bluuebunny/crossref_metadata_2025 huggingface dataset:
Are environmental Kuznets curves misleading us? The case of CO2 emissions
Authors: MOOMAW WILLIAM R. , UNRUH GREGORY C.
Published: July 2002

Environmental Kuznets curve (EKC) analysis links changes in environmental quality to national economic growth. The reduced form models, however, do not provide insight into the underlying processes that generate these changes. We compare EKC models to structural transition models of per capita CO2 emissions and per capita GDP, and find that, for the 16 countries which have undergone such a transition, the initiation of the transition correlates not with income levels but with historic events related to the oil price shocks of the 1970s and the policies that followed them. In contrast to previous EKC studies of CO2 the transition away from positive emissions elasticities for these 16 countries is found to occur as a sudden, discontinuous transition rather than as a gradual change. We also demonstrate that the third order polynomial 'N' dependence of emissions on income is the result of data aggregation. We conclude that neither the 'U'- nor the 'N'-shaped relationship between CO2 emissions and income provide a reliable indication of future behaviour.
The UPIC system as an instrument of learning
Authors: NELSON PETER
Published: July 2002

The conceptual basis of the UPIC system is described and discussed, in particular its relation to the work of its orginator, Iannis Xenakis, to the science of acoustics and to the development of an intuitive graphic imagery. A possible pedagogical approac
h to musical creation using the resources of the UPIC is developed, and the particular pedagogical ethos of the system is emphasised. There follows a detailed description of the practical arrangements for a number of different workshop situations using the UPIC system in which the author has participated, and an evaluation of the outcomes of using the system in this way.
Dyslexia as a Phonological Deficit: Evidence and Implications
Authors: Snowling Margaret
Published: July 2002

In recent years, limitations of the discrepancy definition of specific
reading
difficulties have led researchers to propose that dyslexia is best described

as a core phonological deficit. With studies of the normal development
of
reading as a backdrop, this paper reviews the phonological processing
deficit hypothesis of dyslexia. The extant evidence suggests that
phonological difficulties in dyslexia persist throughout development from

the preschool years into adulthood, despite compensation of reading
deficits. Moreover, individual differences in the behavioural manifestation

of dyslexia are consistent with differences in the severity of underlying

phonological difficulties. Implications for the early identification of

dyslexia and for interventions to prevent reading failure are discussed.
Projective Doll Play
Methodologies for Preschool
Children
Authors: Woolgar Matthew
Published: July 2002

There has been a resurgence of interest in the use of projective doll play
techniques, partly arising out of the recognition of the sophistication of
young children's play. This review considers a number of recent projective
doll play innovations and evaluates the utility of these techniques for
investigating young children's moral development, attachment beyond
infancy, and for predicting behaviour problems. In addition, the use of
these techniques with high-risk and clinical populations is described and
a discussion of factors influencing the quality of projective play responses
is presented.
The Guangzhou Treatment
Authors: Stratford Brian
Published: July 2002

This paper describes, in a humourous way, some of the frustrations, joys,
pleasures and pains of a European psychologist working in a hospital in
the People's Republic of China. It tells tales of families from distant fields
in the remote hinterland and from the more urban communities and
shows how these compare and contrast with similar situations in the U.K.
Parents love their children whether in Guangzhou or Glasgow and this
paper illustrates these cross-cultural connections.
Who Needs to Observe Infants? Infant Observation in the
Training of Child and Adolescent Mental Health Workers
Authors: Coll Xavier
Published: July 2002

Infant Observation is a valuable training experience for workers in child
and adolescent mental health, helping both to conceive the infantile
experience of the children under their care, and to understand the parents'
accounts of a child's history. It is an experience that gives trainees a unique
opportunity to observe the development of an infant, systematically and
practically from birth, in the child's natural setting, thus facilitating the
acquisition of a meaningful understanding of how human relationships
emerge and develop. Infant Observation gives the trainee a clear focus on
the baby and his family, whilst remaining as a participant observer, and
spontaneously encouraging problem-free talk.
THE EXACT THEORETICAL RATIONAL EXPECTATIONS MONETARY AGGREGATE
Authors: Barnett William A. , Hinich Melvin J. , Yue Piyu
Published: July 2002

In aggregation theory, index numbers are judged relative to their ability to track the exact aggregator functions nested within the economy's structure. We compare two statistical index numbers—the Divisia monetary aggregate and the simple-sum monetary aggregate—with the exact rational expectations monetary aggregate, using actual data. Because we are not using simulated data, we estimate the parameters of the Euler equations, and thereby of the nested monetary aggregator function, using the generalized method of moments. We explore the tracking errors of the two index numbers relative to the estimated exact aggregate. We investigate the circumstances under which risk aversion increases tracking error. We also use polyspectral methods to test for the existence of remaining nonlinear structure in the residual tracking errors.
Does nutrition-related stress carry over to spruce budworm,Choristoneura fumiferana(Lepidoptera: Tortricidae) progeny?
Authors: Carisey N. , Bauce É.
Published: July 2002

Three different patterns of feeding of sixth-instar spruce budworm,Choristoneura fumiferanaClemens were simulated in the laboratory. Larvae were fed artificial diets whose nitrogen and total soluble sugar contents varied according to levels similar to those found in three types of balsam fir,Abies balsamea(L.) Miller foliage (current-year foliage from middle and lower crown sections and one-year-old foliage). The biological performance of offspring was studied according to the nutrition of their parents. Although food quality had no impact on pupal weight of female parents and individual mean egg weight, progeny fitness was influenced by parental nutrition. Old foliage simulated diet, poor in nitrogen, clearly affected the early larval development of progeny, especially the percent of egg hatch and first-instar survival. Lower crown current-year foliage simulated diet, with low total soluble sugar content, reduced the first-instar survival of the progeny. However, the selective pressure exerted by low food qualities on the parental generation and on the early stages of their progenies resulted inC. fumiferanapopulations having higher tolerance to starvation and higher survival after the diapause period. These results highlighted the potentially direct and indirect effects ofC. fumiferanaparental nutrition on the next generation. The patterns of feeding of parental generations would appear to affect the quality and size of subsequent populations through several selections on the different life-history stages of both generations.
Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex
Authors: Swarup Ranjan , Friml Jirı́ , Marchant Alan , Ljung Karin , Sandberg Goran , Palme Klaus , Bennett Malcolm
Published: July 2002

Auxins represent an important class of plant hormone that regulate plant development. Plants use specialized carrier proteins to transport the auxin indole-3-acetic acid (IAA) to target tissues. To date, efflux carrier-mediated polar auxin transport has been assumed to represent the sole mode of long distance IAA movement. Localization of the auxin permease AUX1 in the Arabidopsis root apex has revealed a novel phloem-based IAA transport pathway. AUX1, asymmetrically localized to the plasma membrane of root protophloem cells, is proposed to promote the acropetal, post-phloem movement of auxin to the root apex. MS analysis shows that IAA accumulation in aux1 mutant root apices is impaired, consistent with an AUX1 phloem unloading function. AUX1 localization to columella and lateral root cap tissues of theArabidopsis root apex reveals that the auxin permease regulates a second IAA transport pathway. Expression studies using an auxin-regulated reporter suggest that AUX1 is necessary for root gravitropism by facilitating basipetal auxin transport to distal elongation zone tissues.
The antibacterial arm of the Drosophila innate immune response requires an IκB kinase
Authors: Lu Yiran , Wu Louisa P. , Anderson Kathryn V.
Published: July 2002

The ird5 gene was identified in a genetic screen forDrosophila immune response mutants. Mutations in ird5prevent induction of six antibacterial peptide genes in response to infection but do not affect the induction of an antifungal peptide gene. Consistent with this finding, Escherichia coli survive 100 times better in ird5 adults than in wild-type animals. Theird5 gene encodes a Drosophila homolog of mammalian IκB kinases (IKKs). The ird5 phenotype and sequence suggest that the gene is specifically required for the activation of Relish, aDrosophila NF-κB family member.
ABP1 is required for organized cell elongation and division in Arabidopsis embryogenesis
Authors: Chen Jin-Gui , Ullah Hemayet , Young Jeffery C. , Sussman Michael R. , Jones Alan M.
Published: July 2002

To directly address the function of a putative auxin receptor designated ABP1, a reverse genetic approach was taken to identify and characterize ABP1 mutant alleles in Arabidopsis. A homozygous null mutation in ABP1 confers embryo lethality. Null mutant embryos develop normally until the early stages of the globular embryo but are unable to make the transition to a bilaterally symmetrical structure because cells fail to elongate. Cell division was also aberrant both in the suspensor and embryo proper. Antisense suppression of ABP1 in tobacco cells causes slow proliferation and eliminates auxin-induced cell elongation and reduces cell division. The complete lack of auxin-inducible elongation in individual cells confirms the results observed in embryos, indicates a cell autonomous function, and, taken together with biochemical evidence that ABP1 binds auxins, suggests that ABP1 mediates auxin-induced cell elongation and, directly or indirectly, cell division.
Active repression of RAR signaling is required for head formation
Authors: Koide Tetsuya , Downes Michael , Chandraratna Roshantha A.S. , Blumberg Bruce , Umesono Kazuhiko
Published: July 2002

The retinoic acid receptors (RARs) recruit coactivator and corepressor proteins to activate or repress the transcription of target genes depending on the presence of retinoic acid (RA). Despite a detailed molecular understanding of how corepressor complexes function, there is no in vivo evidence to support a necessary function for RAR-mediated repression. Signaling through RARs is required for patterning along the anteroposterior (A-P) axis, particularly in the hindbrain and posterior, although the absence of RA is required for correct anterior patterning. Because RARs and corepressors are present in regions in which RA is absent, we hypothesized that repression mediated through unliganded RARs might be important for anterior patterning. To test this hypothesis, specific reagents were used that either reduce or augment RAR-mediated repression. Derepression of RAR signaling by expressing a dominant-negative corepressor resulted in embryos that exhibited phenotypes similar to those treated by RA. Anterior structures such as forebrain and cement gland were greatly reduced, as was the expression of molecular markers. Enhancement of target gene repression using an RAR inverse agonist resulted in up-regulation of anterior neural markers and expansion of anterior structures. Morpholino antisense oligonucleotide-mediated RARα loss-of-function phenocopied the effects of RA treatment and dominant-negative corepressor expression. Microinjection of wild-type or dominant-negative RARα rescued the morpholino phenotype, confirming that RAR is functioning anteriorly as a transcriptional repressor. Lastly, increasing RAR-mediated repression potentiated head-inducing activity of the growth factor inhibitor cerberus, whereas releasing RAR-mediated repression blocked cerberus from inducing ectopic heads. We conclude that RAR-mediated repression of target genes is critical for head formation. This requirement establishes an important biological role for active repression of target genes by nuclear hormone receptors and illustrates a novel function for RARs during vertebrate development.
COUP-TFI: an intrinsic factor for early regionalization of the neocortex
Authors: Zhou Cheng , Tsai Sophia Y. , Tsai Ming-Jer
Published: July 2002

Regionalization of the cerebral cortex is thought to involve two phases: an early regionalization phase and a later refinement phase. It has been shown that early regionalization of the neocortex does not require thalamic inputs and is regulated by intrinsic factors. Recently, two such intrinsic factors, Pax6 and Emx2, have been identified. In this study, we identified COUP-TFIas a regulatory factor for early neocortical regionalization. The spatial and temporal expression pattern of COUP-TFI suggested a role in specification of the neocortex and in maintaining cortical identity. Altered region-specific expression of marker genes in the cortex as well as miswired area-specific connections between the cortex and the thalamus in COUP-TFI null mice indicateCOUP-TFI plays a critical role in regulating early regionalization. Our results substantiate that COUP-TFI, an intrinsic factor, may work in concert with Pax6 andEmx2 to specify neocortical identity.
Mastermind mediates chromatin-specific transcription and turnover of the Notch enhancer complex
Authors: Fryer Christy J. , Lamar Elise , Turbachova Ivana , Kintner Chris , Jones Katherine A.
Published: July 2002

Signaling through the Notch pathway activates the proteolytic release of the Notch intracellular domain (ICD), a dedicated transcriptional coactivator of CSL enhancer-binding proteins. Here we show that chromatin-dependent transactivation by the recombinant Notch ICD–CBF1 enhancer complex in vitro requires an additional coactivator, Mastermind (MAM). MAM provides two activation domains necessary for Notch signaling in mammalian cells and in Xenopus embryos. We show that the central MAM activation domain (TAD1) recruits CBP/p300 to promote nucleosome acetylation at Notch enhancers and activate transcription in vitro. We also find that MAM expression induces phosphorylation and relocalization of endogenous CBP/p300 proteins to nuclear foci in vivo. Moreover, we show that coexpression with MAM and CBF1 strongly enhances phosphorylation and proteolytic turnover of the Notch ICD in vivo. Enhanced phosphorylation of the ICD and p300 requires a glutamine-rich region of MAM (TAD2) that is essential for Notch transcription in vivo. Thus MAM may function as a timer to couple transcription activation with disassembly of the Notch enhancer complex on chromatin.
Searching for the Memory Trace in a Mini-Brain, the Honeybee
Authors: Menzel Randolf
Published: July 2002

To determine general or species-specific properties in neural systems, it is necessary to use comparative data in evaluating experimental findings. Presented here are data on associative learning and memory formation in honeybees, emphasizing a comparative approach. We focus on four aspects: (1) the role of an identified neuron, VUMmx1, as a neural substrate of appetitive reinforcement; (2) the sequences of molecular events as they correlate with five forms of memory stages; (3) the localization of the memory traces following appetitive olfactory learning; and (4) the brief description of several forms of complex learning in bees (configuration in olfactory conditioning, categorization in visual feature learning, delayed matching-to-sample learning, and latent learning in navigation). VUMmx1activity following the conditioned stimulus odor is sufficient to replace the unconditioned stimulus, and VUMmx1changes its response properties during learning similarly to what is known from dopamine neurons in the basal ganglia of the mammalian brain. The transition from short- to mid- and long-term forms of memory can be related to specific activation of second messenger cascades (involving NOS, PKA, PKC, and PKM) resembling general features of neural plasticity at the cellular level. The particular time course of the various memory traces may be adapted to the behavioral context in which they are used; here, the foraging cycle of the bee. Memory traces for even such a simple form of learning as olfactory conditioning are multiple and distributed, involving first- and second-order sensory neuropils (antennal lobe and mushroom bodies), but with distinctly different properties. The wealth of complex forms of learning in the context of foraging indicates basic cognitive capacities based on rule extraction and context-dependent learning. It is believed that bees might be a useful model for studying cognitive faculties at a middle level of complexity.
Massed and Spaced Learning in Honeybees: The Role of CS, US, the Intertrial Interval, and the Test Interval
Authors: Menzel Randolf , Manz Gisela , Menzel Rebecca , Greggers Uwe
Published: July 2002

Conditioning the proboscis extension reflex of harnessed honeybees (Apis mellifera) is used to study the effect temporal spacing between successive conditioning trials has on memory. Retention is monitored at two long-term intervals corresponding to early (1 and 2 d after conditioning) and late long-term memory (3 and 4 d). The acquisition level is varied by using different conditioned stimuli (odors, mechanical stimulation, and temperature increase at the antenna), varying strengths of the unconditioned stimulus (sucrose), and various numbers of conditioning trials. How learning trials are spaced is the dominant factor both for acquisition and retention, and although longer intertrial intervals lead to better acquisition and higher retention, the level of acquisition per se does not determine the spacing effect on retention. Rather, spaced conditioning leads to higher memory consolidation both during acquisition and later, between the early and long-term memory phases. These consolidation processes can be selectively inhibited by blocking protein synthesis during acquisition.
Ascorbate Deficiency Can Limit Violaxanthin De-Epoxidase Activity in Vivo
Authors: Müller-Moulé Patricia , Conklin Patricia L. , Niyogi Krishna K.
Published: July 2002

As a response to high light, plants have evolved non-photochemical quenching (NPQ), mechanisms that lead to the dissipation of excess absorbed light energy as heat, thereby minimizing the formation of dangerous oxygen radicals. One component of NPQ is pH dependent and involves the formation of zeaxanthin from violaxanthin. The enzyme responsible for the conversion of violaxanthin to zeaxanthin is violaxanthin de-epoxidase, which is located in the thylakoid lumen, is activated by low pH, and has been shown to use ascorbate (vitamin C) as its reductant in vitro. To investigate the effect of low ascorbate levels on NPQ in vivo, we measured the induction of NPQ in a vitamin C-deficient mutant of Arabidopsis, vtc2-2. During exposure to high light (1,500 μmol photons m−2s−1), vtc2-2 plants initially grown in low light (150 μmol photons m−2 s−1) showed lower NPQ than the wild type, but the same quantum efficiency of photosystem II. Crosses between vtc2-2 and Arabidopsis ecotype Columbia established that the ascorbate deficiency cosegregated with the NPQ phenotype. The conversion of violaxanthin to zeaxanthin induced by high light was slower in vtc2-2, and this conversion showed saturation below the wild-type level. Both the NPQ and the pigment phenotype of the mutant could be rescued by feeding ascorbate to leaves, establishing a direct link between ascorbate, zeaxanthin, and NPQ. These experiments suggest that ascorbate availability can limit violaxanthin de-epoxidase activity in vivo, leading to a lower NPQ. The results also demonstrate the interconnectedness of NPQ and antioxidants, both important protection mechanisms in plants.
Abscisic Acid Induces the Alcohol Dehydrogenase Gene in Arabidopsis
Authors: de Bruxelles G. L. , Peacock W. J. , Dennis E. S. , Dolferus R.
Published: July 2002

Exogenous abscisic acid (ABA) induced the alcohol dehydrogenase gene (Adh) in Arabidopsis roots. Both the G-box-1 element and the GT/GC motifs (anaerobic response element) were required for Adh inducibility. Measurement of endogenous ABA levels during stress treatment showed that ABA levels increased during dehydration treatment but not following exposure to either hypoxia or low temperature. Arabidopsis ABA mutants (aba1 and abi2) displayed reduced Adh mRNA induction levels following either dehydration treatment or exogenous application of ABA. Low-oxygen response was slightly increased in the aba1 mutant but was unchanged in abi2. Low-temperature response was unaffected in both aba1 and abi2 mutants. Our results indicate that, although induction of the Adh gene by ABA, dehydration, and low temperature required the same cis-acting promoter elements, their regulatory pathways were at least partially separated in a combined dehydration/ABA pathway and an ABA-independent low-temperature pathway. These pathways were in turn independent of a third signal transduction pathway leading to low-oxygen response, which did not involve either ABA or the G-box-1 promoter element.
Degradation Pattern of Photosystem II Reaction Center Protein D1 in Intact Leaves (The Major Photoinhibition-Induced Cleavage Site in D1 Polypeptide Is Located Amino Terminally of the DE Loop)
Authors: Kettunen R. , Tyystjarvi E. , Aro E. M.
Published: July 2002

Photoinhibition-induced degradation of the D1 protein of the photosystem II reaction center was studied in intact pumpkin (Cucurbita pepo L.) leaves. Photoinhibition was observed to cause the cleavage of the D1 protein at two distinct sites. The main cleavage generated an 18-kD N-terminal and a 20-kD C-terminal degradation fragment of the D1 protein. This cleavage site was mapped to be located clearly N terminally of the DE loop. The other, less-frequent cleavage occurred at the DE loop and produced the well-documented 23-kD, N-terminal D1 degradation product. Furthermore, the 23-kD, N-terminal D1 fragment appears to be phosphorylated and can be detected only under severe photoinhibition in vivo. Comparison of the D1 degradation pattern after in vivo photoinhibition to that after in vitro acceptor-side and donor-side photoinhibition, performed with isolated photosystem II core particles, gives indirect evidence in support of donor-side photoinhibition in intact leaves.
Two Divergent Members of a Tobacco 4-Coumarate:Coenzyme A Ligase (4CL) Gene Family (cDNA Structure, Gene Inheritance and Expression, and Properties of Recombinant Proteins)
Authors: Lee D. , Douglas C. J.
Published: July 2002

Several cDNA clones encoding 4-coumarate:coenzyme A ligase (4CL) were isolated from a tobacco (Nicotiana tabacum) cDNA library and grouped into two classes. Sequencing of one cDNA from each class showed that the clones were similar to other 4CL genes and about 80% identical with each other. Genomic Southern blots using DNA from Nicotiana sylvestris, Nicotiana tomentosiformis, and N. tabacum demonstrated the presence of both classes of 4CL sequences (4CL1 and 4CL2) in the progenitor species and in tobacco. Northern blots indicated that 4CL mRNA transcripts are highest in old stems and higher in the unpigmented corolla tubes than in the pigmented limbs of tobacco flowers. The 4CL genes are developmentally regulated and are wound and methyl jasmonate inducible. The relative abilities of recombinant 4CL1 and 4CL2 proteins to utilize 4-coumarate, ferulate, and caffeate as substrates were similar and comparable with that of 4CL in tobacco stem extracts. Surprisingly, both recombinant 4CL proteins utilized cinnamate as a substrate, an activity not observed in stem extracts. This activity was inhibited by a heat-labile, high-molecular-weight factor found in tobacco stem extracts, suggesting that the substrate specificity of 4CL is, in part, determined by the activity of proteinaceous cellular components.
Synthesis of Small Heat-Shock Proteins Is Part of the Developmental Program of Late Seed Maturation
Authors: Wehmeyer N. , Hernandez L. D. , Finkelstein R. R. , Vierling E.
Published: July 2002

Small heat-shock proteins (sHSPs) accumulate in plants in response to high-temperature stress. Specific sHSPs, the cytosolic class I and class II proteins, are also expressed in the absence of stress in maturing seeds of several species, and a role for these proteins in desiccation tolerance, dormancy, or germination has been hypothesized. We demonstrate that class I sHSPs are expressed during Arabidopsis seed development in a pattern similar to that previously observed in other species: they are first detected during mid-maturation, are most abundant in dry seeds, and decline rapidly during germination. Although the class I sHSP family in Arabidopsis appears to consist of four genes, expression of a single gene, Athsp17.4, accounts for the majority of sHSPs in maturing seeds. sHSP levels were also examined in seeds of several Arabidopsis mutants with reduced sensitivity to abscisic acid inhibition, including aba1, abi1 and abi2, abi3–1, abi3–6, abi4, and abi5–1. The abi3–1 mutant has 10-fold reduced levels of sHSPs; sHSPs are undetectable in the abi3–6 mutant. All other mutants were indistinguishable from wild type. These results suggest that sHSP expression in seeds is regulated by the ABI3 response pathway and wild-type levels of sHSPs are not sufficient for seed dormancy and not necessary for desiccation tolerance. However, roles in either process cannot be ruled out. In total the data indicate that the expression of sHSPs in seeds is part of the normal developmental program of late seed maturation and the presence of sHSPs has adaptive significance for plant reproduction.
De Novo Purine Synthesis in Arabidopsis thaliana (II. The PUR7 Gene Encoding 5[prime]-Phosphoribosyl-4-(N-Succinocarboxamide)-5-Aminoimidazole Synthetase Is Expressed in Rapidly Dividing Tissues)
Authors: Senecoff J. F. , McKinney E. C. , Meagher R. B.
Published: July 2002

The small genome size and excellent genetics of Arabidopsis, as well as the ease with which it is transformed, make it a superb candidate for molecular genetic studies of the purine biosynthetic pathway. Herein we report the isolation, physical characterization, and dissection of the expression patterns of the single gene encoding 5[prime]-phosphoribosyl-4-(N-succinocarboxamide)-5-aminoimidazole synthetase. This enzyme, encoded by the PUR7 gene, catalyzes aspartate addition at the α--amino group to the growing purine backbone. The expression of the PUR7 as directed by the 5[prime] region, containing the promoter, mRNA leader, and leader intron, was examined in Arabidopsis using a transgenic reporter system. Our analysis demonstrates that the highest level of purine biosynthesis occurs in mitotically active tissues of the plant. Furthermore, purine biosynthesis appears to be under developmental and hormonal regulation. Inhibition of purine biosynthesis using substrate analogs results in arrested plant development and induction of purine gene expression. Purine nucleotides and their derivatives provide multiple cofactors for a variety of metabolic processes. Our findings begin to identify some of the regulatory mechanisms that affect the production of purine nucleotides in Arabidopsis and may give important insights into nitrogen metabolism in general.
Pyrophosphorylases in Potato (V. Allelic Polymorphism of UDP-Glucose Pyrophosphorylase in Potato Cultivars and Its Association with Tuber Resistance to Sweetening in the Cold)
Authors: Sowokinos J. R. , Thomas C. , Burrell M. M.
Published: July 2002

UDP-glucose pyrophosphorylase (UGPase) was cloned from six American and nine European potato (Solanum tuberosum L.) cultivars. Restriction mapping of the different UGPase-cDNAs with BamHI, HindIII, and EcoRI revealed that at least two mRNA populations were present in most cultivars. Staining for UGPase activity in nondenaturing gels of proteins extracted from developing potato tubers yielded two major isozymes that were highly active and appeared to be dimeric in nature. Following sodium dodecyl sulfate-polyacrylamide gel electrophoresis, all isozymes were disassociated into a single subunit with a molecular mass of 53 kD. Since UGPase has been demonstrated to be a single-copy gene in the haploid genome of potato (A.Y. Borovkov, P.E. McClean, J.R. Sowokinos, S.H. Ruud, G.A. Secor [1995] J Plant Physiol 147: 644–652), there must be allelic differences at the UGPase locus (chromosome 11). The two alleles, designated ugpA and ugpB, were identified by the absence and presence of a BamHI site, respectively. The relative band intensities of the two cDNA populations following polymerase chain reaction amplification and agarose gel electrophoresis were related to a potato cultivar's ability to resist sweetening when exposed to cold temperatures.
Characterization of AtSEC12 and AtSAR1 (Proteins Likely Involved in Endoplasmic Reticulum and Golgi Transport)
Authors: Bar-Peled M. , Raikhel N. V.
Published: July 2002

Transport of cargo proteins from the endoplasmic reticulum (ER) to the cis-Golgi network is mediated by protein-coated vesicles. The coat, called COPII coat, consists of proteins that are recruited from the cytosol and interact with integral membrane proteins of the ER. In yeast, both cytosolic proteins (Sec13/31, Sec23/24, and Sar1) and ER-associated proteins (Sec12 and others) have been purified and characterized and it has been possible to demonstrate transport vesicle formation in vitro. Arabidopsis thaliana homologs of Sar1 and Sec12 have recently been identified, but little is known about the properties of the proteins or their subcellular distribution. Here we demonstrate that AtSAR1, a 22-kD protein that binds GTP, and AtSEC12, a 43-kD GTP-exchange protein, are both associated with the ER. However, about one-half of the cellular AtSAR1 is present in the cytosol. When AtSAR1 is overexpressed in transgenic plants, the additional protein is also cytosolic. When tissue-culture cells are cold-shocked (12 h at 8[deg]C), AtSAR1 levels appeared to decline and a larger proportion of the total protein was found in the cytosol. Given the known function of AtSAR1 in yeast, we propose that the amount of ER-associated AtSAR1 is an indication of the intensity of the secretory process. Thus, we expect that such a cold shock will adversely affect ER-to-Golgi transport of proteins.
Broad-Range and Binary-Range Acyl-Acyl-Carrier-Protein Thioesterases Suggest an Alternative Mechanism for Medium-Chain Production in Seeds
Authors: Voelker T. A. , Jones A. , Cranmer A. M. , Davies H. M. , Knutzon D. S.
Published: July 2002

In the current model of medium-chain (C8–14) fatty acid biosynthesis in seeds, specialized FatB acyl-acyl-carrier-protein (ACP) thioesterases are responsible for the production of medium chains. We have isolated and characterized FatB cDNAs from the maturing seeds of elm (Ulmus americana) and nutmeg (Myristica fragrans), which accumulate predominantly caprate (10:0)- and myristate (14:0)-containing oils, respectively. In neither species were we able to find cDNAs encoding enzymes specialized for these chain lengths. Nutmeg FatB hydrolyses C14–18 substrates in vitro and expression in Brassica napus seeds leads to an oil enriched in C14–18 saturates. Elm FatB1 displays a binary specificity: one activity is centered on 10:0-ACP, and a second is centered on palmitate (16:0)-ACP. After expression in B. napus seeds the oil is enriched in C10–18 saturates, predominantly 16:0, 14:0, and 10:0. The composition of free fatty acids produced by elm FatB1 in Escherichia coli shifts from C14–16 to mostly C8–10 by increasing the rate of chain termination by this enzyme. These results suggest the existence of an alternative mechanism used in the evolution of medium-chain production, a model of which is presented.
Defense Responses to Tetrapyrrole-Induced Oxidative Stress in Transgenic Plants with Reduced Uroporphyrinogen Decarboxylase or Coproporphyrinogen Oxidase Activity1
Authors: Mock Hans-Peter , Keetman Ulrich , Kruse Elisabeth , Rank Barbara , Grimm Bernhard
Published: July 2002

We analyzed the antioxidative defense responses of transgenic tobacco (Nicotiana tabacum) plants expressing antisense RNA for uroporphyrinogen decarboxylase or coproporphyrinogen oxidase. These plants are characterized by necrotic leaf lesions resulting from the accumulation of potentially photosensitizing tetrapyrroles. Compared with control plants, the transformants had increased levels of antioxidant mRNAs, particularly those encoding superoxide dismutase (SOD), catalase, and glutathione peroxidase. These elevated transcript levels correlated with increased activities of cytosolic Cu/Zn-SOD and mitochondrial Mn-SOD. Total catalase activity decreased in the older leaves of the transformants to levels lower than in the wild-type plants, reflecting an enhanced turnover of this photosensitive enzyme. Most of the enzymes of the Halliwell-Asada pathway displayed increased activities in transgenic plants. Despite the elevated enzyme activities, the limited capacity of the antioxidative system was apparent from decreased levels of ascorbate and glutathione, as well as from necrotic leaf lesions and growth retardation. Our data demonstrate the induction of the enzymatic detoxifying defense system in several compartments, suggesting a photosensitization of the entire cell. It is proposed that the tetrapyrroles that initially accumulate in the plastids leak out into other cellular compartments, thereby necessitating the local detoxification of reactive oxygen species.
Aluminum Induces a Decrease in Cytosolic Calcium Concentration in BY-2 Tobacco Cell Cultures1
Authors: Jones David L. , Kochian Leon V. , Gilroy Simon
Published: July 2002

Al toxicity is a major problem that limits crop productivity on acid soils. It has been suggested that Al toxicity is linked to changes in cellular Ca homeostasis and the blockage of plasma membrane Ca2+-permeable channels. BY-2 suspension-cultured cells of tobacco (Nicotiana tabacumL.) exhibit rapid cell expansion that is sensitive to Al. Therefore, the effect of Al on changes in cytoplasmic free Ca concentration ([Ca2+]cyt) was followed in BY-2 cells to assess whether Al perturbed cellular Ca homeostasis. Al exposure resulted in a prolonged reduction in [Ca2+]cyt and inhibition of growth that was similar to the effect of the Ca2+ channel blocker La3+ and the Ca2+ chelator ethyleneglycol-bis(β-aminoethyl ether)-N,N′-tetraacetic acid. The Ca2+channel blockers verapamil and nifedipine did not induce a decrease in [Ca2+]cyt in these cells and also failed to inhibit growth. Al and La3+, but not verapamil or nifedipine, reduced the rate of Mn2+ quenching of Indo-1 fluorescence, which is consistent with the blockage of Ca2+- and Mn2+-permeable channels. These results suggest that Al may act to block Ca2+ channels at the plasma membrane of plant cells and this action may play a crucial role in the phytotoxic activity of the Al ion.
Actin Depolymerization Affects Stress-Induced Translational Activity of Potato Tuber Tissue1
Authors: Morelli James K. , Zhou Wei , Yu Jia , Lu Chen , Vayda Michael E.
Published: July 2002

Changes in polymerized actin during stress conditions were correlated with potato (Solanum tuberosum L.) tuber protein synthesis. Fluorescence microscopy and immunoblot analyses indicated that filamentous actin was nearly undetectable in mature, quiescent aerobic tubers. Mechanical wounding of postharvest tubers resulted in a localized increase of polymerized actin, and microfilament bundles were visible in cells of the wounded periderm within 12 h after wounding. During this same period translational activity increased 8-fold. By contrast, low-oxygen stress caused rapid reduction of polymerized actin coincident with acute inhibition of protein synthesis. Treatment of aerobic tubers with cytochalasin D, an agent that disrupts actin filaments, reduced wound-induced protein synthesis in vivo. This effect was not observed when colchicine, an agent that depolymerizes microtubules, was used. Neither of these drugs had a significant effect in vitro on run-off translation of isolated polysomes. However, cytochalasin D did reduce translational competence in vitro of a crude cellular fraction containing both polysomes and cytoskeletal elements. These results demonstrate the dependence of wound-induced protein synthesis on the integrity of microfilaments and suggest that the dynamics of the actin cytoskeleton may affect translational activity during stress conditions.
Phytochrome B Affects the Levels of a Graft-Transmissible Signal Involved in Tuberization1
Authors: Jackson Stephen D. , James Pat , Prat Salomé , Thomas Brian
Published: July 2002

Grafting experiments between phytochrome B antisense and wild-type potato (Solanum tuberosum L. subsp. andigena [line 7540]) plants provide evidence that phytochrome B is involved in the production of a graft-transmissible inhibitor of tuberization, the level of which is reduced in the antisense plants, allowing them to tuberize in noninducing photoperiods.
Correlation between Binding Affinity and Necrosis-Inducing Activity of Mutant AVR9 Peptide Elicitors1
Authors: Kooman-Gersmann Miriam , Vogelsang Ralph , Vossen Paul , van den Hooven Henno W. , Mahé Eve , Honée Guy , de Wit Pierre J.G.M.
Published: July 2002

The race-specific peptide elicitor AVR9 of the fungus Cladosporium fulvum induces a hypersensitive response only in tomato (Lycopersicon esculentum) plants carrying the complementary resistance gene Cf-9 (MoneyMaker-Cf9). A binding site for AVR9 is present on the plasma membranes of both resistant and susceptible tomato genotypes. We used mutant AVR9 peptides to determine the relationship between elicitor activity of these peptides and their affinity to the binding site in the membranes of tomato. Mutant AVR9 peptides were purified from tobacco (Nicotiana clevelandii) inoculated with recombinant potato virus X expressing the corresponding avirulence geneAvr9. In addition, several AVR9 peptides were synthesized chemically. Physicochemical techniques revealed that the peptides were correctly folded. Most mutant AVR9 peptides purified from potato virus X::Avr9-infected tobacco contain a single N-acetylglucosamine. These glycosylated AVR9 peptides showed a lower affinity to the binding site than the nonglycosylated AVR9 peptides, whereas their necrosis-inducing activity was hardly changed. For both the nonglycosylated and the glycosylated mutant AVR9 peptides, a positive correlation between their affinity to the membrane-localized binding site and their necrosis-inducing activity in MoneyMaker-Cf9 tomato was found. The perception of AVR9 in resistant and susceptible plants is discussed.
Expression of Small Heat-Shock Proteins at Low Temperatures1
Authors: Sabehat Adnan , Lurie Susan , Weiss David
Published: July 2002

We previously reported that short exposure of tomato (Lycopersicon esculentum L.) fruits to high temperature protects them from chilling injury. To study the involvement of heat-shock proteins (HSPs) in the acquisition of low-temperature tolerance, we cloned two heat-shock-induced genes that are also expressed at low temperatures. The cloned cDNAs belong to the small HSP group. Sequence analyses of the clones showed perfect homology to the tomato-ripening gene tom66 and to the tomato chloroplastic HSP21 gene tom111. The expression of both genes was induced by high temperature in fruits, flowers, leaves, and stems, but not by low or ambient temperatures or by other stresses such as drought and anaerobic conditions. When the heated fruits were transferred to low temperature, tom66and tom111 mRNA levels first decreased but were then reinduced. Induction was not observed in nonheated fruits at low temperature. Immunodetection of tom111-encoded protein indicated that this protein is present at low temperatures in the heated fruits. The results of this study show that the expression oftom66 and tom111 is correlated with protection against some, but not all, symptoms of chilling injury.
The Biosynthesis of Salicylic Acid in Potato Plants1
Authors: Coquoz Jean-Luc , Buchala Antony , Métraux Jean-Pierre
Published: July 2002

Spraying potato (Solanum tuberosum L.) leaves with arachidonic acid (AA) at 1500 μg mL−1 led to a rapid local synthesis of salicylic acid (SA) and accumulation of a SA conjugate, which was shown to be 2-O-β-glucopyranosylsalicylic acid. Radiolabeling studies with untreated leaves showed that SA was synthesized from phenylalanine and that both cinnamic and benzoic acid were intermediates in the biosynthesis pathway. Using radiolabeled phenylalanine as a precursor, the specific activity of SA was found to be lower when leaves were treated with AA than in control leaves. Similar results were obtained when leaves were fed with the labeled putative intermediates cinnamic acid and benzoic acid. Application of 2-aminoindan-2-phosphonic acid at 40 μm, an inhibitor of phenylalanine ammonia-lyase, prior to treatment with AA inhibited the local accumulation of SA. When the putative intermediates were applied to leaves in the presence of 2-aminoindan-2-phosphonic acid, about 40% of the expected accumulation of free SA was recovered, but the amount of the conjugate remained constant.
Dehydration-Stress-Regulated Transgene Expression in Stably Transformed Rice Plants1
Authors: Su Jin , Shen Qingxi , David Ho Tuan-Hua , Wu Ray
Published: July 2002

To confer abscisic acid (ABA) and/or stress-inducible gene expression, an ABA-response complex (ABRC1) from the barley (Hordeum vulgare L.) HVA22gene was fused to four different lengths of the 5′ region from the rice (Oryza sativa L.) Act1 gene. Transient assay of β-glucuronidase (GUS) activity in barley aleurone cells shows that, coupled with ABRC1, the shortest minimal promoter (Act1–100P) gives both the greatest induction and the highest level of absolute activity following ABA treatment. Two plasmids with one or four copies of ABRC1 combined with the same Act1–100P and HVA22(I) of barley HVA22 were constructed and used for stable expression of uidA in transgenic rice plants. Three Southern blot-positive lines with the correct hybridization pattern for each construct were obtained. Northern analysis indicated thatuidA expression is induced by ABA, water-deficit, and NaCl treatments. GUS activity assays in the transgenic plants confirmed that the induction of GUS activity varies from 3- to 8-fold with different treatments or in different rice tissues, and that transgenic rice plants harboring four copies of ABRC1 show 50% to 200% higher absolute GUS activity both before and after treatments than those with one copy of ABRC1.
A Novel Gene, pmgA, Specifically Regulates Photosystem Stoichiometry in the CyanobacteriumSynechocystis Species PCC 6803 in Response to High Light1
Authors: Hihara Yukako , Sonoike Kintake , Ikeuchi Masahiko
Published: July 2002

Previously, we identified a novel gene, pmgA, as an essential factor to support photomixotrophic growth of Synechocystis species PCC 6803 and reported that a strain in which pmgA was deleted grew better than the wild type under photoautotrophic conditions. To gain insight into the role of pmgA, we investigated the mutant phenotype of pmgA in detail. When low-light-grown (20 μE m−2 s−1) cells were transferred to high light (HL [200μE m−2s−1]), pmgA mutants failed to respond in the manner typically associated with Synechocystis. Specifically, mutants lost their ability to suppress accumulation of chlorophyll and photosystem I and, consequently, could not modulate photosystem stoichiometry. These phenotypes seem to result in enhanced rates of photosynthesis and growth during short-term exposure to HL. Moreover, mixed-culture experiments clearly demonstrated that loss ofpmgA function was selected against during longer-term exposure to HL, suggesting that pmgA is involved in acquisition of resistance to HL stress. Finally, early induction ofpmgA expression detected by reverse transcriptase-PCR upon the shift to HL led us to conclude that pmgA is the first gene identified, to our knowledge, as a specific regulatory factor for HL acclimation.
Characterization of Two Glutamate Decarboxylase cDNA Clones from Arabidopsis
Authors: Turano Frank J. , Fang Tung K.
Published: July 2002

Two distinct cDNA clones encoding for the glutamate decarboxylase (GAD) isoenzymes GAD1 andGAD2 from Arabidopsis (L.) Heynh. were characterized. The open reading frames for GAD1 and GAD2 were expressed inEscherichia coli and the recombinant proteins were purified by affinity chromatography. Analysis of the recombinant proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis suggest that GAD1 andGAD2 encode for 58- and 56-kD peptides, respectively. The enzymatic activities of the pure recombinant GAD1 and GAD2 proteins were stimulated 35- and 13-fold, respectively, by Ca2+/calmodulin but not by Ca2+ or calmodulin alone. Southern-blot analysis of genomic DNA suggests that there is only one copy of each gene in Arabidopsis. The GAD1transcript and a corresponding 58-kD peptide were detected in roots only. Conversely, the GAD2 transcript and a corresponding 56-kD peptide were detected in all organs tested. The specific activity, GAD2 transcript, and 56-kD peptide increased in leaves of plants treated with 10 mmNH4Cl, 5 mm NH4NO3, 5 mm glutamic acid, or 5 mm glutamine as the sole nitrogen source compared with samples from plants treated with 10 mm KNO3. The results from these experiments suggest that in leaves GAD activity is partially controlled by gene expression or RNA stability. Results from preliminary analyses of different tissues imply that these tendencies were not the same in flower stalks and flowers, suggesting that other factors may control GAD activity in these organs. The results from this investigation demonstrate that GAD activity in leaves is altered by different nitrogen treatments, suggesting that GAD2 may play a unique role in nitrogen metabolism.
Oxalate Exudation by Taro in Response to Al
Authors: Ma Zhong , Miyasaka Susan C.
Published: July 2002

Roots of taro (Colocasia esculenta [L.] Schott cvs Bun-long and Lehua maoli) exuded increasing concentrations of oxalate with increasing Al stress. This exudation was a specific response to excess Al and not to P deficiency. Addition of oxalate to Al-containing solutions ameliorated the toxic effect of Al.