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Deletion analysis and localization of SbPRP1, a soybean cell wall protein gene, in roots of transgenic tobacco and cowpea.

SbPRP1 is a member of the soybean (Glycine max L. Merr) proline-rich cell wall protein family and is expressed at high levels in root tissue. To characterize the sequences required for this expression, we have fused 1.1 kb of upstream flanking DNA sequence from an SbPRP1 genomic clone to a gene encoding beta-glucuronidase (GUS). This construct was introduced into tobacco using Agrobacterium tumefaciens-mediated transformation. Histochemical staining of GUS activity in transgenic tobacco indicated that SbPRP1 is expressed in the apical and elongating region of both primary and lateral roots, most strongly in the epidermis. A similar localization pattern was found in transformed hairy roots when this construct was introduced into cowpea (Vigna aconitifolia) using Agrobacterium rhizogenes-mediated transformation. Nested 5'-deletion analysis of the SbPRP1 promoter indicated that a minimal promoter for SbPRP1 expression in roots is located within the first 262 bases of upstream flanking DNA and that the region between -1080 and -262 is required for maximal expression of this gene. Gel retardation assays showed that nuclear factors can be detected in soybean roots which specifically bind to sequences located between -1080 and -623, a region which is needed for maximal expression of the SbPRP1 promoter. Northern hybridization analysis was also used to show that little SbPRP1 mRNA was present in roots during the first 24 h after imbibition. These studies indicate that SbPRP1 expression is localized to the actively growing region of the root and that this expression is temporally regulated during very early stages of seedling growth.

Base Sequence↗

Suppression of gravitropic response of primary roots by submergence.

Primary roots of six plant species were placed horizontally either in humid air or under water, and their growth and gravitropic responses were examined. In air, all the roots showed a normal gravitropic curvature. Under water without aeration, roots of rice (Oryza sativa L.), oat (Avena sativa L.), azuki bean (Vigna angularis Ohwi et Ohashi), and cress (Lepidium sativum L.) curved downward at almost same rate as in air, whereas the curvature of roots of maize (Zea mays L.) and pea (Pisum sativum L.) was strongly suppressed. Submergence did not cause a decrease in growth rate of these roots. When roots of maize and pea were placed horizontally under water without aeration and then rotated in three dimensions on a clinostat in air, they showed a significant curvature, suggesting that the step suppressed by submergence is not graviperception but the subsequent signal transmission or differential growth process. Constant bubbling of air through the water partly restored the gravitropic curvature of maize roots and completely restored that of pea roots. The curvature of pea roots was also partly restored by the addition of an inhibitor of ethylene biosynthesis, aminooxyacetic acid. In air, ethylene suppressed the gravitropic curvature of roots of maize and pea. Furthermore, the level of ethylene in the intercellular space of the roots was increased by submergence. These results suggest that the accumulation of ethylene in the tissue is at least partly involved in suppression of transmission of the gravity signal or of differential growth in maize and pea roots under conditions of submergence.

Aminooxyacetic Acid↗

A novel response-regulator is able to suppress the nodulation defect of a Bradyrhizobium japonicum nodW mutant.

The two-component regulatory system Nod-VW of Bradyrhizobium japonicum is essential for the nodulation of the legume host plants Vigna radiata, V. unguiculata and Macroptilium atropurpureum. The NodV protein shares homology with the sensor-kinases, whereas the NodW protein is a member of the response-regulator class. We report here the identification of a new B. japonicum DNA region that is able to suppress the phenotypic defect of a nodW mutant, provided that this region is expressed from a foreign promoter. The minimal complementing region, which itself is not essential for nodulation in a nodW+ background, consists of one gene designated nwsB (nodW-suppressor). The deduced amino acid sequence of the nwsB gene product shows a high degree of homology to NodW. The nws B gene is preceded by a long open reading frame, nwsA, whose putative product appears to be a sensor-kinase. Downstream of nwsB, an open reading frame encoding a second putative response-regulator was identified. Interspecies hybridization revealed the presence of nwsAB-like DNA also in other Bradyrhizobium strains. Using nwsB'-'lacZ fusions, the nwsB gene was found to be expressed rather weakly in B. japonicum. This low level of expression is obviously not sufficient to compensate for a nodW- defect, whereas strong overexpression of nwsB is a condition that leads to suppression of the nodW- mutation.

Amino Acid Sequence↗

Site-directed mutagenesis and DNA sequence of pckA of Rhizobium NGR234, encoding phosphoenolpyruvate carboxykinase: gluconeogenesis and host-dependent symbiotic phenotype.

We have cloned and sequenced the pckA gene of Rhizobium sp. NGR234, a broad host-range strain. The gene encodes phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme of gluconeogenesis. The locus was isolated and subcloned from a genomic library of NGR234 employing hybridization with an R. meliloti pck gene probe and complementation of a Tn5 mutant in this species. The DNA sequence of pckA (NGR234) was determined and encoded a PEPCK protein of 535 amino acids with a molecular weight of 58.4 kDa. The deduced polypeptide sequence was compared to those of three known ATP-dependent PEPCKs. Slightly higher homology was observed with yeast and trypanosome polypeptides than with that of Escherichia coli. We have identified several regions that are conserved in all four PEPCK proteins. A mutant constructed in the pck gene by site-directed mutagenesis with interposon omega failed to grow on succinate, malate and arabinose but grew on glucose and glycerol as sole carbon sources. These data show that NGR234 requires PEPCK-driven gluconeogenesis to grow on TCA cycle intermediates. A host-dependent effect of the pckA mutation was observed on nodule development and nitrogen fixation. Nodules formed by the site-directed mutant on Leucaena leucocephala and Macroptilium atropurpureum were FixRed, but on Vigna unguiculata were Fix-. The expression of the gene was positively regulated in free-living cells of NGR234 by either succinate or host-plant exudates, and was subject to catabolite repression by glucose.

Amino Acid Sequence↗

Termination of transcription of ribosomal RNA genes of mung bean occurs within a 175 bp repetitive element of the spacer region.

In mung bean (Vigna radiata, formerly Phaseolus aureus) one length heterogeneity in the intergenic spacer (IGS) of the ribosomal DNA (rDNA) is due to a variable number of 175-bp subrepeats. This spacer region downstream of the 25S rRNA coding region was characterized by sequencing the 2.4 kb EcoRI/HindIII fragment of a 10.5 kb mung bean rDNA repeat. Within the 175-bp repetitive elements a sequence was detected showing strong similarity to the T2/T3-box (GACTTGC) found in Xenopus rDNA and involved in termination and enhancing transcription. In mung bean this sequence partly forms the stem of a possible stem-loop structure at the 3'end of each subrepeat. Nuclease mapping of transcription termination sites (TTS) results in two signals, 65 bp and 315 bp downstream of the 3'end of the 25S rRNA coding region. The longer transcript terminates 20 bp downstream of the stem-loop structure at the end of the first 175-bp subrepeat. A spacer model is proposed which allows "readthrough enhancement". No cross-hybridization was observed between the 180-bp subrepeats in pea (Pisum sativum) rDNA and the mung bean 175-bp subrepeat.

Base Sequence↗

Mutational analysis of the Bradyrhizobium japonicum common nod genes and further nod box-linked genomic DNA regions.

By insertional and deletional marker replacement mutagenesis the common nod region of Bradyrhizobium japonicum was examined for the presence of additional, essential nodulation genes. An open reading frame located in the 800 bp large intergenic region between nodD1 and nodA did not appear to be essential for nodulation of soybean. Furthermore, a strain with a deletion of the nodI- and nodJ-like genes downstream of nodC had a Nod+ phenotype. A mutant with a 1.7 kb deletion immediately downstream of nodD1 considerably delayed the onset of nodulation. This region carried a second copy of nodD (nodD2). A nodD1-nodD2 double mutant had a similar phenotype to the nodD2 mutant. Using a 22-mer oligonucleotide probe partially identical to the nod box sequence, a total of six hybridizing regions were identified in B. japonicum genomic DNA and isolated from a cosmid library. Sequencing of the hybridizing regions revealed that at least three of them represented true nod box sequences whereas the others showed considerable deviations from the consensus sequence. One of the three nod box sequences was the one known to be associated with nodA, whereas the other two were located 60 to 70 kb away from nif cluster I. A deletion of one of these two sequences plus adjacent DNA material (mutant delta 308) led to a reduced nodulation on Vigna radiata but not on soybean. Thus, this region is probably involved in the determination of host specificity.

Base Sequence↗

Shelf life of weaning foods developed from locally available food stuffs.

Four weaning foods were formulated using locally available cereals and pulses such as wheat (Triticum aestivum), barley (Hordeum vulgare), green gram (Vigna radiata) and jaggery. Cereal, pulse and jaggery were used in the proportion of 70:30:25. Roasting and malting were two processing techniques used. The developed weaning foods were evaluated for their nutritional characteristics and shelf life. All the formulations had a nutrient composition within the range prescribed by the Indian Standard Institute (ISI) for processed weaning foods. Peroxide value and fat acidity of weaning foods increased with increase in storage period. Malting of weaning foods resulted in higher increase of peroxide value and fat acidity as compared to roasted ones during the period of storage. All the blends were found to be acceptable up to 60 days of storage. The results, indicated that weaning foods developed from locally available less inexpensive foods may be used as good supplements for infants.

Dietary Fats↗

Content of antinutrients and in vitro protein digestibility of the African yambean, pigeon and cowpea.

The protein, trypsin inhibitor (TI), tannin, phytate, phytic acid phosphorus and in vitro protein digestibility (IVPD) of cultivars of the African yambean (Sphenostylis stenocarpa) - AYB, pigeon pea (Cajanus cajan) - PP and cowpea (Vigna unguiculata) - CP were determined. The protein content of CP (24-28.0%) was higher than those of PP (21-22.5%) and AYB (21-22.5%). The cream and speckled AYB contained more TI (30.9 and 25.3 mg/g) than PP (7.5-14.1 mg/g) and CP (9.8-20.5 mg/g). Apart from the white CP cultivar, they contained more tannin (1.24-1.42 mg/g) than PP (0.14-0.97 mg/g) and AYB (0.71-1.17 mg/g). Phytate was lowest in the AYB (6.30-7.49 mg/g) than PP (8.31-11.31 mg/g) and CP (8.40-9.92 mg/g). Phytic acid contributed 67-74% of the phosphorous in the AYB, 66-75% in PP and 54-59% in CP. The IVPD of the AYB (73.3 + or - 0.7%) was significantly lower (p <0.05) than those of PP (76.34 + or - 0.2%) and CP (77.8 + or - 0.4%). There was a significant negative correlation between TI and IVPD (r = -0.63, p<0.05). There was no significant correlation between IVPD and phytate and tannin contents. There was a positive correlation between protein content and IVPD (r = 0.69**) for the legumes under study. These legumes may pose no serious problems to populations consuming them especially when heat treatment is applied before consumption.

Africa↗

Nutritive value of the foods cultivated and consumed by the tribals of south India.

Twenty five foods cultivated and consumed by the tribals of Andhra Pradesh, India, comprising cereals/millets, legumes, tubers and miscellaneous foods collected seasonally from 20 tribal villages were analysed for proximate composition, vitamins and minerals. The major findings of the study were as follows: Protein content of cereals/millets ranged from 6.8 to 11.8 g per 100 g and that of legumes from 20 to 23.8 g per 100 g. The uncommon legume, judumulu (Vigna sp.) grown by the tribals had the protein content of 22 g per 100 g. A wild legume, Mucuna pruriens, had the highest protein content of 27.9 g per 100 g. Mineral contents of the foods showed greater variations. Two varieties of ragi and horsegram grown in the area had an iron contents of 38 mgs per 100 g. Among the wild tubers analysed, Diascorea hispida and D. bulbifera had about 134 Kcal per 100 g. In vitro starch digestibility (IVSD) analysed in the raw tubers ranged from 8.7 to 11.5 percent and caryota palm pith had IVSD 5.9 percent. Among the miscellaneous foods analysed, rajkeera seed (Amaranthus paniculatus) had protein content of 22 g per 100 g. Amylase inhibitor units of the wild tubers varied from 80 to 400 A/U and that of caryota palm pith was 712 A/U.

Calcium↗

In vitro starch and protein digestibility and iron availability in weaning foods as affected by processing methods.

In the present investigation, four weaning foods were formulated using locally available cereals and pulses such as wheat (Triticum aestivum), barley (Hordeum vulgare) and green gram (Vigna radiata). Cereal, pulse and jaggery were used in the proportion of 70:30:25. Domestic processing technique like roasting and malting were used to process cereals and pulses for development of weaning foods. All the four blends had a nutrient composition within the range prescribed by the Indian Standard Institute (ISI) for processed weaning foods. The processing of grains resulted in 16-20% increase in starch digestibility and 17-32% increase in protein digestibility. Also 16-32% increase in iron availability was observed on processing. The effect was more remarkable in malted weaning foods as compared to roasted ones.

Biological Availability↗

The nutritive value of some selected Tanzanian plant food sources.

The chemical composition of different varieties of field beans (Vicia faba L.), cowpeas (Vigna unguiculata), groundnuts (Voandzeia subterranea), and sorghum (Sorghum vulgare) were determined. Nutrients analysed in these materials included amino acids, starch, sugar, fibre, minerals and antinutritional factors. All the materials were further tested in balance trials with rats; true protein digestibility (TD), biological value (BV), net protein utilization (NPU) and digestible energy (DE) were evaluated. Based on the chemical analyses as well as on the biological data, the nutritive value of plant materials between species as well as between varieties within species differed considerably. Therefore, more quality evaluation studies along with plant breeding programmes are needed to select the most promising varieties from the nutritional point of view.

Amino Acids↗

Protein quality of weaning foods based on locally available cereal and pulse combination.

Locally available cereals and pulses such as rice (Oryza sativa), kangini (Setaria italica), sanwak (Echinochloa frumentacea), green gram (Vigna radiata) and jaggery were used to formulate three weaning foods. Cereal, pulse and jaggery were mixed in the ratio of 70:30:25. Roasting was the main processing technique used in the formulation of these weaning foods. The developed weaning foods had 5.06 to 5.68 g moisture, 10.28 to 13.71 g protein, 2.91 to 3.77 g ash, 1.08 to 1.87 g fat, 14.42 to 14.98 mg iron, 1.03 to 1.27 g crude fibre, and 357 to 374 Kcal. The weaning foods had a nutrient composition within the range prescribed by the Indian Standard Institute for processed weaning foods. The study indicated that the weaning foods obtained from locally available food stuffs have the potential of being produced locally, adaptable for household consumption and can be good substitute for commercial formulae.

Analysis of Variance↗

Improvement in HC1-extractability of minerals in home made weaning foods.

Three weaning foods were formulated from locally available cereals and pulses such as rice (Oryza sativa), kangini (Setaria italica), sanwak (Echinochloa frumentacea), green gram (Vigna radiata) and jaggery. Cereals and pulses were mixed in the proportion of 7:3. Nutrient composition of developed weaning foods was within range prescribed by Indian Standard Institute and was found to be acceptable. Roasting was the processing technique employed in developing weaning foods which resulted in significant increase in HC1-extractable minerals, an index of their bioavailability to humans. The higher HC1-extractability of the minerals may be ascribed to the decreased phytic acid in the processed home made weaning foods.

Biological Availability↗

Protein digestibility (in vitro) of chickpea and blackgram seeds as affected by domestic processing and cooking.

Protein digestibility (in vitro) of grains of chickpea (Cicer arietinum) and blackgram (Vigna mungo) cultivars varied from 48 to 53% and 52 to 58%, respectively. Soaking, cooking (both of unsoaked and soaked seeds), autoclaving and sprouting improved significantly the protein digestibility of all the cultivars of chickpea and blackgram. Autoclaving was found to be most effective followed by cooking and sprouting; cooking of sprouts had only marginal effect. Protein digestibility was higher when soaked instead of unsoaked grains were cooked.

Cooking↗

Degradation of ribulose-bisphosphate carboxylase by vacuolar enzymes of senescing French bean leaves: immunocytochemical and ultrastructural observations.

The possible involvement of vacuolar cysteine proteinases in degradation of ribulose-bisphosphate carboxylase (Rubisco) in senescing French bean leaves was studied by ultrastructural and immunocytochemical analyses with antibodies raised against the large subunit (LSU) of Rubisco and SH-EP, a cysteine proteinase from Vigna mungo that is immunologically identical to one of the major proteinases of French bean plants. Primary leaves of 10-day-old plants were detached and placed at 25 degrees C in darkness for 0, 4, and 8 days to allow their senescence to proceed. The leaves at each senescence stage were subjected to the conventional electron microscopic and immunocytochemical studies. The results indicated that the chloroplasts of senescing French bean leaves were separated from the cytoplasm of the cell periphery and taken into the central vacuole and that the Rubisco LSU in the chloroplasts was degraded by vacuolar enzymes such as an SH-EP-related cysteine proteinase that developed in senescing leaves. The present results together with the results of previous biochemical studies using vacuolar lysates support the view that Rubisco is degraded through the association of chloroplasts with the central vacuole during the senescence of leaves that were detached and placed in darkness.

Aging↗

Inhibition of inward rectifying tonoplast channels by a vacuolar factor: physiological and kinetic implications.

Regulation of ion-channel activity must take place in order to regulate ion transport. In case of tonoplast ion channels, this is possible on both the cytoplasmic and the vacuolar side. Isolated vacuoles of young Vigna unguiculata seedlings show no or hardly any channel activity at tonoplast potentials greater than 80 mV, in the vacuole-attached configuration. When the configuration is changed to an excised patch or whole vacuole, a fast (excised patch) or slow (whole vacuole) increase of inward rectifying channel activity is seen. This increase is accompanied by a shift in the voltage-dependent gating to less hyperpolarized potentials. In the whole vacuole configuration the level of inward current increases and also the activation kinetics changes. Induction of channel activity takes up to 20 min depending on the age of the plants used and the diameter of the vacuole. On the basis of the estimated diffusion velocities, it is hypothesized that a compound with a mol wt of 20,000 to 200,000 is present in vacuoles of young seedlings, which shifts the population of channels to a less voltage-sensitive state.

Ion Channel Gating↗

Effects of storage and processing on the nutritive value of certain Nigerian foods.

The effects of storage and processing on the nutritive value of two Nigerian foods--raw cowpea (Vigna unguiculata) flour and palm oil, have been investigated. Increased retention of both thiamine and riboflavin as a result of increased water activity (Aw) were recorded for cowpea flour stored for 6 months. A storage temperature of 5 degrees C led to minimal losses of both vitamins in the stored flour. Differences in physico-chemical characteristics were observed between palm oil produced by the traditional method and that produced by a modern commercial method. Increasing Aw led to decreasing loss of unsaturation in the traditionally-produced palm oil during 4-week storage at ambient temperature (25 degrees C).

Fatty Acids↗

Oligosaccharides in several Philippine indigenous food legumes: determination, localization and removal.

The oligosaccharide profile of raw mature seeds of seven different legumes indigenous to the Philippines was measured in 70% ethanol extracts of the seeds by thin layer chromatography using HPTLC plates and quantified by a densitometer. Based on the results, the legumes could be ranked according to decreasing oligosaccharide content or flatulence potential as follows: Sam-samping (Clitoria ternatea) greater than hyacinth bean (Dolichos lablab) greater than sabawel (Mucuna pruriens) greater than lima bean (Phaseolus lunatus) greater than swordbean (Canavalia gladiata) greater than rice bean (Vigna umbellata) greater than jack bean (Canavalia ensiformis). Sam-samping had 4.79% total oligosaccharides and hyacinth bean or batao, 3.66%. A jack bean accession had 1.79% oligosaccharides. Simple processing methods were tested to detoxify the oligosaccharides. Soaking the batao seeds had no effect while boiling even resulted in a net 23-31% increase in the levels of raffinose, stachyose and verbascose. On the other hand, two min of dry roasting resulted in complete removal of oligosaccharides whereas germination resulted in about 30-40% decrease after 1 and 2 days, respectively.

Chromatography, Thin Layer↗