bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential response of maize catalases and superoxide dismutases to the photoactivated fungal toxin cercosporin
Authors: Williamson John D. , Scandalios John G. 
Published: March 2003

SummaryMany fungi of the genus Cercospora produce a light‐induced, photoactivated polyketide toxin called cercosporin. In the presence of light an excited form (triplet state) of the toxin molecule is produced which, depending on the reducing potential of the environment, reacts with molecular oxygen to produce singlet oxygen and/or superoxide radicals. In this paper a system is presented for analysis of antioxidant defense gene response using purified cercosporin under conditions demonstrated to favor superoxide formation. Under the assay conditions employed, changes in total catalase activity, as well as individual isozyme protein levels generally mirrored the changes observed in corresponding steady‐state RNA levels in response to applied cercosporin. In contrast, while transcript accumulation for most maize superoxide dismutases increased dramatically, both total superoxide dismutase activity and individual isozyme protein levels remained constant in all toxin treatments. In one case, the analyses indicated that there are two distinct transcripts that hybridize with a gene‐specific probe for Sod3. These two transcripts responded differentially to applied toxin (levels of the larger transcript increased while the smaller decreased), whereas corresponding steady‐state levels for the SOD‐3 isozyme proteins remained constant. This suggests that protein turnover might play a role in the response of these SODs to activated oxygen species.
Vicilin with carboxy‐terminal KDEL is retained in the endoplasmic reticulum and accumulates to high levels in the leaves of transgenic plants
Authors: Wandelt Christine I. , Khan M. Rafiqul I. , Craig Stuart , Schroeder Harmut E. , Spencer Donald , Higgins Thomas J.V. 
Published: March 2003

SummaryGene constructs were designed to test the effect of the endoplasmic reticulum (ER)‐targeting signal, KDEL, on the level of accumulation of a foreign protein in transgenic plants. The gene for the pea seed protein vicilin was modified by the addition of a sequence coding for this tetrapeptide at its carboxyl terminus. The altered gene was placed under the control of a CaMV 35S promoter and its expression in the leaves of both tobacco and lucerne (alfalfa) was compared with that of an equivalent vicilin construct lacking the KDEL‐coding sequence. The presence of the ER‐targeting signal led to a greatly enhanced accumulation of the heterologous protein. In lucerne and tobacco leaves, the level of vicilin‐KDEL protein was 20 and 100 times greater than that of the unmodified vicilin, respectively. These differences in expression level could not be explained by corresponding differences in the steady‐state levels or the translatability of the mRNAs. However, when the stability of vicilin and vicilin‐KDEL proteins was compared in their respective transgenic hosts, unmodified vicilin was found to be degraded with a half‐life of 4.5 h while vicilin‐KDEL was much more stable with a half‐life of more than 48 h.Immunogold labelling of leaf tissues from transgenic lucerne and tobacco showed the presence of vicilin associated with large aggregates within the ER lumen of vicilin‐KDEL plants. No such aggregates were detected in transgenic plants expressing wild‐type vicilin.It is concluded that the carboxy‐terminal KDEL caused the retention of the modified vicilin in the ER, and that this retention led to the increased stability and higher level of accumulation of vicilin‐KDEL in leaves of transgenic plants.
Characterization of cDNAs encoding two isoforms of granule‐bound starch synthase which show differential expression in developing storage organs of pea and potato
Authors: Dry Ian , Smith Alison , Edwards Anne , Bhattacharyya Madan , Dunn Paul , Martin Cathie 
Published: March 2003

SummaryWe have isolated cDNA clones to two isoforms of granule‐bound starch synthase (GBSS) from pea embryos and potato tubers. The sequences of both isoforms are related to that of glycogen synthase from E. coli and one, GBSSI, is very similar to the waxy protein of maize and other species. In pea, GBSSII carries a novel 203‐amino‐acid domain at its N‐terminus. Genes encoding both proteins are expressed during pea embryo development, but GBSSII is most highly expressed earlier in development than GBSSI. Similarly, GBSSI and GBSSII are differentially expressed in developing potato tubers. Expression of both isoforms is much lower in other organs of pea than in embryos. GBSSII is expressed in every organ tested while GBSSI is not expressed in roots, stipules or flowers. The possible consequences of this differential use of GBSS isoforms are discussed.
Inhibition of plant plasma membrane phosphoinositide phospholipase C by the actin‐binding protein, profilin
Authors: Drøbak Bjørn K. , Watkins Peter A.C. , Valenta Rudolf , Dove Stephen K. , Lloyd Clive W. , Staiger Christopher J. 
Published: March 2003

A key event in signal transduction in many eukaryotes is activation of polyphosphoinositide‐specific phospholipase C (PIC). This enzyme hydrolyses the plasma membrane‐associated lipid, phosphatidylinositol(4,5)bisphosphate (Ptdlns(4,5)P2) which leads to the production of the two second messenger molecules: inositol(1,4,5)trisphosphate (Ins(1,4,5)P3) and 1,2‐diacylglycerol (DG). In plants, an enzyme which functionally resembles mammalian PIC is known to exist in the plasma membrane, but little is understood about how its activity is regulated. The recent discovery of several plant proteins with 30–40% homology to the mammalian actin‐ and phosphoinositide‐binding protein, profilin, has prompted an investigation as to whether these proteins (plant profilins) are able to interact with polyphosphoinositides and, if so, whether such interactions have physiological relevance for signal transduction via the plant phosphoinositide system.In this study it is demonstrated that a direct and highly specific interaction does exist between plant profilin and polyphosphoinositides and that these interactions dramatically affect the ability of plant plasma membrane phosphoinositide phospholipase C to utilize phosphoinositides for second messenger production. These data are the first to demonstrate a functional role of plant profilin in controlling polyphosphoinositide turnover and also provide the first evidence for a direct effect of an actin‐binding protein on a membrane‐associated signalling enzyme. These findings indicate a novel mechanism for control of plant phosphoinositide turnover, and suggest a possible link between plant cell activation, second messenger production and modulation of cytoskeletal dynamics.
Potato lectin: a modular protein sharing sequence similarities with the extensin family, the hevein lectin family, and snake venom disintegrins (platelet aggregation inhibitors)
Authors: Kieliszewski Marcia J. , Showalter Allan M. , Leykam Joseph F. 
Published: March 2003

SummaryPotato (Solanum tuberosum) lectin, is a chimeric chitin‐binding protein comprised of a lectin domain fused to a hydroxyproline‐rich glycoprotein domain. Here peptide sequence information from both domains is presented. A partial sequence of a major tryptic peptide T2: Leu‐Pro‐Ser‐Hyp‐Hyp‐Hyp‐Hyp‐Hyp‐Hyp‐(His)‐Hyp‐Ser‐Hyp‐Hyp‐Hyp‐Hyp‐Ser‐Hyp‐Hyp‐Ser‐Hyp‐Hyp‐Hyp‐Hyp‐Ser‐Hyp‐Hyp‐ was similar to the ‘P3’ type extensin major repetitive sequence: Ser‐Hyp‐Hyp‐Hyp‐Hyp‐Ser‐Hyp‐Ser‐Hyp‐Hyp‐Hyp‐Hyp‐suggesting common evolutionary origins for the extensins and the hydroxyproline‐rich glycoprotein (HRGP) domain of potato lectin. Furthermore, alignment of three chymotryptic peptides from potato lectin, C1: Cys‐Gly‐Thr‐Thr‐Ser‐Asp‐Tyr, C2: Cys‐Ser‐Pro‐Gly‐Tyr, and C8: Thr‐Gly‐Glu‐Cys‐Cys‐Ser‐Ile with similar sequences from the hevein lectin family indicates that they have homologous chitin‐binding domains, and hence have common evolutionary origins. Finally, all plant chitin‐binding domains examined bore a remarkable sequence similarity, particularly in the spacing of Cys residues, to the disintegrins (platelet aggregation inhibitors) which occur in crotalid and viperid snake venoms. As such, sequence similarities not only identify potato lectin as a member of both the hevein and extensin families of plant proteins, but also suggest that an archetypal polypeptide module gave rise to both the plant chitin‐binding domain and the reptile disintegrins.
Xanthophyll biosynthesis in chromoplasts: isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6‐epoxycarotenoid into ketocarotenoid
Authors: Bouvier Florence , Hugueney Philippe , D'Harlingue Alain , Kuntz Marcel , Camara Bilal 
Published: March 2003

SummaryThe late steps of carotenoid biosynthesis in plants involve the formation of xanthophylls. Little is known about the enzymology of these steps. This paper reports the purification to homogeneity of a xanthophyll biosynthetic enzyme from Capsicum annuum chromoplasts, which catalyzes the conversion of the ubiquitous 5,6‐epoxycarotenoids, antheraxanthin and violaxanthin, into capsanthin and capsorubin, respectively. Owing to its bifunctionality, the name capsanthin‐capsorubin synthase is proposed for this new enzyme. The purified enzyme is a monomer with a molecular mass of 50 kDa. Antibodies raised against this enzyme allowed the isolation of a full‐length cDNA clone encoding a capsanthin capsorubin synthase high molecular weight precursor. The primary deduced structure reveals the presence of a consensus nucleotide binding site. The capsanthin‐capsorubin synthase gene is specifically expressed during chromoplast development in fruits accumulating ketocarotenoids, but not in mutants impaired in this biosynthetic step.
Nuclear—organelle interactions: the immutans variegation mutant of Arabidopsis is plastid autonomous and impaired in carotenoid biosynthesis
Authors: Wetzel Carolyn M. , Jiang Cai‐Zhong , Meehan LeAnn J. , Voytas Daniel F. , Rodermel Steven R. 
Published: March 2003

SummaryThe immutans (im) variegation mutant of Arabidopsis thaliana contains green‐ and white‐sectored leaves due to the action of a nuclear recessive gene. The mutation is somatically unstable, and the degree of sectoring is influenced by light and temperature. Whereas the cells in the green sectors contain normal chloroplasts, the cells in the white sectors are heteroplastidic and contain non‐pigmented plastids that lack organized lamellar structures, as well as small pigmented plastids and/or rare normal chloroplasts. This indicates that the plastids in im white cells are not affected equally by the nuclear mutation and that the expression of immutans is ‘plastid autonomous’. In contrast to other variegation mutants with heteroplastidic cells, the defect in im is not maternally inherited. immutans thus represents a novel type of nuclear gene‐induced variegation mutant. It has also been found that the white tissues of immutans accumulate phytoene, a non‐colored C40 carotenoid intermediate. This suggests that immutans controls, either directly or indirectly, the activity of phytoene desaturase (PDS), the enzyme that converts phytoene to zeta‐carotene in higher plants. However, im is not the structural gene for PDS. A secondary effect of carotenoid deficiency, both in immutans and in wild‐type plants treated with a herbicide that blocks carotenoid synthesis, is an increase in acid ribonuclease activity in white tissue. It is concluded that the novel variegation generated by the immutans mutation should offer great insight into the complex circuitry that regulates nuclear—organelle interactions.
Efficient transformation of rice (Oryza sativa L.) mediated by Agrobacterium and sequence analysis of the boundaries of the T‐DNA
Authors: Hiei Yukoh , Ohta Shozo , Komari Toshihiko , Kumashiro Takashi 
Published: March 2003

SummaryA large number of morphologically normal, fertile, transgenic rice plants were obtained by co‐cultivation of rice tissues with Agrobacterium tumefaciens. The efficiency of transformation was similar to that obtained by the methods used routinely for transformation of dicotyledons with the bacterium. Stable integration, expression and inheritance of transgenes were demonstrated by molecular and genetic analysis of transformants in the R0, R1 and R2 generations. Sequence analysis revealed that the boundaries of the T‐DNA in transgenic rice plants were essentially identical to those in transgenic dicotyledons. Calli induced from scutella were very good starting materials. A strain of A. tumefaciens that carried a so‐called ‘super‐binary’ vector gave especially high frequencies of transformation of various cultivars of japonica rice that included Koshihikari, which normally shows poor responses in tissue culture.
Reduction of the chloroplastic fructose‐1,6‐bisphosphatase in transgenic potato plants impairs photosynthesis and plant growth
Authors: Koßmann Jens , Sonnewald Uwe , Willmitzer Lothar 
Published: March 2003

SummaryTransgenic potato plants expressing reduced levels of the chloroplastic isoform of fructose‐1,6‐bisphosphatase (cp‐FBPase) were created via the antisense RNA technique. Transformants with different levels of FBPase activity were selected and analysed with respect to photosynthesis, carbon metabolism, and growth. FBPase activity of less than 15% of wild‐type levels led to reduced growth rates, probably due to the reduction of photosynthetic activity. A significant decrease in tuber yield is observed in plants with a FBPase activity below 15% of wild‐type levels, whereas plants with 36% of wild‐type enzyme activity still give normal tuber yields, even though they demonstrate a lowered photosynthetic capacity. Decreased photosynthesis also results in a reduction of total carbohydrate contents in leaves. Interestingly, increased carbohydrate partitioning towards soluble sugars is observed in plants displaying less than 15% of the wild‐type FBPase activity. When excised leaf discs are placed on sucrose‐containing media in darkness, discs derived from plants with a reduced FBPase activity accumulate higher amounts of starch. Possible implications are discussed.
Osmotic stress enhances the competence of Beta vulgaris vacuoles to respond to inositol 1,4,5‐trisphosphate
Authors: Allen Gethyn J. , Sanders Dale 
Published: March 2003

SummaryIsolated vacuoles from Beta vulgaris storage roots respond to the intracellular signalling molecule inositol 1,4,5‐trisphosphate (InsP3). Whole vacuole patch clamp enables measurement of an inward current (cytosol‐directed) induced by cytosolic InsP3 which is fully reversible upon removal of InsP3. The reversal potentials of the InsP3‐induced whole vacuolar currents indicate a permeability ratio (P,Ca:P,K) of 200:1. Competence of vacuoles to respond to InsP3 is dependent upon the root tissue undergoing hyperosmotic stress before vacuole isolation. The magnitude of the hyperosmotic stress and the density of InsP3‐induced current per unit membrane area are exponentially related. A standing osmotic gradient across the vacuolar membrane further enhances the InsP3‐induced current, the current being larger when there is net water flux from the cytosol to the vacuolar lumen. InsP3‐induced currents are not affected by the cytosolic free Ca2+ concentration. The conductance of InsP3‐induced single channel currents varied greatly between individual outside‐out patches, but all showed a non‐linear increase in single channel current at physiological potentials. The reversal potentials of these currents indicated a PCa:PK of between 100:1 and 800:1.The significance of these findings is discussed in relation to technical aspects of monitoring InsP3‐induced currents in plant vacuoles and in the context of the physiological roles of InsP3 and its receptor in cell water relations.
The phenotype of some late‐flowering mutants is enhanced by a locus on chromosome 5 that is not effective in the Landsberg erecta wild‐type
Authors: Koornneef Maarten , Blankestijn‐de Vries Hetty , Hanhart Corrie , Soppe Wim , Peeters Ton 
Published: March 2003

SummaryLate‐flowering mutants that have been described in ecotypes other than Landsberg erecta (Ler) have been found to be dominant alleles of the FRI locus located on chromosome 4, which determines lateness in many very late ecotypes. The extreme lateness of dominant FRI alleles depends on dominant alleles at the FLC locus that maps on the top of chromosome 5. FLC alleles with this effect have been found in all ecotypes tested (Col, Ws, S96, Est and Li) except Ler. Most likely the same locus confers lateness to the luminidependens (ld) mutant. Genotypes with a dominant FRI allele and the monogenic recessive ld mutant are only slightly later with recessive Ler alleles at the FLC locus. Genotypes where the dominant FLC alleles are combined with FRI or with the ld mutant, are strongly responsive to vernalization, which is much less effective in the FLC‐Ler background.
Arrangement of cell layers in the shoot apical meristems of periclinal chimeras influences cell fate
Authors: Marcotrigiano Michael , Bernatzky Robert 
Published: March 2003

SummaryUtilizing a complete set of six periclinal graft chimeras composed of Nicotiana tabacum and Nicotiana glauca (TGG, GTT, TTG, GGT, TGT, and GTG), the fate of the three apical cell layers in both vegetative and reproductive organs has been traced. An analysis of leaf phenotype indicated that only rarely did deviations from expected cell lineage occur and in only TTG did such deviations originate in the shoot apical meristem rather than during leaf development. In most plants that possess a stratified shoot apical meristem, gametes are derived from the second apical layer (L2). A phenotypic and/or DNA analysis of seed progeny following reciprocal crosses between all chimeras and their component species indicated that pollen and eggs were sometimes derived from non‐L2 lineage in all but one periclinal chimera. There was no evidence for non‐L2‐derived gametes in 95 crosses where GTT was a parent whereas 40 of 104 crosses with TTG as a parent yielded some offspring that resulted from non‐L2‐derived gametes. Of these 40 cases, non‐L2‐derived pollen grains were responsible 39 times while non‐L2‐derived eggs were responsible just once. Therefore, the occurrence of non‐L2‐derived gametes was not random. The disruption of ‘normal’ lineage patterns was dependent on the specific arrangement of genetically dissimilar tissue layers in the shoot apices of the chimeras and was different for different organs.
Distinct CG and CNG DNA methyltransferases in Pisum sativum
Authors: Pradhan Sriharsa , Adams Roger L.P. 
Published: March 2003

SummaryDNA methyltransferase activity, present in low salt extracts of nuclei from young pea shoot apices, has been fractionated into two different species by assaying with model substrates. The CG methyltransferase (an unstable enzyme believed to be of 140 kDa) methylates cytosine only in oligonucleotides with CG and CI dinucleotide targets while an enzyme of 110 kDa (the CNG methyltransferase) methylates the cytosines in 5′‐CAG‐3′ and 5′‐CTG‐3′ target sequences, especially when hemimethylated, but not in 5′‐CCG‐3′ nor in 5′‐CGG‐3′ target sequences present in oligonucleotides.
Nod factors and cytokinins induce similar cortical cell division, amyloplast deposition and MsEnod12A expression patterns in alfalfa roots
Authors: Bauer Petra , Ratet Pascal , Crespi Martin D. , Schultze Michael , Kondorosi Adam 
Published: March 2003

SummaryUnder nitrogen limitation, Rhizobium meliloti Nod factors induce cell divisions in the inner cortex of alfalfa roots in a still unknown way. These cell division clusters subsequently develop into symbiotically nitrogen‐fixing nodules. To study the involvement of plant signals in nodule initiation transgenic alfalfa carrying the promoter of the early nodulin gene MsEnod12A fused to the reporter gene gusA were generated. In untreated plants, low level GUS staining was only found in lateral root primordia and in front of the root apices. After inoculation with R. meliloti or after treatment with purified Nod factors, GUS activity was first induced in the cell division foci of the inner cortex. The GUS staining patterns in nodules and roots were in agreement with the activation of the endogenous MsEnod12A gene as revealed by reverse transcription‐PCR analysis, rendering the MsEnod12A‐gusA fusion a valuable novel marker for studying the onset of nodule and lateral root developmental processes. Treatment of roots with purified Nod factors and cytokinins induced similar patterns of cortical cell division, GUS staining and amyloplast accumulation while upon application of auxin transport inhibitors and auxins these patterns were different. Like the Nod factor responses, the cytokinin responses required photosynthesis and limiting combined nitrogen supply. Thus, cytokinins and Nod factors may share elements of their signal transduction pathways to the inner root cortex. A model on the possible involvement of cytokinins in coordinating plant metabolism with nodule initiation is proposed.
The SHOOT MERISTEMLESS gene is required for maintenance of undifferentiated cells in Arabidopsis shoot and floral meristems and acts at a different regulatory level than the meristem genes WUSCHEL and ZWILLE
Authors: Endrizzi Karin , Moussian Bernard , Haecker Achim , Levin Joshua Z. , Laux Thomas 
Published: March 2003

SummaryThe function of the SHOOT MERISTEMLESS (STM) gene in shoot and floral meristems throughout Arabidopsis development has been analyzed. The results show that STM plays a major role in maintaining shoot and floral meristems. In an allelic series of stm mutants the shoot meristem was either reduced or completely absent in mature embryos and mutant seedling cotyledons showed partial fusion, indicating that the STM gene affects embryonic shoot meristem development and spacing of cotyledons. Postembryonically, stm mutants initiated adventitious shoot development at a position corresponding to the shoot meristem in wild‐type. Repetitively initiated defective mutant shoot and floral meristems were consumed during primordia formation and typically terminated prematurely in fused ectopic primordia, indicating that STM is required for continuous shoot and floral meristem function.Analogous defects were observed in stm embryonic and postembryonic development suggesting that similar mechanisms are employed in embryonic and postembryonic organ primordia initiation. Allelic combinations suggest different thresholds for STM requirement during plant development. STM requirement could not be bypassed by standard growth factor regimes or by shoot regeneration from calli. The results suggest that STM functions by preventing incorporation of cells in the meristem center into differentiating organ primordia and that this role can completely account for all defects observed in stm mutants.Mutations in the WUSCHEL (WUS) and ZWILLE (ZLL) genes result in defective organization and premature termination of shoot meristems. Genetic interactions between STM, WUS and ZLL were analyzed and the results indicate that STM acts upstream of WUS and ZLL. Therefore, while STM appears to function in keeping central meristem cells undifferentiated, WUS and ZLL seem to be subsequently required for proper function of these cells.