bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern of somatic transposition in a high copy Ac tomato line
Authors: Belzile Francois , Yoder John I. 
Published: March 2003

SummaryA transgenic tomato line containing between eight and ten copies per genome of an exceptionally active maize transposable element Ac has previously been described. Southern analyses indicated that these elements are somatically active in these plants. In order to characterize further the pattern of somatic transposition in this line, 24 independent Ac insertion events from a single plant were cloned. In 21 cases, Ac inserted into single copy genomic DMA while in three cases Ac inserted into sequences present at two to four copies per genome; none of the insertions occurred into more highly repetitive DMA. The chromosomal locations of 20 insertion sites were determined by RFLP mapping and a pattern of small dispersed clusters emerged. Thirteen of the 20 insertion sites were linked to at least one other insertion site but these were distributed over nine of the 12 tomato chromosomes. Only one Ac insertion was linked to the T‐DNA locus. The structural integrity of these Ac elements was examined and no evidence of deletions or other rearrangements suggestive of Ds elements was found. The implications of these findings with respect to the use of Ac as a transposon tag in heterologous species are discussed.
The pea plastocyanin promoter directs cell‐specific but not full light‐regulated expression in transgenic tobacco plants
Authors: Pwee Keng‐Hock , Gray John C. 
Published: March 2003

SummaryA series of 5′ deletions of the pea plastocyanin gene (petE) promoter fused to the β‐glucuronidase (GUS) reporter gene has been examined for expression in transgenic tobacco plants. Strong positive and negative cis‐elements which modulate quantitative expression of the transgene in the light and the dark have been detected within the petE promoter. Disruption of a negative regulatory element at −784 bp produced the strongest photosynthesis‐gene promoter so far described. Histochemical analysis demonstrated that all petE‐GUS constructs directed expression in chloroplast‐containing cells, and that a region from −176 bp to +4 bp from the translation start site was sufficient for such cell‐specific expression. The petE‐promoter fusions were expressed at high levels in etiolated transgenic tobacco seedlings but there was no marked induction of GUS activity in the light. The endogenous tobacco plastocyanin genes and the complete pea plastocyanin gene in transgenic tobacco plants were also expressed in the dark, but showed a three‐ to sevenfold increase in the light. This indicates a requirement for sequences 3′ to the promoter for the full light response of the petE gene.
Rescue of a maize mitochondrial cytochrome oxidase mutant by tissue culture†
Authors: Gu Jianying , Dempsey Sandra , Newton Kathleen J. 
Published: March 2003

SummaryThe maize NCS6 mitochondrial mutation is a partial deletion of the cytochrome oxidase subunit 2 gene (cox2) that survives heteroplasmically in the plant. Mutant mitochondria segregate from normal mitochondria during somatic development giving rise to defective sectors on the plants, including areas of kernel abortion on the ears. Embryos from NCS6 kernels can be rescued by tissue culture. Slowly growing Type II callus derived from one of these embryos has been shown by PCR analysis to be homoplasmic for the mutation, carrying only the defective mitochondrial cox2 gene. Most of the rescued embryos were heteroplasmic for normal and mutant genes and heteroplasmy was maintained in the callus cultures. However, when suspension cultures were initiated from heteroplasmic calli, normal cells were shown to have a selective advantage. When the homoplasmic cox2 mutant callus cultures were placed on regeneration medium, plantlets did not regenerate. Heteroplasmic calli were capable of regeneration under the same conditions. These studies suggest that the functioning of mitochondrial cytochrome oxidase is not essential for growth as callus, but is required for the differentiation and development of plants.
Rice phytochrome A controls apical hook opening after a single light pulse in transgenic tobacco seedlings
Authors: Schäfer Eberhard , Emmler Karlheinz , Chua Nam‐Hai 
Published: March 2003

SummaryApical hook opening in tobacco seedlings can be induced by a single red light pulse and this induction can be reverted by a subsequent far‐red light pulse. The slow hook opening kinetics and the reversibility of an inductive light pulse even after 8 h of darkness indicate the involvement of stable phytochrome. Compared with wild‐type, transgenic BN1 seedlings which overexpress rice phytochrome A exhibit a higher sensitivity to low irradiance red light pulses. Moreover, in BN1 seedlings an inductive red light pulse is only partially reversible even after 30 min, whereas wild‐type tobacco seedlings show complete reversibility during the entire hook opening process. The data found show that rice phytochrome A is active in transgenic tobacco seedlings in controlling hook opening and that the introduced rice phytochrome A and the endogenous stable phytochrome behave differently in this response.
Characterization of a binding site for chemically synthesized lipo‐oligosaccharidic NodRm factors in particulate fractions prepared from roots
Authors: Bono Jean‐Jacques , Riond Joëlle , Nicolaou K.C. , Bockovich Nicholas J. , Estevez Virginia A. , Cullimore Julie V. , Ranjeva Raoul 
Published: March 2003

SummaryThis paper describes the characteristics of a binding site for the major, lipo‐oligosaccharide Nod factor of Rhizobium meliloti in roots of the symbiotic host plant, Medicago truncatula. Chemically synthesized NodRm‐IV(Ac, S, C16:2) was labelled by tritiation to a specific activity of 56 Ci mmol−1 and this ligand was shown to be biologically active in the root hair deformation assay at 10−11 M. Binding of the ligand to a particulate fraction from roots of M. truncatula was found to be saturable and reversible with an affinity (Kd) of 86 nM and the binding characteristics were consistent with a single class of binding sites. Competition with modified Nod factors showed that the binding was independent of both the O‐acetyl and the sulphyl group and did not depend on the unsaturation of the fatty acid. However, both moieties of the lipo‐oligosaccharide are required for high‐affinity binding since tetra‐N‐acetyl‐chitotetraose and palmitate were found to be poor competitors of ligand binding. A binding site with analogous characteristics was also found in a similarly prepared particulate fraction of tomato roots. This binding site for Nod factors, termed NFBS1, which is present in both a leguminous and a non‐leguminous plant, may have a more general role than symbiosis.
T‐DNA tagging of genes influencing polyamine metabolism: isolation of mutant plant lines and rescue of DNA promoting growth in the presence of a polyamine biosynthetic inhibitor
Authors: Fritze Klaus , Czaja Inge , Walden Richard 
Published: March 2003

SummaryActivation T‐DNA tagging has been used to generate cell lines characterized by their ability to grow and form callus in vitro under selective concentrations of the polyamine biosynthetic inhibitor methylglyoxal‐bis(guanylhydrazone) (MGBG). These have been regenerated into plants of which the majority have been shown by Southern analysis to contain single T‐DNA inserts. In the mutant lines the T‐DNA is contained on differing restriction fragments of genomic DNA, suggesting that they represent different insertion events. Regenerated plants display characteristic phenotypic changes when compared with untransformed plants including leaf and floral malformation as well as parthenocarpy. In two of the plant lines studied in detail, the activity of S‐adenosylmethionine decarboxylase, the target of MGBG, was increased in callus tissue and in one line this is coupled with elevated levels of putrescine and spermidine. Plant genomic DNA flanking the T‐DNA insert has been rescued from one mutant plant line and Northern blot analysis indicates that transcripts corresponding to this DNA accumulate to higher levels in the T‐DNA tagged line compared with untransformed tobacco. Rescued genomic DNA flanking the T‐DNA, once re‐introduced into untransformed tobacco protoplasts by PEG‐mediated uptake, confers the ability to grow under selective levels of MGBG. This confirms that sequences responsible for the selected phenotype have been isolated. It is anticipated that the analysis of such mutants and the further characterization of the tagged ganomic sequences may shed light on the action of polyamines in plant growth and development.
Post‐transcriptional regulation of gene expression in oxygen‐deprived roots of maize
Authors: Fennoy Sheila L. , Bailey‐Serres Julia 
Published: March 2003

SummaryMaize (Zea mays L.) seedling roots undergo transient changes in gene expression in response to O2 deprivation (hypoxia or anoxia). Previous research has demonstrated the induction of transcription of alcohol dehydrogenase‐1 (adh1) and implicated post‐transcriptional and translational processes in the regulation of gene expression. In this study, the effects of O2 deprivation on expression of mRNA encoding ADH1 and an aerobically synthesized protein, the mitochondrial adenine nucleotide translocator (ANT) were compared. The transcription of adh1 in isolated nuclei and steady‐state level of poly(A)+ mRNA encoding ADH1 increased in response to O2 deprivation. In contrast, transcription of ant was not significantly affected, whereas the steady‐state level of ANT mRNA steadily decreased under O2 deprivation. To further understand the contrasting effect of low‐O2 on the stability of ADH1 and ANT mRNAs, post‐transcriptional processes of gene expression were examined. RNA blot analysis of sucrose density gradient fractions of ribosomes revealed that ADH1 and ANT mRNAs are associated with polyribosomes under aerobic and O2‐deprived growth conditions. However, the number of ribosomes loaded per ANT mRNA was significantly reduced during O2 deprivation. Immunoprecipitation analysis showed that synthesis of ANT was impaired relative to accumulation of ANT mRNA in O2‐deprived roots. The differences in synthesis of ADH1 and ANT in O2‐deprived roots appears to be due not only to increased transcription of adh1, but to competitive differences between transcripts for translation initiation factors and differences in ability to elongate during translation.
The Petunia tra1 gene controls cell elongation and plant development, and mediates responses to cytokinins
Authors: Dubois F. , Dang Ha D. Bui , Sangwan R.S. , Durand J. 
Published: March 2003

SummaryThe molecular control of cell elongation, one of the basic processes of plant morphogenesis, is still largely not understood. This paper describes a Petunia hybrida mutant of dumpy phenotype, trapu, which identifies tra1, a gene required for cell elongation and mediating responses to applied cytokinin. This mutant displayed an extreme reduction in length, due to a single recessive mutation which was expressed in every part of the plant and during the entire life of the plant, including the mature embryo. The mutant was unable to flower. The mutant roots, as well as the leafy organs, were short and thick, and the root elongation zone, hypocotyl and petioles were absent. The mutant plantlets responded neither to applied auxin nor to gibberellin, indicating that this phenotype was not caused by a deprivation of these phytohormones. However, unlike the wildtype, the mutant growth was stimulated by applied cytokinin, even though its morphology remained abnormal. A histological study revealed the presence of all tissue types in normal positions, including root hairs and vascular bundles. The mutant's cells were rounder in every tissue. Both shoot and root meristems were disorganized, without consistent cell shape and size. The regular cell files, which are typical of a normal root apex organization, were totally absent in the mutant root apex. Indirect immunofluorescence of α‐tubulin on root apices showed the cortical microtubules in the mutant cells to be unable to form the parallel arrays in elongating cells and the preprophase band in dividing cells. This default resulted in the prevention of unidirectional cell elongation and formation of regular cell files, thus causing the trapu phenotype. This paper discusses the similarities and differences of trapu to the Arabidopsis mutants, fass and ton, trapu confirming that the establishment of plant body pattern and differentiation can be dissociated from cell elongation.
Purification of the Chlorella HUP1 hexose—proton symporter to homogeneity and its reconstitution in vitro
Authors: Caspari Thomas , Robl Ingrid , Stolz Jürgen , Tanner Widmar 
Published: March 2003

SummaryA prokaryotic biotin acceptor domain was fused to the carboxy terminal end of the Chlorella hexose—proton sym‐ porter. The plant symporter is biotinylated in vivo when expressed in Schizosaccharomyces pombe. The extended biotinylated transport protein is fully active, catalyzes accumulation of d‐glucose analogs and restores growth of a glucose‐uptake‐deficient yeast strain. Crude membranes were solubilized with octyl‐β‐d‐glucoside in the presence of Escherichia colil‐α‐phosphatidylethanolamine. Biotinylated symporter was purified to homogeneity by biotinavidin affinity chromatography. The symporter protein was reconstituted together with cytochrome‐c oxidase prepared from beef heart mitochondria into proteo‐liposomes. Cytochrome‐c oxidase is a redox‐driven H+‐pump generating a proton motive force (inside negative and alkaline) while transferring electrons from cytochrome‐c to oxygen; this energy is used by the symporter to accumulate d‐glucose at least 30‐fold. In the absence of the driving force the transport protein facilitates diffusion of d‐glucose until the concentration equilibrium is reached. It was shown that maximal transport activity depends highly on the amount of co‐reconstituted cytochrome‐c oxidase and that the symporter possesses 10% of its in vivo turnover number under optimized in vitro transport conditions.
Gene identification in a complex chromosomal continuum by local genomic cross‐referencing
Authors: Avramova Zoya , Tikhonov Alexander , SanMiguel Phillip , Jin Young‐Kwan , Liu Changnong , Woo Sung‐Sick , Wing Rod A. , Bennetzen Jeffrey L. 
Published: March 2003

SummaryMost higher plants have complex genomes containing large quantities of repetitive DNA interspersed with low‐copy‐number sequences. Many of these repetitive DNAs are mobile and have homology to RNAs in various cell types. This can make it difficult to identify the genes in a long chromosomal continuum. It was decided to use genic sequence conservation and grass genome co‐linearity as tools for gene identification. A bacterial artificial chromosome (BAC) clone containing sorghum genomic DNA was selected using a maize Adh1 probe. The 165 kb sorghum BAC was tested for hybridization to a set of clones representing the contiguous 280 kb of DNA flanking maize Adh1. None of the repetitive maize DNAs hybridized, but most of the low‐copy‐number sequences did. A low‐copy‐number sequence that did cross‐hybridize was found to be a gene, while one that did not was found to be a low‐copy‐number retrotransposon that was named Reina. Regions of cross‐hybridization were co‐linear between the two genomes, but closer together in the smaller sorghum genome. These results indicate that local genomic cross‐referencing by hybridization of orthologous clones can be an efficient and rapid technique for gene identification and studies of genome organization.
Immunofluorescent quantitation of chloroplast proteins
Authors: Leech Rachel M. , Marrison Joanne L. 
Published: March 2003

SummaryUsing scanning light microscopy software to detect and measure immunofluorescence in leaf sections Rubisco concentration in situ in chloroplasts has been accurately determined throughout development. The fluorescence measurements were calibrated by comparison with values for Rubisco accumulation obtained from rocket immuno‐ electrophoresis profiles of soluble protein from isolated cells and from chloroplasts using a purified sample of Rubisco as the standard. It has been shown that in situ immunofluorescence can be used for cytoquantitation of proteins within individual chloroplasts to a sensitivity of 1fg and also for the comparison of the protein levels in adjacent chloroplasts and cells. Several important applica‐ tions of this new technique are discussed.
mCCG methylation in angiosperms
Authors: Jeddeloh Jeffrey A. , Richards Eric J. 
Published: March 2003

SummaryTwo different methods were used to investigate the abundance of cytosine methylation at the outer (5′) position in 5′‐CCG‐3′ trinucleotides in angiosperm genomes. Mspl is unable to cut its target site if the outer cytosine is methylated (5′‐mCCGG‐3′). Using Mspl restriction analysis, it was shown that 5′‐mCCG‐3′ is present in all angiosperm genomes examined, and that the amount of cytosine methylation at this site varies between species. Subsequently, direct measurements were made of the amount of methylation at both cytosines in a subset of 5′‐CCG‐3′ trinucleotides in the Arabidopsis thaliana genome. Based upon these analyses, it was estimated that approximately 20–30% of 5′‐CCG‐3′ trinucleotides in A. thaliana are methylated at the outer cytosine. Approximately 20% of the 5′‐CCG‐3′ trinucleotides contain 5‐methyl‐cytosine at the inner cytosine position, which corresponds to a previous determination of 5′‐mCG‐3′ methylation in A. thaliana. The implications of 5′‐mCCG‐3′ methylation are discussed.
Pollination induces mRNA poly(A) tail‐shortening and cell deterioration in flower transmitting tissue
Authors: Wang Hong , Wu Hen‐ming , Cheung Alice Y. 
Published: March 2003

SummaryPollination induces many physiological responses in the flower, including deterioration and death in specific pistil cell types. It is shown here that within the style of tobacco, pollination‐induced cell deterioration was restricted to the transmitting tissue while the surrounding cortical tissue was not affected. It was distinct from general senescence since exogenously applying the senescence‐inducing hormone ethylene, or its precursor aminocyclopropane‐1‐carboxylic acid (ACC), to the flower or the pistil induced overall deterioration in the entire flower. Furthermore, both pollen tube growth and ethylene action were needed for the entire spectrum of cellular changes associated with this pollination‐induced transmitting tissue deterioration process. It is also shown that pollination‐induced mRNA poly(A) tail‐shortening for at least three major classes of transmitting tissue‐specific mRNAs. As is commonly observed for poly(A) tail‐shortened mRNAs, the levels of two of these three mRNA classes decline after pollination. On the other hand, the third class of mRNAs, transmitting tissue‐specific (TTs) mRNAs, was maintained at a very high level subsequent to pollination, even after substantial poly(A)‐tail shortening. TTS mRNAs encode a pollen tube growth‐promoting and ‐attracting protein needed for optimal in vivo pollen tube growth. The specific preservation of TTS mRNAs in the deteriorating transmitting tissue cells suggests that these cells can distinguish molecules needed in the pollinated styles from those that are dispensable, and protect them from degradation. It is suggested that the pollination‐induced mRNA poly(A) tail‐shortening and cell death are programmed processes suited to the post‐pollination transmitting tissue environment. Results showing that ACC is a candidate signal molecule for the pollination‐induced mRNA‐shortening which is accentuated by ethylene and mediated via a protein phosphorylation‐dependent signal transduction pathway are also presented.
The viviparous8 mutation delays vegetative phase change and accelerates the rate of seedling growth in maize
Authors: Evans Matthew M.S. , Poethig R. Scott 
Published: March 2003

SummaryPost‐embryonic shoot development in plants can be divided into a juvenile vegetative, an adult vegetative, and a reproductive phase, which are expressed in different domains on the shoot axis. The number and position of the phytomers in each phase are determined by the time at which a plant begins and ceases making phytomers of a particular phase and the rate at which phytomers are made during that phase. The viviparous8 (vp8) mutation of maize increases the number of juvenile vegetative phytomers and decreases the number of adult vegetative phytomers by affecting both of these processes. vp8 increases the number of juvenile vegetative phytomers by increasing the rate of leaf initiation early in shoot development and delaying the juvenile‐to‐adult transition (vegetative maturation). It reduces the number of adult phytomers because the delay in vegetative maturation is not matched by a corresponding delay in flowering time; vp8 plants produce a tassel at the same time as wild‐type plants. Thus, Vp8 normally controls the production of a factor that functions both to repress the rate of growth early in shoot development and to promote vegetative maturation, but which has no major role in floral induction. vp8 dramatically enhances the phenotypes of the dwarf and Teopod mutants and requires a functional Glossy15 gene to prolong the expression of juvenile epidermal traits. Evidence suggesting that vp8 does not affect phase change by reducing the level of abscisic acid is discussed.
Internal AU‐rich elements modulate activity of two competing 3′ splice sites in plant nuclei
Authors: Merritt Hanne , McCullough Andrew J. , Schuler Mary A. 
Published: March 2003

Summary In vivo analyses using an autonomously replicating Agrobacterium/geminivirus vector have enabled identification of AU‐rich intronic elements critical for 5′ and 3′ splice site selection in dicot plant nuclei and development of a model for pre‐mRNA intron recognition in plant nuclei. To determine the minimal length, spacing and nucleotide compositions constraining recognition of the 3′ boundary of an intron, two or four nucleotide substitutions have been introduced into the two AU‐rich elements located between 50 and 66 nucleotides upstream from the 3′ splice site of maize Adh 1 intron 3. In each case tested, substitutions in the distal left element (−62 to −66) inactivate the downstream 3′ splice site at −1 more effectively than substitutions in the proximal right element (−50 to −55). Guanosine or cytosine substitutions in either element reduce recognition of the −1 site significantly; adenosine substitutions have a less severe effect. Mutations in both of these AU elements additively block recognition of the downstream 3′ splice site. The strong additive effect of these mutations supports a model in which short sets of AU islands bind interactive factors and cooperatively modulate usage of the downstream splice site. In contrast to the uridine requirements documented for the 3′ terminus of plant introns, adenosines are partially interchangeable with uridines within this internal region of the intron.