bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of arbuscule formation by carbon in the plant
Authors: Blee Kristopher A. , Anderson Anne J. 
Published: March 2003

Summary Arbuscules are proposed to be the key site of interchange of carbon between root cells and the hyphae of arbuscular mycorrhizal (AM) fungi. This paper addresses how carbon availability is a driving force in regulating location and function of arbuscules in cortical cells. We discuss physical and biological limitations on arbuscule position. Altered expression, specifically in the arbusculated cell, of genes that govern sucrose hydrolysis may create a sink for sucrose in these cells. We propose a role for vacuolar invertase and cytoplasmic sucrose synthase in catalyzing the intracellular hydrolysis of sucrose, thus maintaining a gradient for symplastic influx of sucrose into the arbusculated cell and establishing a gradient for hexose efflux to the apoplast for fungal utilization. AM fungi may regulate hydrolysis of sucrose by stimulating the expression and activities of plant invertases by the production of plant hormones as well as through acidification of the arbuscular interface. We speculate that altered plant defense gene expression in arbusculated cells is consistent with regulation by sugar‐sensing mechanisms.
A male gametophyte‐specific monosaccharide transporter inArabidopsis
Authors: Truernit Elisabeth , Stadler Ruth , Baier Kerstin , Sauer Norbert 
Published: March 2003

Summary The

AtSTP2

gene (sugar transport protein 2) of

Arabidopsis thaliana

encodes a high affinity, low specificity monosaccharide carrier that can transport a number of hexoses and pentoses at similar rates. AtSTP2 has 12 putative transmembrane helices and a molecular mass of 55.0 kDa.

AtSTP2

expression was localized in

AtSTP2

promoter‐β‐glucuronidase (

GUS

)

Arabidopsis

plants showing

AtSTP2

‐driven GUS activity during pollen maturation and also in germinating pollen. Immunohistochemical studies with anti‐AtSTP2 antiserum as well as RNA

in situ

hybridization analyses modified these results and showed that

AtSTP2

expression is confined to the early stages of gametophyte development. Both

AtSTP2

mRNA and AtSTP2 protein are first seen at the time of beginning callose degradation and microspore release from the tetrades.

AtSTP2

mRNA and AtSTP2 protein are no longer detected after the mitotic divisions and the formation of the trinucleate gametophyte. No

AtSTP2

mRNA or AtSTP2 protein is seen in fully developed or germinating pollen. The putative role of AtSTP2 in the uptake of glucose units resulting from callose degradation during pollen maturation is discussed.
Regulation of carotenoid biosynthesis during tomato fruit development: expression of the gene for lycopene epsilon‐cyclase is down‐regulated during ripening and is elevated in the mutantDelta
Authors: Ronen Gil , Cohen Merav , Zamir Dani , Hirschberg Joseph 
Published: March 2003

Summary The red colour of tomato (

Lycopersicon esculentum

) fruits is provided by the carotenoid pigment lycopene whose concentration increases dramatically during the ripening process. A single dominant gene,

Del

, in the tomato mutant

Delta

changes the fruit colour to orange as a result of accumulation of δ‐carotene at the expense of lycopene. The cDNA for lycopene ε‐cyclase (

CrtL‐e

), which converts lycopene to δ‐carotene, was cloned from tomato. The primary structure of CRTL‐E is 71% identical to the homologous polypeptide from

Arabidopsis

and 36% identical to the tomato lycopene β‐cyclase, CRTL‐B. The

CrtL‐e

gene was mapped to a single locus on chromosome 12 of the tomato linkage map. This locus co‐segregated with the

Del

gene. In the wild‐type tomato, the transcript level of

CrtL‐e

decreases at the ‘breaker' stage of ripening to a non‐detectable level in the ripe fruit. In contrast, it increases approximatley 30‐fold during fruit ripening in the

Delta

plants. The

Delta

mutation does not affect carotenoid composition nor the mRNA level of

CrtL‐e

in leaves and flowers. These results strongly suggest that the mutation

Del

is an allele of the gene for ε‐cyclase. Together with previous data, our results indicate that the primary mechanism that controls lycopene accumulation in tomato fruits is based on the differential regulation of expression of carotenoid biosynthesis genes. During fruit development, the mRNA levels for the lycopene‐producing enzymes phytoene synthase (PSY) and phytoene desaturase (PDS) increase, while the mRNA levels of the genes for the lycopene β‐ and ε‐cyclases, which convert lycopene to either β‐ or δ‐carotene, respectively, decline and completely disappear.
A pathogen‐ and salicylic acid‐induced WRKY DNA‐binding activity recognizes the elicitor response element of the tobacco class I chitinase gene promoter
Authors: Yang Peizhen , Chen Chunhong , Wang Zeping , Fan Baofang , Chen Zhixiang 
Published: March 2003

SummaryUsing a simple oligo selection procedure, we have previously identified a tobacco sequence‐specific DNA‐binding activity, TDBA12, that increases markedly during the tobacco mosaic virus (TMV)‐induced hypersensitive response (HR). Based on the binding specificity and the two cDNA clones isolated, TDBA12 is related to a novel class of DNA‐binding factors containing WRKY domains. In the present study, we report that TDBA12 could be induced not only by TMV infection but also by treatment with salicylic acid (SA) or its biologically active analogs capable of inducing pathogenesis‐related (PR) genes and enhanced resistance. TDBA12 was sensitive to temperature and the protein dissociating agent sodium deoxycholate, suggesting that it may be a multimeric factor in which protein–protein interaction is important for the enhanced DNA‐binding activity. Pre‐treatment of nuclear extracts with alkaline phosphatase abolished TDBA12, suggesting that protein phosphorylation is important for its high DNA‐binding activity. TDBA12 specifically recognized the elicitor response element of the tobacco class I basic chitinase gene promoter. The increase in the levels of TDBA12 following TMV infection or SA treatment preceded the induced expression of the tobacco chitinase gene. These results strongly suggest that certain WRKY DNA‐binding proteins may be activated by enhanced protein phosphorylation and regulate inducible expression of defense‐related genes during pathogen‐ and SA‐induced plant defense responses.
The expression of tobacco knotted1‐type class 1 homeobox genes correspond to regions predicted by the cytohistological zonation model
Authors: Nishimura Asuka , Tamaoki Masanori , Sato Yutaka , Matsuoka Makoto 
Published: March 2003

SummaryWe have isolated and characterized four tobacco homeobox genes, NTH1, NTH9, NTH20, NTH22 (Nicotiana tabacum homeobox) which belong to the class 1 knotted1‐type family of homeobox genes. Comparison of the inferred amino acid sequences of the ELK homeodomains of these genes and previously reported kn1‐type class 1 proteins has revealed that the four new tobacco genes belong to distinct subclasses, suggesting that each NTH gene may have distinct functions. Using in situ hybridization and by analysing the distribution of GUS activity in tobacco plants transformed with NTH promoter::GUS constructs, local‐ ized expression of the three NTH genes was observed in the shoot apical meristem (SAM). In the vegetative SAM, NTH1 and NTH15 showed overlapping expression in the corpus, NTH20 was expressed in the peripheral zone, and NTH9 was predominantly expressed in the rib zone. The expression patterns of the different NTH genes correspond to regions predicted by the cytohistological zonation model, suggesting that each NTH gene specifies the function of the SAM zone with which it is associated.
Increased steady state mRNA levels of the STM and KNAT1 homeobox genes in cytokinin overproducing Arabidopsis thaliana indicate a role for cytokinins in the shoot apical meristem
Authors: Rupp Hans‐Michael , Frank Markus , Werner Tomás , Strnad Miroslav , Schmülling Thomas 
Published: March 2003

Summary This study investigates the consequences of endo‐ genously enhanced biosynthesis of the plant hormone cytokinin in Arabidopsis thaliana (L.) Heynh. Tran‐ scriptional control of the bacterial ipt gene by the Drosophila melanogaster hsp70 promoter enabled temperature‐dependent increased cytokinin production in transgenic plants. Heat‐treated plants accumulated higher levels of unbound and bound zeatin‐type cyto‐ kinins, the latter being preferentially N‐conjugated glucosides. Cytokinin overproduction significantly increased the biomass of seedlings. Ipt transgenics had higher steady state mRNA levels of the shoot meristem specifying homeobox genes KNAT1 and STM, similar to the cytokinin‐overproducing shoot meristem mutant amp1 (hpt, cop2, pt) This finding, together with previously described phenotypic similarities between transgenic cytokinin‐overproducing plants and plants overexpressing the KNAT1 or KN1 genes, suggests that these factors act on the same pathway. We hypothesize that cytokinins act upstream of KNAT1 and STM. The influence of cytokinins on homeobox genes provides a link between the hormone and the developmental genes and indicates a role for cytokinins in the shoot apical meristem.
Low‐pH‐mediated elevations in cytosolic calcium are inhibited by aluminium: a potential mechanism for aluminium toxicity
Authors: Plieth Christoph , Sattelmacher Burkhard , Hansen Ulf‐Peter , Knight Marc R. 
Published: March 2003

SummaryAluminium, the most abundant metal in the earth's crust, is highly toxic to most plant species. One of the prevailing dogmas is that aluminium exerts this effect by disrupting cellular calcium homeostasis. However, recent research gives strongly conflicting results: aluminium was shown to provoke either an increase or a decrease in cytosolic free calcium concentration ([Ca2+]c). To solve this question, we have adopted a novel approach: [Ca2+]c measurements in intact plant roots as opposed to isolated cells, and the correlative measurements of intracellular and external pH. The results obtained show that plant roots respond to low external pH by a sustained elevation in [Ca2+]c. In the presence of aluminium, this pH‐mediated elevation in [Ca2+]c does not occur, therefore any potential calcium‐mediated protection against low pH is likely to be irreversibly inhibited. The severity of the inhibitory effect of aluminium on [Ca2+]c depends on the concentration of external calcium, thus perhaps explaining why the effects of aluminium toxicity are ameliorated in calcium‐rich soils. It seems possible that a primary toxic effect of aluminium might be to impair calcium‐mediated plant defence responses against low pH.
Vacuolar processing enzyme is up‐regulated in the lytic vacuoles of vegetative tissues during senescence and under various stressed conditions
Authors: Kinoshita Tetsu , Yamada Kenji , Hiraiwa Nagako , Kondo Maki , Nishimura Mikio , Hara‐Nishimura Ikuko 
Published: March 2003

SummaryVacuolar processing enzyme (VPE) has been shown to be responsible for maturation of various seed proteins in protein‐storage vacuoles. Arabidopsis has three VPE homologues; βVPE is specific to seeds and αVPE and γVPE are specific to vegetative organs. To investigate the activity of the vegetative VPE, we expressed the γVPE in a pep4 strain of the yeast Saccharomyces cerevisiae and found that γVPE has the ability to cleave the peptide bond at the carbonyl side of asparagine residues. An immunocytochemical analysis revealed the specific localization of the γVPE in the lytic vacuoles of Arabidopsis leaves that had been treated with wounding. These findings indicate that γVPE functions in the lytic vacuoles as the βVPE does in the protein‐storage vacuoles. The βVPE promoter was found to direct the expression of the β‐glucuronidase reporter gene in seeds and the root tip of transgenic Arabidopsis plants. On the other hand, both the αVPE and γVPE promoters directed the expression in senescent tissues, but not in young intact tissues. The mRNA levels of both αVPE and γVPE were increased in the primary leaves during senescence in parallel with the increase of the mRNA level of a senescence‐associated gene (SAG2). Treatment with wounding, ethylene and salicylic acid up‐regulated the expression of αVPE and γVPE, while jasmonate slightly up‐regulated the expression of γVPE. These gene expression patterns of the VPEs were associated with the accumulation of vacuolar proteins that are known to respond to these treatments. Taken together, the results suggest that vegetative VPE might regulate the activation of some functional proteins in the lytic vacuoles.
The Arabidopsis blue light receptor cryptochrome 2 is a nuclear protein regulated by a blue light‐dependent post‐transcriptional mechanism
Authors: Guo Hongwei , Duong Hien , Ma Nha , Lin Chentao 
Published: March 2003

SummaryCryptochrome 2 is a flavin‐type blue light receptor mediating floral induction in response to photoperiod and a blue light‐induced hypocotyl growth inhibition. cry2 is required for the elevated expression of the flowering‐time gene CO in response to long‐day photoperiods, but the molecular mechanism underlying the function of cry2 is not clear. The carboxyl domain of cry2 bears a basic bipartite nuclear localization signal, and the cry2 protein was co‐fractionated with the nucleus. Analysis of transgenic plants expressing a fusion protein of CRY2 and the reporter enzyme GUS (GUS–CRY2) indicated that the GUS–CRY2 fusion protein accumulated in the nucleus of transgenic plants grown in dark or light. The C‐terminal domain of cry2 that contains the basic bipartite nuclear localization signal was sufficient to confer nuclear localization of the fusion protein. Phenotypic analysis of transgenic plants expressing the fusion protein GUS–CRY2 demonstrated that GUS–CRY2 acts as a functional photoreceptor in vivo, mediating the blue light‐induced inhibition of hypocotyl elongation. These results strongly suggest that cry2 is a nuclear protein. Although no obvious light regulation was found for the nuclear compartmentation of GUS–CRY2 fusion protein, the abundance of GUS–CRY2 was regulated by blue light in a way similar to that of cry2.
The BANYULS gene encodes a DFR‐like protein and is a marker of early seed coat development
Authors: Devic Martine , Guilleminot Jocelyne , Debeaujon Isabelle , Bechtold Nicole , Bensaude Emmanuelle , Koornneef Maarten , Pelletier Georges , Delseny Michel 
Published: March 2003

SummaryMutations in the BANYULS (BAN) gene lead to precocious accumulation of anthocyanins in immature seed coat in Arabidopsis. The ban–1 allele has been isolated from a collection of T‐DNA transformants and found to be tagged by the integrative molecule. The sequencing of wild‐type and two independent mutant alleles confirmed the identity of the gene. Analysis of the full‐length cDNA sequence revealed an open reading frame encoding a 342 amino acid protein which shared strong similarities with DFR and other enzymes of the phenylpropanoid biosynthesis pathway. BAN expression was restricted to the endothelium of immature seeds at the pre‐globular to early globular stages of development as predicted from the maternal inheritance of the phenotype, and therefore represents a marker for early differentiation and development of the seed coat. BAN is probably involved in a metabolic channelling between the production of anthocyanins and pro‐anthocyanidins in the seed coat.
The auxin, hydrogen peroxide and salicylic acid induced expression of the Arabidopsis GST6 promoter is mediated in part by an ocs element
Authors: Chen Wenqiong , Singh Karam B. 
Published: March 2003

SummaryGlutathione S‐transferases (GSTs) are multi‐functional enzymes that play critical roles in a number of plant stress responses. Ocs elements are enhancer sequences found in some pathogen and GST promoters. We previously isolated an Arabidopsis GST gene, called GST6, which contained an ocs‐like element. Here we tested the role this putative ocs element plays in GST6 expression in response to auxin, salicylic acid (SA) and hydrogen peroxide (H2O2) using a transient assay and transgenic Arabidopsis. The requirement for the ocs element for basal and/or induced expression varied between the transient and transgenic studies, and in different plant tissues. The GST6 promoter showed the largest induction in roots following treatment with SA (84‐fold) or H2O2 (122‐fold), and the effect of mutating the ocs element was most pronounced in root tissue. However, in no case did mutation of the ocs element abolish GST6 expression, suggesting that other promoter element(s) are also important. Using the transient assay, other promoter element(s) critical for GST6 expression were identified that may also help mediate the activity of the ocs element. The finding that the ocs element plays a role in the transcriptional response of a plant GST gene to SA and H2O2 has potential significance for the plant defense response, where SA and H2O2 play critical roles.
Harpin induces disease resistance in Arabidopsis through the systemic acquired resistance pathway mediated by salicylic acid and the NIM1 gene
Authors: Dong Hansong , Delaney Terrence P. , Bauer David W. , Beer Steven V. 
Published: March 2003

SummaryHarpin, the product of the hrpN gene of Erwinia amylovora, elicits the hypersensitive response and disease resistance in many plants. Harpin and known inducers of systemic acquired resistance (SAR) were tested on five genotypes of Arabidopsis thaliana to assess the role of SAR in harpin‐induced resistance. In wild‐type plants, harpin elicited systemic resistance to Peronospora parasitica and Pseudomonas syringae pv. tomato, accompanied by induction of the SAR genes PR‐1 and PR‐2. However, in experiments with transgenic Arabidopsis plants containing the nahG gene which prevents accumulation of salicylic acid (SA), harpin neither elicited resistance nor activated SAR gene expression. Harpin also failed to activate SAR when applied to nim1 (non‐inducible immunity) mutants, which are defective in responding to SA and regulation of SAR. In contrast, mutants compromised in responsiveness to methyl jasmonate and ethylene developed the same resistance as did wild‐type plants. Thus, harpin elicits disease resistance through the NIM1‐mediated SAR signal transduction pathway in an SA‐dependent fashion. The site of action of harpin in the SAR regulatory pathway is upstream of SA.
The different pH optima and substrate specificities of extracellular and vacuolar invertases from plants are determined by a single amino‐acid substitution
Authors: Goetz Marc , Roitsch Thomas 
Published: March 2003

SummaryDifferent plant invertase isoenzymes are characterized by a single amino‐acid difference in a conserved sequence, the WEC‐P/V‐D box. A proline residue is present in this sequence motif of extracellular invertase sequences, whereas a valine is found at the same position of vacuolar invertase sequences. The role of this distinct difference was studied by substituting the proline residue of extracellular invertase CIN1 from Chenopodium rubrum with a valine residue, by site‐directed muta‐ genesis. The mutated gene was heterologously expressed in an invertase‐deficient Saccharomyces cerevisiae strain. The single amino‐acid difference was shown to be the molecular basis for two enzymatic properties of invertase isoenzymes, for both the pH optimum and the substrate specificity. A proline in the WEC‐P/V‐D box determines the more acidic pH optimum and the higher cleavage rate of raffinose of extracellular invertases, compared to vacuolar invertases that have a valine residue at this position.
Glycosyl‐phosphatidylinositol‐anchor addition signals are processed in Nicotiana tabacum
Authors: Takos Adam M. , Dry Ian B. , Soole Kathleen L. 
Published: March 2003

SummaryRecent studies have demonstrated the existence of glycosyl‐phosphatidylinositol (GPI)‐anchored proteins in higher plants. In this study we tested whether GPI‐addition signals from diverse evolutionary sources would function to link a GPI‐anchor to a reporter protein in plant cells. Tobacco protoplasts were transiently transfected with a truncated form of the Clostridium thermocellum endoglucanase E reporter gene (celE′) fused with a tobacco secretion signal (PR‐1a) at the N‐terminus and either a yeast (GAS1), mammalian (Thy‐1) or putative plant (LeAGP‐1) GPI‐anchor addition signal at the C‐terminus. The yeast and plant C‐terminal signals were found to be capable of directing the addition of a GPI‐anchor to the endoglucanase protein (EGE′) as shown by the sensitivity of the lipid component of GPI to phosphatidylinositol‐specific phospholipase C (PI‐PLC) digestion. In contrast, the mammalian signal was poorly processed for anchor addition. When EGE′ was fused to a truncated form of the LeAGP‐1 signal (missing three amino acids predicted to be critical to signal cleavage and anchor addition), a GPI‐anchor was not linked to the EGE′ protein indicating the necessity for the missing amino acids. Our results show the conservation of the properties of GPI‐signals in plant cells and that there may be some similar preferences in GPI‐addition signal sequences for yeast and plant cells.
Premature termination codons destabilize ferredoxin‐1 mRNA when ferredoxin‐1 is translated
Authors: Petracek Marie E. , Nuygen Tuyen , Thompson William F. , Dickey Lynn F. 
Published: March 2003

SummaryFerredoxin‐1 (Fed‐1) mRNA is poorly translated in dark‐treated tobacco (Nicotiana tabacum) leaves, resulting in destabilization of Fed‐1 mRNA and a differential light/dark accumulation of the mRNA. Insertion of nonsense codons within the Fed‐1 coding sequence disrupts the light regulation of Fed‐1 mRNA abundance. Here we show that the nonsense codon effect results primarily from lowering the Fed‐1 mRNA stability in light‐treated leaf tissue and in rapidly growing tobacco cell cultures, but not in dark‐treated leaf tissue. These results suggest that nonsense codons trigger a decay pathway distinct from that seen for Fed‐1 mRNA in the dark. We propose that nonsense‐mediated decay of nonsense‐containing Fed‐1 mRNA occurs in light‐treated leaves and in non‐photosynthetic tobacco culture cells where Fed‐1 mRNA is being actively translated.
Cis‐elements and trans‐factors that regulate expression of the maize Cat1 antioxidant gene in response to ABA and osmotic stress: H2O2 is the likely intermediary signaling molecule for the response
Authors: Guan Lingqiang M. , Zhao Jun , Scandalios John G. 
Published: March 2003

SummaryThe mechanisms by which the maize antioxidant Cat1 gene responds to abscisic acid (ABA) and osmotic stress have been investigated. Results show that during late embryogenesis, Cat1 expression in vivo is independent of endogenous ABA levels. However, exogenously applied ABA significantly enhances Cat1 expression. Transient assays using particle bombardment show that the proximal ABRE2 element on the Cat1 promoter is responsible for the induction of Cat1 expression by ABA. We further show that ABA induces the expression of Cat1 via the interaction between ABRE2 and one of its binding proteins, CBF1 (Cat1 binding factor 1). Using ABA‐deficient mutant embryos, we show that osmotic stress induces Cat1 expression through two alternate signal transduction pathways: an ABA signaling pathway leading to the interaction between the ABRE2 motif and CBF1, and a pathway via the interaction of ABRE2 and CBF2 (Cat1 binding factor 2) that is independent of ABA. The data presented clearly suggest that hydrogen peroxide (H2O2) plays an important intermediary role in the ABA signal transduction pathway leading to the induction of the Cat1 gene.