bluuebunny/crossref_metadata_2025_split huggingface dataset:
High affinity RGD‐binding sites at the plasma membrane ofArabidopsis thalianalinks the cell wall
Authors: Canut Hervé , Carrasco Antoine , Galaud Jean‐Philippe , Cassan Catherine , Bouyssou Huguette , Vita Natalio , Ferrara Pascual , Pont‐Lezica Rafael 
Published: March 2003

Summary The heptapeptide Tyr‐Gly‐

Arg‐Gly‐Asp‐

Ser‐Pro containing the sequence

Arg‐Gly‐Asp

(RGD – the essential structure recognised by animal cells in substrate adhesion molecules) was tested on epidermal cells of onion and cultured cells of Arabidopsis upon plasmolysis. Dramatic changes were observed on both types of cells following treatment: on onion cells, Hechtian strands linking the cell wall to the membrane were lost, while Arabidopsis cells changed from concave to convex plasmolysis. A control heptapeptide Tyr‐Gly‐Asp‐Gly‐Arg‐Ser‐Pro had no effect on the shape of plasmolysed cells. Protoplasts isolated from Arabidopsis cells agglutinate in the presence of ProNectinF, a genetically engineered protein of 72 kDa containing 13 RGD sequences: several protoplasts may adhere to a single molecule of ProNectinF. The addition of the RGD‐heptapeptide disrupted the adhesion between the protoplasts. Purified plasma membrane from Arabidopsis cells exhibits specific binding sites for the iodinated RGD‐heptapeptide. The binding is saturable, reversible, and two types of high affinity sites (Kd1 1 nM, and Kd2 40 nM) can be discerned. Competitive inhibition by several structurally related peptides and proteins noted the specific requirement for the RGD sequence. Thus, the RGD‐binding activity of Arabidopsis fulfils the adhesion features of integrins, i.e. peptide specificity, subcellular location, and involvement in plasma membrane‐cell wall attachments.
Fine structure in cellulose microfibrils: NMR evidence from onion and quince
Authors: Ha Marie‐Ann , Apperley David C. , Evans Boyd W. , Huxham I. Max , Jardine W. Gordon , Viëtor Remco J. , Reis Danièle , Vian Brigitte , Jarvis Michael C. 
Published: March 2003

Summary It has been controversial for many years whether in the cellulose of higher plants, the microfibrils are aggregates of ‘elementary fibrils’, which have been suggested to be about 3.5 nm in diameter. Solid‐state NMR spectroscopy was used to examine two celluloses whose fibril diameters had been established by electron microscopy: onion (8–10 nm, but containing 40% of xyloglucan as well as cellulose) and quince (2 nm cellulose core). Both of these forms of cellulose contained crystalline units of similar size, as estimated from the ratio of surface to interior chains, and the time required for proton magnetisation to diffuse from the surface to the interior. It is suggested that the onion microfibrils must therefore be constructed from a number of cellulose subunits 2 nm in diameter, smaller than the ‘elementary fibrils’ envisaged previously. The size of these subunits would permit a hexagonal arrangement resembling the cellulose synthase complex.
Constituents of the tapetosomes and elaioplasts inBrassica campestristapetum and their degradation and retention during microsporogenesis
Authors: Ting Julie T. L. , Wu Sherry S. H. , Ratnayake Chandra , Huang Anthony H. C. 
Published: March 2003

Summary In

Brassica

anthers during microsporogenesis, the tapetum cells contain two abundant lipid‐rich organelles, the tapetosomes possessing oleosins and triacylglycerols (TAGs), and the elaioplasts having unique polypeptides and neutral esters.

B. campestris

, for its simplicity of possessing only the AA genome and one predominant oleosin of 45 kDa, was studied. In the developing anthers, the lipids and proteins of the tapetosomes and elaioplasts were concomitantly accumulated but selectively degraded or retained. Upon incubation of isolated tapetosomes in a pH‐5 medium, the predominant 45 kDa oleosin underwent selective enzymatic proteolysis to a 37 kDa fragment, which was not further hydrolyzed upon prolonged incubation. The unreacted 45 kDa oleosin was retained in the organelles, whereas the 37 kDa fragment was released to the exterior. The fragment would become the predominant 37 kDa polypeptide in the pollen coat. Isolated tapetosomes did not undergo hydrolysis of the TAGs upon incubation in media of diverse pHs. An alkaline lipase in the soluble fraction of the anther extract was presumed to be the enzyme that would hydrolyze the tapetosome TAGs, which disappeared in the anthers during development. The tapetum elaioplasts contained several unique polypeptides of 31–36 kDa. The gene encoding a 32 kDa polypeptide was cloned, and its deduced amino acid sequence was homologous to those of two proteins known to be present on the surface of fibrils in chromoplasts. Upon incubation of isolated elaioplasts in media of diverse pHs, the organelle polypeptides were degraded completely and most rapidly at pH 5, whereas the neutral esters remained unchanged; these neutral esters would become the major lipid components of the pollen coat. The findings show that the constituents of the two major tapetum organelles underwent very different paths of degradation, or modification, and transfer to the pollen surface.
Use of a proteome strategy for tagging proteins present at the plasma membrane
Authors: Santoni Véronique , Rouquié David , Doumas Patrick , Mansion Monique , Boutry Marc , Degand Hervé , Dupree Paul , Packman Len , Sherrier Janine , Prime Tracy , Bauw Guy , Posada Esmeralda , Rouzé Pierre , Dehais Patrice , Sahnoun Ilhem , Barlier Isabelle , Rossignol Michel 
Published: March 2003

Summary A plasma membrane (PM) fraction was purified from

Arabidopsis thaliana

using a standard procedure and analyzed by two‐dimensional (2D) gel electrophoresis. The proteins were classified according to their relative abundance in PM or cell membrane supernatant fractions. Eighty‐two of the 700 spots detected on the PM 2D gels were microsequenced. More than half showed sequence similarity to proteins of known function. Of these, all the spots in the PM‐specific and PM‐enriched fractions, together with half of the spots with similar abundance in PM fraction and supernatant, have previously been found at the PM, supporting the validity of this approach. Extrapolation from this analysis indicates that (i) approximately 550 polypeptides found at the PM could be resolved on 2D gels; (ii) that numerous proteins with multiple locations are found at the PM; and (iii) that approximately 80% of PM‐specific spots correspond to proteins with unknown function. Among the latter, half are represented by ESTs or cDNAs in databases. In this way, several unknown gene products were potentially localized to the PM. These data are discussed with respect to the efficiency of organelle proteome approaches to link systematically genomic data to genome expression. It is concluded that generalized proteomes can constitute a powerful resource, with future completion of

Arabidopsis

genome sequencing, for genome‐wide exploration of plant function.
TheEMB506 gene encodes a novel ankyrin repeat containing protein that is essential for the normal development of Arabidopsis embryos
Authors: Albert Sylvie , Després Barbara , Guilleminot Jocelyne , Bechtold Nicole , Pelletier Georges , Delseny Michel , Devic Martine 
Published: March 2003

Summary The

EMB

506 gene of Arabidopsis, required for the normal development of the embryo beyond the globular stage, has been cloned. The gene encodes a protein of predicted size 35 kDa that contains five ankyrin (ANK) repeats within the C terminal moiety. ANK repeats are conserved domains of 33 amino acids involved in specific recognition of protein partners. The EMB 506 protein was detected at different stages of silique development but accumulated preferentially in the mature cauline leaves. The rescue of homozygous

emb

506 embryos by complementation with the wild‐type sequence cDNA demonstrated that the

emb

mutation is a consequence of the T‐DNA insertion and that integration and expression of the transgene occurred during gametogenesis and/or early embryo development. In addition to the drastic effect of the

emb

506 mutation during embryo development, complementation experiments revealed another effect of the gene:

emb

506 plants transformed with the wild‐type

EMB

506 sequence were able to produce viable seeds but showed a reduction of apical dominance and the presence of adventitious buds or bracts along the stem. This result supports the idea that genes essential for embryogenesis may also be required at other stages of the plant life cycle.
Molecular cloning and functional expression ofO‐methyltransferases common to isoquinoline alkaloid and phenylpropanoid biosynthesis
Authors: Frick Susanne , Kutchan Toni M. 
Published: March 2003

Summary In cell suspension cultures of the meadow rue

Thalictrum tuberosum

, biosynthesis of the anti‐microbial alkaloid berberine can be induced by addition of methyl jasmonate to the culture medium. The activities of the four methyltransferases involved in the formation of berberine from L‐tyrosine are increased in response to elicitor addition. Partial clones generated by RT–PCR with methyltransferase‐specific primers were used as hybridization probes to isolate four cDNAs encoding

O

‐methyltransferases from a cDNA library prepared from poly(A)+ RNA isolated from methyl jasmonate‐induced cell suspension cultures of

T. tuberosum

. RNA gel blot hybridization indicated that the transcripts for the methyltransferases accumulated in response to addition of methyl jasmonate to the cell culture medium. The cDNAs were functionally expressed in

Spodoptera frugiperda

Sf9 cells and were shown to have varying and broad substrate specificities. A difference of a single amino acid residue between two of the enzymes was sufficient to alter the substrate specificity. The four cDNAs were expressed either as four homodimers or as six heterodimers by co‐infection with all possible combinations of the four recombinant baculoviruses. These 10 isoforms thus produced displayed distinct substrate specificities and in some cases co‐infection with two different recombinant baculoviruses led to the

O

‐methylation of new substrates. The substrates that were

O

‐methylated varied in structural complexity from simple catechols to phenylpropanoids, tetrahydrobenzylisoquinoline, protoberberine and tetrahydrophenethylisoquinoline alkaloids, suggesting that some biosynthetic enzymes may be common to both phenylpropanoid and alkaloid anabolism.
Isoforms of acyl carrier protein involved in seed‐specific fatty acid synthesis
Authors: Suh Mi Chung , Schultz David J. , Ohlrogge John B. 
Published: March 2003

Summary Seeds of
Coriandrum sativum
(coriander) and
Thunbergia alata
(black‐eyed Susan vine) produce unusual monoenoic fatty acids which constitute over 80% of the total fatty acids of the seed oil. The initial step in the formation of these fatty acids is the desaturation of palmitoyl‐ACP (acyl carrier protein) at the D4 or D6 positions to produce D4‐hexadecenoic acid (16 : 1D4) or D6‐hexadecenoic acid (16 : 1D6), respectively. The involvement of specific forms of ACP in the production of these novel monoenoic fatty acids was studied. ACPs were partially purified from endosperm of coriander and
T. alata
and used to generate 3H‐ and 14C‐labelled palmitoyl‐ACP substrates. In competition assays with labelled palmitoyl‐ACP prepared from spinach (
Spinacia oleracea
), D4‐acyl‐ACP desaturase activity was two‐ to threefold higher with coriander ACP than with spinach ACP. Similarly, the
T. alata
D6 desaturase favoured
T. alata
ACP over spinach ACP. A cDNA clone,
Cs
‐ACP‐I, encoding ACP was isolated from a coriander endosperm cDNA library.
Cs
‐ACP‐I mRNA was predominantly expressed in endosperm rather than leaves. The
Cs
‐ACP‐I mature protein was expressed in
E. coli
and co‐migrated on SDS–PAGE with the most abundant ACP expressed in endosperm tissues. In
in vitro
D4‐palmitoyl‐ACP desaturase assays, the
Cs
‐ACP‐I expressed from
E. coli
was four‐ and 10‐fold more active than spinach ACP or
E. coli
ACP, respectively, in the synthesis of D4‐hexadecenoic acid from palmitoyl‐ACP. In contrast, D9‐stearoyl‐ACP desaturase activity from coriander endosperm did not discriminate strongly between different ACP species. These results indicate that individual ACP isoforms are specifically involved in the biosynthesis of unusual seed fatty acids and further suggest that expression of multiple ACP isoforms may participate in determining the products of fatty acid biosynthesis.
Post‐transcriptional gene silencing of chalcone synthase in transgenic petunias, cytosine methylation and epigenetic variation
Authors: O’Dell Michael , Metzlaff Michael , Flavell Richard B. 
Published: March 2003

SummaryPost‐transcriptional degradation of chalcone synthase RNA transcripts often occurs in petunia plants with additional copies of chalcone synthase genes. The cytosine methylation status of selected restriction endonuclease sites was studied in the chalcone synthase endogenous genes and transgenes of these plants. Methylation patterns varied between transformants and within a series of epigenetically related plants. There was heterogeneity in promoter transgene methylation patterns within and/or between cells, between leaves and flowers and between tandemly duplicated sequences. Thus methylation patterns are determined by more than the local DNA sequence or site of insertion. A site in the 5′ enhancer of the 35S promoter was methylated more frequently in white flowers than in purple flowers. An EcoRII site within the coding sequence of the endogenous ChsA genes is developmentally regulated, being frequently methylated in leaves but rarely in petals of wild‐type petunias or stable purple flowered transgenic plants. However, in petals of many transgenic plants, especially those that show extensive post transcriptional RNA degradation, the site is frequently methylated. Thus the transgenes influence developmental methylation of the endogenous genes. In the transgenes the EcoRII site is usually more frequently methylated in petals than in leaves. RNA degradation in petals is correlated in one set of epigenetically related transgenic plants with hypomethylation at the transgene EcoRII site in leaves. Possible relationships between the cytosine methylation patterns in vegetative and floral cells, epigenetic states of ChsA genes and the control of RNA transcript degradation are discussed.
Isolation, characterization and immunolocalization of a novel, modular tomato arabinogalactan‐protein corresponding to the LeAGP‐1 gene
Authors: Gao Minggeng , Kieliszewski Marcia J. , Lamport Derek T. A. , Showalter Allan M. 
Published: March 2003

SummaryArabinogalactan‐proteins (AGPs) are a family of hydroxyproline‐rich glycoproteins implicated to function in plant growth and development. This report focuses on a novel, modular AGP found in tomato, LeAGP‐1, which was predicted by DNA cloning and herein verified at the protein level as a major AGP component. LeAGP‐1 was isolated from tomato suspension‐cultured cells and verified to be an AGP by precipitation with (β‐D‐galactosyl)3 Yariv phenylglycoside and by amino acid composition analysis. Furthermore, LeAGP‐1 was determined to correspond to LeAGP‐1 clones based on three criteria: (1) amino acid composition identity, (2) amino acid sequence identity, and (3) specific immunoreactivity of glycosylated and deglycosylated LeAGP‐1 with an antibody developed against the highly basic subdomain predicted from LeAGP‐1 clones. The antibody was also used to immunolocalize LeAGP‐1 in tomato to the cell surface of suspension‐cultured cells, maturing metaxylem elements in young internodes and petioles, and stylar transmitting tissue cells. At the subcellular level, LeAGP‐1 immunolocalized to the cell walls of these particular cells as well as to intercellular spaces between stylar transmitting tissue cells. LeAGP‐1 now emerges as one of the most comprehensively studied AGPs in terms of (1) characterization at the genomic DNA, cDNA and protein levels, (2) known organ‐specific and developmentally regulated mRNA expression patterns, (3) development of an antibody against a unique, peptide subdomain which specifically recognizes LeAGP‐1 in its glycosylated and deglycosylated states, and (4) immunolocalization of a single, well‐defined AGP molecule at the tissue and subcellular levels.
A tobacco matrix attachment region reduces the loss of transgene expression in the progeny of transgenic tobacco plants
Authors: Ülker Bekir , Allen George C. , Thompson William F. , Spiker Steven , Weissinger Arthur K. 
Published: March 2003

SummaryThe RB7 matrix attachment region (MAR), when flanking a uidA (GUS) reporter gene, has been previously shown to increase uidA gene expression by 60‐fold in stably transformed tobacco suspension cell lines. We have now used the same co‐transformation procedure to determine the effect of flanking MARs on uidA gene expression in tobacco plants. The neomycin phosphotransferase selection gene and uidA reporter gene on separate plasmids were co‐transformed into seedlings by microprojectile bombardment. In primary transgenic plants, the average uidA expression in plants with MARs was twofold greater than in control plants without MARs, but there was no effect on variation of expression. GUS activity was not proportional to the number of integrated uidA transgenes over the entire range of copy numbers. However, in the lower part of the copy number range, MAR lines show a tendency for expression to increase with copy number. Transgene expression in backcross progenies of the MAR‐containing lines averaged threefold higher than in control progenies. MARs also reduced the loss of transgene expression in the BC1 generation. Sixty‐three per cent of the 21 MAR‐containing primary transformants, but only 20% of the 14 control primary transformants, produced backcross progenies in which no loss of transgene expression was observed. These observations are discussed in the context of homology‐dependent gene silencing.
Cryptochrome 1 controls tomato development in response to blue light
Authors: Ninu Luciano , Ahmad Margaret , Miarelli Carolina , Cashmore Anthony R. , Giuliano Giovanni 
Published: March 2003

Summary Cryptochrome genes (CRY) are a novel class of plant genes encoding proteins that bear a strong resemblance to photolyases, a rare class of flavoproteins that absorb light in the blue (B) and UV‐A regions of the spectrum and utilise it for photorepair of UV‐damaged DNA. In Arabidopsis, both CRY1 and CRY2 are implicated in numerous blue light‐dependent responses, including inhibition of hypocotyl elongation, leaf and cotyledon expansion, pigment biosynthesis, stem growth and internode elongation, control of flowering time and phototropism. No information about the in vivo function of CRY genes is available in other plant species. The tomato CRY1 gene (TCRY1) encodes a protein of 679 amino acids, which shows 78% identity and 88% similarity to Arabidopsis CRY1. In order to verify the in vivo function of TCRY1, we constructed antisense tomato plants using the C‐terminal portion of the gene. Partial repression of both mRNA and protein levels was observed in one of the transformants. The progeny from this transformant showed an elongated hypocotyl under blue but not under red light. This character co‐segregated with the transgene and was dependent on transgene dosage. An additional, partially elongated phenotype was observed in adult plants grown in the greenhouse under dim light and short days with no artificial illumination. This phenotype was suppressed by artificial illumination of both short and long photoperiods. The synthesis of anthocyanins under blue light was reduced in antisense seedlings. In contrast, carotenoid and chlorophyll levels and second positive phototropic curvature were essentially unaltered.
Arabidopsis thaliana proteins related to the yeast SIP and SNF4 interact with AKINα1, an SNF1‐like protein kinase
Authors: Bouly Jean‐Pierre , Gissot Lionel , Lessard Philippe , Kreis Martin , Thomas Martine 
Published: March 2003

Summary AKINα1, a Ser/Thr kinase from Arabidopsis thaliana belongs to the highly conserved SNF1 family of protein kinases in eukaryotes. Recent data suggest that the plant SNF1‐related kinases (SnRK1 family) are key enzymes implicated in the regulation of carbohydrate and lipid metabolism. In Saccharomyces cerevisiae and mammals, the SNF1 and AMPKα protein kinases interact with two other families of proteins, namely SNF4/AMPKγ and SIP1/SIP2/GAL83/AMPKβ, to form active heterotrimeric complexes. In this paper, we describe the characterisation of three novel cDNAs. AKINβ1 and AKINβ2 encode proteins similar to SIP1, SIP2 and GAL83 and AKINγ codes for a protein showing similarity with SNF4. Using the two‐hybrid system, specific interactions have been shown between A. thaliana AKINβ1/β2, AKINγ and AKINγ as well as between the A. thaliana and S. cerevisiae subunits. Interestingly, AKINβ1, AKINβ2 and AKINγ mRNAs accumulate differentially in A. thaliana tissues and are modulated during development and under different growth conditions. These data suggest the presence in higher plants of a conserved heterotrimeric complex. Moreover, the differential transcription of different non‐catalytic subunits can constitute a first level of regulation of the SNF1‐like complex in plants.
Gibberellin 2‐oxidation and the SLN gene of Pisum sativum
Authors: Lester Diane R. , Ross John J. , Smith Jennifer J. , Elliott Robert C. , Reid James B. 
Published: March 2003

SummaryTwo cDNAs encoding gibberellin 2‐oxidases were isolated from maturing pea seeds. The first, PsGA2ox1, was isolated by activity screening of a Lambda‐ZAP cDNA library excised into phagemid form and expressed in Escherichia coli. The second, PsGA2ox2, was obtained initially as a PCR product using degenerate primers designed according to conserved regions of plant 2‐oxoglutarate‐dependent dioxygenases. E. coli heterologous expression products of PsGA2ox1 and PsGA2ox2 converted GA1 to GA8, as shown by HPLC‐radiocounting, and gas chromatography‐MS. PsGA2ox1 converted GA20 to GA29, but GA20 was a poor substrate for the PsGA2ox2 expression product. Furthermore, PsGA2ox1 converted GA29 to GA29‐catabolite at a low level of efficiency while PsGA2ox2 did not catalyse this step. A cDNA of PsGA2ox1 isolated from plants of genotype sln contained a single base deletion which was predicted to produce a truncated protein and gibberellin 2‐oxidase activity could not be demonstrated from this cDNA. A 10 bp size difference between the introns of the SLN and sln PsGA2ox1 genes was used to show co‐segregation between the SLN and sln phenotypes and the size of the PCR products. PsGA2ox1 transcripts were more abundant in cotyledons than in shoots, while the reverse was the case for PsGA2ox2. The expression patterns of the genes, together with the effects of the sln mutation, indicate that PsGA2ox1 plays a major role in GA20 deactivation in both shoots and maturing seeds, while the PsGA2ox2 gene might be important for GA1 deactivation in the shoot.