bluuebunny/crossref_metadata_2025 huggingface dataset:
Ssn6–Tup1 interacts with class I histone deacetylases required for repression
Authors: Watson Anjanette D. , Edmondson Diane G. , Bone James R. , Mukai Yukio , Yu Yaxin , Du Wendy , Stillman David J. , Roth Sharon Y.
Published: July 2002

Ssn6–Tup1 regulates multiple genes in yeast, providing a paradigm for corepressor functions. Tup1 interacts directly with histones H3 and H4, and mutation of these histones synergistically compromises Ssn6–Tup1-mediated repression. In vitro, Tup1 interacts preferentially with underacetylated isoforms of H3 and H4, suggesting that histone acetylation may modulate Tup1 functions in vivo. Here we report that histone hyperacetylation caused by combined mutations in genes encoding the histone deacetylases (HDACs) Rpd3, Hos1, and Hos2 abolishes Ssn6–Tup1 repression. Unlike HDAC mutations that do not affect repression, this combination of mutations causes concomitant hyperacetylation of both H3 and H4. Strikingly, two of these class I HDACs interact physically with Ssn6–Tup1. These findings suggest that Ssn6–Tup1 actively recruits deacetylase activities to deacetylate adjacent nucleosomes and promote Tup1–histone interactions.
The endoribonuclease activity of mammalian IRE1 autoregulates its mRNA and is required for the unfolded protein response
Authors: Tirasophon Witoon , Lee Kyungho , Callaghan Brian , Welihinda Ajith , Kaufman Randal J.
Published: July 2002

The unfolded protein response (UPR) is a signal transduction pathway that is activated by the accumulation of unfolded proteins in the endoplasmic reticulum (ER). In Saccharomyces cerevisiae the ER transmembrane receptor, Ire1p, transmits the signal to the nucleus culminating in the transcriptional activation of genes encoding an adaptive response. Yeast Ire1p requires both protein kinase and site-specific endoribonuclease (RNase) activities to signal the UPR. In mammalian cells, two homologs, Ire1α and Ire1β, are implicated in signaling the UPR. To elucidate the RNase requirement for mammalian Ire1 function, we have identified five amino acid residues within IRE1α that are essential for RNase activity but not kinase activity. These mutants were used to demonstrate that the RNase activity is required for UPR activation by IRE1α and IRE1β. In addition, the data support that IRE1 RNase is activated by dimerization-induced trans-autophosphorylation and requires a homodimer of catalytically functional RNase domains. Finally, the RNase activity of wild-type IRE1α down-regulates hIre1α mRNA expression by a novel mechanism involving cis-mediated IRE1α-dependent cleavage at three specific sites within the 5′ end of Ire1α mRNA.
Essential role of BETA2/NeuroD1 in development of the vestibular and auditory systems
Authors: Liu Min , Pereira Fred A. , Price Steven D. , Chu Mei-jin , Shope Cindy , Himes Donna , Eatock Ruth Anne , Brownell William E. , Lysakowski Anna , Tsai Ming-Jer
Published: July 2002

BETA2/NeuroD1 is a bHLH transcription factor that is expressed during development in the mammalian pancreas and in many locations in the central and peripheral nervous systems. During inner ear ontogenesis, it is present in both sensory ganglion neurons and sensory epithelia. Although studies have shown thatBETA2/NeuroD1 is important in the development of the hippocampal dentate gyrus and the cerebellum, its functions in the peripheral nervous system and in particular in the inner ear are unclear. Mice carrying a BETA2/NeuroD1 null mutation exhibit behavioral abnormalities suggestive of an inner ear defect, including lack of responsiveness to sound, hyperactivity, head tilting, and circling. Here we show that these defects can be explained by a severe reduction of sensory neurons in the cochlear-vestibular ganglion (CVG). A developmental study of CVG formation in the null demonstrates that BETA2/NeuroD1 does not play a primary role in the proliferation of neuroblast precursors or in their decision to become neuroblasts. Instead, the reduction in CVG neuron number is caused by a combination both of delayed or defective delamination of CVG neuroblast precursors from the otic vesicle epithelium and of enhanced apoptosis both in the otic epithelium and among those neurons that do delaminate to form the CVG. There are also defects in differentiation and patterning of the cochlear duct and sensory epithelium and loss of the dorsal cochlear nucleus. BETA2/NeuroD1 is, thus, the first gene to be shown to regulate neuronal and sensory cell development in both the cochlear and vestibular systems.
KNOX homeodomain protein directly suppresses the expression of a gibberellin biosynthetic gene in the tobacco shoot apical meristem
Authors: Sakamoto Tomoaki , Kamiya Noriko , Ueguchi-Tanaka Miyako , Iwahori Shuichi , Matsuoka Makoto
Published: July 2002

To identify genes targeted by the tobacco KNOX homeodomain protein,Nicotiana tabacum homeobox 15 (NTH15), we have generated an inducible system using the human glucocorticoid receptor. In this system, steroid treatment strictly induced NTH15 function and immediately suppressed the expression of a gibberellin (GA) biosynthetic gene encoding GA 20-oxidase (Ntc12) and also resulted in a decrease in bioactive GA levels. The repression ofNtc12 was observed even when indirect effects were blocked by cycloheximide. NTH15 mRNA was present in corpus cells of the shoot apical meristem (SAM), whereas Ntc12 mRNA was observed in leaf primordia and rib meristem but not in the corpus. Recombinant NTH15 protein strongly bound to a 5-bp dyadsymmetric sequence, GTGAC, in the first intron of Ntc12 in vitro. Mutation of this sequence in the Ntc12 gene abolished the NTH15-dependent suppression of Ntc12 in the corpus of the SAM. Our results indicate that NTH15 directly represses Ntc12 expression in the corpus of the wild-type SAM to maintain the indeterminate state of corpus cells. The suppression of NTH15 within cells at the flanks of the SAM permits GA biosynthesis, which promotes organized cell proliferation and consequently induces the determination of cell fate.
FIH-1: a novel protein that interacts with HIF-1α and VHL to mediate repression of HIF-1 transcriptional activity
Authors: Mahon Patrick C. , Hirota Kiichi , Semenza Gregg L.
Published: July 2002

Hypoxia-inducible factor 1 (HIF-1) is a master regulator of oxygen homeostasis that controls angiogenesis, erythropoiesis, and glycolysis via transcriptional activation of target genes under hypoxic conditions. O2-dependent binding of the von Hippel-Lindau (VHL) tumor suppressor protein targets the HIF-1α subunit for ubiquitination and proteasomal degradation. The activity of the HIF-1α transactivation domains is also O2regulated by a previously undefined mechanism. Here, we report the identification of factor inhibiting HIF-1 (FIH-1), a protein that binds to HIF-1α and inhibits its transactivation function. In addition, we demonstrate that FIH-1 binds to VHL and that VHL also functions as a transcriptional corepressor that inhibits HIF-1α transactivation function by recruiting histone deacetylases. Involvement of VHL in association with FIH-1 provides a unifying mechanism for the modulation of HIF-1α protein stabilization and transcriptional activation in response to changes in cellular O2concentration.
Fornix and Hippocampal Atrophy in Traumatic Brain Injury
Authors: Tate David F. , Bigler Erin D.
Published: July 2002

This study compared a fornix cross-sectional-area measurement and hippocampal volume in 86 traumatic brain injury (TBI) subjects with 46 normal controls. The TBI group showed a significant reduction in fornix area and hippocampal volume. It was also shown that initial injury severity was related to the degree of atrophy in both structures. Although fornix size and hippocampal volume correlated, such a modest correlation between these two structures suggests differential and potentially independent mechanisms of injury. The General Memory Index score from the Wechsler Memory Scale–Revised was shown to be significantly correlated with hippocampal volume following TBI.
Guard Cell- and Phloem Idioblast-Specific Expression of Thioglucoside Glucohydrolase 1 (Myrosinase) in Arabidopsis
Authors: Husebye Harald , Chadchawan Supachitra , Winge Per , Thangstad Ole P. , Bones Atle M.
Published: July 2002

Thioglucoside glucohydrolase 1 (TGG1) is one of two known functional myrosinase enzymes in Arabidopsis. The enzyme catalyzes the hydrolysis of glucosinolates into compounds that are toxic to various microbes and herbivores. Transgenic Arabidopsis plants carrying β-glucuronidase and green fluorescent protein reporter genes fused to 0.5 or 2.5 kb of the TGG1 promoter region were used to study spatial promoter activity. Promoter activity was found to be highly specific and restricted to guard cells and distinct cells of the phloem. No promoter activity was detected in the root or seed. All guard cells show promoter activity. Positive phloem cells are distributed in a discontinuous pattern and occur more frequent in young tissues. Immunocytochemical localization of myrosinase in transverse and longitudinal sections of embedded material show that the TGG1 promoter activity reflects the position of the myrosinase enzyme. In the flower stalk, the myrosinase-containing phloem cells are located between phloem sieve elements and glucosinolate-rich S cells. Our results suggest a cellular separation of myrosinase enzyme and glucosinolate substrate, and that myrosinase is contained in distinct cells. We discuss the potential advantages of locating defense and communication systems to only a few specific cell types.
Phosphate Availability Alters Architecture and Causes Changes in Hormone Sensitivity in the Arabidopsis Root System
Authors: López-Bucio José , Hernández-Abreu Esmeralda , Sánchez-Calderón Lenin , Nieto-Jacobo Marı́a Fernanda , Simpson June , Herrera-Estrella Luis
Published: July 2002

The postembryonic developmental program of the plant root system is plastic and allows changes in root architecture to adapt to environmental conditions such as water and nutrient availability. Among essential nutrients, phosphorus (P) often limits plant productivity because of its low mobility in soil. Therefore, the architecture of the root system may determine the capacity of the plant to acquire this nutrient. We studied the effect of P availability on the development of the root system in Arabidopsis. We found that at P-limiting conditions (<50 μm), the Arabidopsis root system undergoes major architectural changes in terms of lateral root number, lateral root density, and primary root length. Treatment with auxins and auxin antagonists indicate that these changes are related to an increase in auxin sensitivity in the roots of P-deprived Arabidopsis seedlings. It was also found that the axr1-3, axr2-1, and axr4-1 Arabidopsis mutants have normal responses to low P availability conditions, whereas the iaa28-1mutant shows resistance to the stimulatory effects of low P on root hair and lateral root formation. Analysis of ethylene signaling mutants and treatments with 1-aminocyclopropane-1-carboxylic acid showed that ethylene does not promote lateral root formation under P deprivation. These results suggest that in Arabidopsis, auxin sensitivity may play a fundamental role in the modifications of root architecture by P availability.
Isolation of a cDNA and a Genomic Clone Encoding Cinnamate 4-Hydroxylase from Arabidopsis and Its Expression Manner in Planta
Authors: Mizutani M. , Ohta D. , Sato R.
Published: July 2002

We have isolated a cDNA for a cytochrome P450, cinnamate 4-hydroxylase (C4H), of Arabidopsis thaliana using a C4H cDNA from mung bean as a hybridization probe. The deduced amino acid sequence is 84.7% identical to that of mung bean C4H and therefore was designated CYP73A5. The CYP73A5 protein was expressed in insect cells using the baculovirus expression system and when reconstituted with lipid and NADPH-cytochrome P450 reductase resulted in C4H activity with a specific activity of 68 nmol min-1 nmol-1 P450. Southern blot analysis revealed that CYP73A5 is a single-copy gene in Arabidopsis. C4H (CYP73A5) expression was apparently coordinated in Arabidopsis with both PAL1 and 4CL in response to light and wounding. Although the light induction of CHS followed a time course similar to that observed with C4H, no induction of CHS was detected upon wounding. On the other hand, the C4H expression patterns exhibited no significant coordination with those of PAL2 and PAL3. A C4H promoter region of 907 bp contained all of the three cis-acting elements (boxes P, A, and L) conserved among the PAL and 4CL genes so far reported as controlling expression.
Cellular Localization of Arabidopsis Xyloglucan Endotransglycosylase-Related Proteins during Development and after Wind Stimulation
Authors: Antosiewicz D. M. , Purugganan M. M. , Polisensky D. H. , Braam J.
Published: July 2002

A gene family encoding xyloglucan endotransglycosylase (XET)-related proteins exists in Arabidopsis. TCH4, a member of this family, is strongly up-regulated by environmental stimuli and encodes an XET capable of modifying cell wall xyloglucans. To investigate XET localization we generated antibodies against the TCH4 carboxyl terminus. The antibodies recognized TCH4 and possibly other XET-related proteins. These data indicate that XETs accumulate in expanding cells, at the sites of intercellular airspace formation, and at the bases of leaves, cotyledons, and hypocotyls. XETs also accumulated in vascular tissue, where cell wall modifications lead to the formation of tracheary elements and sieve tubes. Thus, XETs may function in modifying cell walls to allow growth, airspace formation, the development of vasculature, and reinforcement of regions under mechanical strain. Following wind stimulation, overall XET levels appeared to decrease in the leaves of wind-stimulated plants. However, consistent with an increase in TCH4 mRNA levels following wind, there were regions that showed increased immunoreaction, including sites around cells of the pith parenchyma, between the vascular elements, and within the epidermis. These results indicate that TCH4 may contribute to the adaptive changes in morphogenesis that occur in Arabidopsis following exposure to mechanical stimuli.
Biochemical and Molecular Biological Characterization of CAC2, the Arabidopsis thaliana Gene Coding for the Biotin Carboxylase Subunit of the Plastidic Acetyl-Coenzyme A Carboxylase
Authors: Sun J. , Ke J. , Johnson J. L. , Nikolau B. J. , Wurtele E. S.
Published: July 2002

The biotin carboxylase subunit of the heteromeric chloroplastic acetyl-coenzyme A carboxylase (ACCase) of Arabidopsis thaliana is coded by a single gene (CAC2), which is interrupted by 15 introns. The cDNA encodes a deduced protein of 537 amino acids with an apparent N-terminal chloroplast-targeting transit peptide. Antibodies generated to a glutathione S-transferase-CAC2 fusion protein react solely with a 51-kD polypeptide of Arabidopsis; these antibodies also inhibit ACCase activity in extracts of Arabidopsis. The entire CAC2 cDNA sequence was expressed in Escherichia coli and the resulting recombinant biotin carboxylase was enzymatically active in carboxylating free biotin. The catalytic properties of the recombinant biotin carboxylase indicate that the activity of the heteromeric ACCase may be regulated by light-/dark-induced changes in stromal pH. The CAC2 gene is maximally expressed in organs and tissues that are actively synthesizing fatty acids for membrane lipids or oil deposition. The observed expression pattern of CAC2 mirrors that previously reported for the CAC1 gene (J.-K. Choi, F. Yu, E.S. Wurtele, B.J. Nikolau [1995] Plant Physiol 109: 619–625; J. Ke, J.-K Choi, M. Smith, H.T. Horner, B.J. Nikolau, E.S. Wurtele [1997] Plant Physiol 113: 357–365), which codes for the biotin carboxyl carrier subunit of the heteromeric ACCase. This coordination is probably partially established by coordinate transcription of the two genes. This hypothesis is consistent with the finding that the CAC2 and CAC1 gene promoters share a common set of sequence motifs that may be important in guiding the transcription of these genes.
The GA2 Locus of Arabidopsis thalianaEncodes ent-Kaurene Synthase of Gibberellin Biosynthesis
Authors: Yamaguchi Shinjiro , Sun Tai-ping , Kawaide Hiroshi , Kamiya Yuji
Published: July 2002

The ga2 mutant ofArabidopsis thaliana is a gibberellin-deficient dwarf. Previous biochemical studies have suggested that the ga2mutant is impaired in the conversion of copalyl diphosphate toent-kaurene, which is catalyzed byent-kaurene synthase (KS). Overexpression of the previously isolated KS cDNA from pumpkin (Cucurbita maxima) (CmKS) in the ga2 mutant was able to complement the mutant phenotype. A genomic clone coding for KS, AtKS, was isolated from A. thalianausing CmKS cDNA as a heterologous probe. The corresponding A. thaliana cDNA was isolated and expressed in Escherichia coli as a fusion protein. The fusion protein showed enzymatic activity that converted [3H]copalyl diphosphate to [3H]ent-kaurene. The recombinant AtKS protein derived from the ga2–1 mutant is truncated by 14 kD at the C-terminal end and does not contain significant KS activity in vitro. Sequence analysis revealed that a C-2099 to T base substitution, which converts Gln-678 codon to a stop codon, is present in the AtKS cDNA from the ga2–1 mutant. Taken together, our results show that the GA2 locus encodes KS.
Surface Localization of Zein Storage Proteins in Starch Granules from Maize Endosperm1
Authors: Mu-Forster Chen , Wasserman Bruce P.
Published: July 2002

Starch granules from maize (Zea mays) contain a characteristic group of polypeptides that are tightly associated with the starch matrix (C. Mu-Forster, R. Huang, J.R. Powers, R.W. Harriman, M. Knight, G.W. Singletary, P.L. Keeling, B.P. Wasserman [1996] Plant Physiol 111: 821–829). Zeins comprise about 50% of the granule-associated proteins, and in this study their spatial distribution within the starch granule was determined. Proteolysis of starch granules at subgelatinization temperatures using the thermophilic protease thermolysin led to selective removal of the zeins, whereas granule-associated proteins of 32 kD or above, including the waxy protein, starch synthase I, and starch-branching enzyme IIb, remained refractory to proteolysis. Granule-associated proteins from maize are therefore composed of two distinct classes, the surface-localized zeins of 10 to 27 kD and the granule-intrinsic proteins of 32 kD or higher. The origin of surface-localized δ-zein was probed by comparing δ-zein levels of starch granules obtained from homogenized whole endosperm with granules isolated from amyloplasts. Starch granules from amyloplasts contained markedly lower levels of δ-zein relative to granules prepared from whole endosperm, thus indicating that δ-zein adheres to granule surfaces after disruption of the amyloplast envelope. Cross-linking experiments show that the zeins are deposited on the granule surface as aggregates. In contrast, the granule-intrinsic proteins are prone to covalent modification, but do not form intermolecular cross-links. We conclude that individual granule intrinsic proteins exist as monomers and are not deposited in the form of multimeric clusters within the starch matrix.
Identification of the Gene Encoding the Tryptophan Synthase β-Subunit from Chlamydomonas reinhardtii1
Authors: Palombella Anthony L. , Dutcher Susan K.
Published: July 2002

We report the isolation of a Chlamydomonas reinhardtii cDNA that encodes the β-subunit of tryptophan synthase (TSB). This cDNA was cloned by functional complementation of atrp-operon-deleted strain of Escherichia coli. Hybridization analysis indicated that the gene exists in a single copy. The predicted amino acid sequence showed the greatest identity to TSB polypeptides from other photosynthetic organisms. With the goal of identifying mutations in the gene encoding this enzyme, we isolated 11 recessive and 1 dominant single-gene mutation that conferred resistance to 5-fluoroindole. These mutations fell into three complementation groups, MAA2, MAA7, andTAR1. In vitro assays showed that mutations at each of these loci affected TSB activity. Restriction fragment-length polymorphism analysis suggested thatMAA7 encodes TSB. MAA2 andTAR1 may act to regulate the activity ofMAA7 or its protein product.
High Aluminum Resistance in Buckwheat1
Authors: Zheng Shao Jian , Ma Jian Feng , Matsumoto Hideaki
Published: July 2002

High Al resistance in buckwheat (Fagopyrum esculentum Moench. cv Jianxi) has been suggested to be associated with both internal and external detoxification mechanisms. In this study the characteristics of the external detoxification mechanism, Al-induced secretion of oxalic acid, were investigated. Eleven days of P depletion failed to induce secretion of oxalic acid. Exposure to 50 μmLaCl3 also did not induce the secretion of oxalic acid, suggesting that this secretion is a specific response to Al stress. Secretion of oxalic acid was maintained for 8 h by a 3-h pulse treatment with 150 μm Al. A nondestructive method was developed to determine the site of the secretion along the root. Oxalic acid was found to be secreted in the region 0 to 10 mm from the root tip. Experiments using excised roots also showed that secretion was located on the root tip. Four kinds of anion-channel inhibitors showed different effects on Al-induced secretion of oxalic acid: 10 μm anthracene-9-carboxylic acid and 4,4′-diisothiocyanatostilbene-2,2′-disulfonate had no effect, niflumic acid stimulated the secretion 4-fold, and phenylglyoxal inhibited the secretion by 50%. Root elongation in buckwheat was not inhibited by 25 μm Al or 10 μm phenylglyoxal alone but was inhibited by 40% in the presence of Al and phenylglyoxal, confirming that secretion of oxalic acid is associated with Al resistance.
Natural Genetic Transformation byAgrobacterium rhizogenes
Authors: Limami M. Anis , Sun Li-Yan , Douat Corinne , Helgeson John , Tepfer David
Published: July 2002

Genetic transformation of Belgian endive (Cichorium intybus) and carrot (Daucus carota) by Agrobacterium rhizogenes resulted in a transformed phenotype, including annual flowering. Back-crossing of transformed (R1) endive plants produced a line that retained annual flowering in the absence of the other traits associated with A. rhizogenes transformation. Annualism was correlated with the segregation of a truncated transferred DNA (T-DNA) insertion. During vegetative growth, carbohydrate reserves accumulated normally in these annuals, and they were properly mobilized prior to anthesis. The effects of individual root-inducing left-hand T-DNA genes on flowering were tested in carrot, in which rolC(root locus) was the primary promoter of annualism and rolD caused extreme dwarfism. We discuss the possible adaptive significance of this attenuation of the phenotypic effects of root-inducing left-hand T-DNA.
Ectopic Expression of the Maize Homeobox GeneLiguleless3 Alters Cell Fates in the Leaf1
Authors: Muehlbauer Gary J. , Fowler John E. , Girard Lisa , Tyers Randall , Harper Lisa , Freeling Michael
Published: July 2002

The semidominant mutation Liguleless3-O(Lg3-O) causes a blade-to-sheath transformation at the midrib region of the maize (Zea mays L.) leaf. We isolated a full-length lg3 cDNA containing aknotted1-like family homeobox. Six Lg3-Opartial revertant alleles caused by insertion of aMutator (Mu) transposon and two deletion derivatives were isolated and used to verify that ourknotted1-like cDNA corresponds to the LG3 message. In wild-type plants the LG3 mRNA is expressed in apical regions but is not expressed in leaves. In mutant plants harboring any of three dominantlg3 alleles (Lg3-O, -Mlg, and -347), LG3 mRNA is expressed in leaf sheath tissue, indicating that the Lg3 phenotype is due to ectopic expression of the gene. The Lg3-O revertant alleles represent two classes of Lg3 phenotypes that correlate well with the level of ectopic Lg3 expression. High levels of ectopic LG3 mRNA expression results in a severe Lg3 phenotype, whereas weak ectopic Lg3 expression results in a mild Lg3 phenotype. We propose that ectopic Lg3 expression early in leaf development causes the blade-to-sheath transformation, but the level of expression determines the extent of the transformation.
Messenger RNA-Binding Properties of Nonpolysomal Ribonucleoproteins from Heat-Stressed Tomato Cells1
Authors: Stuger Rogier , Ranostaj Sigrid , Materna Tilo , Forreiter Christoph
Published: July 2002

Most cells experiencing heat stress reprogram their translational machinery to favor the synthesis of heat-stress proteins. Translation of other transcripts is almost completely repressed, but most untranslated messengers are not degraded. In contrast to yeast, Drosophila melanogaster, and HeLa cells, plant cells store repressed messengers in cytoplasmic nonpolysomal ribonucleoproteins (RNPs). To follow the fate of untranslated transcripts, we studied protein composition, mRNA content, and RNA-binding properties of nonpolysomal RNPs from heat-stressed tomato (Lycopersicon peruvianum) cells. Contrary to the selective interaction in vivo, RNPs isolated from tomato cells bound both stress-induced and repressed messengers, suggesting that the selection mechanism resides elsewhere. This binding was independent of a cap or a poly(A) tail. The possible role of proteasomes and heat-stress granules (HSGs) in mRNA storage is a topic of debate. We found in vitro messenger-RNA-binding activity in messenger RNP fractions free of C2-subunit-containing proteasomes and HSGs. In addition, mRNAs introduced into tobacco (Nicotiana plumbaginifolia) protoplasts were found in the cytoplasm but were not associated with HSGs.
Subcellular Localization and Speciation of Nickel in Hyperaccumulator and Non-Accumulator ThlaspiSpecies
Authors: Krämer Ute , Pickering Ingrid J. , Prince Roger C. , Raskin Ilya , Salt David E.
Published: July 2002

The ability of Thlaspi goesingense Hálácsy to hyperaccumulate Ni appears to be governed by its extraordinary degree of Ni tolerance. However, the physiological basis of this tolerance mechanism is unknown. We have investigated the role of vacuolar compartmentalization and chelation in this Ni tolerance. A direct comparison of Ni contents of vacuoles from leaves of T. goesingense and from the non-tolerant non-accumulator Thlaspi arvense L. showed that the hyperaccumulator accumulates approximately 2-fold more Ni in the vacuole than the non-accumulator under Ni exposure conditions that were non-toxic to both species. Using x-ray absorption spectroscopy we have been able to determine the likely identity of the compounds involved in chelating Ni within the leaf tissues of the hyperaccumulator and non-accumulator. This revealed that the majority of leaf Ni in the hyperaccumulator was associated with the cell wall, with the remaining Ni being associated with citrate and His, which we interpret as being localized primarily in the vacuolar and cytoplasm, respectively. This distribution of Ni was remarkably similar to that obtained by cell fractionation, supporting the hypothesis that in the hyperaccumulator, intracellular Ni is predominantly localized in the vacuole as a Ni-organic acid complex.
Extracellular H2O2 Induced by Oligogalacturonides Is Not Involved in the Inhibition of the Auxin-Regulated rolB Gene Expression in Tobacco Leaf Explants
Authors: Bellincampi Daniela , Dipierro Nunzio , Salvi Giovanni , Cervone Felice , De Lorenzo Giulia
Published: July 2002

α-1,4-Linked oligogalacturonides (OGs) inhibit auxin-regulated transcriptional activation of arolB-β-glucuronidase (GUS) gene fusion in tobacco (Nicotiana tabacum) leaf explants (D. Bellincampi, M. Cardarelli, D. Zaghi, G. Serino, G. Salvi, C. Gatz, F. Cervone, M.M. Altamura, P. Costantino, G. De Lorenzo [1996] Plant Cell 8: 477–487). In this paper we show that inhibition by OGs is very rapid, with a short lag time, and takes place even afterrolB promoter activation has initiated. OGs also induce a transient and catalase-sensitive accumulation of H2O2 in the leaf explant culture medium. OGs with a degree of polymerization from 12 to 15 are required for both the inhibition of the auxin-induced rolB-driven accumulation of GUS and the induction of H2O2accumulation. However, OG concentration for half-maximal induction of H2O2 accumulation is approximately 3-fold higher than that for half-maximal inhibition ofrolB promoter activity. The inhibition ofrolB promoter activity is not influenced by the addition of catalase or superoxide dismutase, suggesting that H2O2 and superoxide are not involved in this effect. A fungal oligo-β-glucan elicitor induces extracellular H2O2 accumulation at comparable or higher levels than those observed with OGs, but does not prevent the auxin-induced accumulation of GUS. We conclude that H2O2 produced upon treatment with OGs is not involved in the inhibition of the auxin-induced expression of therolB gene.
High-Affinity Potassium Transport in Barley Roots. Ammonium-Sensitive and -Insensitive Pathways
Authors: Santa-Marı́a Guillermo E. , Danna Cristian H. , Czibener Cecilia
Published: July 2002

In an attempt to understand the process mediating K+transport into roots, we examined the contribution of the NH4  +-sensitive and NH4  +-insensitive components of Rb+transport to the uptake of Rb+ in barley (Hordeum vulgare L.) plants grown in different ionic environments. We found that at low external Rb+ concentrations, an NH4  +-sensitive component dominates Rb+ uptake in plants grown in the absence of NH4  +, while Rb+ uptake preferentially occurs through an NH4  +-insensitive pathway in plants grown at high external NH4  + concentrations. A comparison of the Rb+-uptake properties observed in roots with those found in heterologous studies with yeast cells indicated that the recently cloned HvHAK1 K+ transporter may provide a major route for the NH4  +-sensitive component. HvHAK1 failed to complement the growth of a yeast strain defective in NH4  + transport, suggesting that it could not act as an NH4  + transporter. Heterologous studies also showed that the HKT1 K+/Na+-cotransporter may act as a pathway for high-affinity Rb+ transport sensitive to NH4  +. However, we found no evidence of an enhancement of Rb+ uptake into roots due to Na+addition. The possible identity of the systems contributing to the NH4  +-insensitive component in barley plants is discussed.
Detection of Expansin Proteins and Activity during Tomato Fruit Ontogeny
Authors: Rose Jocelyn K.C. , Cosgrove Daniel J. , Albersheim Peter , Darvill Alan G. , Bennett Alan B.
Published: July 2002

Expansins are plant proteins that have the capacity to induce extension in isolated cell walls and are thought to mediate pH-dependent cell expansion. J.K.C. Rose, H.H. Lee, and A.B. Bennett ([1997] Proc Natl Acad Sci USA 94: 5955–5960) reported the identification of an expansin gene (LeExp1) that is specifically expressed in ripening tomato (Lycopersicon esculentum) fruit where cell wall disassembly, but not cell expansion, is prominent. Expansin expression during fruit ontogeny was examined using antibodies raised to recombinant LeExp1 or a cell elongation-related expansin from cucumber (CsExp1). The LeExp1 antiserum detected expansins in extracts from ripe, but not preripe tomato fruit, in agreement with the pattern of LeExp1mRNA accumulation. In contrast, antibodies to CsExp1 cross-reacted with expansins in early fruit development and the onset of ripening, but not at a later ripening stage. These data suggest that ripening-related and expansion-related expansin proteins have distinct antigenic epitopes despite overall high sequence identity. Expansin proteins were detected in a range of fruit species and showed considerable variation in abundance; however, appreciable levels of expansin were not present in fruit of the rin or Nr tomato mutants that exhibit delayed and reduced softening. LeExp1 protein accumulation was ethylene-regulated and matched the previously described expression of mRNA, suggesting that expression is not regulated at the level of translation. We report the first detection of expansin activity in several stages of fruit development and while characteristic creep activity was detected in young and developing tomato fruit and in ripe pear, avocado, and pepper, creep activity in ripe tomato showed qualitative differences, suggesting both hydrolytic and expansin activities.
An Enhancer Trap Line Associated with a D-Class Cyclin Gene in Arabidopsis
Authors: Swaminathan Kankshita , Yang Yingzhen , Grotz Natasha , Campisi Lauren , Jack Thomas
Published: July 2002

In yeast and animals, cyclins have been demonstrated to be important regulators of cell cycle progression. In recent years, a large number of A-, B-, and D-class cyclins have been isolated from a variety of plant species. One class of cyclins, the D-class cyclins, is important for progression through G1 phase of the cell cycle. In Arabidopsis, four D-class cyclins have been isolated and characterized (CYCLIN-D1;1, CYCLIN-D2;1,CYCLIN-D3;1, and CYCLIN-D4;1). In this report we describe the characterization of a fifth D-class cyclin gene,CYCLIN-D3;2 (CYCD3;2), from Arabidopsis. An enhancer trap line, line 5580, contains a T-DNA insertion inCYCD3;2. Enhancer trap line 5580 exhibits expression in young vegetative and floral primordia. In line 5580, T-DNA is inserted in the first exon of the CYCD3;2 gene; in homozygous 5580 plants CYCD3;2 RNA is not detectable. Even thoughCYCD3;2 gene function is eliminated, homozygous 5580 plants do not exhibit an obvious growth or developmental phenotype. Via in situ hybridization we demonstrate that CYCD3;2 RNA is expressed in developing vegetative and floral primordia. In addition,CYCD3;2 is also capable of rescuing a yeast strain that is deficient in G1 cyclin activity.
High- and Low-Affinity Zinc Transport Systems and Their Possible Role in Zinc Efficiency in Bread Wheat
Authors: Hacisalihoglu Gokhan , Hart Jonathan J. , Kochian Leon V.
Published: July 2002

There is considerable variability among wheat (Triticum aestivum L.) cultivars in their ability to grow and yield well in soils that contain very low levels of available Zn. The physiological basis for this tolerance, termed Zn efficiency, is unknown. We investigated the possible role of Zn2+ influx across the root cell plasma membrane in conferring Zn efficiency by measuring short-term 65Zn2+ uptake in two contrasting wheat cultivars, Zn-efficient cv Dagdas and Zn-inefficient cv BDME-10. Plants were grown hydroponically under sufficient and deficient Zn levels, and uptake of 65Zn2+ was measured over a wide range of Zn activities (0.1 nm–80 μm). Under low-Zn conditions, cv BDME-10 displayed more severe Zn deficiency symptoms than cv Dagdas. Uptake experiments revealed the presence of two separate Zn transport systems mediating high- and low-affinity Zn influx. The low-affinity system showed apparent K  m values similar to those previously reported for wheat (2–5 μm). Using chelate buffered solutions to quantify Zn2+ influx in the nanomolar activity range, we uncovered the existence of a second, high-affinity Zn transport system with apparent K  m values in the range of 0.6 to 2 nm. Because it functions in the range of the low available Zn levels found in most soils, this novel high-affinity uptake system is likely to be the predominant Zn2+ uptake system. Zn2+ uptake was similar for cv Dagdas and cv BDME-10 over both the high- and low-affinity Zn2+ activity ranges, indicating that root Zn2+influx does not play a significant role in Zn efficiency.
Aquaporins Constitute a Large and Highly Divergent Protein Family in Maize
Authors: Chaumont François , Barrieu François , Wojcik Eva , Chrispeels Maarten J. , Jung Rudolf
Published: July 2002

Aquaporins (AQPs) are an ancient family of channel proteins that transport water and neutral solutes through a pore and are found in all eukaryotes and most prokaryotes. A comparison of the amino acid sequences and phylogenetic analysis of 31 full-length cDNAs of maize (Zea mays) AQPs shows that they comprise four different groups of highly divergent proteins. We have classified them as plasma membrane intinsic proteins (PIPs), tonoplast intrinsic proteins, Nod26-like intrinsic proteins, and small and basic intrinsic proteins. Amino acid sequence identities vary from 16% to 100%, but all sequences share structural motifs and conserved amino acids necessary to stabilize the two loops that form the aqueous pore. Most divergent are the small and basic integral proteins in which the first of the two highly conserved Asn-Pro-Ala motifs of the pore is not conserved, but is represented by alanine-proline-threonine or alanine-proline-serine. We present a model of ZmPIP1-2 based on the three-dimensional structure of mammalian AQP1. Tabulation of the number of times that the AQP sequences are found in a collection of databases that comprises about 470,000 maize cDNAs indicates that a few of the maize AQPs are very highly expressed and many are not abundantly expressed. The phylogenetic analysis supports the interpretation that the divergence of PIPs through gene duplication occurred more recently than the divergence of the members of the other three subfamilies. This study opens the way to analyze the function of the proteins in Xenopus laevis oocytes, determine the tissue specific expression of the genes, recover insertion mutants, and determine the in planta function.
Expression Profile Matrix of Arabidopsis Transcription Factor Genes Suggests Their Putative Functions in Response to Environmental Stresses[W]
Authors: Chen Wenqiong , Provart Nicholas J. , Glazebrook Jane , Katagiri Fumiaki , Chang Hur-Song , Eulgem Thomas , Mauch Felix , Luan Sheng , Zou Guangzhou , Whitham Steve A. , Budworth Paul R. , Tao Yi , Xie Zhiyi , Chen Xi , Lam Steve , Kreps Joel A. , Harper Jeffery F. , Si-Ammour Azzedine , Mauch-Mani Brigitte , Heinlein Manfred , Kobayashi Kappei , Hohn Thomas , Dangl Jeffery L. , Wang Xun , Zhu Tong
Published: July 2002

Numerous studies have shown that transcription factors are important in regulating plant responses to environmental stress. However, specific functions for most of the genes encoding transcription factors are unclear. In this study, we used mRNA profiles generated from microarray experiments to deduce the functions of genes encoding known and putative Arabidopsis transcription factors. The mRNA levels of 402 distinct transcription factor genes were examined at different developmental stages and under various stress conditions. Transcription factors potentially controlling downstream gene expression in stress signal transduction pathways were identified by observed activation and repression of the genes after certain stress treatments. The mRNA levels of a number of previously characterized transcription factor genes were changed significantly in connection with other regulatory pathways, suggesting their multifunctional nature. The expression of 74 transcription factor genes responsive to bacterial pathogen infection was reduced or abolished in mutants that have defects in salicylic acid, jasmonic acid, or ethylene signaling. This observation indicates that the regulation of these genes is mediated at least partly by these plant hormones and suggests that the transcription factor genes are involved in the regulation of additional downstream responses mediated by these hormones. Among the 43 transcription factor genes that are induced during senescence, 28 of them also are induced by stress treatment, suggesting extensive overlap responses to these stresses. Statistical analysis of the promoter regions of the genes responsive to cold stress indicated unambiguous enrichment of known conserved transcription factor binding sites for the responses. A highly conserved novel promoter motif was identified in genes responding to a broad set of pathogen infection treatments. This observation strongly suggests that the corresponding transcription factors play general and crucial roles in the coordinated regulation of these specific regulons. Although further validation is needed, these correlative results provide a vast amount of information that can guide hypothesis-driven research to elucidate the molecular mechanisms involved in transcriptional regulation and signaling networks in plants.
Conductive gel gaskets for aircraft antennas reduce installation costs, corrosion and downtime
Authors: Sitler Ben , Lo Ken
Published: July 2002

Considers the causes of corrosion of avionics antennae and the damage damage it causes. Gives the authors’ view of the disadvantages of conventional antenna attachment and sealing techniques. Details an alternative technique ‐ conductive gel gaskets ‐ using a gel sealant developed by Raychem Corporation.
Creating the futures we desire ‐ getting the whole system into the room: part I
Authors: Nixon Bruce
Published: July 2002

For our organisations to flourish, they need to engage the intelligence, creativity and energy of the whole workforce and involve all stakeholders. One way of doing this is to use whole system approaches to planning and implementing change and what have come to be known as large‐group methods. This article, the first of two parts, makes a case for these approaches and describes the major benefits, outlines their history and describes two well‐tried methods: future search and open space technology.
Creating a learning organisation in higher education
Authors: Rowley Jennifer
Published: July 2002

The need for organisations to survive in a changing environment has led to the development of the concept of the learning organisation. A learning organisation is an organisation that facilitates learning for all of its members, and thereby continuously transforms itself. The organisation needs to create a climate in which experiential learning is managed effectively throughout the workplace, and in which individual learning is harnessed to achieve organisational learning. In higher education institutions, although they may have a learning culture, the creation of a learning organisation is dependent on embedding learning in the management processes of the organisation by extending the focus on learning from the classroom and the research laboratory to the wider organisation, so that the organisation creates and disseminates knowledge that informs the development of the organisation. The article considers the nature of a learning organisation, and how such an organisation might be created, in the context of higher education.
Promoting learning style analysis among vocational students
Authors: Briggs Ann R.J.
Published: July 2002

Reports on project work in six further education colleges in central England, supported by funding from the Further Educational Development Agency as part of its inclusive learning initiative. The project team investigated a range of materials for student analysis of learning styles, carried out a trial of chosen materials with class groups across a range of vocational subjects, and evaluated the usefulness of the materials to both students and lecturers. The outcomes of the project are analysed and set within the context of current developments in post‐16 education. A follow‐up study at one of the colleges is presented, and the implications of the project as a whole for college management are considered.
Making the connection: the effectiveness of Internet training in small businesses
Authors: Blackburn Robert , Athayde Rosemary
Published: July 2002

Aims to provide an analysis of the introduction of Internet‐based skills into small firms. Seeks to contribute to the wider debate on the content and style of training most appropriate for employees and managers of SMEs.
Evaluating levels of strategic integration and devolvement of human resource management in the UK
Authors: Budhwar Pawan S.
Published: July 2002

Evaluates the levels of strategic “integration” of human resource management (HRM) into the corporate strategy and “devolvement” of responsibility for HRM to line managers in the UK manufacturing sector. Summarises, initially, some of the primary theoretical debates existing in the HRM literature and then presents empirical results of a large‐scale study. Bases the findings on a questionnaire survey and in‐depth interviews. Not only highlights the present scenario regarding the concepts of integration and devolvement from the “subject‐matter experts”’ viewpoint, but also reveals the main logic surrounding them and the main factors and variables which determine these two practices in the UK. Contributes to the field of strategic HRM and opens avenues for further research.
Managing human resources in a post‐command economy: personnel administration or strategic HRM
Authors: Garavan Thomas , Morley Michael , Heraty Noreen , Lucewicz Jacinta , Suchodolski Adam
Published: July 2002

Reviews the changes in personnel/HRM practices within a post‐command economy. Explores personnel/HRM practices within 25 Polish companies and reports on the diversity of personnel/HRM practices in evidence. The data suggest significant under‐development in terms of practices and little evidence of strategic HRM approaches.
The meanings, consequences and implications of the management of downsizing and redundancy: a review
Authors: Thornhill Adrian , Saunders Mark N.K.
Published: July 2002

Review paper which draws together the various theoretical and disciplinary strands used in the literature to evaluate downsizing and redundancy. Defines downsizing and redundancy within the organisational context. Explores complexity of the relationships with performance and effectiveness at both organisation and sub‐organisation levels. Evaluates downsizing strategies and implementation methods that organisations may use. Utilises the individual perspective to examine and discuss the consequences of downsizing relative to survivors. Considers the implications of this for managers. Relates theories of equity, organisational justice, job insecurity, job redesign and organisational stress to approaches which may mitigate negative responses to downsizing that impact on organisations’ performance and effectiveness.
The links between absenteeism and commitment during downsizing
Authors: Savery Lawson K. , Travaglione Anthony , Firns Ian G.J.
Published: July 2002

Reports results of research into commitment levels and absenteeism among employees at Westrail, the Western Australian Government Railway. Suggests that high absenteeism is associated mainly with a group of people who have submitted expressions of interest in severance benefits. Absenteeism rates correlated negatively with measures of commitment to work itself and to the organisation. Seems likely that lower commitment to work leads to higher absenteeism. Commitment measures correlated with attitudes to change and communications, past achievement of personal goals, expectation of achieving career goals, trust in senior management and propensity to stay with the organisation. Makes suggestions for strategies to contain the incidence and rate of absenteeism.
Applying strategies for dealing with workplace bullying
Authors: Sheehan Michael , Rayner Charlotte
Published: July 2002

This article provides a brief overview of some of the applied approaches being taken in four countries to deal with workplace bullying and serves as a preamble to the articles by Archer, Crawford, Lewis, Sheehan and Zapf in this section. The work undertaken by the Beyond Bullying Association in Australia and that of the Anti Bullying Centre in Dublin is discussed. Swedish legislation that addresses bullying and the ways that employers, unions, university researchers and voluntary sector organisations attempt to deal with bullying in the UK follows. The article concludes by mentioning the likely legal and economic implications for organisations and society.