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Hypocotyls
Terms modified by Hypocotyls Selected AbstractsELF4 is a phytochrome-regulated component of a negative-feedback loop involving the central oscillator components CCA1 and LHYTHE PLANT JOURNAL, Issue 2 2005Elise A. Kikis Summary Evidence has been presented that a negative transcriptional feedback loop formed by the genes CIRCADIAN CLOCK ASSOCIATED (CCA1), LATE ELONGATED HYPOCOTYL (LHY) and TIMING OF CAB (TOC1) constitutes the core of the central oscillator of the circadian clock in Arabidopsis. Here we show that these genes are expressed at constant, basal levels in dark-grown seedlings. Transfer to constant red light (Rc) rapidly induces a biphasic pattern of CCA1 and LHY expression, and a reciprocal TOC1 expression pattern over the first 24 h, consistent with initial induction of this synchronous oscillation by the light signal. We have used this assay with wild-type and mutant seedlings to examine the role of these oscillator components, and to determine the function of ELF3 and ELF4 in their light-regulated expression. The data show that whereas TOC1 is necessary for light-induced CCA1/LHY expression, the combined absence of CCA1 and LHY has little effect on the pattern of light-induced TOC1 expression, indicating that the negative regulatory arm of the proposed oscillator is not fully functional during initial seedling de-etiolation. By contrast, ELF4 is necessary for light-induced expression of both CCA1 and LHY, and conversely, CCA1 and LHY act negatively on light-induced ELF4 expression. Together with the observation that the temporal light-induced expression profile of ELF4 is counter-phased to that of CCA1 and LHY and parallels that of TOC1, these data are consistent with a previously unrecognized negative-feedback loop formed by CCA1/LHY and ELF4 in a manner analogous to the proposed CCA1/LHY/TOC1 oscillator. ELF3 is also necessary for light-induced CCA1/LHY expression, but it is neither light-induced nor clock-regulated during de-etiolation. Taken together, the data suggest (a) that ELF3, ELF4, and TOC1 all function in the primary, phytochrome-mediated light-input pathway to the circadian oscillator in Arabidopsis; and (b) that this oscillator consists of two or more interlocking transcriptional feedback loops that may be differentially operative during initial light induction and under steady-state circadian conditions in entrained green plants. [source] Varietal Differences in Allelopathic Potential of AlfalfaJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2002Tran Dang Xuan Alfalfa (Medicago sativa L.) plants were found to contain water-soluble substances that inhibited the germination and seedling growth of alfalfa (Chung and Miller 1990, Agron. J. 87, 762,767). Tsuzuki et al. (1999, Rep. Kyushu Branch Crop Sci. Soc. Japan 65, 39,40) discovered allelochemicals in alfalfa plants that could have adverse effects on the growth of some lowland weeds. This study was conducted to investigate varietal differences in allelopathic potential in alfalfa plants. Eight common varieties of Japanese alfalfa (Medicago sativa L.), namely Batasu, Hisawakaba, Kitawakaba, Makiwakaba, Natsuwakaba, Lucerne, Tachiwakaba and Yuba, were grown by conventional methods in the Experimental Field of the Crop Science Laboratory, Faculty of Agriculture, Miyazaki University. Aqueous extracts of both fresh and dried material of alfalfa plants of all varieties significantly inhibited both germination and growth of lettuce (Lactuca sativa L.). Leachates from germinating seeds of almost all alfalfa varieties inhibited elongation of the radicle but produced a negligible increase in germination and only slightly inhibited elongation of the hypocotyl of lettuce plants. Results demonstrated that the degree of inhibition of germination and growth of lettuce varied with the variety of alfalfa. In particular, Lucerne was identified as having the strongest allelopathic potential of the varieties studied. The results suggested that the allelopathic potential of alfalfa might be relating to a gene. Varietätsunterschiede im allelopathischen Potential von Luzerne Luzerne (Medicago sativa L.)-Pflanzen weisen wasserlösliche Substanzen auf, die die Keimung und das Sämlingswachstum von Luzerne inhibieren. Es kann angenommen werden, daß Luzernepflanzen allelopathisch wirkende Verbindungen aufweisen, die das Wachstum von Unkrautpflanzen des Tieflands beeinträchtigen. Die Untersuchung wurde durchgeführt, um das Potential allelopathischer Sortenunterschiede bei Luzerne zu bestimmen. Acht im Anbau verwendete Luzernesorten , Batasu, Hisawakaba, Kitawakaba, Makiwakaba, Natsuwakaba, Lucerne, Tachiwakaba und Yuba , wurden nach konventionellen Verfahren auf dem Versuchsfeld des Pflanzenbauinstitutes der Fakultät der Miyazaki-Universität angebaut. Wässerige Extrakte von frischen und trockenen Luzernepflanzen hemmten bei allen Sorten signifikant die Keimung und das Wachstum von Salat (Lactuca sativa L.). Auszüge keimender Samen der meisten Luzernesorten inhibierten das Längenwachstum der Wurzel, hatten aber kaum Einfluß auf eine Förderung der Keimung und zeigten eine geringe Inhibierung des Längenwachstum des Hypokotyls von Salat. Die Ergebnisse zeigen, daß der Grad der Inhibierung der Keimung des Wachstums von Salat abhängig von den geprüften Luzernesorten ist. Lucerne hat das stärkste allelopathische Potential der Sorten. Die Ergebnisse lassen vermuten, daß das allelopathische Potential genetisch bedingt ist. [source] DEFINITION OF INTERNAL MORPHOLOGY AND STRUCTURAL CHANGES DUE TO DEHYDRATION OF RADISH (RAPHANUS SATIVUS L. CV. SUPRELLA) USING MAGNETIC RESONANCE IMAGING SPECTROSCOPYJOURNAL OF FOOD QUALITY, Issue 5-6 2005ANNA SALERNO ABSTRACT Magnetic resonance imaging (MRI) spectroscopy is a promising nondestructive analytical technique in food science. It offers the unique opportunity of studying vegetables, fruits and other foods in general, in their wholeness without any preparative manipulation of the sample. The aim of this study was to investigate the internal structure of radish and to monitor the variations induced by postharvest storage at low relative humidity. The MRI allowed for a clear definition of the internal structure of radishes with distinct visibility of xylematic and phloematic vessels distributed in a radial way. A decrease in water content, which results in the breakdown of tissues and the formation of large cavities with the detachment of the external cortex, is the main consequence of a few days' storage in low relative humidity. Both of these are factors that drastically decrease the quality of the radish's fleshy root. The MRI images give a novel insight into the internal organization of the hypocotyl, and this offers opportunities for further studies with regard to the structural differences related to the cultivars as well as the cultivation system. [source] Polycapillary-optics-based micro-XANES and micro-EXAFS at a third-generation bending-magnet beamlineJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2009Geert Silversmit A focusing system based on a polycapillary half-lens optic has been successfully tested for transmission and fluorescence µ-X-ray absorption spectroscopy at a third-generation bending-magnet beamline equipped with a non-fixed-exit Si(111) monochromator. The vertical positional variations of the X-ray beam owing to the use of a non-fixed-exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K -edge is approximately 200,µm on the lens input side and this was reduced to ,1,µm for the focused beam. Beam sizes (FWHM) of 12,16,µm, transmission efficiencies of 25,45% and intensity gain factors, compared with the non-focused beam, of about 2000 were obtained in the 7,14,keV energy range for an incoming beam of 0.5 × 2,mm (vertical × horizontal). As a practical application, an As K -edge µ-XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant. [source] Plastid signals that affect photomorphogenesis in Arabidopsis thaliana are dependent on GENOMES UNCOUPLED 1 and cryptochrome 1NEW PHYTOLOGIST, Issue 2 2009Michael E. Ruckle Summary ,,When plastids experience dysfunction they emit signals that help coordinate nuclear gene expression with their functional state. One of these signals can remodel a light-signaling network that regulates the expression of nuclear genes that encode particular antenna proteins of photosystem II. These findings led us to test whether plastid signals might impact other light-regulated processes. ,,Photomorphogenesis was monitored in genomes uncoupled 1 (gun1), cryptochrome 1 (cry1), and long hypocotyl 5 (hy5), which have defects in light and plastid signaling, by growing Arabidopsis thaliana seedlings under various light conditions and either treating or not treating them with antibiotics that induce chloroplast dysfunction and trigger plastid signaling. ,,It was found that plastid signals that depend on GUN1 can affect cotyledon opening and expansion, anthocyanin biosynthesis, and hypocotyl elongation. We also found that plastid signals that depend on CRY1 can regulate cotyledon expansion and development. ,,Our findings suggest that plastid signals triggered by plastid dysfunction can broadly affect photomorphogenesis and that plastid and light signaling can promote or antagonize each other, depending on the responses studied. These data suggest that GUN1 and cry 1 help to integrate chloroplast function with photomorphogenesis. [source] Developmental anatomy of seedlings of Indodalzellia gracilis (Podostemaceae)PLANT BIOLOGY, Issue 5 2010S. Koi Abstract In Tristichoideae, aquatic angiosperms in the family Podostemaceae, Terniopsis, Tristicha, Indotristicha and Cussetia have creeping roots with flanking (sub)cylindrical shoots, while Dalzellia is rootless and has crustose shoots. Indodalzellia gracilis, sister to a clade of Dalzellia zeylanica and Indotristicha ramosissima, has subcrustose shoots on the side of creeping roots, suggesting that I. gracilis may be a key species to reveal how saltational evolution of the body plan occurred in these three species. We investigated developmental morphology of I. gracilis seedlings grown in culture, using scanning electron microscopy and semi-thin serial sections. As in D. zeylanica, the plumular apical meristem in the seedling gives rise to two shoot apical meristems, which develop into horizontal subcrustose shoots with dorsal and marginal leaves. Neither radicle nor adventitious root is produced from the hypocotyl, but an adventitious root arises endogenously from the juvenile shoot and from some shoots of adult plants. These results, together with the phylogenetic relationships, suggest that the Indodalzellia seedling evolved by loss of the adventitious root derived from the hypocotyl, appearance of shoots in the axil of cotyledons, and appearance of adventitious roots from adventitious shoots. The difference in place of origin of the root between Indodalzellia and I. ramosissima suggests differing evolutionary origin of the root in Tristichoideae. [source] Effect of steady torque twisting on the orientation of cortical microtubules in the epidermis of the sunflower hypocotylPLANT BIOLOGY, Issue 4 2008J. Elsner Abstract Orientation of cortical microtubules (cMTs) is suggested to be affected by mechanical stress existing in cell walls. However, in mutants exhibiting helical (chiral) growth, there is a correlation between orientation of cMTs in outer tissues and helical growth direction. The aim of this research was to examine the effect of a chiral mechanical stimulation on cMTs. For this purpose, the orientation of cMTs was investigated in hypocotyls subjected to either a right- or a left-handed twist, resulting from a steady torque. cMTs were visualised in fixed material using the immunofluorescence method. The cMTs in untouched control hypocotyls were mostly transverse with respect to the cell long axis. In immobilised, but not twisted control hypocotyls, the transverse orientation was also most frequent, while applied twisting resulted in a change in cMT orientation from transverse to oblique. The data provide additional evidence that changes in tissue stress can be reorganized by cortical microtubules. [source] Effects of cold-girdling on flows in the transport phloem in Ricinus communis: is mass flow inhibited?PLANT CELL & ENVIRONMENT, Issue 1 2006ANDREAS D. PEUKE ABSTRACT The effects of cold girdling of the transport phloem at the hypocotyl of Ricinus communis on solute and water transport were investigated. Effects on the chemical composition of saps of phloem and xylem as well as of stem tissue were studied by conventional techniques and the water flow in the phloem was investigated by NMR imaging. Cold girdling reduced the concentration of sucrose but not that of inorganic solutes or amino acids in phloem saps. The possibility that cold treatment inhibited the retrieval of sucrose into the phloem, following leaching from the sieve tubes along a chemical gradient is discussed. Leaching of other solutes did not occur, as a result of missing promoting gradients in stem tissue. Following 3 d of cold girdling, sugar concentration increased and starch was synthesized and accumulated in stem tissue above the cold girdling region and along the cold-treated phloem pathway due to leaching of sugars from the phloem. Only in the very first period of cold girdling (< 15,30 min) was mass flow inhibited, but recovered in the rest of cold treatment period to values similar to the control period before and the recovery period after the cold treatment. It is concluded that cold treatment affected phloem transport through two independent and reversible processes: (1) a permanent leaching of sucrose from the phloem stem without normal retrieval during cold treatment, and (2) a short-term inhibition of mass flow at the beginning of cold treatment, possibly involving P proteins. Possible further mechanisms for reversible inhibition of water flow are discussed. [source] Simultaneous measurement of water flow velocity and solute transport in xylem and phloem of adult plants of Ricinus communis over a daily time course by nuclear magnetic resonance spectrometryPLANT CELL & ENVIRONMENT, Issue 5 2001A. D. Peuke ABSTRACT A new method for simultaneously quantifying rates of flow in xylem and phloem using the FLASH imaging capabilities of nuclear magnetic resonance (NMR) spectrometry was applied in this study. The method has a time resolution of up to 4 min (for the xylem) and was used to measure the velocity of flows in phloem and xylem for periods of several hours to days. For the first time, diurnal time course measurements of flow velocities and apparent volume flows in phloem and xylem in the hypocotyl of 40-d-old Ricinus communis L were obtained. Additional data on gas exchange and the chemical composition of leaves, xylem and phloem sap were used to assess the role of leaves as sinks for xylem sap and sources for phloem. The velocity in the phloem (0·250 ± 0·004 mm s,1) was constant over a full day and not notably affected by the light/dark cycle. Sucrose was loaded into the phloem and transported at night, owing to degradation of starch accumulated during the day. Concentrations of solutes in the phloem were generally less during the night than during the day but varied little within either the day or night. In contrast to the phloem, flow velocities in the xylem were about 1·6-fold higher in the light (0·401 ± 0·004 mm s,1) than in the dark (0·255 ± 0·003 mm s,1) and volume flow varied commensurately. Larger delays were observed in changes to xylem flow velocity with variation in light than in gas exchange. The relative rates of solute transport during day and night were estimated on the basis of relative flow and solute concentrations in xylem and phloem. In general, changes in relative flow rates were compensated for by changes in solute concentration during the daily light/dark cycle. However, the major solutes (K+, NO3,) varied appreciably in relative concentrations. Hence the regulation of loading into transport systems seems to be more important to the overall process of solute transport than do changes in mass flow. Due to transport behaviour, the chemical composition of leaves varied during the day only with regard to starch and soluble carbohydrates. [source] Evaluation of carrot resistance to alternaria leaf blight in controlled environmentsPLANT PATHOLOGY, Issue 1 2006A. Pawelec The objective of this study was to find a technique for plant resistance screening to alternaria leaf blight (ALB), caused by the fungus Alternaria dauci, in controlled environments. Glasshouse and laboratory screening methods were compared using three cultivars and F2 genotypes segregating for ALB resistance evaluated against self-pollinated F3 field-grown plants. Plant disease was assessed through a disease index obtained from the size and number of symptoms on carrot leaves. The results indicated the value of glasshouse evaluation and the inadequacy of detached leaf and hypocotyl assays for carrot screening for ALB resistance. Spearman's rank correlation, applied to results obtained with both F2 plants and their progeny, indicated that the optimal evaluation stage for ALB resistance in carrot is 20 days after inoculation. This test was powerful enough to be used as a prescreening test in breeding programmes. [source] Chemistry and biology of phototropism-regulating substances in higher plantsTHE CHEMICAL RECORD, Issue 5 2001Shosuke Yamamura Abstract Most people are familiar with the sight of a young seedling bending towards a window or the brightest source of light to which it is exposed. This directional growth response is known as phototropism, which is caused by a lateral growth-promoting auxin in the bending organ (Cholodny-Went theory, cited in high school textbook). Recently, however, Bruinsma et al., Weiler et al., and Hasegawa et al. independently found that the shaded half did not contain more auxin than the illuminated one. Instead it was found that the even distribution of auxin was accompanied by a lateral gradient of growth inhibiting substances during phototropic curvature (Bruinsma-Hasegawa theory). We have isolated some photo-induced growth inhibitory substances related to phototropism, benzoxazolinones from light-grown maize shoots (Zea mays L.), raphanusanins from radish hypocotyl (Raphanus sativus var. hortensis f. gigantissimus M.), indolyacetonitrile from light-grown shoots (Brassica oleacea L.), 8-epixanthatin from sunflower hypocotyl (Helianthus annus L.), and quite recently uridine from oat coleoptile (Avena sativa L.). Chemical analyses have shown phototropic stimulations to cause curvature by inducing a local unequal distribution of growth-inhibiting substances that antagonize auxin in its cell-elongating activity. Finally, a model is presented for further studies on phototropism. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:362,372, 2001 [source] The AT-hook-containing proteins SOB3/AHL29 and ESC/AHL27 are negative modulators of hypocotyl growth in ArabidopsisTHE PLANT JOURNAL, Issue 1 2008Ian H. Street Summary SOB3, which encodes a plant-specific AT-hook motif containing protein, was identified from an activation-tagging screen for suppressors of the long-hypocotyl phenotype of a weak phyB allele, phyB-4. sob3-D (suppressor of phyB-4#3 dominant) overexpressing seedlings have shorter hypocotyls, and as adults develop larger flowers and leaves, and are delayed in senescence compared with wild-type plants. At the nucleotide level, SOB3 is closely related to ESCAROLA (ESC), which was identified in an independent activation-tagging screen. ESC overexpression also suppresses the phyB-4 long-hypocotyl phenotype, and confers an adult morphology similar to sob3-D, suggesting similar functions. Analysis of transgenic plants harboring SOB3:SOB3-GUS or ESC:ESC-GUS translational fusions, driven by their endogenous promoter regions, showed GUS activity in the hypocotyl and vasculature tissue in light- and dark-grown seedlings. A loss-of-function SOB3 allele (sob3-4) was generated through an ethyl methanesulfonate intragenic suppressor screen of sob3-D phyB-4 plants, and this allele was combined with a predicted null allele, disrupting ESC (esc-8), to examine potential genetic interactions. The sob3-4 esc-8 double mutant had a long hypocotyl in multiple fluence rates of continuous white, far-red, red and blue light. sob3-4 esc-8 phyB-9 and sob3-4 esc-8 cry-103 triple mutants also had longer hypocotyls than photoreceptor single mutants. In contrast, the sob3-4 esc-8 phyA-211 triple mutant was the same length as phyA-211 single mutants. Taken together, these data indicate that SOB3 and ESC act redundantly to modulate hypocotyl growth inhibition in response to light. [source] Mutants in DEFECTIVE GLYCOSYLATION, an Arabidopsis homolog of an oligosaccharyltransferase complex subunit, show protein underglycosylation and defects in cell differentiation and growthTHE PLANT JOURNAL, Issue 4 2005Olivier Lerouxel Summary A mutant called defective glycosylation1-1 (dgl1-1) was identified in Arabidopsis based on a growth defect of the dark-grown hypocotyl and an abnormal composition of the non-cellulosic cell wall polysaccharides. dgl1-1 is altered in a protein ortholog of human OST48 or yeast WBP1, an essential protein subunit of the oligosaccharyltransferase (OST) complex, which is responsible for the transfer in the ER of the N-linked glycan precursor onto Asn residues of candidate proteins. Consistent with the known function of the OST complex in eukaryotes, the dgl1-1 mutation led to a reduced N-linked glycosylation of the ER-resident protein disulfide isomerase. A second more severe mutant (dgl1-2) was embryo-lethal. Microscopic analysis of dgl1-1 revealed developmental defects including reduced cell elongation and the collapse and differentiation defects of cells in the central cylinder. These defects were accompanied by changes in the non-cellulosic polysaccharide composition, including the accumulation of ectopic callose. Interestingly, in contrast to other dwarf mutants that are altered in early steps of the N -glycan processing, dgl1-1 did not exhibit a cellulose deficiency. Together, these results confirm the role of DGL1 in N-linked glycosylation, cell growth and differentiation in plants. [source] Trade-offs between the shade-avoidance response and plant resistance to herbivores?FUNCTIONAL ECOLOGY, Issue 6 2005Tests with mutant Cucumis sativus Summary 1Plants exhibit adaptations to many stresses, including light competition and herbivory. The expression of these traits may interact negatively, potentially instigating a trade-off. 2We employed a combination of genetically altered Cucumis sativus varieties and phenotypic manipulations to test for trade-offs in field experiments. The different genetic lines of C. sativus were altered in their phytochrome-mediated shade responses and the production of terpenoid defence compounds. 3Cucumber plants constitutively expressing the shade-avoidance response had 93% more herbivory by specialist beetles compared with wild types. The long-hypocotyl mutants also produced leaves with fewer trichomes, greater toughness and a higher carbon to nitrogen ratio (C : N) than wild types. Plants lacking defensive cucurbitacins had 23% longer internodes than the cucurbitacin-producing line. 4We then manipulated the plant phenotype by artificially imposing neighbours' shade on plants with and without cucurbitacins. As expected, plants responded to shade by growing longer hypocotyls and first internodes, but few trade-offs were found between plant line and shade treatment and, although herbivory levels were very low, there was a trend towards reduced damage on shaded plants. 5The use of genetically altered plant lines provided strong evidence for the trade-off hypothesis, while phenotypic manipulations did not support the hypothesis. [source] Medium, Explant and Genotype Factors Influencing Shoot Regeneration in Oilseed Brassica spp.JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2003G. X. Tang Abstract The effects of culture media, explants and genotypes on shoot regeneration in oilseed Brassica species were examined in this study. The maximum shoot regeneration frequency was obtained in Murashige and Skoog medium supplemented with 3 mg l,1 6-benzylaminopurine and 0.15 mg l,1 1-naphthaleneacetic acid. The addition of 2.5 mg l,1 AgNO3 was very beneficial to shoot regeneration in B. napus and Ag2S2O3 (10 mg l,1) was even superior to AgNO3 (2.5 mg l,1). Explant age, explant type and carbon source also significantly affected shoot regeneration. Four-day-old seedlings of cotyledonary explants showed the maximum shoot regeneration frequency and number of shoots per explant. Of the four explants , peduncles, hypocotyls, cotyledons and leaf petioles , cotyledons produced the highest shoot regeneration frequency (56.67 %). Four carbon sources , glucose, maltose, starch and sucrose , were compared for their respective effects on shoot regeneration from cotyledonary explants. Sucrose appeared to be the best carbon source for shoot regeneration with the highest shoot regeneration frequency (76.00 %). Considerable variation in shoot regeneration from cotyledonary explants was observed both between and within Brassica species. The shoot regeneration frequency ranged from 10.00 % for cv. R5 (B. rapa) to 83.61 % for cv. N1 (B. napus). Two B. napus, one B. carinata and one B. juncea cultivars exhibited shoot regeneration frequency higher than 70 %. In terms of the number of shoots produced per explant, B. rapa showed the highest variation, ranging from 5.64 for cv. R3 to 1.33 for cv. R5. Normal plantlets were regenerated from all induced shoots and developed normally. The regenerated plants were fertile and identical with the source plants. [source] Internalization of bioluminescent Escherichia coli and Salmonella Montevideo in growing bean sproutsJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2003K. Warriner Abstract Aims: Investigate the interaction of bioluminescent Escherichia coli and Salmonella Montevideo with germinating mung bean sprouts. Methods and Results:E. coli or Salm. Montevideo introduced on mung beans became established both internally and externally on sprouts after the initial 24 h germinating period. In both cases the inoculated bacterium formed the predominant microflora on the sprouted beans throughout. From the bioluminescent profile of inoculated sprouting beans, bacterial growth was found to be in close proximity to the roots but not on the hypocotyls. Clumps (biofilms) of cells with low viability were observed within the grooves between epidermal cells on hypocotyls. Treatment with 20 000 ppm sodium hypochlorite removed the majority of bacteria from the surface of hypocotyls although nonviable single cells were occasionally observed. However, viable bacteria were recovered from the apoplastic fluid, and extracts of surface-sterilized sprouts indicating that the internal bacterial populations had been protected. This was confirmed using in situ , -glucuronidase staining of surface-sterilized sprouts where cleaved enzyme substrate (by the action of internalized E. coli) was visualized within the plant vascular system. Conclusions:E. coli or Salmonella present on seeds become internalized within the subsequent sprouts and cannot be removed by postharvest biocidal washing. Significance and Impact of the Study: Mung bean production should be carefully controlled to prevent contamination occurring in order to minimize the health risk associated with raw bean sprouts. [source] First Report of Rhizoctonia solani AG-7 on Cotton in EgyptJOURNAL OF PHYTOPATHOLOGY, Issue 4 2010Kamel A. Abd-Elsalam Abstract Eighty-two isolates of Rhizoctonia solani were recorded from roots of naturally-infected seedlings of the Egyptian cotton (Gossypium barbadense L.). Anastomosis groups (AGs) of the isolates were determined by using 13 different AGs testers. Three (3.7%) of the isolates were identified as R. solani AG7, while the remaining isolates were belonging to the AG 2-1, AG4 and AG5. The identification of the three isolates was based on the frequency of the C2 reaction with the AG7 tester isolate. No fusion was observed between AG7 and isolates representing the other 13 AGs. Colonies of AG7 isolates grown on potato dextrose agar (PDA), malt yeast agar (MYA) and melt peptone agar (MPA) were brown to dark brown with aerial mycelium and sclerotia. The isolates had pitted sclerotial clusters and brownish exudates after 21 days of culturing on PDA, but without clear zonation. Pathogenicity test under greenhouse conditions revealed that AG7 caused the common symptoms of damping,off, which included seed rot, lesions on the hypocotyls and root rot. [source] Development of a Sensitive Serological Method for Specific Detection of Latent Infection of Macrophomina phaseolina in CowpeaJOURNAL OF PHYTOPATHOLOGY, Issue 1 2009Leonard Afouda Abstract A double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for the specific detection and quantification of Macrophomina phaseolina in plant tissue. Both polyclonal antisera produced against immunogens from mycelium and culture filtrate of M. phaseolina detected the fungus in mycelial and plant extracts, although the antibodies raised against mycelium were more sensitive. No cross-reaction occurred with Rhizopus stolonifer, Pythium ultimum, Mucor hiemalis, Fusarium oxysporum, Septoria nodorum, Rhizoctonia solani, Sclerotinia sclerotiorum, Phytophthora infestans and Aspergillus niger. In enzyme assays, activity of the endo-acting hydrolytic enzymes 1,3-,-glucanase and, less, cellulase, but not xylanase was detected in infected plants. DAS-ELISA was more sensitive than the 1,3-,-glucanase assay. In polyacrylamide gel electrophoresis (PAGE) up to 18 protein bands were observed, with four bands occurring in the 12 tested isolates deriving from various geographical origin in Niger and Nigeria. The enzyme assays and protein patterns were considered not suitable for specific M. phaseolina detection. Macrophomina phaseolina was essentially located in the roots and hypocotyls, and less in epicotyls and leaves of infected plants. The antibodies were also useful to detect latent infection and the infection of cowpea seeds. [source] Herbicidal cyanoacrylates with antimicrotubule mechanism of actionPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2005Stefan Tresch Abstract The herbicidal mode of action of the new synthetic cyanoacrylates ethyl (2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and its isopropyl ester derivative CA2 was investigated. For initial characterization, a series of bioassays was used indicating a mode of action similar to that of mitotic disrupter herbicides such as the dinitroaniline pendimethalin. Cytochemical fluorescence studies including monoclonal antibodies against polymerized and depolymerized tubulin and a cellulose-binding domain of a bacterial cellulase conjugated to a fluorescent dye were applied to elucidate effects on cell division processes including mitosis and microtubule and cell wall formation in maize roots. When seedlings were root treated with 10 µM of CA1 or CA2, cell division activity in meristematic root tip cells decreased within 4 h. The chromosomes proceeded to a condensed state of prometaphase, but were unable to progress further in the mitotic cycle. The compounds caused a complete loss of microtubular structures, including preprophase, spindle, phragmoplast and cortical microtubules. Concomitantly, in the cytoplasm, an increase in labelling of free tubulin was observed. This suggests that the herbicides disrupt polymerization and microtubule stability, whereas tubulin synthesis or degradation appeared not to be affected. In addition, cellulose labelling in cell walls of root tip cells was not influenced. The effects of CA1 and CA2 were comparable with those caused by pendimethalin. In transgenic Arabidopsis plants expressing a green fluorescent protein-microtubule-associated protein4 fusion protein, labelled arrays of cortical microtubules in living epidermal cells of hypocotyls collapsed within 160 min after exposure to 10 µM CA1 or pendimethalin. Moreover, a dinitroaniline-resistant biotype of goosegrass (Eleusine indica (L) Gaertn) with a point mutation in ,-tubulin showed cross-resistance against CA1 and CA2. The results strongly indicate that the cyanoacrylates are a new chemical class of herbicide which possess the same antimicrotubule mechanism of action as dinitroanilines, probably including interaction with the same binding site in ,-tubulin. Copyright © 2005 Society of Chemical Industry [source] A role for PSK signaling in wounding and microbial interactions in ArabidopsisPHYSIOLOGIA PLANTARUM, Issue 4 2010Maaria Loivamäki PSK- , is a disulfated peptide that acts as a growth factor in plants. PSK- , is derived from preproproteins which are encoded by five PSK precursor genes in Arabidopsis thaliana (L.) Heynh and is perceived by leucine-rich repeat receptor kinases. Arabidopsis has two PSK receptor genes, PSKR1 and PSKR2. Although ligand and receptor are well characterized, the biological functions of PSK signaling are not well understood. Using reporter lines and receptor knockout mutants of Arabidopsis, a role for PSK signaling in biotic interactions and in wounding was analyzed. Treatment of Arabidopsis leaves with the fungal elicitor E-Fol, or the fungal pathogens Alternaria brassicicola and Sclerotinia sclerotiorum resulted in induction of PSK2 and PSKR1 as shown by promoter:GUS analysis. Wounding of hypocotyls or leaves induced PSK3:GUS, PSK5:GUS and PSKR1:GUS expression indicating that PSK precursor genes are differentially regulated in response to specific stresses. The receptor knockout lines pskr1-3 and pskr2-1 showed significantly reduced photosynthesis in response to the fungal elicitor E-Fol which indicates that fungal defence is impaired. pskr1-3 plants further showed reduced growth of crown galls after infection with Agrobacterium tumefaciens. A role for PSK signaling in Agrobacterium tumefaciens tumor growth was supported by the finding that PSK precursor genes and PSKR1 are expressed in crown galls. Overall, the results indicate that PSK signaling may play a previously undescribed role in pathogen or herbivore interactions and is crucial for Agrobacterium -induced cell proliferation in crown gall formation. [source] Chemical induction of rapid and reversible plastid filamentation in Arabidopsis thaliana rootsPHYSIOLOGIA PLANTARUM, Issue 2 2010Ryuuichi D. Itoh Plastids assume various morphologies depending on their developmental status, but the basis for developmentally regulated plastid morphogenesis is poorly understood. Chemical induction of alterations in plastid morphology would be a useful tool for studying this; however, no such chemicals have been identified. Here, we show that antimycin A, an effective respiratory inhibitor, can change plastid morphology rapidly and reversibly in Arabidopsis thaliana. In the root cortex, hypocotyls, cotyledon epidermis and true leaf epidermis, significant differences in mitochondrial morphology were not observed between antimycin-treated and untreated tissues. In contrast, antimycin caused extreme filamentation of plastids in the mature cortices of main roots. This phenomenon was specifically observed in the mature root cortex. Other mitochondrial respiratory inhibitors (rotenone and carbonyl cyanide m -chlorophenylhydrazone), hydrogen peroxide, S -nitroso- N -acetylpenicillamine [a nitric oxide (NO) donor] and 3-(3,4-dichlorophenyl)-1,1-dimethylurea did not mimic the phenomenon under the present study conditions. Antimycin-induced plastid filamentation was initiated within 5 min after the onset of chemical treatment and appeared to complete within 1 h. Plastid morphology was restored within 7 h after the washout of antimycin, suggesting that the filamentation was reversible. Co-applications of antimycin and cytoskeletal inhibitors (demecolcine or latrunculin B) or protein synthesis inhibitors (cycloheximide or chloramphenicol) still caused plastid filamentation. Antimycin A was also effective for plastid filamentation in the chloroplast division mutants atftsZ1-1 and atminE1. Salicylhydroxamic acid, an alternative oxidase inhibitor, was solely found to suppress the filamentation, implying the possibility that this phenomenon was partly mediated by an antimycin-activated alternative oxidase in the mitochondria. [source] Chilling tolerance of maize, cucumber and rice seedling leaves and roots are differentially affected by salicylic acidPHYSIOLOGIA PLANTARUM, Issue 4 2002Ho-Min Kang Salicylic acid (SA) is one component of a complex signalling pathway that is induced by a number of biotic and abiotic stresses. Exposing seedling radicles to aqueous solutions of 0.5 mM salicylic acid for 24 h before chilling at 2.5°C for 1,4 days reduced the chilling-induced increase in electrolyte leakage from maize and rice leaves, and cucumber hypocotyls, but not from their radicles. The SA treatments that induced chilling tolerance in the aerial portion of the seedlings did not induce chilling tolerance in the radicles, even though the SA treatments were applied to the radicles. A comparison of activity among five antioxidant enzymes showed that SA did not alter enzyme activities in the radicles, but that chilling tolerance induced by SA in the aerial portions of maize and cucumber plants was associated with an increase in the activity of glutathione reductase and guaiacol peroxidase. [source] Effect of steady torque twisting on the orientation of cortical microtubules in the epidermis of the sunflower hypocotylPLANT BIOLOGY, Issue 4 2008J. Elsner Abstract Orientation of cortical microtubules (cMTs) is suggested to be affected by mechanical stress existing in cell walls. However, in mutants exhibiting helical (chiral) growth, there is a correlation between orientation of cMTs in outer tissues and helical growth direction. The aim of this research was to examine the effect of a chiral mechanical stimulation on cMTs. For this purpose, the orientation of cMTs was investigated in hypocotyls subjected to either a right- or a left-handed twist, resulting from a steady torque. cMTs were visualised in fixed material using the immunofluorescence method. The cMTs in untouched control hypocotyls were mostly transverse with respect to the cell long axis. In immobilised, but not twisted control hypocotyls, the transverse orientation was also most frequent, while applied twisting resulted in a change in cMT orientation from transverse to oblique. The data provide additional evidence that changes in tissue stress can be reorganized by cortical microtubules. [source] Disease resistance conferred by the expression of a gene encoding a synthetic peptide in transgenic cotton (Gossypium hirsutum L.) plantsPLANT BIOTECHNOLOGY JOURNAL, Issue 6 2005Kanniah Rajasekaran Summary Fertile, transgenic cotton plants expressing the synthetic antimicrobial peptide, D4E1, were produced through Agrobacterium -mediated transformation. PCR products and Southern blots confirmed integration of the D4E1 gene, while RT-PCR of cotton RNA confirmed the presence of D4E1 transcripts. In vitro assays with crude leaf protein extracts from T0 and T1 plants confirmed that D4E1 was expressed at sufficient levels to inhibit the growth of Fusarium verticillioides and Verticillium dahliae compared to extracts from negative control plants transformed with pBI-d35S,- uidA-nos (CGUS). Although in vitro assays did not show control of pre-germinated spores of Aspergillus flavus, bioassays with cotton seeds in situ or in planta, inoculated with a GFP-expressing A. flavus, indicated that the transgenic cotton seeds inhibited extensive colonization and spread by the fungus in cotyledons and seed coats. In planta assays with the fungal pathogen, Thielaviopsis basicola, which causes black root rot in cotton, showed typical symptoms such as black discoloration and constriction on hypocotyls, reduced branching of roots in CGUS negative control T1 seedlings, while transgenic T1 seedlings showed a significant reduction in disease symptoms and increased seedling fresh weight, demonstrating tolerance to the fungal pathogen. Significant advantages of synthetic peptides in developing transgenic crop plants that are resistant to diseases and mycotoxin-causing fungal pathogens are highlighted in this report. [source] Enhanced fungal resistance in transgenic cotton expressing an endochitinase gene from Trichoderma virensPLANT BIOTECHNOLOGY JOURNAL, Issue 5 2003Chandrakanth Emani Summary Mycoparasitic fungi are proving to be rich sources of antifungal genes that can be utilized to genetically engineer important crops for resistance against fungal pathogens. We have transformed cotton and tobacco plants with a cDNA clone encoding a 42 kDa endochitinase from the mycoparasitic fungus, Trichoderma virens. Plants from 82 independently transformed callus lines of cotton were regenerated and analysed for transgene expression. Several primary transformants were identified with endochitinase activities that were significantly higher than the control values. Transgene integration and expression was confirmed by Southern and Northern blot analyses, respectively. The transgenic endochitinase activities were examined in the leaves of transgenic tobacco as well as in the leaves, roots, hypocotyls and seeds of transgenic cotton. Transgenic plants with elevated endochitinase activities also showed the expected 42 kDa endochitinase band in fluorescence, gel-based assays performed with the leaf extracts in both species. Homozygous T2 plants of the high endochitinase-expressing cotton lines were tested for disease resistance against a soil-borne pathogen, Rhizoctonia solani and a foliar pathogen, Alternaria alternata. Transgenic cotton plants showed significant resistance to both pathogens. [source] Chilling induces a decrease in pyrophosphate-dependent H+ -accumulation associated with a ,pHvac -stat in mung bean, a chill-sensitive plantPLANT CELL & ENVIRONMENT, Issue 3 2008YUKIO KAWAMURA ABSTRACT Chilling leads to cytoplasmic acidification in chill-sensitive plants. A possible explanation for this observation is that a ,pH-stat between the cytosol and vacuole (,pHvac -stat) is perturbed by chilling. To understand the nature of this ,pHvac -stat, the effect of temperature, between 20 and 0 °C, on pyrophosphate (PPi)- or ATP-dependent acidification of vacuolar vesicles, isolated from mung bean hypocotyls, was determined. Over the temperature range investigated, the H+ -influx mediated by PPase was balanced with the H+ -efflux, which was PPi-dependently suppressed, and consequently a constant pH in vesicles (pHin) of ca. 5 was maintained against temperature changes. However, the ,pHin driven by ATP decreased as the temperature dropped. Thus, the PPi-dependent H+ -accumulation may function as an essential factor to form a ,pHvac -stat against temperature changes. Next, to study the chilling sensitivity of PPi-dependent H+ -accumulation, vacuolar vesicles were isolated from control seedlings or from seedlings chilled at 0 °C for 1 d. Chilling treatment resulted in a decrease in the H+ -accumulation rate and in the steady-state ,pHin formed by PPi, the causes of which were enhanced by PPi-dependent H+ -efflux and reduced by H+ -influx driven by PPase. Together, the results suggest that the decrease of PPi-dependent H+ -accumulation associated with the ,pHvac -stat could result in cytoplasmic acidification. [source] The interaction of light quality and irradiance with gibberellins, cytokinins and auxin in regulating growth of Helianthus annuus hypocotylsPLANT CELL & ENVIRONMENT, Issue 2 2007LEONID V. KUREPIN ABSTRACT A reduced red to far-red (R/FR) light ratio and low photosynthetically active radiation (PAR) irradiance are both strong signals for inducing etiolation growth of plant stems. Under natural field conditions, plants can be exposed to either a reduced R/FR ratio or lower PAR, or to a combination of both. We used Helianthus annuus L., the sunflower, to study the effect of reduced R/FR ratio, low PAR or their combination on hypocotyl elongation. To accomplish this, we attempted to uncouple light quality from light irradiance as factors controlling hypocotyl elongation. We measured alterations in the levels of endogenous gibberellins (GAs), cytokinins (CKs) and the auxin indole-3-acetic acid (IAA), and the effect of exogenous hormones on hypocotyl growth. As expected, both reduced R/FR ratio and lower PAR can significantly promote sunflower hypocotyl elongation when given separately. However, providing the reduced R/FR ratio at a low PAR resulted in the greatest hypocotyl growth, and this was accompanied by significantly higher levels of endogenous IAA, GA1, GA8, GA20 and of a wide range of CKs. Providing a reduced R/FR ratio under normal PAR also significantly increased growth and again gave significantly higher levels of endogenous IAA, GAs and CKs. However, only under the de-etiolating influence of a normal R/FR ratio did lowering PAR significantly increase levels of GA1, GA8 and GA20. We thus conclude that light quality (e.g. the R/FR ratio) is the most important component of shade for controlling hypocotyl growth and elevated growth hormone content. [source] Distinguishing characteristics and vegetative compatibility of Colletotrichum kahawe in comparison with other related species from coffeePLANT PATHOLOGY, Issue 2 2002V. M. P. Varzea On the basis of pathogenicity tests on green berries or hypocotyls of coffee and by morphological and biochemical characteristics in culture, 31 isolates of Colletotrichum were classified into C. kahawe (24 isolates), C. gloeosporioides (six isolates) or C. acutatum (one isolate). Within these groups of isolates, vegetative compatibility groups (VCGs) were determined by complementation tests with mutants in the nitrate assimilation pathway. There were distinct incompatibility barriers between the three species. Among the C. gloeosporioides group, the three isolates tested were self-compatible but incompatible with each other. Within C. kahawe, 18 isolates were self-compatible and only one main VCG was detected. However, partial compatibility in C. kahawe was also indicated by variation in the intensity of heterokaryon formation between different pairs of isolates and between different types of mutant. The existence of only one VCG in C. kahawe is consistent with the low level of variation found in previous work on DNA polymorphism. [source] Genetic dissection of the role of ethylene in regulating auxin-dependent lateral and adventitious root formation in tomatoTHE PLANT JOURNAL, Issue 1 2010Sangeeta Negi Summary In this study we investigated the role of ethylene in the formation of lateral and adventitious roots in tomato (Solanum lycopersicum) using mutants isolated for altered ethylene signaling and fruit ripening. Mutations that block ethylene responses and delay ripening ,Nr (Never ripe), gr (green ripe), nor (non ripening), and rin (ripening inhibitor) , have enhanced lateral root formation. In contrast, the epi (epinastic) mutant, which has elevated ethylene and constitutive ethylene signaling in some tissues, or treatment with the ethylene precursor 1-aminocyclopropane carboxylic acid (ACC), reduces lateral root formation. Treatment with ACC inhibits the initiation and elongation of lateral roots, except in the Nr genotype. Root basipetal and acropetal indole-3-acetic acid (IAA) transport increase with ACC treatments or in the epi mutant, while in the Nr mutant there is less auxin transport than in the wild type and transport is insensitive to ACC. In contrast, the process of adventitious root formation shows the opposite response to ethylene, with ACC treatment and the epi mutation increasing adventitious root formation and the Nr mutation reducing the number of adventitious roots. In hypocotyls, ACC treatment negatively regulated IAA transport while the Nr mutant showed increased IAA transport in hypocotyls. Ethylene significantly reduces free IAA content in roots, but only subtly changes free IAA content in tomato hypocotyls. These results indicate a negative role for ethylene in lateral root formation and a positive role in adventitious root formation with modulation of auxin transport as a central point of ethylene,auxin crosstalk. [source] Hormonal regulation of temperature-induced growth in ArabidopsisTHE PLANT JOURNAL, Issue 4 2009Jon A. Stavang Summary Successful plant survival depends upon the proper integration of information from the environment with endogenous cues to regulate growth and development. We have investigated the interplay between ambient temperature and hormone action during the regulation of hypocotyl elongation, and we have found that gibberellins (GAs) and auxin are quickly and independently recruited by temperature to modulate growth rate, whereas activity of brassinosteroids (BRs) seems to be required later on. Impairment of GA biosynthesis blocked the increased elongation caused at higher temperatures, but hypocotyls of pentuple DELLA knockout mutants still reduced their response to higher temperatures when BR synthesis or auxin polar transport were blocked. The expression of several key genes involved in the biosynthesis of GAs and auxin was regulated by temperature, which indirectly resulted in coherent variations in the levels of accumulation of nuclear GFP,RGA (repressor of GA1) and in the activity of the DR5 reporter. DNA microarray and genetic analyses allowed the identification of the transcription factor PIF4 (phytochrome-interacting factor 4) as a major target in the promotion of growth at higher temperature. These results suggest that temperature regulates hypocotyl growth by individually impinging on several elements of a pre-existing network of signaling pathways involving auxin, BRs, GAs, and PIF4. [source] | ||||||||||||||||