bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon metabolism in leaves of transgenic tobacco (Nicotiana tabacum L.) containing elevated fructose 2,6‐bisphosphate levels
Authors: Scott Peter , Lange Alex J. , Pilkis Simon J. , Kruger Nicholas J. 
Published: March 2003

SummaryThe aim of this work was to investigate the role of fructose 2,6‐bisphosphate (Fru 2,6‐P2) during photosynthesis. The level of Fru 2,6‐P2 in tobacco plants was elevated by the introduction of a modified mammalian gene encoding 6‐phosphofructo‐2‐kinase (6‐PF‐2‐K). Estimates of the metabolite control coefficient (C) for Fru 2,6‐P2 levels in response to increased 6‐PF‐2‐K activity, suggest that small increases in 6‐PF‐2‐K activity have little effect upon steady‐state Fru 2,6‐P2 levels (C = +0.08 for a 0–58% increase in 6‐PF‐2‐K activity). However, larger changes resulted in dramatic rises in Fru 2,6‐P2 levels (C = +3.35 for 206–268% increase in 6‐PF‐2‐K activity). Transgenic plants contained Fru 2,6‐P2 levels in the dark that ranged from 104 to 230% of the level in wild‐type tobacco. Plants with altered levels of Fru 2,6‐P2 were used to determine the effects of this signal metabolite upon carbohydrate metabolism during the initial phase of the light period. Here we provide direct evidence that Fru 2,6‐P2 contributes to the regulation of carbon partitioning in tobacco leaves by inhibiting sucrose synthesis.
Purification and cDNA cloning of anthranilate synthase from Ruta graveolens: modes of expression and properties of native and recombinant enzymes
Authors: Bohlmann Jörg , DeLuca Vincenzo , Eilert Udo , Martin William 
Published: March 2003

Summary Ruta graveolens utilizes anthranilate synthase (AS) for the synthesis both of tryptophan in primary metabolism and acridone alkaloids in secondary metabolism. AS has been purified from plants and cell cultures of R. graveolens 670‐ and 1700‐fold, respectively. Glutamine‐ and ammonia‐ dependent AS activities were strictly co‐purified in all steps. Through cDNA cloning and complementation of Escherichia coli deletion mutants defective for AS, it is shown that young Ruta plants express two genes for functional ASα subunits, ASα1 and ASα2. The data indicate that ASα from Ruta requires an ASβ subunit with a native molecular weight of 60–65 kDa for the glutamine‐dependent reaction. Protein synthesized invitro from cloned cDNA is processed upon import into isolated chloroplasts, indicating that mature ASα subunits are active in plastids in vivo. ASα1 and ASα2 are constitutively expressed in Ruta cell cultures, but ASα1 steady‐state mRNA levels are increased 100‐fold 6 h subsequent to elicitation whereas ASα2 expression remains constitutive. Increased ASα1 transcription corresponds to elicitor‐induced alkaloid accumulation. The data indicate that Ruta regulates anthranilate flux into primary and secondary metabolism through differential regulation of AS genes specific to these pathways.
A promoter for strong and ubiquitous anaerobic gene expression in tobacco
Authors: Köhler Uwe , Mendel Ralf R. , Cerff Rüdiger , Hehl Reinhard 
Published: March 2003

SummaryThe maize GapC4 promoter confers strong and ubiquitous anaerobic expression of the β‐glucuronidase reporter gene in transgenic tobacco. Among 21 transgenic tobacco lines harboring 785 or 461 bp from the GapC4 promoter, 18 show anaerobic gene expression. In six lines anaerobic fluorescence values were more than 1000‐fold over non‐specific background and in five lines anaerobic gene expression exceeded aerobic expression of a reporter gene construct under the control of the strong cauliflower mosaic virus 35S promoter. Aerobic gene expression was detected in only three lines. Anaerobic induction is observed in all tissues including mature leaves and flowers and is transcriptionally induced within at least 12 h. Within 3 h of transfer of tobacco seedlings from anaerobic to aerobic conditions reporter gene transcription is turned off. Among other environmental factors only wounding and UV light result in a 10‐ to 40‐fold induction of reporter gene expression above background. The strong inducibility, mode of expression under non‐inducing conditions, the specificity, and the ubiquitous induction distinguishes the GapC4 promoter from all previously analyzed anaerobic promoter‐reporter gene constructs.
Identification of a salicylic acid‐responsive element in the promoter of the tobacco pathogenesis‐related β‐1,3‐glucanase gene, PR‐2d
Authors: Shah Jyoti , Klessig Daniel F. 
Published: March 2003

SummaryThe tobacco pathogenesis‐related PR‐2d gene encodes an acidic β‐1,3‐glucanase. Expression of the PR‐2d:uidA(GUS) chimeric gene is induced in leaves undergoing the hyper‐sensitive resistance response to tobacco mosaic virus and after treatment with salicylic acid (SA), a chemical believed to play an important role(s) in disease resistance. We have constructed transgenic tobacco plants which carry various segments of the PR‐2d promoter fused to a heterologous core 35S promoter driving the uidA(GUS) reporter gene. Their analysis indicates that sequences from −364 to −288 upstream of the PR‐2d transcription start site confer a high level of activation by SA (20‐fold). Mutations within this sequence, located between −339 and −333, depressed SA activation. This region is also required for the SA‐inducibility of a truncated PR‐2d:GUS chimeric gene. Contained within this region is a 25 bp element located between −348 and −324 which was specifically recognized by nuclear factors from tobacco leaves. No conclusive differences were observed in the ability of proteins in nuclear extracts from water‐treated versus SA‐treated plants to bind to this cis element in vitro.
Influence of auxin on the establishment of bilateral symmetry in monocots
Authors: Fischer Christiane , Neuhaus Gunther 
Published: March 2003

SummaryTo study the influence of auxin on the shift from radial to bilateral symmetry during monocot embryogenesis, the fate of young wheat (Triticum aestivum L.) zygotic embryos has been manipulated in vitro by adding auxins, an auxin transport inhibitor and an auxin antagonist to the culture medium. The two synthetic auxins used, 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T), induced identical phenotypes. In the most severe cases, the shift from radial to bilateral symmetry was blocked resulting in continuous uniform radial growth. The natural auxin indole‐3‐acetic acid (IAA) induced the same phenotype. The effect of 2,4,5‐T and 2,4D depended on their concentrations and on the developmental stage of the isolated embryos. In the presence of 2,3,5‐triiodobenzoic acid (TIBA), an auxin transport inhibitor, the overall embryo symmetry was abnormal. The relative position of the shoot apical meristem in comparison with the scutellum was anomalous. The quality of shoot apical meristem and the scutellum differentiation was altered compared with normal developed embryos. No root meristem was differentiated. The effect of TIBA depends on its concentration and on the developmental stage of the isolated embryos. By contrast, 2‐(pchlorophenoxy)‐2‐methylpropionic acid (PCIB) which is described as an auxin antagonist, has no visible direct effect on the embryonic symmetry. These observations indicate that auxin influences the change from radial symmetry to embryonic polarity during monocot embryogenesis. A model of auxin action during early wheat embryo development is proposed.
A carbonic anhydrase gene is induced in the nodule primordium and its cell‐specific expression is controlled by the presence of Rhizobium during development
Authors: De La Peña Teodoro Coba , Frugier Florian , McKhann Heather I. , Bauer Petra , Brown Spencer , Kondorosi Adam , Crespi Martin 
Published: March 2003

SummaryUnder nitrogen starvation, Rhizobium meliloti is able to induce nitrogen‐fixing nodules on alfalfa roots. Certain alfalfa cultivars spontaneously develop pseudonodules in the absence of bacteria. A transcript, Msca1, expressed in spontaneous and R. meliloti‐induced nodules, that codes for a carbonic anhydrase (CA), an enzyme catalyzing the hydration of CO2 has been identified. This is the first CA gene cloned from a non‐photosynthetic tissue in plants. Msca1 was activated initially in all cells of the bacterium‐induced nodule primordium and was also induced by cytokinin treatment of alfalfa roots. The presence of CA enzymatic activity in different nodule types was demonstrated. Thus, Msca1 is a new early nodulin gene with a function possibly related to the increased amyloplast deposition of the dividing cortical cells. Msca1 transcripts were subsequently found mainly in a peripheral envelope of cells in developing and mature nodules. This novel pattern of gene expression is controlled by the presence of the bacterium inside the nodule. Sucrose synthase and phosphoenol pyruvate carboxylase (PEPC), other genes of the carbon fixation metabolism, were expressed in the same peripheral cells and even more strongly in the nitrogen‐fixing region. Analysis of expression patterns of these genes indicated that early CA function may not be related to carbon fixation through PEPC. CA might be acting in pH regulation and/or CO2/HCO3− transport during nodule initiation. Thus, carbonic anhydrase may play different roles at several stages of nodule development and function.
Expression of a soybean nodule‐enhanced phosphoenolpyruvate carboxylase gene that shows striking similarity to another gene for a house‐keeping isoform
Authors: Hata Shingo , Izui Katsura , Kouchi Hiroshi 
Published: March 2003

SummaryThree different cDNAs for phosphoenolpyruvate carboxylase (PEPC) were isolated from soybean root nodules. The full‐length cDNA of the most abundant isoform (GmPEPC7) was very similar to another one (GmPEPC15), the nucleotide sequence of which is identical to that of a reported clone (gmppc1) (Vazquez‐Tello, A., Whittier, R.F., Kawasaki, T., Sugimoto, T., Kawamura, Y., Shibata, D. (1993) Plant Physiol. 103, 1025–1026). In the coding region, the newly isolated GmPEPC7 and the previously reported were gmppc1 99% and 98% identical at the amino acid and nucleotide levels, respectively. In contrast, they exhibited only 39% identity in the 3′ non‐coding region, indicating that they are encoded by distinct genes. Northern blot analysis with 3′ non‐coding regions as isoform‐specific probes showed that GmPEPC7 is nodule‐enhanced whereas GmPEPC15 (gmppc1) is expressed in most soybean tissues. The third clone (GmPEPC4) was much less homologous to the above two clones and thus was not further characterized. It was also shown by in situ hybridization that the nodule‐enhanced isoform is expressed in all cell types in nodules, including in Bradyrhizobium‐infected and uninfected cells and cortical cells. A relatively strong hybridization signal was detected in the vascular bundle pericycle. Southern blot analysis indicated that there are only two PEPC genes exhibiting a high degree of similarity in the soybean genome, one for the nodule‐enhanced GmPEPC7 and the other for the constitutively expressed gmppc1. A phylogenetic tree based on the amino acid sequences of soybean PEPCs and nodule‐enhanced PEPCs of alfalfa and pea suggested that the soybean nodule‐enhanced isoform evolved from the housekeeping PEPC gene after the ureid‐translocating and amide‐translocating legumes diverged from each other.
The maize Lc regulatory gene up‐regulates the flavonoid biosynthetic pathway of Petunia
Authors: Bradley J. Marie , Davies Kevin M. , Deroles Simon C. , Bloor Stephen J. , Lewis David H. 
Published: March 2003

SummaryPetunia (cv. Mitchell) transformants were produced which expressed the maize Leaf colour (Lc) cDNA under the control of the CaMV 35S promoter and had enhanced pigmentation in both vegetative and floral tissues. In flowering transgenic lines, intense pigmentation of leaves, stems and sepals occurred, along with lower levels of pigmentation in the flower tube and limb. No anthocyanins were detected in leaves, sepals and flower limb of wild‐type Mitchell petunia. Of the 12 phenylpropanoid genes examined, transcript levels for nine flavonoid‐specific biosynthetic genes were up‐regulated in the transgenic Lc lines, including weak activation of CHS, CHI and F3H along with stronger activation of DFR, F3′H, F3′5′H, ANS, UFGT and 3RT. PAL, C4H and FLS were unaffected by Lc. Lc‐induced pigmentation in Mitchell petunia appears to be specific to the sub‐epidermal layer in all tissues examined, including the flower limb. The results show that the monocot Lc regulatory gene from maize can up‐regulate the expression of both early and late flavonoid biosynthetic genes and enhance anthocyanin production in the dicot species Petunia.
Two isoforms of plant RAD23 complement a UV‐sensitive rad23 mutant in yeast
Authors: Sturm Arnd , Lienhard Susanne 
Published: March 2003

SummaryDNA repair by nucleotide excision (NER) has been demonstrated in plant cells at the biochemical level but until now none of the molecular components of the plant NER complex has been identified. In this paper, the cloning and characterization of two isoforms of RAD23 from carrot (Daucus carota L.) are reported. It has been suggested that RAD23 in yeast is an assembly factor of the NER complex required for transcription‐coupled repair as well as efficient overall genome repair. A functional assay demonstrated that both plant homologues complement the UV‐sensitive phenotype of a rad23 deletion mutant of yeast. This result suggests that homologous polypeptides may catalyse NER in plants and yeast and, possibly, by a similar mechanism.
5′‐ and 3′‐sequences of satellite tobacco necrosis virus RNA promoting translation in tobacco
Authors: Meulewaeter Frank , Danthinne Xavier , Va Marc , Montagu  , Cornelissen Marc 
Published: March 2003

SummaryThe RNA of satellite tobacco necrosis virus (STNV) is a monocistronic messenger that lacks both a 5′ cap and a 3′ poly(A) tail. The STNV trailer contains an autonomous translational enhancer domain (TED) that promotes translation in vitro by more than one order of magnitude when combined with the 5′‐terminal 173 nt of STNV RNA. We now show that the responsible sequence within the 5′ region maps to the first 38 nt of the STNV RNA. Mutational analysis indicated that the primary sequence of the STNV 5′ 38 nt and TED is important for translation stimulation in vitro, but did not reveal a role for the complementarity between the two. Translation of chimeric STNV‐cat RNAs in tobacco protoplasts showed that TED promotes translation in vivo of RNAs lacking a cap and/or a poly(A) tail. Similar to in vitro, TED‐dependent translation in tobacco was stimulated further by the STNV 5′ 38 nt.
More than 80R2R3‐MYB regulatory genes in the genome of Arabidopsis thaliana
Authors: Romero  , Fuertes  , Benito  , Malpica  , Leyva  , Paz‐Ares  
Published: March 2003

SummaryTranscription factors belonging to the R2R3‐MYB family contain the related helix‐turn‐helix repeats R2 and R3. The authors isolated partial cDNA and/or genomic clones of 78 R2R3‐MYB genes from Arabidopsis thaliana and found accessions corresponding to 31 Arabidopsis genes of this class in databanks, seven of which were not represented in the authors’ collection. Therefore, there are at least 85, and probably more than 100, R2R3‐MYB genes present in the Arabidopsis thaliana genome, representing the largest regulatory gene family currently known in plants. In contrast, no more than three R2R3‐MYB genes have been reported in any organism from other phyla. DNA‐binding studies showed that there are differences but also frequent overlaps in binding specificity among plant R2R3‐MYB proteins, in line with the distinct but often related functions that are beginning to be recognized for these proteins. This large‐sized gene family may contribute to the regulatory flexibility underlying the developmental and metabolic plasticity displayed by plants.
Genetic evidence for an essential role for potyvirus CI protein in cell‐to‐cell movement
Authors: Carrington James C. , Jensen Patricia E. , Schaad Mary C. 
Published: March 2003

SummaryThe potyvirus cylindrical inclusion (CI) protein, an RNA helicase required for genome replication, was analyzed genetically using alanine‐scanning mutagenesis. Thirty‐one mutations were introduced into the CI protein coding region of modified tobacco etch virus (TEV) genomes expressing either β‐glucuronidase or green fluorescent protein reporters. Twelve of the mutants were replication‐defective in protoplast inoculation assays. Among the 19 replication‐competent mutants, several possessed cell‐to‐cell or long‐distance movement defects in tobacco plants. Two mutants, AS1 and AS8, were restricted to single cells in inoculated leaves despite genome amplification levels that were equivalent to that of parental virus. Other mutants, such as AS9 and AS14, were able to move cell to cell slowly but were debilitated in long‐distance movement. These data provide genetic evidence for a direct role of CI protein in potyvirus intercellular movement, and for distinct roles of the CI protein in genome replication and movement. In combination with high‐resolution ultrastructural analyzes and previous genetic data, these results support a model in which CI protein interacts directly with plasmodesmata and capsid protein‐containing ribonucleoprotein complexes to facilitate potyvirus cell‐to‐cell movement.
Oxidative stress tolerance and longevity in Arabidopsis: the late‐flowering mutant gigantea is tolerant to paraquat
Authors: Kurepa Jasmina , Smalle Jan , Va Marc , Montagu N , Inzé Dirk 
Published: March 2003

SummaryRecent genetic analyses of longevity in animals have revealed that long‐lived strains are more tolerant to environmental stresses. To investigate whether extended longevity in Arabidopsis also correlates with an increase in stress tolerance, the response was tested of 11 late‐flowering mutants to the superoxide radical‐generating herbicide paraquat. A tight correlation between flowering time and paraquat tolerance was found when plants were exposed to low doses of herbicide. Furthermore, the mutant gigantea (gi‐3) with the longest delay in flowering time had a high tolerance level to paraquat‐induced oxidative stress. All the tested gi alleles had an increased tolerance to paraquat toxicity compared to wild‐type, although the actual levels of tolerance differed. In addition, the gi‐3 mutant was more tolerant to hydrogen peroxide. These results suggest that the link between longevity and oxidative stress resistance in plants is similar to that found in animals, implying that this phenomenon may be general for all aerobic organisms.
The untranslated leader sequence of the barleylipoxygenase 1(Lox1) gene confers embryo‐specific expression
Authors: Rouster Jacques , Van Mechelen Jan , Cameron‐Mills Verena 
Published: March 2003

Summary The barley

lipoxygenase 1

(

Lox1

) gene encodes a protein expressed in embryos during grain development and germination and in leaves after methyl‐jasmonate (MeJA) treatment. Transient gene expression assays in germinating barley embryos were used to identify

cis

‐regulatory elements involved in the embryo‐specific expression of the

Lox1

gene. Analysis of transcriptional or translational fusions between

Lox1

5′ upstream sequences and the

gusA

reporter gene indicated that the 5′‐untranslated leader sequence was involved in embryo‐specific expression. Replacement of the leader sequence from the aleurone‐specific

Chi26

gene with the

Lox1

leader sequence resulted in a chimeric gene expressed at high levels in embryo as well as in aleurone cells. Insertion of the

Lox1

leader sequence between the 35S minimum promoter (A domain –90/+8) and the

gusA

reporter gene greatly enhanced promoter activity in a tissue‐specific manner. Deletion/replacement analysis of the

Lox1

leader sequence, combined with transient expression in germinating embryos and

in vitro

transcription/translation assays, suggests that the

Lox1

leader sequence contains

cis

‐elements regulating qualitative (tissue‐specific) and quantitative gene expression.
An ordered Arabidopsis thaliana mitochondrial cDNA library on high‐density filters allows rapid systematic analysis of plant gene expression: a pilot study
Authors: Giegé Philippe , Konthur Zoltán , Walter Gerald , Brennicke Axel 
Published: March 2003

SummaryThe availability of the complete sequence of a genome allows a systematic analysis of its expression. Gene‐specific variations of transcription levels and phenomena such as transcript processing and RNA editing require large numbers of clones to be examined. For the completely sequenced mitochondrial genome of Arabidopsis thaliana we adapted robot technology to identify and characterize expressed genes. A cDNA library of about 50 000 clones was constructed, robot‐ordered into 384‐well microtitre plates and spotted onto high‐density filter membranes. These filters permit the isolation of large numbers of specific cDNA clones in a single hybridization step. The cox1, cox2 and cox3 genes were used to evaluate the feasibility and efficiency of this approach. A cluster of RNA editing sites observed outside the cox3 coding region identifies a novel reading frame orf95 in higher plants with significant similarity to a subunit of respiratory chain complex II.
Properties of proteins and the glassy matrix in maturation‐defective mutant seeds ofArabidopsis thaliana
Authors: Wolkers Willem F. , Alberda Mark , Koornneef Maarten , Léon‐Kloosterziel Karen M. , Hoekstra Folkert A. 
Published: March 2003

Summary
In situ

Fourier transform infrared microspectroscopy was used to study the heat stability of proteins and hydrogen bonding interactions in dry maturation‐defective mutant seeds of

Arabidopsis thaliana

. α‐Helical, turn and β‐sheet conformations were the major protein secondary structures in all of these seeds. On heating, intermolecular extended β‐sheet structures, typical of protein denaturation, were formed in abscisic acid‐insensitive (

abi3

) and leafy cotyledon (

lec

) mutant seeds. Proteins in dry wild‐type seeds did not denature up to 150°C, but those in dry desiccation‐sensitive,

lec1–1

,

lec1–3

and

abi3–5

seeds did at 68, 89 and 87°C, respectively. In the desiccation‐tolerant

abi3–7

and

abi3–1

seeds, denaturation commenced above 120 and 135°C, respectively. Seeds of the

aba1–1 abi3–1

double mutant showed signs of denaturation already upon drying. The molecular packing in the seeds was studied by observing the shift in the position of the OH‐stretching vibration band with temperature. The maximal rate of change of this band with temperature was much higher in the desiccation‐sensitive

abi3–5

,

aba1–1 abi3–1

,

lec1–1

, and

lec1–3

mutant seeds than in the desiccation‐tolerant wild‐type,

abi3–1

,

abi3–7

, and

lec2–1

seeds. We interpret this to mean that the molecular packing density is higher in dry desiccation‐tolerant than in dry desiccation‐sensitive seeds, which is associated with a higher or lower protein denaturation temperature, respectively. The results are discussed in relation to the physiological and biochemical characteristics of these mutant seeds.