bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of cDNAs for stylar transmitting tissue‐specific proline‐rich proteins in tobacco
Authors: Cheung Alice Y. , May Bruce , Kawata Evelynn E. , Gu Qing , Wu Hen‐ming 
Published: March 2003

SummaryThe pistil of flowers is a specialized organ which contains the female gametophytes and provides the structures necessary for pollination and fertilization. Pollen deposited on the stigmatic surface of a compatible plant germinates a pollen tube which penetrates the stigmatic papillae and grows intercellularly through the style towards the ovules in the ovary. Pollen tube growth is largely restricted to the transmitting tissue in the style. Therefore the stylar transmitting tissue is extremely important for the migration of the pollen cell towards the ovary. We have isolated two related cDNAs, transmitting tissue‐specific (TTS)‐1 and TTS‐2, derived from two proline‐rich protein (PRP)‐encoding mRNAs that accumulate specifically in the transmitting tissue of tobacco. The deduced PRP sequences share similarities with proline‐rich cell wall glycoproteins found in a variety of plants. TTS‐1 and TTS‐2 mRNAs are induced in very young floral buds, accumulate most abundantly during the later stages of flower development when style elongation is the most rapid, and remain at relatively high levels at anthesis. These mRNAs become undetectable in maturing green fruits. In situ hybridization shows that TTS‐1 and TTS‐2 mRNA accumulation is restricted to the transmitting tissue of the style. The possible roles that these transmitting tissue‐specific PRPs may play in maintaining the structural integrity of the style or in the function of this organ is discussed.
Cloning and structural analysis of the anthocyanin pigmentation locus Rt of Petunia hybrida: characterization of insertion sequences in two mutant alleles
Authors: Kroon Johan , Souer Erik , De Graaff Alja , Xue Yongbiao , Mol Joseph , Koes Ronald 
Published: March 2003

SummaryAnthocyanin biosynthesis in flowers of Petunia hybrida is controlled by the regulatory genes an1, an2 and an11. Seven classes of cDNA clones homologous to transcripts that are down‐regulated in an1−, an2− and an11− mutants were isolated via differential cDNA cloning. Genetic mapping, antisense RNA experiments and analyses of mutant alleles demonstrated that one class of clones originated from the Rt locus. The rt gene has no introns and encodes a protein with homology to mammalian glucuronosyl transferases and flavonoid 3‐O‐glucosyl‐transferase (UF3GT) encoded by the bz1 gene from Zea mays. As the Rt locus controls the rhamnosylation of reddish anthocyanin‐3‐O‐glucosides which is the first in a series of modifications that finally yield magenta or blue/purple coloured anthocyanins, this suggests that rt encodes an anthocyanin rhamnosyl transferase.Molecular analysis of two mutant rt alleles showed that their expression is blocked by different DNA insertion elements. Mutability of the rt‐vu15 allele results from the presence of a 284 bp transposable element (dTph1) in the rt promoter region, causing a block in transcription. The protein coding region of the rt‐r27 allele contains a 442 bp insertion (dTph3) resulting in premature polyadenylation of rt transcripts. Although dTph3 cannot transpose, it has sequence characteristics of transposable elements, suggesting that it is a defective member of a new family of transposable elements.
Mutations at two new Arabidopsis ABA response loci are similar to the abi3 mutations
Authors: Finkelstein Ruth R. 
Published: March 2003

SummaryTwo new Arabidopsis loci involved in ABA response, ABA‐insensitive (ABI)4 and ABI5, have been identified by mutation. The abi4 and abi5 mutants were characterized in terms of ABA sensitivity of seed germination, dormancy, seed‐specific gene expression and stomatal regulation. Their phenotypes are similar to mutations in ABI3, which is thought to encode a seed‐specific transcriptional activator. Analysis of double mutants combining abi4 and abi5 mutations with abi1, abi2 or abi3 mutations also suggests that ABI4 and ABI5 act in the same transduction pathway as ABI3.
Changes in pectin structure and localization during the growth of unadapted and NaCl‐adapted tobacco cells
Authors: McCann Maureen C. , Shi Jun , Roberts Keith , Carpita Nicholas C. 
Published: March 2003

SummaryTobacco cells adapted to grow in high concentrations of NaCl exhibit a drastically altered growth physiology that results in cells whose fully expanded volume is only one‐fifth to one‐eighth those of unadapted cells. Comparison between NaCl‐adapted and unadapted tobacco cells provides an opportunity to evaluate current concepts of the structural and mechanical determinants of cell wall expansion. Both biochemical studies of pectic polymers and the ultrastructural localization of pectic epitopes at three specific phases of cell culture, maximal cell division, maximal elongation, and stationary phase are reported here.One‐half of the galactosyluronic acid units in wall polymers of NaCl‐adapted cells are esterified throughout the culture period, while wall polymers of unadapted cells show a rise in esterified polygalacturonic acid from 50 to 80% during elongation and then a decrease to 70% at stationary phase. Methyl esters account for only a proportion of the total esterified polygalacturonic acid at any stage in both unadapted and NaCl‐adapted cell walls. Using monoclonal antibodies, we show differences in the localization of relatively methyl‐esterified and unesterified pectic epitopes at different stages of growth and corroborate the chemical determinations. Fourier transform infrared (FTIR) microspectroscopy of representative walls of both NaCl‐adapted and unadapted cells confirms, at the single cell wall level, that results obtained from chemical analysis of bulk samples are applicable to the entire cell population.FTIR microspectroscopy also reveals an increase in wall protein in the walls of adapted cells. Images obtained by the fast‐freeze, deep‐etch, rotary‐shadowed replica technique show clearly different cell wall architectures in NaCl‐adapted compared with unadapted cells; walls of elongating unadapted cells contain long, thin fibres that show a net orientation with respect to the long axis of the cell, whereas walls of adapted cells have thicker, flatter bundles of fibres with no clear net orientation. Polarized FTIR microspectroscopy indicates that, in unadapted tobacco cells during elongation, pectin molecules may be oriented within the wall in a similar manner to cellulose. Possible ways in which pectin structure and conformation may affect the behaviour of the cellulose‐xyloglucan network are discussed.
Identification of S‐locus linked PCR fragments in rye (Secale cereale L.) by denaturing gradient gel electrophoresis
Authors: Wehling P. , Hackauf B. , Wricke G. 
Published: March 2003

SummaryRye inbred lines segregating at the S‐locus and homozygous at the Z‐locus were investigated by PCR with primers derived from Brassica SLG‐sequences. After denaturing gradient gel electrophoresis (DGGE), a 280 bp PCR‐fragment displays a polymorphism perfectly correlated to the underlying S‐genotypes. This is the first report on S‐related DNA polymorphism in a bifactorial self‐incompatibility system of the Poaceae.
Water channels in the plant plasma membrane cloned by immunoselection from a mammalian expression system
Authors: Kammerloher Werner , Fischer Utz , Piechottka Gerd P. , Schäffner Anton R. 
Published: March 2003

SummaryExpression in mammalian COS cells and an efficient microtiter‐based strategy for immunoselection was used in a novel approach to identify genes encoding plant membrane proteins. COS cells were transfected with an Arabidopsis thaliana root cDNA library constructed in a bacterial mammalian shuttle vector and screened with an antiserum raised against purified deglycosylated integral plasma membrane proteins from A. thaliana roots. Antibodies directed against a prominent 27 kDa antigen led to the identification of five different genes. They comprised two subfamilies related to the major intrinsic protein (MIP) superfamily and were named plasma membrane intrinsic proteins, PIP1 and PIP2, since the cellular localization of PIP1 and most probably PIP2 proteins in the plasma membrane was independently confirmed by their co‐segregation with marker enzymes during aequeous two‐phase partitioning. Surprisingly, expression in Xenopus laevis oocytes revealed that all five PIP mRNAs coded for Hg2+‐sensitive water transport facilitating activities. There had been no previous evidence of the existence of water channels in the plasma membrane of plant cells and the high diffusional water permeability of the lipid bilayer was considered to be sufficient for water exchange. Nevertheless, Northern and Western analyses showed that the PIP genes are constitutively and possibly even redundantly expressed from the small A. thaliana genome.
Malate‐sensitive anion channels enable guard cells to sense changes in the ambient CO2 concentration
Authors: Hedrich Rainer , Marten Irene , Lohse Gabi , Dietrich Petra , Winter Heike , Lohaus Gertrud , Heldt Hans‐Walter 
Published: March 2003

SummaryMalate is a characteristic metabolite in the photosynthesis of C4 and CAM plants. Furthermore, changes in the intracellular concentration of this organic acid provide part of the osmotic motor for guard cells. Since alterations in the malate concentration influence the photosynthetic capacity on one side and stomatal action on the other, it was studied whether the extracellular malate level represents an indicator of changes in the ambient CO2 concentration and a key regulator of ion transport in guard cells.Here it is demonstrated that alterations in the ambient CO2 level modify the extracellular malate concentration of Vicia faba leaves. Elevated external malate caused stomatal closure in a concentration‐dependent manner (Kmmal = 0.3 mM). Slight variations in the external malate concentration strongly regulate the voltage‐dependent properties of GCAC1, an anion‐release channel in the plasma membrane of guard cells. Superfusion of guard cell protoplasts with malate levels in the physiological range (Kmmal = 0.4 mM) caused the voltage gate to shift towards the resting potential of the cell‐activating GCAC1. Single‐channel conductance was dependent on the extracellular chloride concentration (KmCl = 3 mM). In the absence of extracellular chloride the plasma membrane lacked anion conductance until the addition of malate induced channel opening. Isophthalate was a powerful agonist in both malate‐induced processes, channel regulation and stomatal closure, indicating that modulation of GCAC1 is a key step in stomatal action. It was thus concluded that feedback regulation of volume and turgor with respect to the ambient CO2 concentration via malate‐sensitive anion channels may provide a CO2 sensor to guard cells.
Isolation and immobilization of various plastid subtypes by magnetic immunoabsorption
Authors: Kausch Albert P. , Bruce Barry D. 
Published: March 2003

SummaryAntibodies have been prepared which immuno‐localize to the outer membrane of the pea chloroplast envelope and cause agglutination of isolated chloroplasts. This antisera is immunoreactive with a variety of plastid forms from both monocotyledonous and dicotyledonous plants. Whether such antibodies might be effectively used for isolation and immobilization of plastids from whole cell lysates has been tested. A system has been developed for immunolabeling various forms of higher plant plastids with biotinylated antibody and streptavidin magnetic nano‐particles followed by separation of the plastids in a 0.6 Tesla high gradient magnetic field. Using this magnetic immunoabsorption procedure it has been possible to achieve a high degree of positive enrichment for chromoplasts, amyloplasts, and chloroplasts from whole cell lysates of several plant species. The integrity of these plastids has been examined by in organellar protein synthesis, 14C‐ADP‐glucose uptake, flow cytometry, in vitro synthesized precursor import and FITC‐cationized ferritin staining of the plastid envelope. Western blot analysis showed significant enrichment for amyloplasts from cytosolic sucrose synthase in maize endosperm. Magnetic immunoabsorption of subcellular structures from whole cell lysates is a new method that may be useful in the in vitro analysis of many different cellular compartments from a wide range of organisms.
Transgene‐mediated suppression of chalcone synthase expression in Petunia hybrida results from an increase in RNA turnover
Authors: Van Blokland R. , Van der Geest N. , Mol J.N.M. , Kooter J.M. 
Published: March 2003

SummaryCo‐suppression of the pigmentation gene chalcone synthase (chs) in Petunia hybrida by chs transgenes leads to white or variegated flowers and is characterized by a reduction in steady‐state mRNA levels. To determine the level at which suppression occurs different petunia transformants were analysed containing CaMV‐35S RNA promoter‐driven hybrid genes consisting of the β‐glucuronidase gene (uidA) linked to the full‐length chsA cDNA, the 5′ half or to the 3′ half. With these transgenes one out of 12–15 primary transformants showed suppression of the transgenes and of the resident chs genes throughout the flower or in sectors. The reduction in steady‐state chs mRNA was not the result of a transcriptional inactivation event. As determined by nuclear run‐on experiments, transcription of suppressed chs genes was similar to that of non‐suppressed genes. This indicates that co‐suppression occurs post‐transcriptionally. Among individual transformants the transgenes were transcribed at different levels but neither a high nor a low level correlated with a particular degree or pattern of suppression. Surprisingly, even a promoterless chs transgene construct was found to suppress the endogenous chs genes in three out of 15 transformants. It remains, however, unknown whether or not transcription of the transgene locus is required to induce co‐suppression. The data suggest that properties of the chs transgene locus other than the expression level are important for inducing co‐suppression. The possible role of antisense RNA, which was detected in all transformants, ectopic pairing and the structure of the integrated T‐DNAs in the mechanism of the selective increase in chs RNA turnover are discussed.
Characterization of the S locus genes, SLG and SRK, of the Brassica S3 haplotype: identification of a membrane‐localized protein encoded by the S locus receptor kinase gene
Authors: Delorme Valérie , Giranton Jean‐Loïc , Hatzfeld Yves , Friry Aline , Heizmann Philippe , Ariza María José , Dumas Christian , Gaude Thierry , Cock J. Mark 
Published: March 2003

SummaryThe S locus, which controls the self‐incompatibility response in Brassica, has been shown to contain at least two genes. SLG encodes a secreted S locus glycoprotein whilst SRK encodes a putative S locus receptor kinase. SRK has been shown potentially to encode a functional kinase and genetic evidence indicates that this gene is essential for the self‐incompatibility response. Here the characterization of the SRK and SLG genes of a Brassica line homozygous for the S3 haplotype is described. A 120 kDa glycoprotein was identified in stigmas and several lines of evidence indicated that this protein is encoded by the SRK3 gene. First, the 120 kDa glycoprotein was recognized by antibodies raised against peptides based on the SRK3 gene sequence. Secondly, this protein is polymorphic and, in an F2 population segregating for the S3 haplotype, was expressed only in plants possessing the S3 haplotype. Thirdly, the 120 kDa protein was expressed specifically in stigmas. Finally, the 120 kDa protein was only extracted from stigmas in the presence of detergent indicating that it is anchored in the membrane. SRK has been predicted to encode a transmembrane glycoprotein based on the deduced amino acid sequence. Located on the membrane, SRK is in a position to interface between an extracellular recognition event between pollen and pistil and an intracellular signal transduction pathway which initiates the self‐incompatibility response.
Construction of a rice bacterial artificial chromosome library and identification of clones linked to the Xa‐21 disease resistance locus
Authors: Wang Guo‐Liang , Holsten Thomas E. , Song Wen‐Yuan , Wang He‐Ping , Ronald Pamela C. 
Published: March 2003

SummaryA bacterial artificial chromosome (BAC) library consisting of 11 000 clones with an average DNA insert size of 125 kb was constructed from rice nuclear DNA. The BAC clones were stable in E. coli after 100 generations of serial growth. Transformation of the BAC clones by electroporation into E. coli was highly efficient and increased with decreasing size of the DNA inserts. The library was evaluated for the presence of organellar, repeated, and telomeric sequences. A very low percentage (<0.3%) of the library consisted of chloroplast and mitochondrial clones. Eighteen BACs were identified that hybridized with an Arabidopsis telomere repeat. Sixteen BACs hybridized with the AA genome‐specific repetitive sequence pOs48. Twelve clones were isolated that hybridized with three DNA markers linked to the Xa‐21 disease resistance locus. The results indicate that the BAC system can be used to clone and manipulate large pieces of plant DNA efficiently.
Gibberellin promotes histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes
Authors: Sauter Margret , Mekhedov Sergei L. , Kende Hans 
Published: March 2003

SummaryPartial submergence or treatment with either ethylene or gibberellin (GA) promotes rapid internodal growth in deepwater rice (Oryza sativa L.). Earlier work has shown that GA is the immediate hormonal signal for this growth response, which involves induction of the cell cycle at the G2/M phase transition and subsequent enhancement in the rate of DNA synthesis. In all eukaryotes, onset of mitosis is regulated by the p34cdc2/CDC28 protein kinase, whose activity is assayed by in vitro phosphorylation of histone H1. It was found that GA enhanced the activity of p34cdc2/CDC28‐like histone H1 kinase in the intercalary meristem of rice internodes. The enzyme activity showed a sharp peak that correlated with a decrease in the population of cells in the G2 phase during the first 4 h of GA treatment but not with changes in DNA synthesis. The level of histone H1 kinase activity increased again when cell division activity in the intercalary meristem is known to be high. The expression of two cdc2 homologs was examined. The mRNA level of one of these, cdc2Os‐2, was increased after 1 h of GA treatment, whereas the mRNA level of the other, cdc2Os‐1, was not affected. Two cDNAs, cycOs1 and cycOs2, which show high homology to cyclin cDNAs, were cloned from rice. They share 75.1% sequence identity at the amino acid level, and both of them are encoded by mRNAs of 1.6 kb. Expression of the two corresponding cyclin genes was enhanced by GA, and the time course of the induction was compatible with a role for both cyclins in regulating the G2/M phase transition. The cyclins were expressed in the intercalary meristem and the elongation zone of the internode, but the GA‐induced increase in transcript levels was restricted to the meristem only. The results support the hypothesis that induction of mitosis by GA is brought about by increased p34cdc2/CDC28 protein kinase activity, which may be the result of transcriptional activation of the cdc2Os‐2, cycOs1 and cycOs2 genes.
Yeast 5‐aminolevulinate synthase provides additional chlorophyll precursor in transgenic tobacco
Authors: Zavgorodnyaya Anna , Papenbrock Jutta , Grimm Bernhard 
Published: March 2003

SummarySynthesis of the tetrapyrrole precursor 5‐aminolevulinate (ALA) in plants starts with glutamate and is a tRNA‐dependent pathway consisting of three enzymatic steps localized in plastids. In animals and yeast, ALA is formed in a single step from succinyl CoA and glycine by aminolevulinate synthase (ALA‐S) in mitochondria. A gene encoding a fusion protein of yeast ALA‐S with an amino‐terminal transit sequence for the small subunit of ribulose bisphosphate carboxylase was introduced into the genome of wild‐type tobacco and a chlorophyll‐deficient transgenic line expressing glutamate 1‐semi‐aldehyde aminotransferase (GSA‐AT) antisense RNA. Expression of ALA‐S in the GSA‐AT antisense transgenic line provided green‐pigmented co‐transformants similar to wild‐type in chlorophyll content, while transformants derived from wild‐type plants did not show phenotypical changes. The capacity to synthesize ALA and chlorophyll was increased in transformed plants, indicating a contribution of ALA‐S to the ALA supply for chlorophyll synthesis. ALA‐S activity was detected in plastids of the transformants. Preliminary evidence is presented that succinyl CoA, the substrate for ALA‐S, can be synthesized and metabolized in plastids. The transgenic plants formed chlorophyll in the presence of gabaculine, an inhibitor of GSA‐AT. Steady‐state RNA and protein levels and, consequently, the enzyme activity of GSA‐AT were reduced in plants expressing ALA‐S. In analogy to the light‐dependent ALA synthesis attributed to feedback regulation, a mechanism at the level of intermediates or tetrapyrrole end‐products is proposed, which co‐ordinates the need for heme and chlorophyll precursors and restricts synthesis of ALA by regulating GSA‐AT gene expression. The genetically engineered tobacco plants containing the yeast ALA‐S activity demonstrate functional complementation of the catalytic activity of the plant ALA‐synthesizing pathway and open strategies for producing tolerance against inhibitors of the C5 pathway.
ACL5: an Arabidopsis gene required for internodal elongation after flowering
Authors: Hanzawa Yoshie , Takahashi Taku , Komeda Yoshibumi 
Published: March 2003

SummaryIn rosette plants, the formation of initial flowers is closely linked to the lengthening of internodes (bolting). In order to clarify the molecular basis of bolting, mutants with reduced lengths of internodes were screened. This paper presents the identification and characterization of recessive mutations in ACAULIS5 (ACL5), a gene required for internodal growth in Arabidopsis thaliana. Unlike previously described mutants with reduced size of organs, the acl5 mutant has a severe defect that is restricted to the process of cell elongation after transition to the reproductive stage and shows no phenotype before floral induction. The results of RNA blot hybridizations showed that the acl5 mutation causes a striking reduction in the transcript levels of genes encoding the tonoplast intrinsic protein (γ‐TIP) and the endoxyloglucan transferase (EXGT‐A1), both of which have recently been suggested to be important for cell elongation. Furthermore, our morphological study indicates that the mutation also causes proliferative arrest of the apical inflorescence meristem. These results strongly suggest that, during the reproductive phase, the wild‐type ACL5 gene product has a critical function not only in the control of elongation growth of organs but also in the continued maintenance of the proliferative activity of flower‐producing meristems.