bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogeny of the Pyretophorus Series of Anopheles subgenus Cellia (Diptera: Culicidae)
Authors: Anthony ThomaS. G.. , And RalpH. E. HarbacH. , Kitching IaN. J..
Published: March 2003

A cladistic analysis based on morphological characters is presented for the Pyretophorus Series of subgenus Cellia of Anopheles. The cibarial armature was investigated for the first time since the pioneering work of Christophers (1933), which is still used to define taxonomic series within Cellia, and for the first time ever using scanning electron microscopy. Christophers’ observations of characters of the cibarial armature were corroborated and several novel characters discovered. Despite difficulties in delimiting and encoding morphological characters at the species level, the analysis provided insights into relationships within the Pyretophorus Series. The data support the monophyly of the Series and establish the Oriental species as a monophyletic group. The Afrotropical species are basal and paraphyletic relative to the Oriental species, with Anopheles christyi placed in the most basal position. The pattern of relationships suggests that the capacity to transmit malaria is an ancestral condition subsequently lost independently in several lineages.
Phylogeny of the riodinid butterfly subtribe Theopeina (Lepidoptera: Riodinidae: Nymphidiini)
Authors: Hall Jason P. W.
Published: March 2003

AbstractThe almost exclusively Neotropical butterfly family Riodinidae is poorly represented in both ecological and systematic studies of Lepidoptera. A comparative morphological study of all seventy‐five species in subtribe Theopeina (tribe Nymphidiini) yielded 104 characters, predominantly from wing pattern, male and female genitalia, and abdominal structures. All morphological characters and adults representing the range of wing pattern variation are illustrated. Phylogenetic analysis of the data produced a large number of most parsimonious cladograms, but the strict consensus of these, both when using equal weights and after successive weighting, is well resolved and the majority of terminal clades have high character and branch support. Theopeina is found to consist of five monophyletic genera,Protonymphidia,Archaeonympha,Calicosama,BehemothiaandTheope(= ParnesandDinoplotis), with the largest genusTheopecontaining thirteen monophyletic species groups, which are delineated to facilitate a discussion of broad evolutionary patterns in this morphologically diverse subtribe.
A new genus and two new species of felt scales (Hemiptera: Coccoidea: Eriococcidae) from Chile, with comments on zoogeographical affinities between the eriococcid faunas of southern South America and New Zealand
Authors: Hodgson Chris J. , Miller Douglass R.
Published: March 2003

Abstract A new eriococcid genus (Chilechiton Hodgson & Miller) and the adult female, second‐instar female and first‐instar nymphs of two new species of Eriococcidae (Chilechiton lynnae on Nothofagus and Icelococcus lithreae on Lithraea) are described. Chilechiton is closely related to the New Zealand genus Eriochiton Maskell in tribe Eriochitonini, previously considered to be restricted to New Zealand. A phylogenetic analysis was undertaken to investigate the relationships of the Chilean and New Zealand eriococcid genera included in the study, the systematic boundaries of Eriochitonini and the relationship of Coccidae to Eriochitonini. The study suggests that the Chilean eriococcid fauna is closely related to that in New Zealand, Eriochitonini should be enlarged to include C. lynnae, genus Eriococcus is polyphyletic, Eriococcidae is monophyletic, and Coccidae and Eriococcidae are not closely related.
Electrokinetic geophysics — a review
Authors: Beamish  , Peart
Published: March 2003

Electrokinetic phenomena occur in porous rocks and include streaming potential, electro‐osmotic and electrophoretic effects. Geophysical techniques can generate acoustic body waves that stimulate electrokinetic coupling at subsurface boundaries. The electromagnetic effects generated are observed using surface electric field sensors. Improved methodologies, aided by recent modelling of the coupled acoustic and electromagnetic wave equations, are re‐exploring electrokinetic behaviour in the near surface. The methodologies are aimed at providing geophysical tools that may characterize environmentally sensitive parameters such as the fluid content, the fluid geochemistry and the microstructural fabric of the subsurface.
Las Hijas Seamounts—the next Canary Island?
Authors: Rihm Roland , Jacobs Colin L. , Krastel Sebastian , Schmincke Hans‐Ulrich , Alibes Barbara
Published: March 2003

Volcanic structures on the seafloor off the NW African coast between 25°N and 32°N were imaged by GLORIA side scan sonar and SIMRAD EM12 multibeam bathymetry. The newly discovered Las Hijas Seamounts, located 70 km south‐east of Hierro, are interpreted as young volcanic edifices. Their location is consistent with the spacing and timing of propagation of volcanism of the Canary Archipelago and may represent future sites of volcanic islands.
The global network of plate boundaries can be divided into two discrete subnetworks containing the spreading and subduction boundaries, respectively. We advocate that this division is a stable pattern that derives from consistency rules in rigid‐plate rotations. Subduction is distributed along a single, long subnetwork, hence organizing the mantle convection as a single, long downwelling wall and two lower mantle upwelling columns, at the Pacific and African sides of the Earth, respectively. The columns should merge upward between Antarctica and Australia to reach the single, long spreading subnetwork. The flow encircles two toric volumes that escape convectional mixing and are the likely sources of the two, Atlantic–Indian and Pacific, hot spot domains.
Authors: Ricou L.‐E.
Published: March 2003

The global network of plate boundaries can be divided into two discrete subnetworks containing the spreading and subduction boundaries, respectively. We advocate that this division is a stable pattern that derives from consistency rules in rigid‐plate rotations. Subduction is distributed along a single, long subnetwork, hence organizing the mantle convection as a single, long downwelling wall and two lower mantle upwelling columns, at the Pacific and African sides of the Earth, respectively. The columns should merge upward between Antarctica and Australia to reach the single, long spreading subnetwork. The flow encircles two toric volumes that escape convectional mixing and are the likely sources of the two, Atlantic–Indian and Pacific, hot spot domains.
Magnetic anomaly map for Northern, Western, and Eastern Europe*
Authors: Wonik Thomas , Trippler Klaus , Geipel Helmut , Greinwald Siegfried , Pashkevitch Inna
Published: March 2003

All of the available data describing the Earth’s magnetic field in Northern, Western, and Eastern Europe (c. 3 × 106 data points) are compiled and presented at a scale of 1:20 400 000. The compilation meets two requirements (i) that the total field intensity anomalies reflect a survey acquired at an altitude of 3000 m above m.s.l. and during the same epoch, 1980.0; and (ii) that the anomalies are residuals after subtracting the common reference field DGRF1980. As the data span many epochs, geomagnetic data recorded at observatories and repeat stations were used to determine the best model for estimating the secular variation in all data up to 1980. This yielded magnetic anomalies with wavelengths up to the order of 2000 km. The precision of the resultant anomalies (amplitudes about – 1700 nT to 8000 nT) differ between ± 10 nT in Central Europe and ± 20 nT in the outer parts of the compilation.

The resultant anomaly map contains a wealth of information to geoscientists studying global tectonic processes and the deep crustal composition of major continental crusts. It clearly shows the different anomaly patterns between the Palaeozoic and Precambrian crusts of Central and Eastern Europe. These anomalies are interpreted as lateral changes of magnetization in a horizontal plate. A comparison between the low‐level compilation and maps derived from the MAGSAT satellite at about 360 km altitude allows the description of the two different crust types in Europe.
Long‐term uplift rate of the Etna volcano basement (southern Italy) based on biochronological data from Pleistocene sediments
Authors: Di Stefano Agata , Branca Stefano
Published: March 2003

The eastern flank of Mt. Etna volcano rests on Pleistocene marine sediments, which unconformably cover the Apenninic–Maghrebian Chain units. A quantitative biostratigraphic analysis was carried out based on the calcareous nannofossil content of the Pleistocene deposits outcropping along the S and NE periphery of the volcano. Sediments were constrained to the MNN19e and MNN19f biozones, deposited from 1.2 to 0.589 Ma. According to the depth of deposition and the present altitude of the Pleistocene succession, uplift rates are estimated between 1.1 and 1.7 mm yr−1 for the northeastern sector of the Etna edifice, and between 0.36 and 0.61 mm yr−1 for the southern one. This inhomogeneous long‐term uplift rate affecting the Etna region, probably results from a buried thrust below the northern flank of Etna, which is related to the post‐Tortonian geodynamic evolution of NE Sicily.
Magnetic and plagioclase linear fabric discrepancy in dykes: a new way to define the flow vector using magnetic foliation
Authors: Geoffroy L. , Callot J. P. , Aubourg C. , Moreira M.
Published: March 2003

In basaltic dykes the magnetic lineation K1 (maximum magnetic susceptibility axis) is generally taken to indicate the flow direction during solidification of the magma. This assumption was tested in Tertiary basaltic dykes from Greenland displaying independent evidence of subhorizontal flow. The digital processing of microphotographs from thin sections cut in (K1, K2) planes yields the preferred linear orientation of plagioclase, which apparently marks the magma flow lineation. In up to 60% of cases, the angular separation between K1 and the assumed flow direction is greater than 45°. This suggests that the uncorroborated use of magnetic lineations in dykes is risky. A simple geometrical method is proposed to infer the flow vector from AMS in dykes based solely on magnetic foliations.
Nanometre‐scale spheroids on sands, Vulcano, Sicily: possible nannobacterial alteration
Authors: Folk Robert L. , Rasbury Emma T.
Published: March 2003

ABSTRACT Spheroids in the size range of 30–200 nm coat sand grains on sediments around the island of Vulcano. They occur as single individuals, as ball‐shaped clumps resembling biological colonies with radiating chains of bodies, and eventually merge into sheets in which the individual nannobacteria are no longer evident. Rarely, they appear to bore into the glass grains. Older rocks are composed mainly of closely packed nanospheroids. These spheroids are believed to be nannobacterial cells based on their resemblance to nannobacteria found in other surficial environments, and their occurrence in colony‐like groups. If so, nannobacteria play a very important role in the destruction of volcanic materials on Vulcano.
Third‐order depositional sequences controlled by synsedimentary extensional tectonics: evidence from Upper Triassic carbonates of the Carnian Prealps (NE Italy)
Authors: Cozzi Andrea , Hardie Lawrence A.
Published: March 2003

ABSTRACT The Upper Triassic platform‐margin deposits of the Carnian Prealps fail to show the succession of the two global sea‐level lowerings predicted for the Norian and Rhaetian by the Haq global sea‐level curve. In both cases a relative sea‐level rise occurs, a discrepancy that can be explained by an increase in tectonically controlled subsidence, a consequence of the plate‐scale rifting in the NW Tethys Gulf preceding oceanic spreading in the Jurassic. Pulses of tectonic subsidence followed by relative quiescence are capable of generating depositional sequences similar in gross geometry and duration to the third‐order eustatic cycles of Haq et al. The Late Triassic part of the Exxon global sea‐level curve, partly derived from correlatable strata within the same palaeogeographical domain, is likely to reflect pulses of tectonically induced subsidence rather than eustatic sea‐level changes.
The effects of post‐orogenic extension on different scales: an example from the Apennine–Maghrebide fold‐and‐thrust belt, SW Sicily
Authors: Tavarnelli Enrico , Renda Pietro , Pasqui Valeria , Tramutoli Mariano
Published: March 2003

ABSTRACT Many structures produced under one single deformation regime, namely extensional, contractional or strike‐slip, exhibit remarkable geometrical analogies when analysed at different scales. By contrast, field examples that illustrate the scale effects on structures resulting from superimposed deformations, which were produced under different tectonic regimes, are rare. Yet the change from contraction to extension is known to occur often in the most thickened portions of the continental crust. The Apennine–Maghrebide fold‐and‐thrust belt of Sicily shows many examples of post‐orogenic extensional deformations. Composite structures, resulting from late normal faults that offset folds and thrusts, are observed at four different scales, from regional to mesoscopic, in the south‐western portion of Sicily and in the adjacent Isle of Favignana. The recognized analogies in the geometry of these composite structures may provide a key for the interpretation of the features of regional structures, whose deep geometry is often poorly constrained. Moreover, comparison of normalized displacements accommodated by contractional and extensional faults of different scales indicates that self‐similarity is not unique to structures produced under single tectonic regimes.
Promoter elements involved in environmental and developmental control of potato proteinase inhibitor II expression
Authors: Lorberth Ruth , Dammann Christian , Ebneth Marcus , Amati Simone , Sánchez‐Serrano Jose J.
Published: March 2003

The proteinase inhibitor II (pin2) gene family exhibits two different modes of expression. It is, on the one hand, constitutively expressed in flowers of potato and tomato plants, and in potato tubers. On the other hand, its expression is induced in the plant foliage by mechanical wounding. To define cis‐regulatory elements involved in pin2 promoter activity, deletion analysis of a potato pin2 promoter has been performed in stably and transiently transformed potato and tobacco plants. Two different elements, a quantitative enhancer and a regulatory element, are required for promoter activity. While functional promoter elements required for pin2 activity in tubers and wounded leaves could not be separated, its expression in flowers is mediated by different cis‐acting sequences. Induction of pin2 expression in leaves by treatment with the plant growth regulators abscisic acid and jasmonic acid, and the general metabolite sucrose, depends on the presence of the regulatory element involved in expression in tubers and wounded leaves. Thus, pin2 expression in tubers and wounded leaves apparently results from the action of similar hormonal signals on closely linked promoter elements, while a different signal pathway leads to its constitutive expression in flowers.
A nuclear protein binding to dA/dT‐rich sequences upstream from the radish DMA promoter
Authors: Echeverria Manuel , Delcasso‐Tremousaygue Dominique , Delseny Michel
Published: March 2003

The external spacer (ES) of rRNA nuclear genes (rDNA) contains the sequences that control rDNA transcription initiation and enhancement. The ES is also characterized in most species by the presence of multiple repeated elements. In higher plants very few data are available on the cis‐ and fransacting elements which control rDNA transcription. Using electrophoretic mobility shift assays (EMSA) it is shown that nuclear extracts from young radish leaves (NER) contain a protein fraction which binds to specific sequences in the radish ES. DNase I footprinting analysis allows mapping of the NER protein binding to dA/dT homo‐polymer stretches and to a 13‐bp dA/dT‐rich short repeat, found both in the seven approximately 100 bp repeat regions (located ‐1077 to‐740 from transcription initiation site) and the region (‐120 to ‐55) containing the putative promoter for rDNA transcription initiation. Whether this ES binding is due to a single or several different proteins is not known. So far, protein(s) binding to dA/dT‐rich regions of a plant rDNA ES has not yet been described. Whether it is a specific RNA polymerase I transcription factor(s) or plays a more general role in genome expression remains to be elucidated.
Petunia hybrida genes related to the maize regulatory C1 gene and to animal myb proto‐oncogenes
Authors: Avila Julio , Nieto Concepción , Cañas Luis , Benito María Jesús , Paz‐Ares Javier
Published: March 2003

The maize C1 gene is a regulatory gene of the anthocyanin pathway. It is a part of a multigene family whose predicted protein products contain a region with homology to the DNA‐binding domain of myb protooncogene products. Using as a probe an oligonucleotide mixture encoding a highly conserved region in plant MYB proteins, cDNAs encoding three related polypeptides expressed in the flower of Petunia hybrida have been isolated. Predicted proteins are 280–517 amino acids long and shows sequence similarities among themselves as well as with other MYB proteins (45–80% amino acid identity) in the MYB DNA‐binding domain. Outside this domain no significant sequence similarity was found. However, in all cases regions with structural characteristics of activator domains were found. Analysis with Southern blots allowed an estimation of at least 20–30 myb genes in P. hybrida. Expression patterns were specific for each gene as shown by Northern blotting analysis. Subcellular location studies of the largest MYB product, by both immunoblotting of the protein in subcellular fractions and by ‘in situ’ immunolocation experiments, showed that it is a nuclear protein. The role of MYB proteins as transcriptional activators regulating the synthesis of different anthocyanin(flavonoid)‐related compounds is discussed.
Identification of cis elements involved in Commelina yellow mottle virus promoter activity
Authors: Medberry Scott L. , Olszewski Neil E.
Published: March 2003

Commelina yellow mottle virus (CoYMV) is a double‐stranded DNA virus that infects a monocot host. A promoter fragment isolated from CoYMV is a strong promoter when assayed after transient introduction into monocot and dicot suspension cells and is highly active in vascular cells of flowers, leaves, stems and roots of stably transformed tobacco plants. Here it is reported that in stably transformed maize calli and transgenic tobacco leaves the CoYMV and CaMV 35S promoters exhibit similar amounts of activity. Deletion of the sequences located distal to nucleotide −230 relative to the start of transcription has no significant effect on promoter strength or tissue specificity. The region between −230 and −200 shares sequence similarity with the as‐1 promoter element of the CaMV 35S promoter. Deletion of this as‐1‐like motif decreases promoter activity in maize suspension cells by 85%. Analysis of deletions affecting the −200 to −52 region indicates that sequences located between −159 and −84 are required for activity in vascular tissues. In addition, this region exhibits properties of a vascular tissue‐specific enhancer since it confers vascular expression in an orientation‐independent manner when fused to promoters that are not normally active in vascular tissues.
Analysis of a desiccation and ABA‐responsive promoter isolated from the resurrection plant Craterostigma plantagineum
Authors: Michel Detlef , Salamini Francesco , Bartels Dorothea , Dale Phyllis , Baga Monica , Szalay Aladar
Published: March 2003

The resurrection plant Craterostigma plantagineum can recover from severe desiccation within 24 h of contact with water, and it is used as a model system to analyse desiccation tolerance in higher plants. During drying or ABA treatment a specific set of transcripts accumulates rapidly in leaves and other tissues. In order to study transcriptional mechanisms of stress‐induced gene expression one gene (CDeT27‐45) was selected for promoter analysis. Chimeric gene fusions were constructed of the CDeT27‐45 promoter and β‐glucuronidase or luciferase. These constructs were tested in a homologous transient expression system which allowed the identification of promoter elements conferring ABA inducibility. By introducing the chimeric gene fusions into tobacco via Agrobacterium‐mediated transformation we found that the promoter activity is under strict tissue‐specific and developmental control. In tobacco the promoter was only active in developing embryos and in mature pollen grains — two tissues which are naturally desiccation tolerant in tobacco. The specific temporal expression pattern was attributed to particular 5′ upstream sequences. The promoter analysis presented here should allow the separation of important regulatory components as a first step in dissecting events in the signal transduction chain.
Identification of 3‐ and 4‐phosphorylated phosphoinositides and inositol phosphates in stomatal guard cells
Authors: Parmar Paroo Narsi , Brearley Charles Alistair
Published: March 2003

Components of the polyphosphoinositide signalling pathway have been identified in stomatal guard cells of Commelina communis L., one of the few plant systems shown unequivocally to be capable of responding to release of inositol 1,4,5‐trisphosphate in the cytoplasm by increase in cytoplasmic Ca2+. ‘Isolated’ epidermal strips of C. communis (in which all cells other than guard cells have been killed by treatment at low pH) were radiolabelled with myo‐[2n‐3H]inositol or [32P]orthophosphate for 17–18 h. The phosphoinositides and inositol phosphates were extracted. Phosphoinositides were deacylated and the head groups resolved by HPLC. The water‐soluble products generated by mild periodate cleavage of HPLC‐purified, deacylated lipid fractions were examined. The resulting biochemical analysis led to the identification of: PtdIns, PtdIns3P, PtdIns4P, PtdIns(3,4)P2 and PtdIns(4,5)P2. Thex inositol phosphates were resolved by HPLC. Preliminary analysis of HPLC‐purified putative inositol phosphate fractions resulted in the identification of each inositol phosphate class, that is, InsP, InsP2, InsP3, InsP4, InsP5 and InsP6. Many of these inositol phosphates occurred in different isomeric forms. The presence of 3‐phosphorylated phosphoinositides suggests that they may have a role in signalling in stomatal guard cells.
Does the ocs‐element occur as a functional component of the promoters of plant genes?
Authors: Ellis Jeffrey G. , Tokuhisa James G. , Llewellyn Danny J. , Bouchez David , Singh Karam , Dennis Elizabeth S. , Peacock W. James
Published: March 2003

The structural requirements of the ocs‐element, a promoter element in several genes transferred to the host plant nucleus by Agrobacterium tumefaciens and certain DNA viruses, have been further characterized both in vitro and in vivo. Two adjacent and functionally identical protein‐binding sites separated by an exact number of nucleotides are required for in vivo activity of the ocs‐element. Plant pathogens have presumably recruited cellular transcription factors that interact with these binding sites to drive the high‐level expression of their essential genes. Our functional analyses of the ocs‐elements from two pathogen promoters define the structure of a sequence motif that might also be expected to occur in plant nuclear genes, and a search of the plant gene database has identified a number of plant gene promoters that contain sequences that resemble the ocs‐element. These sequences were analysed for their ability both to bind the maize nuclear protein OCSTF and to activate transcription of an inactive promoter. A functional ocs‐element was identified in only one of the plant genes, the soybean heat‐shock gene, Gmhsp26‐A. The apparent rarity of the ocs‐element in plant genes contrasts with its frequent use by pathogens that transform the plant nucleus. Sequences resembling half of an ocs‐element, on the other hand, are common in plant promoters and may form part of multi‐element control motifs with a variety of regulatory functions. Plant pathogens may, therefore, have evolved to circumvent tight regulatory control of their promoters by the host by duplicating the half ocs‐element promoter motifs to take advantage of the ubiquitous ocs‐element‐binding transcription factors in plants.
Interaction between the tobacco DNA‐binding activity CBF and the cyt‐1 promoter element of the Agrobacterium tumefaciens T‐DNA gene T‐CYT correlates with cyt‐1 directed gene expression in multiple tobacco tissue types
Authors: Neuteboom Saskia T.C. , Stoffels Arjan , Hulleman Esther , Memelink Johan , Schilperoort Rob A. , Hoge J. Harry C.
Published: March 2003

A novel DNA‐binding activity, designated CBF, has been identified in nuclear extracts from tobacco leaf, stem and root tissue. CBF interacts specifically with a 30 bp promoter fragment, referred to as cyt‐1, of the Agrobacterium tumefaciens T‐DNA cytokinin (T‐cyt) gene. The T‐cyt promoter, although of bacterial origin is active in planta and the 30 bp cyt‐1 element is located within a region that is essential for T‐cyt promoter activity in leaf, stem and root cells of tobacco plants. Gel retardation assays using different synthetic oligonucleotides and methylation interference experiments pinpointed the binding site of CBF to a GC‐rich sequence ATGCCCCACA within the cyt‐1 element. Site‐directed mutagenesis of the CBF binding site within the T‐cyt promoter by using PCR resulted in an almost complete loss of T‐cyt promoter activity in transgenic tobacco plants. In a gain‐of‐function experiment a hexamer of cyt‐1 was shown to be able to confer leaf, stem and root expression when fused upstream of a TATA box containing −55 derivative of the T‐cyt promoter. A mutant cyt‐1 hexamer, defective in CBF binding, did not show activity above background levels. These results indicate that binding of CBF to the cyt‐1 element is required for cyt‐1 directed gene expression, suggesting that CBF might act as a transcriptional activator. Apart from the ASF‐1 binding site of the CaMV 35S promoter, which is also present in the T‐DNA nopaline and octopine synthase genes, the cyt‐1 element is the only other identified element reported until now that in combination with a TATA box is sufficient to drive gene expression in multiple tobacco tissue types.
The promoter of the Arabidopsis thaliana plastocyanin gene contains a far upstream enhancer‐like element involved in chloroplast‐dependent expression
Authors: Vorst Oscar , Kock Patricia , Lever Alice , Weterings Bettina , Weisbeek Peter , Smeekens Sjef
Published: March 2003

Plastocyanin is part of the photosynthetic electron transport chain in the chloroplast and is encoded in the nucleus. Expression of the Arabidopsis thaliana plastocyanin gene is organ specific: high mRNA levels are observed in young green parts of the plant. Furthermore, expression is dependent on the presence of light and functional chloroplasts. When grown in the presence of norflurazon under white light conditions, resulting in the photo‐oxidative destruction of the chloroplast, plastocyanin mRNA levels are strongly reduced. A −1579 to −9 promoter fragment confers light‐regulated and chloroplast‐dependent expression to the β‐glucuronidase reporter gene in transgenic tobacco plants. This suggests that regulation takes place at the level of transcription. A plastocyanin promoter deletion series ranging from −1579 to −121 which was also tested in tobacco, revealed the presence of a strong positive regulating element (PRE) in the −1579 to −705 region. Deletion of this part of the promoter resulted in a ≈100‐fold reduction of GUS expression as measured in mature leaves. Surprisingly, this enhancer‐like element was capable of stimulating transcription from a position downstream of its reporter. Moreover, it could also activate a truncated CaMV 35S promoter. Deletion of this element coincides with the loss of chloroplast‐dependency of reporter gene expression, as judged by norflurazon treatment of transgenic seedlings. So, the activity of the PRE itself might depend on the presence of functional chloroplasts.
Differential expression of two related amino acid transporters with differing substrate specificity in Arabidopsis thaliana
Authors: Kwart Marion , Hirner Brigitte , Hummel Sabine , Frommer Wolf B.
Published: March 2003

A general amino acid permease cDNA (AAP2) was isolated from Arabidopsis by complementation of a yeast mutant defective in citrulline uptake. Direct transport measurements in yeast show that the protein mediates uptake of l‐[14C]‐citrulline and l‐[14C]‐proline. Detailed analyses of the substrate specificity by competition studies demonstrate that all proteogenic amino acids are recognized by the carrier, including those that represent the major transport forms of reduced nitrogen in many species, i.e. glutamine, glutamate and asparagine. Thus, AAP2 is less selective as compared with AAP1 and transports basic amino acids such as histidine as shown by expression in a histidine transport‐deficient yeast strain. The predicted polypeptide of 53 kDa is highly hydrophobic with 12 putative membrane‐spanning regions and shows significant homologies to the Arabidopsis broad specificity permease AAP1, and a limited homology to bacterial branched chain amino acid transporters, but not to any other known proteins. Alterations in the charged residues as compared with AAP1 in four regions might be involved in the difference in selectivity towards basic amino acids. Both genes are highly expressed in developing pods indicating a role in supplying the developing seeds with reduced nitrogen. AAP2 is selectively expressed in the stem and might therefore play a role in xylem‐to‐phloem transfer of amino acids during seed filling. Furthermore in situ hybridization shows that both genes are expressed in the vascular system of cotyledons in developing seedlings.
Pokeweed antiviral protein inactivates pokeweed ribosomes; implications for the antiviral mechanism
Authors: Bonness Maureen S. , Ready Michael P. , Irvin James D. , Mabry Tom J.
Published: March 2003

Pokeweed antiviral protein (PAP) and other ribosome‐inactivating proteins (RIPs) had previously been thought to be incapable of attacking conspecific ribosomes, thus having no effect on endogenous processes. This assertion conflicts with a model for PAP’s in vivo antiviral mechanism in which PAP (a cell wall protein) selectively enters virus‐infected cells and disrupts protein synthesis, thus causing local suicide and preventing virus replication. We show here that pokeweed (Phytolacca americana) ribosomes, as well as endod (Phytolacca dodecandra) ribosomes, are indeed highly sensitive to inactivation by conspecific RIPs. Ribosomes isolated from RIP‐free pokeweed and endod suspension culture cells were found to be highly active in vitro, as measured by poly(U)‐directed polyphenylalanine synthesis. Phytolacca ribosomes challenged with conspecific RIPs generated doseresponse curves (IC50 of 1 nM PAP or dodecandrin) very similar to those from wheat germ ribosomes. To determine if Phytolacca cells produce a cytosolic ‘anti‐RIP’ protective element, ribosomes were combined with Phytolacca postribosomal supernatant factors from culture cells, then challenged with conspecific RIPs. Resulting IC50 values of 3–7 nM PAP, PAP‐II, PAP‐S or dodecandrin indicate that supernatants from these Phytolacca cells lack a ribosomal protective element. This research demonstrates that PAP inactivates pokeweed ribosomes (and is therefore potentially toxic to pokeweed cells) and supports the local suicide model for PAP’s in vivo antiviral mechanism. The importance of spatial separation between PAP and ribosomes of cells producing this RIP is emphasized, particularly if crop plants are transformed with the PAP gene to confer antiviral protection.
Cytokinin induces the developmentally restricted synthesis of an extracellular protein in Physcomitrella patens
Authors: Neuenschwander Urs , Fleming Andrew J. , Kuhlemeier Cris
Published: March 2003

Early development of the moss Physcomitrella patens follows a simple course leading to the formation of a filamentous protonema containing only two cell‐types, chloronema and caulonema. The addition of the hormone cytokinin leads to the induction of multicellular buds from such protonema. The spectrum of extracellular proteins (ECPs) synthesized by P. patens has been investigated at defined stages of development and under defined hormone treatments. It is found that in contrast to the limited changes in intracellular protein synthesis detectable, in the extracellular environment major and specific changes in the patterns of proteins synthesized occur. For example, the presence of caulonema cells is characterized by the synthesis of a 25 kDa ECP whereas early chloronema differentiation is distinguished by the presence of a 38 kDa ECP. The analysis of the pattern of ECPs synthesized by developmental mutants altered in bud formation, and in response to cytokinin in tunicamycin treated protonema (in which bud induction is blocked) indicate that the synthesis of a 14 kDa ECP is specifically induced by cytokinin. This protein represents a novel cytokinin‐induced ECP.

These data show that the differentiation of particular cell types in plants is associated with the synthesis of particular ECPs, and suggest that hormones which induce specific morphogenic events may do so via the synthesis of specific ECPs.
An anion current at the plasma membrane of tobacco protoplasts shows ATP‐dependent voltage regulation and is modulated by auxin
Authors: Zimmermann Sabine , Thomine Sébastien , Guern Jean , Barbier‐Brygoo Hélène
Published: March 2003

Plasma membrane ion channels of protoplasts from tobacco cell suspensions were characterized by patch‐clamp experiments. In the whole‐cell configuration, a voltage‐dependent current with a current maximum around −90 mV was observed that displayed a reversal potential close to the Nernst potential for chloride. This whole‐cell current was identified as an anion current by replacing the internal Cl− with glutamate. The tobacco suspension anion channel (TSAC) was characterized by fast activation/deactivation and slow inactivation kinetics with voltage‐dependent time constants in the range of milliseconds and seconds, respectively. Among the plant channels, TSAC exhibits original properties in terms of phosphorylation‐dependent voltage regulation while sharing similarities with the fast anion channel from stomatal guard cells (GCAC1). The voltage dependence of the whole‐cell current reflecting the fast deactivation of the current at potentials of less than −100 mV was observed only in the presence of internal ATP or when ATP was replaced by the protein phosphatase inhibitor okadaic acid, and was suppressed by staurosporine. This suggests that protein phosphorylation may be involved in regulating the activity of the anion channel. As observed on GCAC1 the active auxin 1‐NAA caused a time‐ and concentration‐dependent shift of the activation potential of TSAC. In addition, TSAC reacted to the auxin agonist antibody D16 providing evidence for the recognition of the auxin signal at the outer face of the plasma membrane.
The forever young gene encodes an oxidoreductase required for proper development of the Arabidopsis vegetative shoot apex
Authors: Callos Joseph D. , DiRado Marion , Xu Bibo , Behringer Friedrich J. , Link Bruce M. , Medford June I.
Published: March 2003

In plant development, leaf primordia are formed on the flanks of the shoot apical meristem in a highly predictable pattern. The cells that give rise to a primordium are sequestered from the apical meristem. Maintenance of the meristem requires that these cells be replaced by the addition of new cells. Despite the central role of these activities in development, the mechanism controlling and coordinating them is poorly understood. These processes have been characterized in the Arabidopsis mutant forever young (fey). The fey mutation results in a disruption of leaf positioning and meristem maintenance. The predicted FEY protein shares significant homology to a nodulin and limited homology to various reductases. It is proposed that FEY plays a role in communication in the shoot apex through the modification of a factor regulating meristem development.
Induction kinetics of the nuclear proteins encoded by the early indoleacetic acid‐inducible genes, PS‐IAA4/5 and PS‐IAA6, in pea (Pisum sativum L.)
Authors: Oeller Paul W. , Theologis Athanasios
Published: March 2003

The plant hormone indoleacetic acid (IAA) rapidly induces transcription of two genes, PS‐IAA4/5 and PS‐IAA6, in pea that encode nuclear proteins. The proteins were expressed in Escherichia coli and polyclonal antibodies were raised. The proteins can neither be detected on immunoblots of pea extracts from IAA‐treated epicotyls nor subcellularly localized by immunofluorescence, suggesting that they are of low abundance. However, they can be immunoprecipitated as 35S‐methionine‐labeled proteins synthesized in vivo from control and IAA‐treated tissue segments. Short‐term time‐course experiments indicate that the amounts of PS‐IAA4/5 and PS‐IAA6 proteins decrease dramatically in non‐lAA‐treated tissue. However, the hormone slightly increases the PS‐IAA4/5 and significantly enhances the PS‐IAA6 proteins compared with the initial amounts present in the tissue, despite a large induction of both mRNAs. A net increase in the amount of the in vivo synthesized PS‐IAA6 is observed after a lag period of 30 min after addition of IAA. Little or no PS‐IAA4/5 or PS‐IAA6 protein is detected after 6 h of induction, even though PS‐IAA4/5 and PS‐IAA6 mRNAs remain detectable. Immunoprecipitation of in vitro translated polypeptides with mRNAs from various auxin‐treated and untreated mono‐ and dicotyledonous plants reveals that similar proteins are encoded by constitutive or IAA‐induced mRNAs. Phylogenetic analysis of 10 PS‐IAA4‐like proteins from various plant species reveals that the PS‐IAA4 and PS‐IAA6 proteins belong to different lineages, suggesting that they may have distinct functions. The data suggest that as a primary response to IAA plant tissues produce short‐lived nuclear proteins whose synthesis is regulated at the transcriptional and post‐transcriptional levels.
Cell‐to‐cell movement of potato virus X revealed by micro‐injection of a viral vector tagged with the β‐glucuronidase gene
Authors: Angell Susan M. , Baulcombe David C.
Published: March 2003

The replication and cell‐to‐cell movement of potato virus X (PVX) has been studied using a PVX vector construct which expressed the β‐glucuronidase (GUS) reporter gene in infected cells. Nicotiana clevelandii leaf trichome cells were micro‐injected with the PVX‐GUS vector and histochemical staining was used to locate GUS activity. The distribution of GUS activity revealed that PVX had moved from the injected cell into other trichome cells and into the cells along the leaf margin. GUS activity was always restricted to the cells at the edge of the leaf suggesting that PVX was unable to move out of the marginal cells. At the infection front, scattered along the leaf margin, there were isolated groups of cells staining for GUS activity. The absence of GUS activity in the intervening cells suggests that PVX had moved through several cells without replicating within them. This latter observation is consistent with previously reported observations that viral movement proteins are capable of moving between cells.
Early nodulin gene expression during Nod factor‐induced processes in Vicia sativa
Authors: Vijn Irma , Martinez‐Abarca Francisco , Yang Wei‐Cai , das Neves Lucinda , van Brussel Anton , van Kammen Ab , Bisseling Ton
Published: March 2003

Rhizobium leguminosarum bv. viciae‐secreted Nod factors are able to induce root hair deformation, the formation of nodule primordia and the expression of early nodulin genes in Vicia sativa (vetch). To obtain more insight into the mode of action of Nod factors the expression of early nodulin genes was followed during Nod factor‐induced root hair deformation and nodule primordium formation. The results of these studies suggested that the expression of VsENOD5 and VsENOD12 is not required for root hair deformation. In the Nod factor‐induced primordia both VsENOD12 and VsENOD40 are expressed in a spatially controlled manner similar to that found in Rhizobium‐induced nodule primordia. In contrast, VsENOD5 expression has never been observed in Nod factor‐induced primordia, showing that the induction of VsENOD5 and VsENOD12 expression are not coupled. VsENOD5 expression is induced in the root epidermis by Nod factors and in Rhizobium‐induced nodule primordia only in cells infected by the bacteria, suggesting that the Nod factor does not reach the inner cortical cells.
The CIC library: a large insert YAC library for genome mapping in Arabidopsis thaliana
Authors: Creusot Francine , Fouilloux Eric , Dron Michel , Lafleuriel Jacqueline , Picard Georges , Billault Alain , Le Paslier Denis , Cohen Daniel , Chabouté Marie‐Edith , Durr Andrée , Fleck Jacqueline , Gigot Claude , Camilleri Christine , Bellini Catherine , Caboche Michel , Bouchez David
Published: March 2003

A new Arabidopsis thaliana (ecotype Columbia) genomic library has been constructed in Yeast Artificial Chromosomes: the CIC library (for CEPH, INRA and CNRS). Optimization of plant culture conditions and protoplast preparation allowed the recovery of large amounts of viable protoplasts. Mechanical shearing of DNA was minimized by isolation of DNA from protoplasts embedded in agarose. Cloning of large inserts was favored by including two successive size fractionation steps (after partial EcoRI digestion and after ligation with the vector arms), which selected DNA fragments larger than 350 kb. The library consists of 1152 clones with an average insert size of 420 kb. Clones carrying chloroplast DNA and various nuclear repeated sequences have been identified. Twenty‐one per cent of the clones are found to contain chloroplast DNA. Therefore, the library represents around four nuclear genome equivalents. The clones containing 5S rDNA genes, 18S‐25S rDNA sequences and the 180 bp paracentromeric repeated element account for 3.6%, 8.9% and 5.8%, respectively. Only one clone was found to carry the 160 bp paracentromeric repeated element. Given the smaller size of clones carrying Arabidopsis repeated DNA, the average size of remaining clones is around 480 kb. The library was screened by PCR amplification using pairs of primers corresponding to sequences dispersed in the genome. Seventy out of 76 pairs of primers identified from one to seven YAC clones. Thus at least 92% of the genome is represented in the CIC library. The survey of the library for clones containing unlinked DNA sequences indicates that the proportion of chimeric clones is lower than 10%.
Identification of amplified restriction fragment polymorphism (AFLP) markers tightly linked to the tomato Cf‐9 gene for resistance to Cladosporium fulvum
Authors: Thomas Colwyn M. , Vos Pieter , Zabeau Marc , Jones David A. , Norcott Karen A. , Chadwick Brian P. , Jones Jonathan D.G.
Published: March 2003

Using the technique of amplified restriction fragment polymorphism (AFLP) analysis, and bulked segregant pools from F2 progeny of the cross Lycopersicon esculentum (Cf9)×L. pennellii, approximately 42 000 AFLP loci for tight linkage to the tomato Cf‐9 gene for resistance to Cladosporium fulvum have been screened. Analysis of F2 recombinants identified three markers which co‐segregated with Cf‐9. The Cf‐9 gene has recently been isolated by transposon tagging using the maize transposon Dissociation (Ds). Analysis of plasmid clones containing Cf‐9 shows that two of these markers are located on opposite sides of the gene separated by 15.5 kbp of intervening DNA. AFLP analysis provides a rapid and efficient technique for detecting large numbers of DNA markers and should expedite plant gene isolation by positional cloning and the construction of high‐density molecular linkage maps of plant genomes.
Morphogenesis in pinoid mutants of Arabidopsis thaliana
Authors: Bennett Sally R.M. , Alvarez John , Bossinger Gerd , Smyth David R.
Published: March 2003

A series of mutants of Arabidopsis thaliana was selected in which the inflorescence stem elongates but loses the ability to produce flower primordia on its flanks. Mutants fell into two classes, further occurrences of pin‐formed mutants and mutations at a new locus named pinoid. As well as causing inflorescence defects, pinoid mutations result in pleiotropic defects in the development of floral organs, cotyledons and leaves. Most changes involve the number of organs produced rather than their differentiation suggesting that PINOID controls an early general step in meristem development. pinoid mutant defects are similar to those seen in pin‐formed mutants for inflorescences and flowers, but different for cotyledons and leaves indicating that the two genes have separate but overlapping functions. A defect in polar auxin transport is implicated in the pin‐formed mutant phenotype, but in young inflorescence stems of even the strongest pinoid mutants it occurs at close to wild‐type levels. It is markedly reduced only after stems have ceased elongating. Thus, it is likely that polar auxin transport is secondarily affected in pinoid mutants rather than being directly controlled by the PINOID gene product. Even so, double mutant studies indicate that the process controlled by PINOID overlaps with that specified by the AUXIN RESISTANT1 gene, suggesting that PINOID plays some role in an auxin‐related process.
Blue and UV‐A light‐regulated CHS expression in Arabidopsis independent of phytochrome A and phytochrome B
Authors: Batschauer Alfred , Rocholl Martin , Kaiser Thomas , Nagatani Akira , Furuya Masaki , Schäfer Eberhard
Published: March 2003

Light plays a fundamental role in the development of higher plants. It influences the activity of many genes and is sensed through at least three different photoreceptor systems (phytochromes, blue/UV‐A‐ and UV‐B photoreceptors). In contrast to UV‐B and blue/UV‐A photoreceptors, phytochromes absorb both in the long‐wavelength (red and far‐red) and short‐wavelength region of light, making it extremely difficult to differentiate the exact function of different photoreceptors in the blue/UV region. The availability of phytochrome mutants in combination with a transgenic approach has enabled clarification of the question whether or not phytochromes are a prerequisite for the action of blue/UV‐A photoreceptors on gene expression. This paper reports that the light‐responsive element of a gene encoding chalcone synthase, the key enzyme of the flavonoid pathway, mediates blue‐ and UV‐A‐induced transcription in the absence of phytochrome A and phytochrome B.
Variegation and silencing of the Heat Shock Cognate 80 gene are relieved by a bipartite downstream regulatory element
Authors: Chinn Anna M. , Payne Shannon R. , Comai Luca
Published: March 2003

Transgenes are important tools for plant molecular biologists. However, some aspects of their regulation are not completely understood. First, the contribution of elements separate from the promoter has been documented for several genes, but a general requirement for such elements is still unclear. Second, transgene expression can be subject to variability from chromosomal position effects and from epigenetic effects, often due to the presence of repeated sequences. While studying the regulation of the developmentally expressed Heat Shock Cognate 80(HSC80) gene, several peculiarities were found which involve both of these questions. First, HSC80 transgenes are subject to silencing and variegation at a high frequency. Second, a bipartite element downstream of the transcriptional start is necessary to achieve efficient expression from the HSC80 promoter in stable transformants. Finally, this bipartite element is not required for expression in a transient system, where the promoter alone is sufficient. These results together support a role for chromatin structure in the regulation of HSC80.