Champa Sengupta-Gopalan - Academia.edu (original) (raw)

Papers by Champa Sengupta-Gopalan

Current plant science and biotechnology in agriculture, 1991

The root nodule is a specialized plant organ in which the resident bacteria belonging to the genu... more The root nodule is a specialized plant organ in which the resident bacteria belonging to the genus Rhizobium/Bradyrhizobium, fix N2 while the plant provides the ideal environment for the bacteria to fix N2. The fixed N2 is assimilated by host encoded enzymes. Several unique host genes are specifically expressed in the nodule and these gene products, nodulins, probably have specific functions in the nodule. To date, all studies appear to show that nodulin gene expression is regulated primarily at the transcriptional level and induction of transcription precedes the onset of nitrogenase activity. In this chapter, we will focus on the regulatory role of specific AT rich DNA elements, distributed in the 5’ and 3’ flanking regions of a representative soybean nodulin gene. This chapter will also focus on the regulation of glutamine synthetase (GS) genes and demonstrate that regulation of nodulin gene expression can be controlled at a step other than transcription. Nodule-specific GS genes, like other nodulin genes appears to be developmentally regulated independent of N2-fixation (5), while the activation of nodule-specific GS enzyme appears to require the products of active N2-fixation.

CAB International eBooks, 2015

Nitrogen is the most essential plant macronutrient and the major limiting factor for plant growth... more Nitrogen is the most essential plant macronutrient and the major limiting factor for plant growth and productivity. It is assimilated into glutamine by the activity of the enzyme glutamine synthetase (GS), and the activity of this enzyme plays a central role in the assimilation and re-assimilation of ammonia in higher plants. GS catalyses the ATP-dependent condensation of ammonia with glutamate to yield glutamine. There are two major isoforms of (GS in plants, GS1, which is cytosolic, and GS2, which is located in the chloroplast), and these two isoforms play non-redundant, non-overlapping metabolic roles. GS2 is the main isoform that is responsible for the assimilation of ammonia produced by nitrate reduction and photorespiration, but its function in non-photosynthetic tissues is not known. GS1 assimilates ammonia produced by all other physiological processes. While the norm is for there being one GS2 gene member, GS1 in all plants is encoded by small gene families, with each member of the family performing different functions. With the goal of improving plant performance, several attempts have been made to modulate the levels of GS enzyme in different plants using genetic engineering tools. However, outcomes have been rather inconsistent. The inconsistency points to the complexity of the regulatory mechanisms underlying the GS genes, specifically GS1. The indispensability of GS, and its role in maintaining homeostasis between the prevention of ammonia build-up and depletion of carbon skeletons, requires that it be regulated very precisely. In plants, GS is regulated at multiple steps, which include transcription, through the stability of mRNA, translation rates and post-translational modification. The stability of the transcript is regulated via the 3′UTR (untranslated sequence) and is in response to plant nitrogen status, while translation can be regulated via the TOR (target of rapamycin) signalling pathway. The highest level of regulation appears to be at the post-translational level, and involves oxidative modification, phosphorylation, tyrosine (Tyr) nitration, ubiquitination and association with other phosphoproteins. The available data further suggest that GS genes in plants may be regulated at different steps in the flow of gene expression, and by C and N metabolites or the C/N ratio.

Plant Physiology, Dec 1, 1996

Gln synthetase (GS) catalyzes the ATP-dependent condensation of ammonia with glutamate to yield G... more Gln synthetase (GS) catalyzes the ATP-dependent condensation of ammonia with glutamate to yield Gln. In higher plants GS is an octameric enzyme and the subunits are encoded by members of a small multigene family. In soybeans (Glycine max), following the onset of N2 fixation there is a dramatic increase in GS activity in the root nodules. GS activity staining of native polyacrylamide gels containing nodule and root extracts showed a common band of activity (GSrs). The nodules also contained a slower-migrating, broad band of enzyme activity (GSns). The GSns activity band is a complex of many isozymes made up of different proportions of two kinds of GS subunits: GSr and GSn. Root nodules formed following inoculation with an Nif- strain of Bradyrhizobium japonicum showed the presence of GS isoenzymes (GSns1) with low enzyme activity, which migrated more slowly than GSns. Gsns1 is most likely made up predominantly of GSn subunits. Our data suggest that, whereas the class I GS genes encoding the GSr subunits are regulated by the availability of NH3, the class II GS genes coding for the GSn subunits are developmentally regulated. Furthermore, we have demonstrated that the GSns1 isozymes in the Nif- nodules are relatively more labile. Our overall conclusion is that GSns activity in soybean nodules is regulated by N2 fixation both at the level of transcription and at the level of holoprotein stability.

The Plant Cell, Sep 1, 1997

Zeins, the major seed storage proteins of maize, are of four distinct types: (Y, p, S, and y. The... more Zeins, the major seed storage proteins of maize, are of four distinct types: (Y, p, S, and y. They are synthesized on the rough endoplasmic reticulum (ER) in a sequential manner and deposited in ER-derived protein bodies. We investigated the potential for producing sulfur-rich p-zein and 6-zein proteins in leaf and seed tissues by expressing the corresponding genes in a constitutive manner in transgenic tobacco. The 6-zein and @-zein, when synthesized individually, were stable in the vegetative tissues and were deposited in unique, zein-specific ER-derived protein bodies. Coexpression of 6-zein and p-zein genes, however, showed that 6-zein was colocalized in p-zein-containing protein bodies and that the leve1 of 6-zein was fivefold higher in 6-/@-zein plants than in S-zein plants. We conclude that 6-zein interacts with p-rein and that the interaction has a stabilizing effect on 6-zein.

Plant Physiology, 1995

Zeins, the seed storage proteins of maize, are a group of alcohol-soluble polypeptides of differe... more Zeins, the seed storage proteins of maize, are a group of alcohol-soluble polypeptides of different molecular masses that share a similar amino acid composition but vary in their sulfur amino acid composition. They are synthesized on the rough endoplasmic reticulum (ER) in the endosperm and are stored in ER-derived protein bodies. Our goal is to balance the amino acid composition of the methionine-deficient forage legumes by expressing the sulfur amino acid-rich 15-kD zeins in their leaves. However, it is crucial to know whether this protein would be stable in nonseed tissues of transgenic plants. The major focus of this paper is to compare the accumulation pattern of the 15-kD zein protein with a vacuolar targeted seed protein, [beta]-phaseolin, in nonseed tissues and to determine the basis for its stability/instability. We have introduced the 15-kD zein and bean [beta]-phaseolin-coding sequences behind the 35S cauliflower mosaic virus promoter into tobacco (Nicotiana tabacum) and analyzed the protein's accumulation pattern in different tissues. Our results demonstrate that the 15-kD seed protein is stable not only in seeds but in all nonseed tissues tested, whereas the [beta]-phaseolin protein accumulated only in mid- and postmaturation seeds. Interestingly, zein accumulates in novel protein bodies both in the seeds and in nonseed tissues. We attribute the instability of the [beta]-phaseolin protein in nonseed tissues to the fact that it is targeted to protease-rich vacuoles. The stability of the 15-kD zein could be attributed to its retention in the ER or to the protease-resistant nature of the protein.

Planta, Jun 10, 2004

Higher plants assimilate nitrogen in the form of ammonia through the concerted activity of glutam... more Higher plants assimilate nitrogen in the form of ammonia through the concerted activity of glutamine synthetase (GS) and glutamate synthase (GOGAT). The GS enzyme is either located in the cytoplasm (GS 1) or in the chloroplast (GS 2). To understand how modulation of GS activity affects plant performance, Lotus japonicus L. plants were transformed with an alfalfa GS 1 gene driven by the CaMV 35S promoter. The transformants showed increased GS activity and an increase in GS 1 polypeptide level in all the organs tested. GS was analyzed by non-denaturing gel electrophoresis and ion-exchange chromatography. The results showed the presence of multiple GS isoenzymes in the different organs and the presence of a novel isoform in the transgenic plants. The distribution of GS in the different organs was analyzed by immunohistochemical localization. GS was localized in the mesophyll cells of the leaves and in the vasculature of the stem and roots of the transformants. Our results consistently showed higher soluble protein concentration, higher chlorophyll content and a higher biomass accumulation in the transgenic plants. The total amino acid content in the leaves and stems of the transgenic plants was 22-24% more than in the tissues of the non-transformed plants. The relative abundance of individual amino acid was similar except for aspartate/asparagine and proline, which were higher in the transformants.

Planta, Nov 8, 2009

Sucrose phosphate synthase (SPS) catalyzes the first step in the synthesis of sucrose in photosyn... more Sucrose phosphate synthase (SPS) catalyzes the first step in the synthesis of sucrose in photosynthetic tissues. We characterized the expression of three different isoforms of SPS belonging to two different SPS gene families in alfalfa (Medicago sativa L.), a previously identified SPS (MsSPSA) and two novel isoforms belonging to class B (MsSPSB and MsSPSB3).

Current Plant Science and Biotechnology in Agriculture, 1995

Glutamine synthetase (GS) is the key enzyme responsible for the assimilation and reassimilation o... more Glutamine synthetase (GS) is the key enzyme responsible for the assimilation and reassimilation of ammonia. GS catalyzes the ATP dependent condensation of NH3 with glutamate to produce glutamine. Subsequently, glutamate synthase transfers an amido group of glutamine to ∝-ketoglutarate to produce two molecules of glutamate (Lea et al., 1990). Glutamine is one of the major nitrogen transport compounds in plants and acts as the nitrogen donor for the synthesis of most nitrogenous compounds. GS in plants, is made up of eight subunits, each subunit having a molecular weight of between 38-45kD. The GS isoenzyme localized in the plastid/chloroplast (GS2) functions in the reassimilation of NH3 produced by photorespiration, while the cytosolic isoforms of GS (GS,), depending on the organ/tissue where it is located, assimilates ammonia produced by different physiological processes (McGrath, Corruzzi, 1991). The GS1 in roots, stems and leaves is localized around the vasculature and it is believed to function in generating glutamine for nitrogen transport (Brears et al., 1991). The GS1 in the root vasculature is believed to be involved in the assimilation of ammonia produced by the reduction of nitrate obtained from the soil water. In root nodules, GS1 is localized mostly in the infected cells where it assimilates ammonia produced by the N2-fixing bacteroids.

Journal of nematology, 1996

The early events of Meloidogyne incognita behavior and associated host responses following root p... more The early events of Meloidogyne incognita behavior and associated host responses following root penetration were studied in resistant (cv. Moapa 69) and susceptible (cv. Lahontan) alfalfa. Ten-day-old seedlings of alfalfa cultivars were inoculated with second-stage juveniles (J2) and harvested 12, 24, 48, and 72 hours and 7, 14, and 21 days later. Both cultivars supported similar root penetration and initial J2 migration. By 72 hours after inoculation the majority of J2 were amassed inside the vascular cylinder in roots of susceptible Lahontan, while J2 had not entered the vascular cylinder of resistant Moapa 69 and remained clumped at the root apex. Nematode development progressed normally in Lahontan, but J2 were not observed in Moapa 69 after day 7. The greatest differences between RNA translation products isolated from inoculated and uninoculated roots of Lahanton occurred 72 hours after inoculation. Only minor differences in gene expression were observed between inoculated and ...

We report on the effects of administering a unique glutamine synthetase inhibitor to cereals and ... more We report on the effects of administering a unique glutamine synthetase inhibitor to cereals and N/sub 2/-fixing legumes. A bacterium (Pseudomonas syringae pv. tabaci) delivers this inhibitor to provide extended treatment periods; we inoculated the root systems of oat and legume plants with pv. tabaci to provide for delivery of this inhibitor to their root or root/nodule systems. Inoculation of legumes is accompanied by increased plant growth, total plant nitrogen, nodulation, and nitrogen fixation activity. Inoculation of the oats is accompanied by either of two results depending upon the genotype of the oat plant. One result is inhibition of plant growth followed by plant death as consequences of the loss of all of the glutamine synthetase activities in the plant and the subsequent accumulation of ammonia and cessation of nitrate uptake. The second and opposite result is observed in a small population of oats screened from a commercial cultivar and includes increased plant growth ...

Oats (Avena sativa L. Jodi) tolerant of rhizosphere infestation by Pseudomonas syningae pv. tabac... more Oats (Avena sativa L. Jodi) tolerant of rhizosphere infestation by Pseudomonas syningae pv. tabaci when challenged by the pathogen experience tissue-specific alterations of ammonia assimilatory capabilities. Altered ammonia assimilatory potentials between root and leaf tissue result from selective inactivation of glutamine synthetase (GS) by the toxin Tabtoxinine-B-lactam (TBL). TRL inactivation. decreases but leaf GS specific activity increase. Higher leaf GS activity is due to decreased rates of degradation rather than increased GS synthesis. Higher leaf GS activity and elevated levels of GS polypeptide appear to result from a limited interaction between GS and TBL leading to the accumulation of a less active but more stable GS holoenzyme. experience enhanced growth. activity and whole plant fresh weight, suggesting that tissue-specific changes in ammonia assimilatory capability provides the plant a more efficient mechanism for uptake and utilization of nitrogen. Root GS is sensitive and leaf GSs are resistant to With prolonged challenge by the pathogen root GS activity Tolerant challenged oats besides surviving rhizosphere infestation, A strong correlation exists between leaf GS DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Planta, 2019

Main conclusion In alfalfa, the B form of Sucrose phosphate synthase synthesizes sucrose in the l... more Main conclusion In alfalfa, the B form of Sucrose phosphate synthase synthesizes sucrose in the leaves while the A form participates in regulatory cycles of synthesis/breakdown of sucrose/starch in the root nodules.

Leguminous forage crops are high in proteins but deficient in S- amino acids. It has been shown t... more Leguminous forage crops are high in proteins but deficient in S- amino acids. It has been shown that both wool quality and milk production can be limited by the post-ruminal supply of sulfur-containing amino acids. Efforts to use conventional plant breeding and cell selection techniques to increase the S-amino acid content of alfalfa have met with little success. With the objective to increase the S-amino acid content of forage legumes, the goal of this project was to co- express the methionine rich zein genes from corn along with a gene for a key enzyme in methionine biosynthesis, aspartate kinase(AK). The zeins are seed storage proteins from corn and are groupec into four distinct classes based on their amino acid sequence homologies. The b-zein (15kd) and the 6zein (10kD and 18kD) have proportionately high levels of methionine (10%, 22% and 28%, respectively). Initial studies from our lab had shown that while the 15kD zein accumulated to high levels in vegetative tissues of trans...

Molecular Plant-Microbe Interactions, 1989

... Characterization of Root Exudates and Extracts from Nonnodulating and Supernodulating Soybean... more ... Characterization of Root Exudates and Extracts from Nonnodulating and Supernodulating Soybean Mutants Anne Mathews,1 Renee M. Kosslak,3 ... fractionated by sodium dodecyl sulfate (SDS)-PAGE (Laemmli 1970) or two-dimensional gel electrophoresis (O&#x27;Farrell 1975) and ...

Plant Molecular Biology, 1992

... 607 Niels N. Sandal, 1 Kirsten Bojsen, 1'3 Hannes Richter, 2 Champa Sengupta-Gopalan... more ... 607 Niels N. Sandal, 1 Kirsten Bojsen, 1'3 Hannes Richter, 2 Champa Sengupta-Gopalan 2 and Kjeld A. Marcker 1 1 Laboratory of Gene Expression, Dept. ... 8. Rohde W, Rosch K, KrOger K, Salamini F: Nucleotide sequence of a Hordeum vulgare gene encoding a glycine-...

... limitation (Benjamin et al., 1989). Considerable evidence is accumulating suggesting the invo... more ... limitation (Benjamin et al., 1989). Considerable evidence is accumulating suggesting the involvement of metabolites in the expression of GS genes in plants (Kozaki et al., 1991; Miao et al., 1991; Sukanya et al., 1994). With the aim of ...

La presente invention concerne des materiaux et des procedes pour des plantes transformees et pou... more La presente invention concerne des materiaux et des procedes pour des plantes transformees et pour des tissus de plantes qui permettent d'exprimer de fortes teneurs en proteines stables qui sont localisees sous forme de corps proteiques dans la cellule de la plante. L'invention concerne des plantes transformees co-exprimant des fortes concentrations de proteines de zeine 15kD et 10 kD qui s'accumulent sous forme de taux eleves de corps proteiques dans le tissu vegetatif de la plante. Les plantes transformees co-exprimant les proteines de zeine 15kD et 10kD permettent de constituer des cultures fourrageres contenant des taux accrus d'acides amines a base de soufre, comme la methionine, dans l'alimentation des animaux nourris par ces cultures. L'invention concerne egalement des plantes ou des tissus de plantes transformes comprenant des corps proteiques stables qui renferment un materiau proteinique heterologue. Selon un mode de realisation, un corps proteique ...

PLOS ONE

Phytophthora capsici is a soil borne pathogen, and is among the most destructive pathogens for Ca... more Phytophthora capsici is a soil borne pathogen, and is among the most destructive pathogens for Capsicum annuum (chile). P. capsici is known to cause diseases on all parts of the chile plants. Therefore, it requires independent resistance genes to control disease symptoms that are induced by each of the P. capsici strains. This requirement of multiple resistance genes to confer resistance to P. capsici, in chile makes breeding for resistance a daunting pursuit. Against this backdrop, a genetic engineering approach would be to introduce a broad host resistance gene into chile in order to protect it from different races of P. capsici. Notably, a broad host resistance gene RB from Solanum bulbocastanum has been shown to confer resistance to P. infestans in both S. tuberosum and S. lycopersicum. We agroinfiltrated the RB gene into the leaves of susceptible chile plants, demonstrating that the gene is also capable of lending resistance to P. capsici in chile. We introduced the RB gene into chile by developing an Agrobacterium tumefaciens mediated transformation system. The integration of the RB gene into the genome of the primary transformants and its subsequent transfer to the F1 generation was confirmed by genomic PCR using primers specific for the RB gene. A 3:1 ratio for the presence and absence of the RB gene was observed in the F1 progeny. In addition to showing resistance to P. capsici in a leaf inoculation experiment, about 30% of the F1 progeny also exhibited resistance to root inoculation. Our data, when taken together, suggests that the RB gene from S. bulbocastanum confers resistance against P. capsici in C. annuum, thereby demonstrating that the RB gene has an even broader host range than reported in the literature-both in terms of the host and the pathogen.