bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential activation of the primary auxin response genes, PS‐IAA4/5 and PS‐IAA6, during early plant development
Authors: Wong Lu Min , Abel Steffen , Shen Nancy , De La Foata Monique , Mall Yasmeen , Theologis Athanasios 
Published: March 2003

SummaryThe plant growth hormone auxin typified by indoleacetic acid (IAA) transcriptionally activates early genes in pea, PS‐IAA4/5 and PS‐IAA6, that are members of a multigene family encoding short‐lived nuclear proteins. To gain first insight into the biological role of PS‐IAA4/5 and PSIAA6, promoter‐β‐glucuronidase (GUS) gene fusions were constructed and their expression during early development of transgenic tobacco seedlings was examined. The comparative analysis reveals spatial and temporal expression patterns of both genes that correlate with cells, tissues, and developmental processes known to be affected by auxin. GUS activity in seedlings of both transgenic lines is located in the root meristem, sites of lateral root initiation and in hypocotyls undergoing rapid elongation. In addition, mutually exclusive cell‐specific expression is evident. For instance, PS‐IAA4/5—GUS but not PS‐IAA6—GUS is expressed in root vascular tissue and in guard cells, whereas only PS‐IAA6—GUS activity is detectable in glandular trichomes and redistributes to the elongating side of the hypocotyl upon gravitropic stimulation. Expression of PS‐IAA4/5 and PS‐IAA6 in elongating, dividing, and differentiating cell types indicates multiple functions during development. The common and yet distinct activity patterns of both genes suggest a combinatorial code of spatio‐temporal co‐expression of the various PS‐IAA4/ 5‐like gene family members in plant development that may mediate cell‐specific responses to auxin.
Reduction of the cytosolic fructose‐1,6‐bisphosphatase in transgenic potato plants limits photosynthetic sucrose biosynthesis with no impact on plant growth and tuber yield
Authors: Zrenner Rita , Krause Klaus‐Peter , Apel Peter , Sonnewald Uwe 
Published: March 2003

SummarySucrose produced in source leaves is the predominant carbon source for developing sink tissues in most higher plants. Consequently the rate of sucrose synthesis is likely to be important for sink development and final crop yield. Two sucrose biosynthetic enzymes are believed to possess regulatory properties with respect to the rate of sucrose synthesis: (i) cytosolic FBPase and (ii) sucrose phosphate synthase. To study the impact of reduced photosynthetic sucrose biosynthesis on plant growth and crop yield a cDNA clone encoding cytosolic FBPase was isolated from a potato leaf cDNA library and used for antisense experiments in transgenic potato plants. The cDNA clone cy‐F1, containing an open reading frame of 1020 bp highly homologous (85%) to other known sequences of plant cytosolic FBPases, was cloned in reversed orientation between the 35S CaMV promoter and the octopine synthase polyadenylation signal. Out of 75 independent transformants five transgenic lines having 9 to 55% of the wild‐type FBPase activity were chosen for further analysis.A 45% reduction of the cytosolic FBPase activity did not cause any measurable change in metabolite concentrations, growth behaviour or photosynthetic parameters of the transgenic plants. Inhibition of cytosolic FBPase activity below 20% of the wild‐type activity led to an accumulation of 3‐PGA, triose‐phosphates and fructose‐1,6bisphosphate in source leaves. This resulted in a reduced light‐saturated rate of assimilation measured via gas exchange and a decreased photosynthetic rate under conditions of the leaf disc electrode with saturating light and CO2. Measuring photosynthetic carbon fluxes by labelling leaf discs with 14CO2 revealed a 53–65% reduction of sucrose synthesis whereas starch synthesis decreased only by 18–24%. The flux into the anionic and cationic fraction was not altered. Despite these changes steadystate sucrose concentrations were not effected in source leaves from transgenic plants. Starch accumulated by more than a factor of 3 compared with wild‐type leaves and was degraded during the night. This provides strong evidence for the hypothesis that hexoses and/or hexosephosphates are exported out of the chloroplasts, thereby circumventing the limitation of sucrose biosynthesis caused by the inhibition of cytosolic FBPase in the dark. Accordingly, plant growth and potato tuber yield remained unaltered. From these data it can be concluded that a reduced photosynthetic sucrose biosynthetic capacity can be efficiently compensated without any reduction in crop yield under greenhouse or growth chamber conditions by changing carbon export strategy. Whether the same holds true for field conditions remains to be elucidated.
Genetic evidence for an essential role of brassinosteroids in plant development
Authors: Kauschmann Annette , Jessop Alison , Koncz Csaba , Szekeres Miklos , Willmitzer Lotbar , Altmann Thomas 
Published: March 2003

SummaryBrassinosteroids which show high structural similarity to animal steroid hormones elicit a variety of growth responses when exogeneously applied to plant tissues. Thus far however, the function of endogeneous brassinosteroids in higher plants has been unclear. This paper describes three extremely dwarfed Arabidopsis thaliana mutants, cbb1 (dwf1‐6), cbb2 and cbb3, which are impared in cell elongation controlled by brassinosteroids. While cbb1 (dwf1‐6) and cbb3 can be phenotypically normalized to wild‐type by feeding with brassinosteroids indicating deficiencies of brassinosteroid biosynthesis, cbb2 is brassinosteroid‐insensitive and defines a function required for further metabolic conversion necessary for biological activity or for perception/signal transduction of these growth‐regulating plant steroid hormones. Expression of the meri5 and TCH4 genes is low in all three cbb mutants and can be restored to wild‐type levels by brassinosteroid treatment in the cbb1 (dwf1‐6) and cbb3 mutants but are unaffected in the cbb2 mutant. These data indicate that brassinosteroids are essential for proper plant development and play an important role in the control of cell elongation.
Xyloglucan sidechains modulate binding to cellulose during in vitro binding assays as predicted by conformational dynamics simulations
Authors: Levy Samuel , Maclachlan Gordon , Staehelin L. Andrew 
Published: March 2003

SummaryCross‐links between cellulose microfibrils and xyloglucan (XG) molecules play a major role in defining the structural properties of plant cell walls and the regulation of growth and development of dicotyledonous plants. How these cross‐links are established and how they are regulated has yet to be determined. In a previous study, preliminary data were presented which suggested that the different sidechains of XG may play a role in controlling cellulose microfibril‐XG interactions. In this study, this question is addressed directly by analyzing to what extent the different sidechains of pea cell wall XG and nasturtium seed storage XG affect their binding to cellulose microfibrils. Of particular importance to this study are the chemical data indicating that pea XG possesses a trisaccharide sidechain, which is not found in nasturtium XG. To this end, conformational dynamic simulations have been used to predict whether oligosaccharides representative of pea and nasturtium XG can adopt a hypothesized cellulose‐binding conformation and which of these XGs exhibits a preferential ability to bind cellulose. Extensive analysis of the conformational forms populated during 300 K and high‐temperature Monte Carlo simulations established that a planar, sterically accessible, glucan backbone is essential for optimal cellulose‐binding. For the trisaccharide sidechain‐containing oligosaccharide as found in pea XG, sidechain orientation appeared to regulate the gradual acquisition of this hypothesized cellulose binding conformation. Thus, conformational forms were identified that included the twisted backbone (non‐planar) putative solution form of XG, forms in which the trisaccharide sidechain orientation enables increased backbone planarity and steric accessibility, and finally a planar, sterically accessible, backbone. By applying these conformational requirements for cellulose binding, it has been determined that pea XG possesses a two‐ to threefold occurrence of the cellulose binding conformation than nasturtium XG. Based on this finding, it was predicted that pea XG would bind to cellulose at a higher rate than nasturtium XG. In vitro binding assays showed that pea XG‐avicel binding does indeed occur at a twofold higher rate than nasturtium XG‐avicel binding. The enhanced ability of pea cell wall XG over nasturtium seed storage XG to associate with cellulose is consistent with a structural role of the former during epicotyl growth where efficient association with cellulose is a requirement. In contrast, the relatively low ability of nasturtium XG to bind cellulose is consistent with the need to enhance the accessibility of this polymer to glycanases during germination. These findings suggest potential roles for XG sidechain substitution, enabling XG to function in a variety of different biological contexts.
Dynamic reorganization of microfilaments and microtubules is necessary for the expression of non‐host resistance in barley coleoptile cells
Authors: Kobayashi Yuhko , Kobayashi Issei , Funaki Yasuro , Fujimoto Shigeo , Takemoto Tsuyoshi , Kunoh Hitoshi 
Published: March 2003

SummaryTo show the involvement of microfilaments and microtubules in non‐host resistance of barley, partially dissected coleoptiles which had been inoculated with a non‐pathogen, Erysiphe pisi, were treated with several actin and tubulin inhibitors. If the coleoptiles were not treated with any of the inhibitors, the non‐pathogen always failed to penetrate the coleoptile cells. However, when coleoptiles were treated with actin or tubulin polymerization or depolymerization inhibitors, the non‐pathogen was able to penetrate successfully and to form haustoria in coleoptile cells of a non‐host plant, barley. Actin polymerization inhibitors, cytochalasins, were more effective in causing an increase in penetration efficiency of E. pisi than tubulin inhibitors. The effects of cytochalasins depended on the kind of cytochalasin; the strength of the actin depolymerizing activity correlated significantly with the efficiency of increasing the penetration of the non‐pathogen. When both actin and tubulin inhibitors were added simultaneously, the polarization of defense‐related responses, such as massive cytoplasmic aggregation, deposition of papillae and accumulation of autofluorescent compounds, at fungal penetration sites was suppressed. Actin inhibitors did not affect arrangement and stability of microtubules and vice versa, and a double treatment of coleoptile cells with both microfilament and microtubule inhibitors showed an additive effect in increasing the penetration efficiency of E. pisi. Furthermore, cytochalasin A treatment allowed other non‐pathogens, Colletotrichum lagenarium and Alternaria alternata, to penetrate successfully into the non‐host barley cells. These results strongly suggest that microfilaments and microtubules might play important roles in the expression of non‐host resistance of barley.
Style‐specific self‐compatible mutation caused by deletion of the S‐RNase gene in Japanese pear (Pyrus serotina)
Authors: Sassa Hidenori , Hirano Hisashi , Nishio Takeshi , Koba Takato 
Published: March 2003

SummaryMonofactorial gametophytic self‐incompatibility in the family Rosaceae is controlled by the single multi‐allelic S‐locus. In Japanese pear, a naturally occurring self‐compatible mutant was found as a sport of a self‐incompatible cultivar with an S‐genotype of S2,S4. The S,4 allele has been shown to be non‐functional in the style of the mutant, but functional in pollen. The present study shows the S2‐RNase gene to be transcribed normally in the style of the mutant, but that the S4‐RNase gene transcript is not detectable. Furthermore, the S4‐RNase gene could not be detected in the mutant by genomic Southern blot, indicating that the mutant lacks the gene. The extent of deletion in the mutant was estimated to be more than 4 kbp, and spans the entire length of the S4‐RNase gene. These findings provide evidence that the S‐RNase gene is essential for the self‐incompatibility reaction in the style, but is not involved in controlling the self‐incompatibility behavior of pollen.
Expression of a luteoviral movement protein in transgenic plants leads to carbohydrate accumulation and reduced photosynthetic capacity in source leaves
Authors: Herbers Karin , Tacke Eckhardt , Hazirezaei Mohammad , Krause Klaus‐Peter , Melzer Michael , Rohde Wolfgang , Sonnewald Uwe 
Published: March 2003

SummaryElucidating the role of viral genes in transgenic plants revealed that the movement protein (MP) from tobacco mosaic virus is responsible for altered carbohydrate allocation in tobacco and potato plants. To study whether this is a general feature of viral MPs, the movement protein MP17 of potato leafroll virus (PLRV), a phloem‐restricted luteovirus, was constitutively expressed in tobacco plants. Transgenic lines were strongly reduced in height and developed bleached and sometimes even necrotic areas on their source leaves. Levels of soluble sugars and starch were significantly increased in source leaves. Yet, in leaf laminae the hexose—phosphate content was unaltered and ATP reduced to only a small extent, indicating that these leaves were able to maintain homeostatic conditions by compartmentalization of soluble sugars, probably in the vacuole. On the contrary, midribs contained lower levels of soluble sugars, ATP, hexose—phosphates and UDP‐glucose supporting the concept of limited uptake and catabolism of sucrose in the phloem. The accumulation of carbohydrates led to a decreased photosynthetic capacity and carboxylation efficiency of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (rubisco) probably owing to decreased expression of photosynthetic proteins. In parallel, levels of pathogenesis‐related proteins were elevated which may be the reason for the obtained limited resistance against the unrelated potato virus Y (PVY)N in the transgenic tobacco plants. Ultrathin sections of affected leaves harvested from 2‐week‐old plants revealed plasmodesmal alterations in the phloem tissue while plasmodesmata between mesophyll cells were indistinguishable from wild‐type. These data favour the phloem tissue to be the primary site of PLRV MP17 action in altering carbohydrate metabolism.
Stress‐responsive accumulation of plastid chaperonin 60 during seedling development
Authors: Holland Neta , Belkind Anna , Holland Doron , Pick Uri , Edelman Marvin 
Published: March 2003

SummaryPlastid chaperonin 60 (cpn60) is a chloroplast protein, presumed to assist in assembly and folding of plastid proteins. Although molecular chaperones often accumulate significantly in response to stress, this has never been demonstrated for cpn60. In this study, the accumulation of cpn60 in Nicotiana seedlings during their development was followed under different stress conditions. It was found that cpn60 accumulates markedly in developing seedlings in response to tentoxin and several other (but not all) stresses. Cpn60 accumulates only during a narrow period of seedling development. It is proposed that cpn60 accumulation under stress is developmentally regulated.
A robust method for detecting single‐nucleotide changes as polymorphic markers by PCR
Authors: Michaels Scott D. , Amasino Richard M. 
Published: March 2003

SummaryNumerous techniques in plant molecular genetic analysis, such as mapping and positional cloning techniques, rely on the availability of molecular markers that can differentiate between alleles at a particular locus. PCR‐based cleaved amplified polymorphic sequences (CAPS) markers have been widely used as a means of rapidly and reliably detecting a single‐base change that creates a unique restriction site in one of a pair of alleles. However, the majority of single‐nucleotide changes do not create such sites and thus cannot be used to create CAPS markers. In this paper, a modification of the CAPS technique that allows detection of most single‐nucleotide changes by utilizing mismatched PCR primers is described. The mismatches in the PCR primers, in combination with the single‐nucleotide change, create a unique restriction site in one of the alleles.
Aberrant splicing of intron 1 leads to the heterogeneous 5′ UTR and decreased expression of waxy gene in rice cultivars of intermediate amylose content
Authors: Cai Xiu‐Ling , Wang Zong‐Yang , Xing Yan‐Yan , Zhang Jing‐Liu , Hong Meng‐Min 
Published: March 2003

SummaryWe have previously reported that three distinct patterns of waxy (Wx) gene transcript accumulation were present in 31 rice cultivars. The cultivars with high amylose content (group I) contain a 2.3 kb mature Wx mRNA, cultivars with intermediate amylose content (group II) produce both a 3.3 kb Wx pre‐mRNA, which contains intron 1, and the 2.3 kb Wx mature mRNA, and cultivars with no amylose (group III) accumulate only the 3.3 kb Wx pre‐mRNA. Analyses of the cDNAs reveals that four splice donor sites and three splice acceptor sites in intron 1 give rise to six splicing patterns in 2.3 kb Wx mRNA of group II cultivars. In addition, aberrant intron 1 excision causes either deletion of 4 or 5 nucleotides, or addition of 7 and 13 nucleotides at the junction of exon 1 and exon 2 of the 2.3 kb mRNA. In contrast, only one normal splicing pattern (one splice donor site and one splice acceptor site) was found in the 2.3 kb mRNA of group I cultivars. Nucleotide sequences of the Wx intron 1 in group I and group II cultivars differ by 16 individual bases. We suggest that these deletions or additions contribute to inefficient splicing of intron 1 from the 3.3 kb Wx pre‐mRNA, as well as an aberrant splicing of the Wx intron 1 to produce the 2.3 kb mRNA with a heterogeneous 5′ untranslated region (5′‐UTR). As a consequence, the total amount of translatable Wx mRNA, and therefore the Wx protein and amylose content, are reduced in the group II cultivars compared with the group I cultivars.
Guard cell cation channels are involved in Na+–induced stomatal closure in a halophyte
Authors: Véry Anne‐Aliénor , Robinson Michael F. , Mansfield Terry A. , Sanders Dale 
Published: March 2003

SummaryThe halophyte Aster tripolium, unlike well‐studied non‐halophytic species, partially closes its stomata in response to high Na+ concentrations. Since A. tripolium possesses no specific morphological adaptation to salinity, this stomatal response, preventing excessive accumulation of Na+ within the shoot via control of the transpiration rate, is probably a principal feature of its salt tolerance within the shoot. The ionic basis of the stomatal response to Na+ was studied in guard cell protoplasts from A. tripolium and from a non‐halophytic relative, Aster amellus, which exhibits classical stomatal opening on Na+. Patch‐clamp studies revealed that plasma membrane K+ channels (inward and outward rectifiers) of the halophytic and the non‐halophytic species are highly selective for K+ against Na+, and are very similar with respect to unitary conductance and direct sensitivity to Na+. On the other hand, both species possess a significant permeability to Na+ through non‐rectifying cation channels activated by low (physiological) external Ca2+ concentrations. Finally, it appeared that the differential stomatal response between the two species is achieved, at least in part, by a Na+‐sensing system in the halophyte which downregulates K+ uptake. Thus, increases in guard cell cytosolic Na+ concentration in A. tripolium but not in A. amellus, lead to a delayed (20–30 min) and dramatic deactivation of the K+ inward rectifier. This deactivation is probably mediated by an increase in cytosolic Ca2+ since buffering it abolishes the response. The possible role of K+ inward rectifiers in the response of A. tripolium’s stomata to Na+, suggested by patch‐clamp studies, was confirmed by experiments demonstrating that specific blockade of inward rectifying channels mimics Na+ effects on stomatal aperture, and renders aperture refractory to Na+.
Developmental control of H+/amino acid permease gene expression during seed development of Arabidopsis
Authors: Hirner Brigitte , Fischer Wolf N. , Rentsch Doris , Kwart Marion , Frommer Wolf B. 
Published: March 2003

SummaryLong distance transport of amino acids is mediated by several families of differentially expressed amino acid transporters. The two genes AAP1 and AAP2 encode broad specificity H+‐amino acid co‐transporters and are expressed to high levels in siliques of Arabidopsis, indicating a potential role in supplying the seeds with organic nitrogen. The expression of both genes is developmentally controlled and is strongly induced in siliques at heart stage of embryogenesis, shortly before induction of storage protein genes. Histochemical analysis of transgenic plants expressing promoter‐GUS fusions shows that the genes have non‐overlapping expression patterns in siliques. AAP1 is expressed in the endosperm and the cotyledons whereas AAP2 is expressed in the vascular strands of siliques and in funiculi. The endosperm expression of AAP1 during early stages of seed development indicates that the endosperm serves as a transient storage tissue for organic nitrogen. Amino acids are transported in both xylem and phloem but during seed filling are imported only via the phloem. AAP2, which is expressed in the phloem of stems and in the veins supplying seeds, may function in uptake of amino acids assimilated in the green silique tissue, in the retrieval of amino acids leaking passively out of the phloem and in xylem‐to‐phloem transfer along the path. The promoters provide excellent tools to study developmental, hormonal and metabolic control of nitrogen nutrition during development and may help to manipulate the timing and composition of amino acid import into seeds.
Tetrad pollen formation in quartet mutants of Arabidopsis thaliana is associated with persistence of pectic polysaccharides of the pollen mother cell wall
Authors: Rhee Seung Y. , Somerville Chris R. 
Published: March 2003

SummaryThe quartet (qrt) mutants of Arabidopsis thaliana produce tetrad pollen in which microspores fail to separate during pollen development. Because the amount of callose deposition between microspores is correlated with tetrad pollen formation in other species, and because pectin is implicated as playing a role in cell adhesion, these cell‐wall components in wild‐type and mutant anthers were visualized by immunofluorescence microscopy at different stages of microsporogenesis. In wild‐type, callose was detected around the pollen mother cell at the onset of meiosis and around the microspores during the tetrad stage. Microspores were released into the anther locule at the stage where callose was no longer detected. Deposition and degradation of callose during tetrad pollen formation in qrt1 and qrt2 mutants were indistinguishable from those in wild‐type. Enzymatic removal of callose from wild‐type microspores at the tetrad stage did not release the microspores, suggesting that callose removal is not sufficient to disperse the microspores in wild‐type. Pectic components were detected in the primary wall of the pollen mother cell. This wall surrounded the callosic wall around the pollen mother cell and the microspores during the tetrad stage. In wild‐type, pectic components of this wall were no longer detectable at the time of microspore release. However, in qrt1 and qrt2 mutants, pectic components of this wall persisted after callose degradation. This result suggests that failure of pectin degradation in the pollen mother cell wall is associated with tetrad pollen formation in qrt mutants, and indicates that QRT1 and QRT2 may be required for cell type‐specific pectin degradation to separate microspores.