bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conifer reproductive development involves B‐type MADS‐box genes with distinct and different activities in male organ primordia
Authors: Sundström Jens , Engström Peter 
Published: March 2003

SummaryThe Norway spruce MADS‐box genes DAL11, DAL12 and DAL13 are phylogenetically related to the angiosperm B‐function MADS‐box genes: genes that act together with A‐function genes in specifying petal identity and with C‐function genes in specifying stamen identity to floral organs. In this report we present evidence to suggest that the B‐gene function in the specification of identity of the pollen‐bearing organs has been conserved between conifers and angiosperms. Expression of DAL11 or DAL12 in transgenic Arabidopsis causes phenotypic changes which partly resemble those caused by ectopic expression of the endogenous B‐genes. In similar experiments, flowers of Arabidopsis plants expressing DAL13 showed a different homeotic change in that they formed ectopic anthers in whorls one, two or four. We also demonstrate the capacity of the spruce gene products to form homodimers, and that DAL11 and DAL13 may form heterodimers with each other and with the Arabidopsis B‐protein AP3, but not with PI, the second B‐gene product in Arabidopsis. In situ hybridization experiments show that the conifer B‐like genes are expressed specifically in developing pollen cones, but differ in both temporal and spatial distribution patterns. These results suggest that the B‐function in conifers is dual and is separated into a meristem identity and an organ identity function, the latter function possibly being independent of an interaction with the C‐function. Thus, even though an ancestral B‐function may have acted in combination with C to specify micro‐ and megasporangia, the B‐function has evolved differently in conifers and angiosperms.
Two distantly related genes encoding 1‐deoxy‐d‐xylulose 5‐phosphate synthases: differential regulation in shoots and apocarotenoid‐accumulating mycorrhizal roots
Authors: Walter Michael H. , Hans Joachim , Strack Dieter 
Published: March 2003

SummaryIsopentenyl diphosphate, the universal precursor of isoprenoids, is synthesized by two separate routes, one in the cytosol and the other in plastids. The initial step of the plastidial pathway is catalysed by 1‐deoxy‐d‐xylulose 5‐phosphate synthase (DXS), which was previously thought to be encoded by a single‐copy gene. We have identified two distinct classes of DXS‐like cDNAs from the model legume Medicago truncatula. The deduced mature MtDXS1 and MtDXS2 proteins, excluding the predicted plastid‐targeting peptides, are similar in size (72.7 and 71.2 kDa) yet share only 70% identity in their amino acid sequences, and both encode functional DXS proteins as shown by heterologous expression in Escherichia coli. Available DXS sequences from other plants can easily be assigned to either class 1 or class 2. Partial sequences of multiple DXS genes in a single genome may be found in the databases of several monocot and dicot plants. Blot analyses of RNA from M. truncatula, maize, tomato and tobacco demonstrate preferential expression of DXS1 genes in many developing plant tissues except roots. By contrast, DXS2 transcript levels are low in most tissues but are strongly stimulated in roots upon colonization by mycorrhizal fungi, correlated with accumulation of carotenoids and apocarotenoids. Monoterpene‐synthesizing gland cells of leaf trichomes appear to be another site of DXS2 gene activity. The potential importance of DXS1 in many housekeeping functions and a still hypothetical role of DXS2 in the biosynthesis of secondary isoprenoids is discussed.
Insect‐resistant transgenic plants in a multi‐trophic context
Authors: Groot Astrid T. , Dicke Marcel 
Published: March 2003

SummarySo far, genetic engineering of plants in the context of insect pest control has involved insertion of genes that code for toxins, and may be characterized as the incorporation of biopesticides into classical plant breeding. In the context of pesticide usage in pest control, natural enemies of herbivores have received increasing attention, because carnivorous arthropods are an important component of insect pest control. However, in plant breeding programmes, natural enemies of herbivores have largely been ignored, although there are many examples that show that plant breeding affects the effectiveness of biological control. Negative influences of modified plant characteristics on carnivorous arthropods may induce population growth of new, even more harmful pest species that had no pest status prior to the pesticide treatment. Sustainable pest management will only be possible when negative effects on non‐target, beneficial arthropods are minimized. In this review, we summarize the effects of insect‐resistant crops and insect‐resistant transgenic crops, especially Bt crops, from a food web perspective. As food web components, we distinguish target herbivores, non‐target herbivores, pollinators, parasitoids and predators. Below‐ground organisms such as Collembola, nematodes and earthworms should also be included in risk assessment studies, but have received little attention. The toxins produced in Bt plants retain their toxicity when bound to the soil, so accumulation of these toxins is likely to occur. Earthworms ingest the bound toxins but are not affected by them. However, earthworms may function as intermediaries through which the toxins are passed on to other trophic levels. In studies where effects of insect‐resistant (Bt) plants on natural enemies were considered, positive, negative and no effects have been found. So far, most studies have concentrated on natural enemies of target herbivores. However, Bt toxins are structurally rearranged when they bind to midgut receptors, so that they are likely to lose their toxicity inside target herbivores. What happens to the toxins in non‐target herbivores, and whether these herbivores may act as intermediaries through which the toxins may be passed on to the natural enemies, remains to be studied.
A novel cold‐inducible gene from Arabidopsis, RCI3, encodes a peroxidase that constitutes a component for stress tolerance
Authors: Llorente Francisco , López‐Cobollo Rosa María , Catalá Rafael , Martínez‐Zapater José Miguel , Salinas Julio 
Published: March 2003

SummaryA cDNA from Arabidopsis corresponding to a new cold‐inducible gene, RCI3 (for Rare Cold Inducible gene 3), was isolated. Isoelectric focusing electrophoresis and staining of peroxidase activity demonstrated that RCI3 encodes an active cationic peroxidase. RNA‐blot analysis revealed that RCI3 expression in response to low temperature is negatively regulated by light, as RCI3 transcripts were exclusively detected in etiolated seedlings and roots of adult plants. RCI3 expression was also induced in etiolated seedlings, but not in roots, exposed to dehydration, salt stress or ABA, indicating that it is subjected to a complex regulation through different signaling pathways. Analysis of transgenic plants containing RCI3::GUS fusions established that this regulation occurs at the transcriptional level during plant development, and that cold‐induced RCI3 expression in roots is mainly restricted to the endodermis. Plants overexpressing RCI3 showed an increase in dehydration and salt tolerance, while antisense suppression of RCI3 expression gave dehydration‐ and salt‐sensitive phenotypes. These results indicate that RCI3 is involved in the tolerance to both stresses in Arabidopsis, and illustrate that manipulation of RCI3 has a potential with regard to plant improvement of stress tolerance.
Two long‐chain acyl‐CoA synthetases from Arabidopsis thaliana involved in peroxisomal fatty acid β‐oxidation
Authors: Fulda Martin , Shockey Jay , Werber Martin , Wolter Frank P. , Heinz Ernst 
Published: March 2003

SummaryPost‐germinative growth of oilseeds is dependent on the breakdown of the stored lipid reserves. Long‐chain acyl‐CoA synthetase activities (LACS) are critically involved in this process by activating the released free fatty acids and thus feeding the β‐oxidation cycle in glyoxysomes. Here we report on the identification of two LACS genes, AtLACS6 and AtLACS7 from Arabidopsis thaliana coding for peroxisomal LACS proteins. The subcellular localization was verified by co‐expression studies of spectral variants of the green fluorescent protein (GFP). While AtLACS6 is targeted by a type 2 (PTS2) peroxisomal targeting sequence, for AtLACS7 a functional PTS1 as well as a PTS2 could be demonstrated. Possible explanations for this potentially redundant targeting information will be discussed. Expression studies of both genes revealed a strong induction 1 day after germination resembling the expression pattern of other genes involved in β‐oxidation. Analysis of the substrate specificities of the two LACS proteins demonstrated enzymatic activity for both enzymes with the whole spectrum of fatty acids found in stored lipid reserves. These results suggest that both LACS proteins might have overlapping functions and are able to initiate β‐oxidation in plant peroxisomes.
Nuclear genes that promote splicing of group I introns in the chloroplast 23S rRNA and psbA genes in Chlamydomonas reinhardtii
Authors: Li Fei , Holloway Stephen P. , Lee Jaesung , Herrin David L. 
Published: March 2003

SummarySingle nucleotide substitutions were made in the core helices P4, P6, and P7, and in the metal‐binding GAAA motif in the J4/5 region of the chloroplast group I rRNA intron of Chlamydomonas reinhardtii, Cr.LSU. In vitro assays showed that these substitutions had surprisingly strong effects on Cr.LSU self‐splicing; however, splicing of all but the P6 mutations could be at least partially recovered by increasing the Mg2+ concentration. The mutant constructs were transformed into chloroplasts to replace the wild‐type intron; however, only the P4 mutants became homoplasmic, indicating that the other mutations were lethal. The splicing‐deficient P4125A mutant, which exhibited slow growth and light sensitivity, was used to isolate suppressor strains that showed a substantial restoration of Cr.LSU splicing. Genetic analysis of the 7151, 7120 and 71N1 suppressors indicated that these mutations are in at least two nuclear genes. The 7151 suppressor mutation, which defines the chloroplast‐splicing suppressor (css1) gene, had no obviously altered growth phenotype with the wild‐type intron, and was dominant in vegetative diploids containing the mutant intron. All three of the suppressor strains also suppressed a mutation in the P4 region of the fourth psbA intron, Cr.psbA4, indicating that these genes play a role in splicing of multiple group I introns in the chloroplast.
The auxin influx carrier is essential for correct leaf positioning
Authors: Stieger Pia A. , Reinhardt Didier , Kuhlemeier Cris 
Published: March 2003

SummaryAuxin is of vital importance in virtually every aspect of plant growth and development, yet, even after almost a century of intense study, major gaps in our knowledge of its synthesis, distribution, perception, and signal transduction remain. One unique property of auxin is its polar transport, which in many well‐documented cases is a critical part of its mode of action. Auxin is actively transported through the action of both influx and efflux carriers. Inhibition of polar transport by the efflux inhibitorN‐1‐naphthylphthalamic acid (NPA) causes a complete cessation of leaf initiation, a defect that can be reversed by local application of the auxin, indole‐3‐acetic acid (IAA), to the responsive zone of the shoot apical meristem. In this study, we address the role of the auxin influx carrier in the positioning and outgrowth of leaf primordia at the shoot apical meristem of tomato. By using a combination of transport inhibitors and synthetic auxins, we demonstrate that interference with auxin influx has little effect on organ formation as such, but prevents proper localization of leaf primordia. These results suggest the existence of functional auxin concentration gradients in the shoot apical meristem that are actively set up and maintained by the action of efflux and influx carriers. We propose a model in which efflux carriers control auxin delivery to the shoot apical meristem, whereas influx and efflux carriers regulate auxin distribution within the meristem.
Mutation in domain II of IAA1 confers diverse auxin‐related phenotypes and represses auxin‐activated expression of Aux/IAA genes in steroid regulator‐inducible system
Authors: Park Jin‐Young , Kim Hye‐Joung , Kim Jungmook 
Published: March 2003

SummaryMost of Aux/IAA genes are rapidly induced by auxin. The Aux/IAA proteins are short‐lived nuclear proteins sharing the four conserved domains. Domain II is critical for rapid degradation of Aux/IAA proteins. Among these gene family members, IAA1 is one of the earliest auxin‐inducible genes. We used a steroid hormone‐inducible system to reveal putative roles and downstream signaling of IAA1 in auxin response. Arabidopsis transgenic plants were generated expressing fusion protein of IAA1 (IAA1‐GR) or IAA1 with a mutation in domain II (iaa1‐GR) and the glucocorticoid hormone‐binding domain (GR). IAA1‐GR transgenic plants did not exhibit any discernable phenotypic differences by DEX treatment that allows nuclear translocation of the fusion protein. In contrast, diverse auxin‐related physiological processes including gravitropism and phototropism were impaired by DEX treatment in roots, hypocotyls, stems, and leaves in iaa1‐GR transgenic plants. Auxin induction of seven Aux/IAA mRNAs including IAA1 itself was repressed by DEX treatment, suggesting that IAA1 functions in the nucleus by mediating auxin response and might act as a negative feedback regulator for the expression of Aux/IAA genes including IAA1 itself. Auxin induction of Aux/IAA genes in the presence of cycloheximide can be repressed by DEX treatment, showing that the repression of transcription of the Aux/IAAs by the iaa1 mutant protein is primary. Wild‐type IAA1‐GR could not suppress auxin induction of IAA1 and IAA2. These results indicate that inhibition of auxin‐activated transcription of Aux/IAA genes by the iaa1 mutant protein might be responsible for alteration of various auxin responses.
pistillata‐5, anArabidopsisB class mutant with strong defects in petal but not in stamen development
Authors: Yang Yingzhen , Xiang Hongjun , Jack Thomas 
Published: March 2003

SummaryTheArabidopsisfloral organ identity genesAPETALA3(AP3) andPISTILLATA(PI) encode related DNA‐binding proteins of the MADS family. Considerable evidence supports the hypothesis that a heterodimer of AP3 and PI is an essential component of B class activity. Allap3andpialleles characterized to date exhibit equivalent phenotypic defects in both whorls 2 and 3. In strongap3andpimutants, petals and stamens are missing and sepals and carpels develop in their place. Weakap3andpimutants exhibit partial conversions of petals to sepals and stamens to carpels. In this report, we describe the isolation and characterization ofpi‐5,an unusual B class mutant that exhibits defects in whorl 2 where sepals develop in place of petals, but third whorl stamens are most often normal.pi‐5flowers resemble those from 35S::SEP3 antisense plants.pi‐5contains missense mutation in the K domain (PIE125K). PIE125Kexhibits defects in heterodimerization with its partner protein AP3. Via a reverse yeast two‐hybrid screen, AP3K139Ewas isolated as a compensatory mutant of PIE125K. The compensatory interaction between PIE125Kand AP3K139Eis observed both in yeast two‐hybrid assays andin planta. On its own, AP3K139Eexhibits defects in specifying both petal and stamen identity. In addition, PIE125Kis defective in interaction with SEPALLATA proteins in both two‐ and three‐hybrid assays suggesting that PIE125Kis defective in forming higher order complexes of MADS proteins. The decreased concentration of PI/AP3/SEP complexes offers an explanation for the petal defects observed in bothpi‐5and 35S::SEP3 antisense plants.
Transcriptome analysis of sulfur depletion in Arabidopsis thaliana: interlacing of biosynthetic pathways provides response specificity
Authors: Nikiforova Victoria , Freitag Jens , Kempa Stefan , Adamik Monika , Hesse Holger , Hoefgen Rainer 
Published: March 2003

SummaryHigher plants assimilate inorganic sulfate into cysteine, which is subsequently converted to methionine, and into a variety of other sulfur‐containing organic compounds. To resist sulfur deficiency, plants must demonstrate physiological flexibility: the expression of an extensive set of genes and gene regulators that act in the affected pathways or signalling cascades must be delicately tuned in response to environmental challenges. To elucidate this network of interactions, we have applied an array hybridisation/transcript profiling method to Arabidopsis plants subjected to 6, 10 and 13 days of constitutive and induced sulfur starvation. The temporal expression behaviour of approximately 7200 non‐redundant genes was analysed simultaneously. The experiment was designed in a way to identify statistically significant changes of gene expression based on sufficient numbers of repeated hybridisations performed with five uniform pools of plant material. The expression profiles were processed to select differentially expressed genes. Among the 1507 sulfur‐responsive clones implicated in this way, 632 genes responded specifically to sulfur deficiency by significant over‐expression. The sulfur‐responsive genes were grouped according to functional categories or biosynthetic pathways. As expected, genes of the sulfur assimilation pathway were altered in expression. Furthermore, genes involved in flavonoid, auxin, and jasmonate biosynthesis pathways were upregulated in conditions of sulfur deficiency. Based on the correlative analysis of gene expression patterns, we suggest that a complex co‐ordination of systematic responses to sulfur depletion is provided via integration of flavonoid, auxin and jasmonate pathway elements. Plait concept for transduction of specificity via the main non‐specific signalling stream is proposed.
Arabidopsis phosphatidylglycerophosphate synthase 1 is essential for chloroplast differentiation, but is dispensable for mitochondrial function
Authors: Babiychuk Elena , Müller Frank , Eubel Holger , Braun Hans‐Peter , Frentzen Margrit , Kushnir Sergei 
Published: March 2003

SummaryGenetic dissection of the lipid bilayer composition provides essential in vivo evidence for the role of individual lipid species in membrane function. To understand the in vivo role of the anionic phospholipid, phosphatidylglycerol, the loss‐of‐function mutation was identified and characterized in the Arabidopsis thaliana gene coding for phosphatidylglycerophosphate synthase 1, PGP1. This mutation resulted in pigment‐deficient plants of the xantha type in which the biogenesis of thylakoid membranes was severely compromised. The PGP1 gene coded for a precursor polypeptide that was targeted in vivo to both plastids and mitochondria. The activity of the plastidial PGP1 isoform was essential for the biosynthesis of phosphatidylglycerol in chloroplasts, whereas the mitochondrial PGP1 isoform was redundant for the accumulation of phosphatidylglycerol and its derivative cardiolipin in plant mitochondrial membranes. Together with findings in cyanobacteria, these data demonstrated that anionic phospholipids play an important, evolutionarily conserved role in the biogenesis and function of the photosynthetic machinery. In addition, mutant analysis suggested that in higher plants, mitochondria, unlike plastids, could import phosphatidylglycerol from the endoplasmic reticulum.
Risk of hepatitis C infection in neonates transfused with blood from donors infected with hepatitis C
Authors: O'Riordan  , Conroy  , Nourse  , Yap  , McDonald  , Kaminski  , Leong  , Lawlor  , Davoren  , Strong  , Davidson  , Lloyd  , Power  
Published: March 2003

This look‐back study was undertaken to identify newborn infants who had been infected with the hepatitis C virus (HCV) as a result of transfusions received before the introduction of routine screening in 1991 and to determine the transmission rates and persistence of transfusion‐transmitted HCV infection acquired in the neonatal period.A total of 24 infants, transfused between 1980 and 1991, were identified as having received potentially infected blood from 11 blood donors. Ten of the donors had been administered batches of anti‐D in 1977 known to have transmitted HCV genotype 1b infection. HCV RNA was detected in five of these donors when tested in 1994–95; the past donations of five of the donors, who had received anti‐D immunoglobulin and had serological evidence of previous HCV infection but who were PCR negative when tested in 1994–95, were considered of lower risk. The source and time of acquisition of HCV infection for the one remaining donor in the study was not determined.Twenty‐one (88%) of the 24 children were living at time of lookback. The median age at transfusion was 12 days. The median age at time of testing was 6.3 years. One child, who tested negative, was excluded from further analysis of HCV transmission, due to incomplete transfusion records. Overall, 12 of 20 (60%) children tested were positive for anti‐HCV and seven (35%) were HCV RNA positive. Twelve (71%) of the 17 recipients of viraemic blood were ELISA positive and seven (41%) were PCR positive. Resolved HCV infection, as determined by ELISA pos, RIBA pos or indeterminate and PCR negativity, occurred in five of 12 (42%). In many instances there was more than one recipient per HCV infected donation. All of the reported children are clinically asymptomatic. However, the duration of HCV infection is relatively short and there is evidence of a degree of hepatitis in five of the seven children who are HCV RNA positive as judged by mildly elevated transaminase levels. The three who have undergone liver biopsy show mild hepatitis.The lower rates of persistence of HCV infection in this study may be due to the young age at exposure or to the source of infection which for all but one of the children was linked to one HCV genotype from female donors. Sharing of units of blood among multiple infants should be discouraged.
Neonatal alloimmune thrombocytopenia (NATP) caused by anti‐BAKa (HPA‐3a) maternal antibody detectable only in reactions with intact platelets
Authors: Curtis B. R. , McFarland J. G. , Harrison C. R. , Ebert D. D. , Aster R. H. 
Published: March 2003

The first child of pt 1 (NZ) was born with generalized petechiae and a platelet count of 9000/µL. Three random‐platelet transfusions were given during the first week, and the platelet count rose to normal about Day 10. Pt 2 (AG) had given birth to an infant with severe thrombocytopenia 11 years previously. At 22 weeks of her second pregnancy, an umbilical vein platelet count was 56,000/µL. IV IgG was given and she was delivered at 38 weeks of an infant with extensive ecchymoses and a platelet count of 6000/µL. The infant was given IV IgG and three transfusions of washed maternal platelets, but achieved a stable platelet count in the normal range only after 44 days.By DNA‐based typing, both mothers were HPA‐3b/b and both fathers were HPA 3a/a. No other maternal/paternal incompatibilities were found. In flow cytometry, sera from both mothers reacted with platelets positive for HPA‐3a (Baka) and failed to react with platelets homozygous for HPA‐3b. On repeated occasions, however, the sera failed to give positive reactions against HPA‐3a positive platelets in MAIPA, modified antigen capture ELISA (MACE) and antigen capture ELISA (ACE), in contrast to other anti‐HPA‐3a abs. Negative reactions were also obtained when the mild detergent octyl glucoside was used for platelet lysis, rather than Triton X‐100.The findings indicate that these two alloantibodies recognize an epitope that is present on GPIIb/IIIa in its native state but is lost when platelets are lysed, even with mild detergent. In these cases, the antibodies were detected on the basis of their reactions with intact platelets in flow cytometry but this would not have been possible if HLA antibodies, often found in pregnant women, had been present.