bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the protein import apparatus in isolated outer envelopes of chloroplasts
Authors: Waegemann Karin , Soil Jürgen 
Published: February 2005

SummaryIsolated outer envelope membrane from pea (Pisum sativum L.) chloroplasts can be used in vitro to study binding and partial translocation of precursor proteins destined for the inside of the organelle. Efficient binding to a receptor protein on the outside of the membrane vesicle and generation of a translocation intermediate depends strictly on the presence of ATP. Protease treatment of the translocation intermediate demonstrates its insertion into the membrane. The membrane‐inserted precursor protein cannot be extracted by 1 M NaCl and is also NaOH resistant to a large extent. Mild solubilization of outer envelope membranes by detergent resulted in the isolation of a complex which still contained the precursor protein. We have identified a constitutively expressed homologue hsc 70 as part of this membrane complex. Antibodies against hsp 70 (inducible heat shock protein 70) were able to immuno‐precipitate the complex bound precursor protein. A second protein of 86 kDa molecular weight (OEP 86) from the outer envelope membrane was also identified as a major component of this complex.
Localization of tandemly repeated DMA sequences in Arabidopsis thaliana
Authors: Maluszynska J. , Heslop‐Harrison J.S. 
Published: February 2005

Summary In‐situ hybridization to interphase nuclei and chromosomes of Arabidopsis thaliana (2n= 10) shows that there are four sites of rDNA in a diploid nucleus. The sites are located on chromosomes 2 and 4, and the strength of hybridization indicates that copy number is similar at both pairs of sites. Hybridization to trisomic line 4 revealed five hybridization sites. Silver staining of nucleoli demonstrates that all four loci can be active in diploid interphase nuclei. The tandemly repeated probe pAL1 hybridizes near to the centromeres of all five chromosome pairs. In diploid interphase nuclei, 10 sites of hybridization are detected, while 15 are seen in triploid nuclei. The sites of hybridization co‐localize with the centromeric heterochromatin visualized by staining DNA with the fluorochrome DAPI. The results demonstrate that molecular cytogenetics can be applied to A. thaliana and high resolution physical chromosome maps can be generated. Both probes may be useful for interphase cytogenetics, where they enable chromosome number and aneuploidy to be examined in tissues without divisions. The physical localization of these hybridization sites provides a starting point for linking RFLP and physical chromosome maps.
Molecular characterization of an Arabidopsis thaliana cDNA encoding a small GTP‐binding protein, Rha1
Authors: Anuntalabhochai S. , Terryn N. , Van Montagu M. , Inzé D. 
Published: February 2005

SummaryWe have isolated a cDNA encoding a small GTP‐binding protein from an Arabidopsis thaliana cDNA library using an oligonucleotide probe derived from the most conserved domain of the ras superfamily. The cDNA encodes a 21.8 kDa protein, designated Rha1, which shows high homology to members of the ras super‐family in the regions involved in GTP binding, GTPase activity, and membrane attachment. The amino acid sequence is 60% identical to the sequence of the mammalian RabS protein, a small GTP‐binding protein which is believed to be involved in endocytosis. Several regions, including the putative effector domain are completely conserved. This high percentage of amino acid identity suggests that the Rha1 protein is the functional plant counterpart of the Rab5 protein. When expressed in E. coli, the Rha1 protein was shown to bind GTP. The rha 1 gene is most highly expressed in root and callus tissue, weakly expressed in stems and inflorescences and virtually not expressed in leaves and seed pods. Genomic Southern analysis revealed that rha 1 is part of a small multigene family.
Simulations of the static and dynamic molecular conformations of xyloglucan. The role of the fucosylated sidechain in surface‐specific sidechain folding
Authors: Levy Samuel , York William S. , Stuike‐Prill Rainer , Meyer Bernd , Staehelin L. Andrew 
Published: February 2005

SummaryThe hemicellulosic polysaccharide xyloglucan binds with a strong affinity to cellulosic cell wall microfibrils, the resulting heterogeneous network constituting up to 50% of the dry weight of the cell wall in dicotyledonous plants. To elucidate the molecular details of this interaction, we have performed theoretical potential energy calculations of the static and dynamic equilibrium conformations of xyloglucan using the GEGOP software.In particular, we have evaluated the preferred side‐chain conformations of hexa‐, octa‐, deca‐ and heptadecasaccharide model fragments of xyloglucan for molecules with a cellulose‐like, flat, glucan backbone, and a cellobiose‐like, twisted, glucan backbone conformation. For the flat backbone conformation the determination of static equilibrium molecular conformations revealed a tendency for sidechains to fold onto one surface of the backbone, defined here as the H1s face, in the fucosylated region of the polymer. This folding produces a molecule that is sterically accessible on the opposite face of the backbone, the H4s face. Typically, this folding onto the H1s surface is significantly stabilized by favorable interactions between the fucosylated, trisaccharide sidechain and the backbone, with some stabilization from adjacent terminal xylosyl sidechains. In contrast, the trisaccharide sidechain folds onto the H4S face of xyloglucan fragments with a twisted backbone conformation. Preliminary NMR data on nonasaccharide fragments isolated from sycamore suspension‐cultured cell walls are consistent with the hypothesis that the twisted conformation of xyloglucan represents the solution form of this molecule.Metropolis Monte Carlo (MMC) simulations were employed to assess sidechain flexibility of the hepta decasaccharide fragments. Simulations performed on the flat, rigid, backbone xyloglucan indicate that the trisaccharide sidechain is less mobile than the terminal xylosyl sidechains. MMC calculations on a fully relaxed molecule revealed a positive correlation between a specific trisaccharide sidechain orientation and the ‘flatness’ of the backbone glucosyl residues adjacent to this sidechain. These results suggest that the trisaccharide sidechain may play a role in the formation of nucleation sites that initiate the binding of these regions to cellulose.Based on these conformational preferences we suggest the following model for the binding of xyloglucan to cellulose. Nucleation of a binding site is initiated by the fucosylated, trisaccharide sidechain that flattens out an adjacent region of the xyloglucan backbone. Upon contacting a cellulose microfibril this region spreads by step‐wise flattening of successive segments of the backbone. Self‐association of xyloglucan molecules in solution may be prevented by the low frequency of formation of these nucleation sites and the geometry of the molecules in solution.
Transcriptional repression of light‐induced flavonoid synthesis by elicitor treatment of cultured parsley cells
Authors: Lozoya Edmundo , Block Annette , Lois Rodrigo , Hahlbrock Klaus , Scheel Dierk 
Published: February 2005

SummaryCultured parsley (Petroselinum crispum) cells respond differentially to UV‐containing white light and fungal elicitor. Both stimuli activate the transcription of genes encoding enzymes of partly overlapping phenylpropanoid biosynthetic pathways. Irradiation induces vacuolar accumulation of flavonoids, whereas elicitor treatment stimulates the secretion of furanocoumarins. Simultaneous treatment of parsley cells with UV light and elicitor results in quantitative changes in both responses. Irradiation reduces elicitor‐induced furanocoumarin synthesis, possibly by post‐transcriptional mechanisms, whereas elicitor treatment completely blocks the light‐induced accumulation of flavonoids by repressing the transcription of the chalcone synthase gene. We have identified elicitor‐sensitive regions in the chalcone synthase promoter by transient expression analysis of selected promoter constructs linked to the β‐D‐glucuronidase reporter gene in parsley protoplasts. These regions are identical to those that were found to be sufficient for light inducibility of the chalcone synthase promoter.
Arabidopsis thaliana as a new model host for plant‐parasitic nematodes
Authors: Sijmons Peter C. , Grundler Florian M.W. , von Mende Nicola , Burrows Paul R. , Wyss Urs 
Published: February 2005

SummaryWe have established culture conditions for successful infection and development of several economically important cyst‐forming and root‐knot nematodes on Arabidopsis thaliana under monoxenic conditions. Complete life cycles were obtained with the sedentary cyst nematodes Heterodera schachtii, H. trifolii, H. cajani and the root‐knot nematodes Meloidogyne incognita and M. arenariaas well as with the migratory nematode Pratylenchus penetrans. In contrast, H. goettingiana and Globodera rostochiensis were unable to develop on Arabidopsis roots. Tissue‐culture quality agar and medium conditions optimized for hydroponic root culture were essential for successful infections. Detailed in‐vivo observations were made inside Arabidopsis roots during the early infection stages of M. incognita and during complete development of H. schachtii. Seventy‐four different ecotypes of Arabidopsis were screened for their susceptibility towards H. schachtii resulting in a range of infection rates. None of the ecotypes tested showed complete resistance in vitro. The use of Arabidopsis as a host for plant‐parasitic nematodes will provide a new model system for the molecular genetic analysis of this interaction.
Constitutive nitrate reductase: a dominant conditional marker for plant genetics
Authors: Nussaume Laurent , Vincentz Michel , Caboche Michel 
Published: February 2005

SummaryWe describe the development of a counter‐selection system based on the use of an engineered nitrate reductase (NR) gene. The engineered gene consists of an NR cDNA placed under the control of the CaMV 35S promoter (35S‐NR). Seedlings and cells derived from transgenic Nicotiana plumbaginifolia plants transformed with 35S‐NR are efficiently killed by the selective agent chlorate on medium containing ammonium as the sole nitrogen source. Under these nitrate‐free conditions wild‐type plants are not affected by chlorate because the endogenous wild‐type Niagene is not expressed.
Identification of a cDNA for the plastid‐located geranylgeranyl pyrophosphate synthase from Capsicum annuum: correlative increase in enzyme activity and transcript level during fruit ripening
Authors: Kuntz M. , Römer S. , Suire C. , Hugueney P. , Weil J.H. , Schantz R. , Camara B. 
Published: February 2005

SummaryGeranylgeranyl pyrophosphate synthase is a key enzyme in plant terpenoid biosynthesis. Using specific antibodies, a cDNA encoding geranylgeranyl pyrophosphate synthase has been isolated from bell pepper (Capsicum annuum) ripening fruit. The cloned cDNA codes for a high molecular weight precursor of 369 amino acids which contains a transit peptide of approximately 60 amino acids. In‐situ immunolocalization experiments have demonstrated that geranylgeranyl pyrophosphate synthase is located exclusively in the plastids. Expression of the cloned cDNA in E. coli has unambiguously demonstrated that the encoded polypeptide catalyzes the synthesis of geranylgeranyl pyrophosphate by the addition of isopentenyl pyrophosphate to an allylic pyrophosphate. Peptide sequence comparisons revealed significant similarity between the sequences of the C. annuum geranylgeranyl pyrophosphate synthase and those deduced from carotenoid biosynthesis (crtE) genes from photosynthetic and non‐photosynthetic bacteria. In addition, four highly conserved regions, which are found in various prenyltransferases, were identified.Furthermore, evidence is provided suggesting that conserved and exposed carboxylates are directly involved in the catalytic mechanism. Finally, the expression of the geranylgeranyl pyrophosphate synthase gene is demonstrated to be strongly induced during the chloroplast to chromoplast transition which occurs in ripening fruits, and is correlated with an increase in enzyme activity.
terminal flower: a gene affecting inflorescence development in Arabidopsis thaliana
Authors: Alvarez John , Guli Catherine L. , Yu Xiang‐Hua , Smyth David R. 
Published: February 2005

SummaryGrowth of flowering stems in wild‐type Arabidopsis is indeterminate. Many flowers arise sequentially on the flanks of apical meristems in a phyllotactic spiral. We have isolated eight recessive mutants of a gene, terminal flower, in which inflorescences become determinate. Flower primordia sooner or later ‘invade’ the meristem summit leading to cessation of its further growth. Primary apical meristems usually terminate with several part‐flowers which lack pedicels, and several normal pedicellate flowers may arise first. By contrast apical meristems of secondary branches usually produce only a single pedicellate flower. Plant height is also reduced and more rosette inflorescences develop. These growth patterns occur in six strong mutants raised at 25°C under continuous light. In two weak mutants termination occurs much later with many more flowers arising before eventual termination. Termination is similarly delayed in at least one of the strong mutants grown at lower temperatures. The tfl mutation does not affect the indeterminate growth of flower meristems, at least in‐so‐far as this occurs in agamous mutants. The tfl locus is at the top of linkage group 5, close to RFLP 447.We propose that the TFL gene product supports the activity of an inhibitor of flower primordium initiation. This inhibitor would normally prevent flowers from arising on the inflorescence apex but in tfl mutants it may readily fall below its threshold of activity. The TFL gene may be one of a class responsible for evolutionary changes between indeterminate and determinate growth.
Increased lysine synthesis in tobacco plants that express high levels of bacterial dihydrodipicolinate synthase in their chloroplasts
Authors: Shaul Orit , Galili Gad 
Published: February 2005

SummaryA major nutritional drawback of many crop plants is their low content of several essential amino acids, particularly lysine. The biosynthesis of lysine in plants is regulated by several feedback loops. Dihydrodipicolinate synthase (DHPS) from Escherichia coli, a key enzyme in lysine biosynthesis, which is considerably less sensitive to lysine accumulation than the endogenous plant enzyme has been expressed in chloroplasts of tobacco leaves. Expression of the bacterial enzyme was accompanied by a significant increase in the level of free lysine. No increase in protein‐bound lysine was evident. Free lysine accumulation was positively correlated with the level of DHPS activity in various transgenic plants. Compartmentalization of DHPS in the chloroplast was essential for its participation in lysine biosynthesis as no lysine overproduction was obtained in transgenic plants that expressed the bacterial enzyme in the cytoplasm. The elevated level of free lysine in the transgenic plants was sufficient to inhibit, in vivo, a second key enzyme in lysine biosynthesis, namely, aspartate kinase, with no apparent influence on lysine accumulation. The present report not only provides a better understanding of the regulation of lysine biosynthesis in higher plants but also offers a new strategy to improve the production of this essential amino acid.
Prediction of germ‐line transformation events in chimeric Ro transgenic soybean plantlets using tissue‐specific expression patterns
Authors: Christou Paul , McCabe Dennis E. 
Published: February 2005

SummaryChimeric soybean plants derived from electric discharge particle acceleration experiments were used to develop relationships between tissue‐specific expression patterns of a marker gene and germ‐line transformation events in Ro plants. Using the GUS histochemical assay the likelihood of germ‐line transformation was correlated to the localization of enzyme activity in specific tissues of the parent plant. The expression patterns of the 35S‐GUS marker gene in specific tissue types in Ro plants and correlation with transmission of the introduced gene to progeny allowed the production of a clear picture of the development of these plants and their germ‐line cells. Advances reported in this article resulted in the development of a commercial process for the genetic improvement of this important staple crop which until recently was very recalcitrant to conventional transformation methods.
Formation and cell lineage patterns of the shoot apex of maize
Authors: Bossinger Gerd , Maddaloni Massimo , Motto Mario , Salamini Francesco 
Published: February 2005

SummaryIn maize, glossy (gl) mutants lack the wax layer normally present on the epidermis of young leaves. By insertion mutagenesis, unstable alleles (gl1‐m) have been induced at the Gl1 locus. In the gl1‐m8 strain, somatic reversions to wild‐type frequently result in the formation of large sectors occupying predictable positions in all seedlings' leaves. In studies of 230 gl1‐m8 seedlings with large reverted sectors covering around 50% of the first leaf, four patterns of sectoring were recognized: one large sector ending in all leaves at the main midrib (32.6% of cases); one central sector on leaves 1, 3 and 5 (or 2 and 4), corresponding to lateral stripes of Gl1 tissue on the other leaves (7.9%); a sector decreasing or increasing in successive leaves (9.1%); other types with one sector covering a leaf surface between 33 and 50% (19.1%) or with complex variegations (31.3%). Based on leaf sectoring, the pattern and stability of cell lineages during shoot apex establishment and embryonic activity leading to leaf primordia, are inferred from the genetic state (Gl or gl1‐m) of leaf founder cells present in the apex at the ring of primordia insertion. A genetic experiment indicates that the large somatic reversions considered derived from both the LI and the LII layers of the apex. A large majority of the observed patterns of reversion can be interpreted as due to a single event of transposition. The data are discussed and relevant conclusions proposed in relation to the age of the proembryo at the time of apex formation, the permanent or impermanent state of initial cells of the apex, the polarization of cell divisions and the plane of early apex cell division as a mechanism leading to the bilateral symmetry of the maize seedling.
A mutant of Arabidopsis which is defective in seed development and storage protein accumulation is a new abi3 allele
Authors: Nambara Eiji , Naito Satoshi , McCourt Peter 
Published: February 2005

SummaryIn order to investigate the role of the plant hormones gibberellin (GA) and abscisic acid (ABA) in seed development and germination the GA biosynthetic inhibitor, Uniconazol, was used to isolate mutants with abnormal germination profiles. In one of these mutants, the ability to germinate on Uniconazol is due to a mutation in the ABI3 gene. However, unlike the previously reported abi3 mutant, this line displays an array of seed‐specific developmental defects. The accumulation of seed reserve proteins is dramatically reduced due to reduced levels of the storage protein mRNA. The embryos remain green throughout development and are desiccation intolerant. However, immature seeds are completely non‐dormant and grow normally. These results suggest the ABI3 gene is essential for the synthesis of seed storage proteins and for the protection of the embryo during desiccation.
A Brassica S‐locus related gene promoter directs expression in both pollen and pistil of tobacco
Authors: Hackett Rachel M. , Lawrence Michael J. , Franklin F. Christopher H. 
Published: February 2005

SummaryA portion (1.5 kb) of the promoter region of an S63 S‐locus related (SLR) glycoprotein gene from the sporophytically self‐incompatible species Brassica oleracea was inserted upstream of the β‐glucuronidase (GUS) gene in binary vector pBI101.1. The resulting construct was then introduced into Nicotiana tabacum through Agrobacterium‐mediated transformation. The expression pattern of GUS under the control of the S63 SLR promoter fragment was found to be similar to that already reported for expression of the GUS gene directed by an S‐locus specific gene promoter in transgenic N. tabacum. Furthermore, this pattern of expression resembled more closely that reported for S‐genes of the self‐incompatible species Nicotiana alata, which has a gametophytic self‐incompatibility system, than the predicted pattern of expression of S‐genes in B. oleracea.
Maternal mRNA and early development in Fucus serratus
Authors: Masters A. K. , Shirras A. D. , Hetherington A. M. 
Published: February 2005

SummaryIntact total and polyadenylated RNA have been isolated from unfertilized eggs of the brown marine macroalga Fucus serratus. The presence of functional messenger RNA has been demonstrated by translation in vitro. The major in‐vitro translation product has an apparent molecular mass of 42 kDa. Immunoprecipitation of translation products of egg RNA using an anti‐actin antibody yields a polypeptide which co‐migrates with this major translation product.
Enrichment of vitronectin‐ and fibronectin‐like proteins in NaCl‐adapted plant cells and evidence for their involvement in plasma membrane–cell wall adhesion
Authors: Zhu Jian‐Kang , Shi Jun , Singh Utpal , Wyatt Sarah E. , Bressan Ray A. , Hasegawa Paul M. , Carpita Nicholas C. 
Published: February 2005

SummaryCells of tobacco adapted to grow in high concentrations of NaCl develop tight zones of adhesion between the plasma membrane and cell wall, revealed by concave plasmolysis in osmotic solutions. Unadapted cells exhibit mostly convex plasmolysis and exhibit little or no adhesive character. Wall‐less protoplasts isolated from the adapted cells retain the complementary adhesive character and adhere tightly to each other, whereas protoplasts from unadapted cells do not. The hexapeptide gly‐arg‐gly‐asp‐ser‐pro, in which the arg‐gly‐asp represents the integrin‐binding domain of several animal extracellular matrix proteins, specifically blocks adhesion of the protoplasts. A control hexapeptide, gly‐arg‐gly‐glu‐ser‐pro, is ineffective in blocking adhesion. Tobacco proteins immunologically related to human vitronectin were found in cell walls and membranes of unadapted and NaCl‐adapted cells, but the total extractable vitronectin‐like protein was enriched in the adapted cells. Tobacco proteins immunologically related to human fibronectin were found in membranes and cell walls of NaCl‐adapted cells but not in those from unadapted cells. Our observations indicate that plant cells possess cell‐matrix adhesion complexes similar to animal cells, and these adhesion complexes accumulate in growth‐limited cells adapted to saline stress.