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Abstract.The assimilation of ammonium into organic nitrogen catalyzed by the enzyme glutamine synthetase (GS; EC 6.3.1.2) has been suggested to be the limiting step for plant nitrogen utilization (H-M. Lam etal. 1995, Plant Cell 7: 887898). We have developed a molecular approach to increase glutamine production in transgenic poplar by the overexpression of a conifer GS gene. A chimeric construct consisting...
Abstract. Phosphoenolpyruvate carboxykinase (PEPCK) was shown to be present in a range of developing seeds by measurement of its activity and by immunoblotting. Its function was investigated during grape (Vitis vinifera L.) seed development. The maximum abundance of PEPCK coincided with the deposition of storage reserves. At this stage of development, immunohistochemistry showed that PEPCK was very...
Abstract. The physiological characteristics of seed dormancy in Nicotiana plumbaginifolia Viv. are described. The level of seed dormancy is defined by the delay in seed germination (i.e the time required prior to germination) under favourable environmental conditions. A wild-type line shows a clear primary dormancy, which is suppressed by afterripening, whereas an abscisic acid (ABA)-deficient mutant...
Abstract. The hydraulic conductivity of roots (Lpr) of 6- to 8-d-old maize seedlings has been related to the chemical composition of apoplastic transport barriers in the endodermis and hypodermis (exodermis), and to the hydraulic conductivity of root cortical cells. Roots were cultivated in two different ways. When grown in aeroponic culture, they developed an exodermis (Casparian band in the hypodermal...
Abstract.Rhodococcus fascians is a Gram-positive bacterium that infects dicotyledonous and monocotyledonous plants, leading to an alteration in the normal growth process of the host. The disease results from the modulation of the plant hormone balances, and cytokinins are thought to play an important role in the induction of symptoms. Generally, on the aerial parts of the plants, existing meristems...
Abstract. Seed germination, greening of etiolated plants and inhibition of hypocotyl elongation are stimulated by light, which is sensed by various types of photoreceptor. Nitric oxide (NO) has proven to be a bioactive molecule, especially in mammalian cells and, most recently, in plants. Like some phytochrome-dependent processes, many NO-mediated ones are accomplished through increases in cGMP levels...
Abstract. The concentration of cytoplasmic free calcium ([Ca2+]cyt) required to close higher plant plasmodesmata was investigated using corn (Zea mays L. cv. Black Mexican Sweet) suspension-culture cells. Physiological elevations of [Ca2+]cyt were applied by cold treatment, and ion injection was also used to increase [Ca2+]cyt, by diffusion (for small increases) or by iontophoresis (for larger increases)...
Abstract. Herbivory induces both direct and indirect defenses in plants; however, some combinations of these defenses may not be compatible. The jasmonate signal cascade activated both direct (nicotine accumulations) and indirect (mono- and sesquiterpene emissions) whole-plant defense responses in the native tobacco Nicotiana attenuata Torr. Ex Wats. Nicotine accumulations were proportional to the...
Abstract. Cotyledon explants of 10 soybean [Glycine max (L.) Merr.] cultivars were inoculated with Agrobacterium rhizogenes strain K599 with and without binary vectors pBI121 or pBINm-gfp5-ER possessing both neomycin phosphotransferase II (nptII) and -glucuronidase (gus) or nptII and green fluorescent protein (gfp) genes, respectively. Hairy roots were produced from the wounded surface of 5495% of...
Abstract. Glycerol 3-phosphate acyltransferase (GPAT, EC 2.3.15) catalyses the first step of the Kennedy pathway for acyl lipid formation. This enzyme was studied using high-speed particulate fractions from oil palm (Elaeis guineensis Jacq.) tissue cultures and mesocarp acetone powders. The fractions were incubated with [14C]glycerol 3-phosphate and incorporation of radioactivity into Kennedy pathway...
Abstract. The impact of increased plastidic glutamine synthetase (GS-2; EC 6.1.3.2) activity on foliar amino-acid levels and on biomass production was examined in transgenic tobacco. For that, tobacco was transformed via Agrobacterium tumefaciens with a binary vector containing a tobacco GS-2 cDNA downstream of the leaf-specific soybean ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit...
Abstract. As feeding by the tobacco specialist Manduca sexta L. is known to result in significantly higher jasmonate (JA) concentrations in Nicotiana plants than do mechanical simulations of the larval damage, we investigated whether M. sexta, which is known to rapidly consume large quantities of leaf material, can impair this recognition response by consuming the leaf tissue before it can respond...
Abstract. Geranylhydroquinone 3-hydroxylase, which is likely to be involved in shikonin and dihydroechinofuran biosynthesis, was identified in cell suspension cultures of Lithospermum erythrorhizon Sieb. et Zucc. (Boraginaceae). The enzyme hydroxylates the isoprenoid side chain of geranylhydroquinone (GHQ), a known precursor of shikonin. Proton/proton correlation spectroscopic and proton/proton long-range...
Abstract. The effect of cold hardening on the accumulation of glutathione (GSH) and its precursors was studied in the shoots and roots of wheat (Triticum aestivum L.) cv. Cheyenne (Ch, frost-tolerant) and cv. Chinese Spring (CS, moderately frost-sensitive), in a T. spelta L. accession (Tsp, frost-sensitive) and in chro- mosome substitution lines CS (Ch 5A) and CS (Tsp 5A). The fast induction of total...
Abstract. Mastoparan induces Ca2+-dependent deflagellation of the unicellular green alga Chlamydomonas moewusii Gerloff, as well as the activation of phospholipase C and the production of inositol 1,4,5-trisphosphate (InsP3; T. Munnik etal., 1998, Planta 207: 133145). Even in the absence of extracellular Ca2+, mastoparan still induces deflagellation (L.M. Quarmby and H.C. Hartzell, 1994, J Cell Biol...
Abstract. The exodermal layers that are formed in maize roots during aeroponic culture were investigated with respect to the radial transport of cis-abscisic acid (ABA). The decrease in root hydraulic conductivity (Lpr) of aeroponically grown roots was stimulated 1.5-fold by ABA (500nM), reaching Lpr values of roots lacking an exodermis. Similar to water, the radial flow of ABA through roots (JABA)...
Abstract. In protoplast-derived Solanum nigrum microcalluses, plasmodesmal connectivity and cell division behaviour of the sister cells were examined by repeated pressure-injection experiments with the fluorescent dye Lucifer Yellow (LYCH; Mr 457) and concomitant light-microscopical long-term live observations. The studies revealed that the plasmodesmal permeability of the cultured cells differs in...
Abstract. Microscopic examination of suspension- cultured cells of Phleum pratense L., Panicum miliaceum L., Phalarisaquatica L. and Oryza sativa L. showed that they were comprised of numerous root primordia. Polysaccharides secreted by these suspension cultures contained glycosyl linkages consistent with the presence of high proportions of root mucilage-like polysaccharides. In contrast, suspension-cultured...
Abstract. Two cDNA clones encoding F1F0-ATPase inhibitor proteins, which are loosely associated with the F1 part of the mitochondrial F1F0-ATPase, were characterized from rice (Oryza sativa L. cv. Nipponbare). A Northern hybridization showed that the two genes (designated as IF1-1 and IF1-2) are transcribed in all the organs examined. However, the steady-state mRNA levels varied among organs. A comparison...
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