 48 and 72 hrs after incubation with GA. GA at concentrations of 10(-6) and 10(-5) stimulates the incorporation of [3H]uridine into polysomal mRNA during the first 1--3 hours after treatment and enhances the accumulation of newly synthesized mRNA in pea embryonic polyribosomes. The stimulating effect is directly proportional to the dose of the hormone. The mechanisms of GA effect on the transcription and translation in pea plant cells are discussed.

Gibberellins↗

The crystal structure of pea lectin at 6-A resolution.

The three-dimensional crystal structure of the mitogenic lectin from the green pea (Pisum sativum) has been determined at 6-A resolution by x-ray diffraction methods. Pea lectin was isolated by use of affinity chromatography and was crystallized from polyethylene glycol solutions. Crystals of pea lectin are orthorhombic, space group P212121, and diffract to at least 1.2-A resolution. The unit cell dimensions are a = 50.85(5), b = 61.23(5), and c = 137.3(2) A. The calculated mass of protein per asymmetric unit is 49,000 daltons, and the crystals are 44% solvent by volume. There are two pea lectin monomers per crystallographic asymmetric unit. Diffractometer data were collected from a native crystal and from a single site uranyl heavy atom derivative crystal. The position of the uranium atom, determined from three-dimensional Patterson maps, was refined by least squares techniques (R index - 0.46 for centric data). A three-dimensional electron density map was calculated by use of phases determined by isomorphous-replacement and anomalous-dispersion contributions. The boundaries of the pea lectin molecule are clearly visible in the map. The molecule appears to be a dimer, roughly peanut-shaped, formed by the close association of the two monomer units. In shape and size, it bears a striking resemblance to the concanavalin A dimer, in which monomers combine to form a dimer-wide contiguous antiparallel pleated sheet.

Chromatography, Affinity↗

Chromatographic behavior of pea lectin receptors from the 6C3HED murine ascites tumor.

We have previously shown that pea lectin and concanavalin A bind to different receptors as well as to common receptors on the cell surface of 6C3HED murine ascites tumor cells (Allen, H.J. nd Johnson, E.A.Z. (1976) Biochim. Biophys. Acta 436, 557-566). We have characterized the metabolically labeled pea lectin receptor from trypsinates of viable tumor cells by gel filtration and affinity chromatography. The pea lectin receptor eluted as an apparent high molecular weight glycopeptice (Mr 200 000) from Sephadex G-200 columns. Other glycopeptides were present in the trypsinates but they did not bind to either concanavalin A or to pea lectin in significant amounts. The high molecular weight glycopeptide was resistant to digestion by a high concentration of trypsin but it was absent in non-specific protease digests of viable cells. Sequential lectin affinity chromatography of Nonidet P-40 extracts of cells permitted the probable identification of the native glycoprotein corresponding to the high molecular weight glycopeptide which binds to pea lectin.

Cell Membrane↗

Growth, activity of phytohormones and inhibitors, and photosynthesis of dwarf pea mutants under different conditions of illumination.

A clear correlation was found between the growth of mutant forms of pea plants and the light intensity: With an increase in the latter the growth of the plants was inhibited and the rate of photosynthesis increased. The inhibitory action of light on stem growth affected not only tall pea plants, but also dwarf forms. A definite link was observed between the genetic apparatus and the balance of endogenous phytohormones and inhibitors. The content of bound forms of gibberellins was directly related to the growth intensity--the content of these substances was highest in the tall Torsdag pea plant, it was lower in the semidwarf K-29, and it was very low in the dwarf K-202. The content of quercetin glucosylcoumarate was lowest in Torsdag pea plants, in dwarf mutants the greater the amount of this compound the shorter the stem. The genetically determined ratio of phytohormones and inhibitors in the original tall and dwarf forms of pea plants is retained under all illumination conditions at various intensities.

Fabaceae↗

Identification of the SecA protein homolog in pea chloroplasts and its possible involvement in thylakoidal protein transport.

Recently, we identified the SecA and SecY proteins in the cyanobacterium Synechococcus PCC7942. Antibodies raised against cyanobacterial SecA specifically reacted with a 110-kDa protein of pea chloroplasts, suggesting the presence of SecA in higher plant chloroplasts. A part of the pea secA cDNA was polymerase chain reaction-amplified with degenerated oligonucleotide primers and with pea cDNA as a template. The deduced amino acid sequence shows 62% identity with cyanobacterial SecA and 52% identity with Escherichia coli SecA. Antibodies raised against the pea SecA fragment, which was expressed in E. coli cells from the obtained polymerase chain reaction-amplified cDNA, reacted with the 110-kDa chloroplast protein; the 110-kDa protein was mainly found in the stroma but partly in the thylakoid membrane. The anti-pea SecA IgG inhibited the in vitro import of the 33-kDa protein of the oxygen-evolving complex, but not of the 23-kDa protein of the oxygen-evolving complex, into thylakoids. These results suggest that SecA facilitates transport of a subset of thylakoid lumenal proteins including the 33-kDa protein into thylakoids. We propose that a bacterial-type Sec protein-dependent transport system operates for protein transport into thylakoids in higher plant chloroplasts.

Amino Acid Sequence↗

Expression of legumin and vicilin genes in pea mutants and the production of legumin in transgenic plants.

Pea seeds contain two major storage proteins, legumin and vicilin, in proportions that are genetically and environmentally determined. They are synthesized from at least 40 genes and at least 10 different genetic loci. Mutant alleles at loci involved in starch synthesis, which result in perturbations in starch accumulation, also affect the expression of legumin genes, thereby influencing the legumin: vicilin ratio within the total seed protein. Examples of such alleles include r (starch-branching enzyme) and rb (ADP-glucose pyrophosphorylase), both of which result in a reduction in legumin synthesis; double mutants (rrb) show a particularly severe reduction in the amount of legumin. The effects of such mutations are specific to legumins. The amounts of vicilin are unaffected by mutations at r or rb. One of the consequences of the production of legumin from many genes is structural heterogeneity that is believed to preclude the purification of homogeneous legumin for crystallization and 3D-structure determination. Expression of cloned legumin cDNA in E. coli can result in sequence homogeneity, but E. coli is unable to carry out the normal proteolytic processing of legumin precursors and consequently such material is different from that produced in pea seeds. This paper describes the high-level synthesis, processing and assembly of pea legumin in transgenic wheat seeds, leading to the spontaneous in vitro formation of paracrystalline arrays of legumin, which may be attributed to the fact that the legumin consists of a single type of subunit. Such material might be used as a source of single-sequence, processed and assembled pea legumin for structural investigation.

Gene Expression Regulation, Plant↗

The pea aphid, Acyrthosiphon pisum: an emerging genomic model system for ecological, developmental and evolutionary studies.

Aphids display an abundance of adaptations that are not easily studied in existing model systems. Here we review the biology of a new genomic model system, the pea aphid, Acyrthosiphon pisum. We then discuss several phenomena that are particularly accessible to study in the pea aphid: the developmental genetic basis of polyphenisms, aphid-bacterial symbioses, the genetics of adaptation and mechanisms of virus transmission. The pea aphid can be maintained in the laboratory and natural populations can be studied in the field. These properties allow controlled experiments to be performed on problems of direct relevance to natural aphid populations. Combined with new genomic approaches, the pea aphid is poised to become an important model system for understanding the molecular and developmental basis of many ecologically and evolutionarily relevant problems.

Adaptation, Biological↗

Synthesis, transport and localization of a nuclear coded 22-kd heat-shock protein in the chloroplast membranes of peas and Chlamydomonas reinhardi.

The synthesis, transport and localization of a nuclear coded 22-kd heat-shock protein (HSP) in the chloroplast membranes was studied in pea plants and Chlamydomonas reinhardi. HSPs were detected in both systems by in vivo labeling and in vitro translation of poly(A)RNA, using the wheat-germ and reticulocyte lysate systems. Heat-shock treatment of pea plants for 2 h at 42-45 degrees C induces the expression of 10 nuclear coded proteins, among which several (18 kd, 19 kd, 22 kd) are predominant. A 22-kd protein is synthesized as a 26-kd precursor protein and is localized in a chloroplast membrane fraction in vivo. Following post-translational transport into intact chloroplasts in vitro of the 26-kd precursor, the protein is processed but the resulting 22-kd mature protein is localized in the chloroplast stroma. If, however, the in vitro transport is carried out with chloroplasts from heat-shocked plants, the 22-kd protein is preferentially transported to the chloroplast membrane fraction. In C. reinhardi the synthesis of poly(A)RNAs coding for several HSPs is progressively and sequentially induced when raising the temperature for 1.5 h from 36 degrees C to 42 degrees C, while that of several preexisting RNAs is reduced. Various pre-existing poly(A)RNAs endure in the cells at 42 degrees C up to 5 h but are no longer translated in vivo, whereas some poly(A)RNAs persist and are translated. As in pea, a poly(A)RNA coded 22-kd HSP is localized in the chloroplast membranes in vivo, although it is translated as a 22-kd protein in vitro. The in vitro translated protein is not transported in isolated pea chloroplast which, however, processes and transports other nuclear coded chloroplast proteins of Chlamydomonas. The poly(A)RNA coding for the 22-kd HSP appears after 1 h at 36 degrees C. Its synthesis increases with the temperature of incubation up to 42 degrees C, although it decreases after 2 h of heat treatment and the already synthesized RNA is rapidly degraded. The degradation is faster upon return of the cells to 26 degrees C. None of the heat-induced proteins is identical to the light-inducible proteins of the chloroplast membranes.

Journal Article↗

Glutamine synthetase genes of pea encode distinct polypeptides which are differentially expressed in leaves, roots and nodules.

We have characterized the distinct polypeptides, primary translation products and mRNAs encoding glutamine synthetase (GS) in the various organs of pea. Western blot analysis of soluble protein has identified five distinct GS polypeptides which are expressed at different relative levels in leaves, roots and nodules of pea. Of the two GS polypeptides in leaves (44 and 38 kd), the 44-kd GS polypeptide is predominant and is localized to the chloroplast stroma. In roots, the predominant GS polypeptide is 38 kd. Upon Rhizobium infection of roots, three 37-kd GS polypeptides increase in abundance in the nodules relative to uninfected roots. cDNA clones encoding three different GS mRNAs have been characterized. Hybrid-select translation has identified three different GS primary translation products (49, 38 and 37 kd). Two cDNA clones (pGS134 and pGS341) are homologous to GS mRNAs most abundant in nodules which encode the 38- and 37-kd GS primary translation products. A third cDNA (pGS197) corresponds to a larger GS mRNA species specific to leaf poly(A) RNA, which encodes a 49-kd putative precursor to the mature chloroplast GS polypeptide. cDNA sequence analysis and Southern blot analysis of pea nuclear DNA identifies at least three genes encoding GS in pea which are related but distinct in structure and in vivo pattern of expression.

Amino Acid Sequence↗

The early nodulin transcript ENOD2 is located in the nodule parenchyma (inner cortex) of pea and soybean root nodules.

A pea cDNA clone homologous to the soybean early nodulin clone pGmENOD2 that most probably encodes a cell wall protein was isolated. The derived amino acid sequence of the pea ENOD2 protein shows that it contains the same repeating pentapeptides, ProProHisGluLys and ProProGluTyrGln, as the soybean ENOD2 protein. By in situ hybridization the expression of the ENOD2 gene was shown to occur only in the inner cortex of the indeterminate pea nodule. The transcription of the pea ENOD2 gene starts when the inner cortical cells develop from the nodule meristem. In the determinate soybean nodule the ENOD2 gene is expressed in the inner cortex as well as in cells surrounding the vascular bundle that connects the nodule with the root central cylinder. The term 'nodule inner cortex' is misleading, as there is no direct homology with the root inner cortex. Therefore, we propose to consider this tissue as nodule parenchyma. A possible role of ENOD2 in a major function of the nodule parenchyma, namely creating an oxygen barrier for the central tissue with the Rhizobium containing cells, is discussed.

Amino Acid Sequence↗

The phosphoprotein protein PEA-15 inhibits Fas- but increases TNF-R1-mediated caspase-8 activity and apoptosis.

We have characterized a phosphoprotein protein with a death effector domain that has a novel bifunctional role in programmed cell death. The 15-kDa phosphoprotein enriched in astrocytes (PEA-15) inhibits Fas-mediated apoptosis and increases tumor necrosis factor receptor-1 (TNF-R1)-mediated apoptosis in the same cell type in a ligand-dependent manner. Phosphorylation appears to play a role in its differential effects, since point mutations at one or both phosphorylation consensus sites within PEA-15 destroy its effect on Fas-mediated, but not TNF-R1-mediated, apoptosis. Furthermore, the differential effect is evident at the level of caspase-8 activity which is inhibited via Fas activation, but increased via TNF-R1 activation upon PEA-15 expression. These results show that PEA-15 provides a potential mechanism during development for distinguishing between diverse extracellular death-inducing signals that culminate either in apoptosis or in survival.

3T3 Cells↗

Homology between a human protein and a protein of the green garden pea.

In screening a rat mucosa cDNA subtraction library, a clone that exhibited a remarkable degree of homology with a previously described cDNA from the green garden pea, designated the 26g pea turgor protein, was found. A partial cDNA sequence from rat and a complete cDNA sequence from human were obtained. The deduced human protein had a molecular weight of 55,285 and was designated antiquitin because of its remarkable level of conservation through evolution. Human antiquitin was 60% homologous to the green pea 26g with only a single amino acid gap in each sequence. The 66 amino acids at the carboxyl ends of the human antiquitin and pea 26g proteins were 86% identical, and one segment of 52 amino acids was 92% identical. A similar partial sequence encoding 164 amino acids has been detected in Caenorhabditis elegans. Yeast DNA was found to have sequences that hybridize with a human antiquitin probe on Southern blotting. Analysis of the amount of mRNA in various rat and human tissues indicated that the largest amounts were found in rat kidney and liver and in cultured human hepatoma cells. Only minimal amounts were detected in human peripheral blood leukocytes, rat lung, or cultured human fibroblasts. Attempts to induce the mRNA by heat-shock, dehydration, ionizing irradiation, or treatment with iron, t-butylhydroperoxide, or glucocorticoids were unsuccessful. The function of the protein remains unknown.

Aldehyde Dehydrogenase↗

Characterization of the pea chloroplast DNA OriA region.

One of the two origins of replication in pea chloroplast DNA (oriA) maps in the rRNA spacer region downstream of the 16S rRNA gene, and further characterization of this origin is presented here. End-labeling of nascent DNA strands from in vivo replicating ctDNA was used to generate probes for Southern hybridization. Hybridization data identified the same region that was previously mapped to contain D-loops by electron microscopy. Subclones of the oriA region were tested for their ability to support in vitro DNA replication using a partially purified pea ctDNA replication system. Two-dimensional agarose gel electrophoresis identified replication intermediates for clones from the region just downstream of the 16S rRNA gene, with a 450-bp SacI-EcoRI clone showing the strongest activity. The experiments presented in this paper identify the 940 base pair region in the rRNA spacer between the 3' end of the 16S rRNA gene and the EcoRI site as containing oriA. Previous studies by electron microscopy localized the D-loop in the spacer region just to the right of the BamHI site, but the experiments presented here show that sequences to the left of the BamHI site are required for replication initiation from oriA. DNA sequence analysis of this region of pea ctDNA shows the presence of characteristic elements of DNA replication origins, including several direct and inverted repeat sequences, an A + T rich region, and dnaA-like binding sites, most of which are unique to the pea ctDNA oriA region when compared with published rRNA spacer sequences from other chloroplast genomes.

Base Sequence↗

Pea embryonic tissues show common responses to the replication of a wide range of viruses.

The response of pea embryonic tissues to the replication of a range of different viruses was investigated using in situ hybridization to analyze changes in the expression of two host genes, heat shock protein 70 (hsp70) and lipoxygenase (lox1). Excised pea embryos were infected using microprojectile bombardment with a nonseed transmissible strain of Pea seed-borne mosaic potyvirus, or with Pea early browning tobravirus (PEBV), White Clover mosaic potexvirus, or Beet curly top geminivirus. Collectively, these examples represent families of viruses with differing genomic features, differing numbers of genomic components and differing replication strategies. In all cases, there was an induction of hsp70 associated with virus replication and, in most cases, a downregulation of lox1. Hence, either each virus has a direct inducer of these common responses or the induction is indirectly the result of a generic feature of virus infection. By exploiting the bipartite nature of the PEBV genome, the coat protein gene and genes involved in vector transmission were excluded as potential inducers.

Cotyledon↗

Turgor-responsive gene transcription and RNA levels increase rapidly when pea shoots are wilted. Sequence and expression of three inducible genes.

Reduction of turgor in pea shoots caused the accumulation of several poly(A) RNAs. cDNA clones derived from three different poly(A) RNAs which accumulate in wilted pea shoots were isolated, sequenced and expression of the corresponding genes examined. Clone 7a encoded a 289 amino acid protein. The C-terminal 180 amino acids of this protein were homologous to soybean nodulin-26. RNA hybridizing to cDNA 7a was abundant in roots, and induced in shoots by dehydration, heat shock and to a small extent by ABA. Hydropathic plots indicate that the protein encoded by cDNA 7a contains six potential membrane spanning domains similar to proteins which form ion channels. Clone 15a encoded a 363 amino acid protein with high homology to cysteine proteases. RNA hybridizing to cDNA 15a was more abundant in roots than shoots of control plants. Dehydration of pea shoots induced cDNA 15a mRNA levels whereas heat shock or ABA treatment did not. Clone 26g encoded a 508 amino acid protein with 30% residue identity to several aldehyde dehydrogenases. RNA hybridizing to cDNA 26g was induced by dehydration of shoots but not roots and heat shock and ABA did not modulate RNA levels. Levels of the three poly(A) RNAs increased 4-6-fold by 4 h after wilting and this increase was not altered by pretreatment of shoots with cycloheximide. When wilted shoots were rehydrated, RNA hybridizing to cDNA 26g declined to pre-stress levels within 2 h. Run-on transcription experiments using nuclei from pea shoots showed that transcription of the genes which encode the three poly(A) RNAs was induced within 30 min following reduction of shoot turgor. One of the genes showed a further increase in transcription by 4 h after dehydration whereas transcription of the other 2 genes declined. These results indicate that plant cells respond to changes in cell turgor by rapidly increasing transcription of several genes. Furthermore, the expression of the turgor-responsive genes varies with respect to the time course of induction and reversibility of the wilting-induced changes.

Amino Acid Sequence↗

Molecular cloning, nuclear gene structure, and developmental expression of NADPH: protochlorophyllide oxidoreductase in pea (Pisum sativum L.).

Complementary DNA clones and a corresponding nuclear gene (lpcr) encoding the NADPH-dependent protochlorophyllide oxidoreductase (pchlide reductase, EC 1.6.99.1) have been characterized from pea (Pisum sativum L.). The pea lpcr gene encodes a 43,118 Da precursor polypeptide comprised of a transit peptide of 64 amino acids and a mature protein of 336 amino acids. The coding portion of the gene is interrupted by four introns, two of which are located within the transit peptide coding portion of the gene. The deduced primary structure for the pea protein is similar to those reported for Arabidopsis and two monocot species. Northern blot analysis revealed little to no decrease in steady-state levels of mRNA encoding the enzyme in etiolated leaves illuminated with continuous white light for up to 48 h. In contrast, western blot analysis showed that the major immunoreactive species present in whole leaf extracts decreased to nearly undetectable levels during this same 48 h period. These results suggest that pchlide reductase activity in pea is primarily regulated post-transcriptionally, most likely at the level of translation initiation/elongation or protein turnover.

Amino Acid Sequence↗

On the role of calcium in indole-3-acetic acid movement and graviresponse in etiolated pea epicotyls.

To determine whether Ca2+ plays a special role in the early graviresponse of shoots, as has been reported for roots, we treated etiolated pea epicotyls with substances known to antagonize Ca2+ (La3+), to remove Ca2+ from the wall (spermidine, EGTA), to inhibit calmodulin mediated reactions (chlorpromazine), or to inhibit IAA transport (TIBA). We studied the effect of these substances on IAA and Ca2+ uptake into 7 mm long subapical 3rd internode etiolated pea epicotyl sections and pea leaf protoplasts, on pea epicotyl growth, and graviresponse and on lateral IAA redistribution during gravistimulation. Our results support the view that adequate Ca2+ in the apoplast is required for normal IAA uptake, transport and graviresponse. Experiments with protoplasts indicate that Ca2+ may be controlling a labile membrane porter, possibly located on the external surface of cell membrane, while inhibitor experiments suggest that calmodulin is also implicated in both the movement of IAA and graviresponse. Since a major transfer of Ca2+ through free space during graviresponse has not yet been demonstrated, and since inhibition of calcium channels does not affect IAA redistribution (Migliaccio and Galston, 1987, Plant Physiology 85:542), we conclude that no clear evidence links prior Ca2+ movement with IAA redistribution during graviresponse in stems.

Biological Transport↗