Etude du phytochrome des graines de Pinus nigra Arn par spectrophotométrie bichromatique in vivo

Summary Phytochrome photoconversions P_rP_fr and P_frP_r can be measured by differential spectrophotometry in dry seeds (6% water content) of Pinus nigra Arn. A red light irradiation given before imbibition induces germination when the seeds are subsequently wetted and kept in darkness.In continuous darkness the phytochrome content shows a drastic increase at the beginning of moistening.The detectable pigment is entirely in the P_r form. The normal P_frP_r dark reversion is observed. P_fr destruction does not take place.     

Dependence of phytochrome dark reactions on the initial photostationary state

Summary Under conditions of continuous irradiation, the P _jr destruction rate constants (k _d ) of phytochrome in hooks and cotyledons of squash (Cucurbita pepo L.) seedlings do not depend on the photostationary state and are the same in both organs. On the other hand, the rate constants of the dark reversion and the first destruction step, plotted as a function of ⁰ , show optimum curves with maxima between ⁰ and 0.5. Similar results were obtained for dark reactions of mustard (Sinapis alba L.)-hook phytochrome in vivo. This indicates a cooperative behaviour of these phytochrome dark reactions.Abbreviations P _r red-absorbing form of phytochrome - P _fr far-red-absorbing form of phytochrome - [P _tot] [P _r ]+[P _fr ] - [P _tot] ([P _fr ]/[P _tot]), photostationary state - ⁰ at t=0, immediately after saturating irradiation     

The capacity of chlorophyll-a biosynthesis in the mustard seedling cotyledons as modulated by phytochrome and circadian rhythmicity

Within the temporal pattern of primary differentiation the capacity of chlorophyll — a biosynthesis in the cotyledons ofSinapis alba L. seedlings is controlled by phytochrome (in continuous light) or by releasing the circadian rhythm either with lightdark cycles or by a lightdark transition. The sensor pigment for this process is phytochrome. It is very probable that in continuous light as well as under conditions under which the circadian rhythm plays the major part, the capacity of chlorophyll a biosynthesis is limited by the capacity of the biosynthetic step which produces 5-aminolaevulinate.Abbreviations Chl chlorophyll(ide) a - ALA 5-aminolaevulinate - LA laevulinate - PChl protochlorophyll(ide) - ALAD aminolaevulinate dehydratase (EC4.2.1.24) - [P_fr]/[P_10c], photoequilibrium of the phytochrome system at the wavelength - whereby [P_10c] [P_r]+[P_fr]. P_fr is the physiologically active, far-red absorbing form of the phytochrome system     

The appearance of competence for phytochrome-mediated anthocyanin synthesis in the cotyledons of Sinapis alba L.

Summary It is demonstrated that phytochrome-mediated anthocyanin synthesis in the epidermal cells of mustard seedling cotyledons takes place only 27 h after sowing onwards (at 25°C). This starting point cannot be shifted by light treatments or by nutrients. The late appearance of competence for P _fr (P _r and P _fr, red- and far-red absorbing forms of phytochrome, respectively) with regard to anthocyanin synthesis is not related to the phytochrome system per se (P _rP _fr) as this is fully functional immediately after sowing of the seed; nor is it related to the primary reaction of phytochrome: P _fr+XP _fr XP _fr X (X, X, two forms of a receptor for P _fr) or to the initial action of P _fr X:P _fr X+KY (K, coupling element, leading to the product Y, which is no longer photoreversible). Rather, the starting point is determined by internal factors only and is thus not accessible to any specific control by external factors. On the other hand, however, the beginning of the initial action of P _fr X (coupling point) can be shifted by light via phytochrome under high irradiance conditions. Moreover, it is shown that there is no phytochrome-independent effect of blue light on photomorphogenesis in the young mustard seedling and that there is no rapid dark reversion of P _fr which can be detected by physiological means, at least duringAbbreviations P _r red-absorbing forms of phytochrome - P _fr far-red-absorbing forms of phytochrome - P ₁ total spectrophotometrically detectable phytochrome - HS Hoagland's nutrient solution - HIR high irradiance response     

The energy transmission in ATP synthase: From the γ-c rotor to the α3β3 oligomer fixed by OSCP-b stator via the βDELSEED sequence

ATP synthase (F₀F₁) is driven by an electrochemical potential of H⁺ (H⁺). F₀F₁ is composed of an ion-conducting portion (F₀) and a catalytic portion (F₁). The subunit composition of F₁ is ₃₃. The active ₃₃ oligomer, characterized by X-ray crystallography, has been obtained only from thermnophilic F₁ (TF₁). We proposed in 1984 that ATP is released from the catalytic site (C site) by a conformational change induced by the DELSEED sequence via -F₀. In fact, cross-linking of DELSEED to stopped the ATP-driven rotation of in the center of ₃₃. The torque of the rotation is estimated to be 420 pN·å from the H⁺ and H⁺-current through F₀F₁. The angular velocity () of is the rate-limiting step, because H⁺ increased theV _max of H⁺ current through F₀, but not theK _m (ATP). The rotational unit of F₀ (=ab₂c₁₀) is /5, while that in ₃₃ is 2/3. This difference is overcome by an analog-digital conversion via elasticity around DELSEED with a threshold to release ATP. The distance at the C site is about 9.6 å (2,8-diN₃-ATP), and tight Mg-ATP binding in ₃₃ was shown by ESR. The rotational relaxation of TF₁ is too rapid (=100 nsec), but the rate of AT(D)P-induced conformational change of ₃₃ measured with a synchrotron is close to . The ATP bound between the P-loop and E188 is released by the shift of DELSEED from RGL. Considering the viscosity resistance and inertia of the free rotor (-c), there may be a stator containing OSCP (= of TF₁) and F₀-d to hold free rotation of ₃₃.     

Uptake of Zn++ and aflatoxin from perlite and liquid culture by Zea mays seedlings

The present paper reports our attempts to determine whether the inclusion of 0.0014 mM Zn⁺⁺ within a hydroponic culture medium affects the ability of 12-day-old Zea mays, cv. SS-522 to take-up [³H]-aflatoxin B₁. Data from the corollary experiment, i.e., whether inclusion of aflatoxin affects the ability of Zea mays, cvs. Truckers White, X-Sweet and Merit to take-up ⁶⁵ZnCl₂ are presented also. This report is a preliminary to one regarding an in-progress analysis of whether pollutant levels of Zn⁺⁺ affect aflatoxin uptake and distribution. In the absence of irrigating seedlings, which were grown in Perlite containing ⁶⁵ZnCl₂, with a solution containing mixed aflatoxins, the stem contained the greatest amount of label with root plus seed the next highest and the leaf the least for each of the cvs. In contrast, when the seedlings were irrigated with a solution containing mixed aflatoxins, the root plus seed contained either an amount nearly identical to (cv. Truckers White) or in excess of that within the stem (cvs. X-Sweet and Merit). Calculation of the percentages of aflatoxin-induced diminutions in leaf, stem and root label suggested that the aflatoxins interfered with the translocation of ⁶⁵ZnCl₂ from the root to the stem and leaf, at least for cvs X-Sweet and Merit. When 0.0014mM Zn⁺⁺ as ZnSO₄ was added to an incubation medium in which 12-day-old seedlings were suspended and plant growth assessed over 72 hours, a 15% increase (significant at 0.05 level) in seedling height over that of Zn⁺⁺-deficient plants was observed. No differences in [³H]-aflatoxin B₁ uptake were noted between those seedlings which were grown in either Zn⁺⁺-containing or lacking media. Less than one % of the[³H]-aflatoxin B₁ which was taken-up was recovered within chloroform extracts of the seedlings. The distributions of radioactivity from [³H]-aflatoxin B₁ for leaf, stem, seed and root were 0, 57, 26 and 19% and 0, 26, 58 and 18% for Zn⁺⁺-containing and -lacking media, respectively.     

The phytochrome system in light-grown Zea mays L.

The phytochrome system is analyzed in light-grown maize (Zea mays L.) plants, which were prevented from greening by application of the herbicide SAN 9789. The dark kinetics of phytochrome are not different in the first, second or third leaf. It is concluded that in light-grown maize plants phytochrome levels are regulated by P_r formation and P_fr and P_r destruction, rather than by P_frP_r dark reversion. P_r undergoes destruction after it has been cycled through P_fr. The consequences of this P_r destruction on the phytochrome system are discussed.Abbreviations SAN 9789 4-chloro-5-(methylamino)-2-(,,-trifluoro-m-tolyl)-3(2H) pyridazinone - P_fr far-red absorbing form of phytochrome - P_r red absorbing form of phytochrome - P_tot P_fr+P_r     

Hydrogen isotope discrimination in higher plants: Correlations with photosynthetic pathway and environment

Summary The ratio of deuterium to hydrogen (expressed as D) in hydrogen released as water during the combustion of dried plant material was examined. The D value (metabolic hydrogen) determined on plant materials grown under controlled conditions is correlated with pathways of photosynthetic carbon metabolism. C₃ plants show mean D values of-132 for shoots and -117 for roots; C₄ plants show mean D values of -91 for shoots and-77 for roots and CAM plants a D value of-75 for roots and shoots. The difference between the D value of shoot material from C₃ and C₄ plants was confirmed in species growing under a range of glasshouse conditions. This difference in D value between C₃ and C₄ species does not appear to be due to differences in the D value (tissue water) in the plants as a result of physical fractionation of hydrogen isotopes during transpiration. In C₃ and C₄ plants the hydrogen isotope discrimination is in the same direction as the carbon isotope discrimination and factors contributing to the difference in D values are discussed. In CAM plants grown in the laboratory or collected from the field D values range from-75 to +50 and are correlated with ¹³C values. When deprived of water, the D value (metabolic hydrogen) in both soluble and insoluble material in leaves of Kalanchoe daigremontiana Hamet et Perr., becomes less negative. These changes may reflect the deuterium enrichment of tissue water during transpiration, or in field conditions, may reflect the different D value of available water in areas of increasing aridity. Whatever the origin of the variable D value in CAM plants, this parameter may be a useful index of the water relations of these plants under natural conditions.     

Analysis of the effect of rye chromosomes 4R, 6R and telomeric heterochromatin on 7R on homologous chromosome pairing in pentaploid hybrids (AABBR,AABBD)

Summary Meiotic pairing in Triticum turgidum cv. Ma (4x) with a mean chiasmata frequency of 27.16 per cell was compared with chiasmata frequencies in its hybrids with several triticale strains, Chinese Spring wheat and its addition lines for Imperial rye chromosomes 4R and 6R. In hybrids between Ma and x Triticosecale cv. Rosner the chiasmata frequency was marginally reduced by an average of 1.25%, by 8.8% in hybrids with x Triticosecale cv. DRIRA HH and by 6.7% with DRIRA EE (lacking 90% telomeric heterochromatin from chromosome arm 7RL). In pentaploid hybrids between Ma and T. aestivum cv. Chinese Spring the reduction was an average of 10.30%, while addition lines with rye chromosome 6R reduced chiasmata frequencies by an average of 7.4% and rye addition line for 4R showed the greatest depression in chiasmata frequency in hybrids by a 25.04% reduction. An interchange difference involving long chromosome segments was observed between Ma and Rosner.Contribution No. 819 Ottawa Research Station     

Fromβ-lactams toα- andβ-amino acid derived peptides

Summary The potential of-lactams as intermediates for the access to- and-amino acid-derived peptides is shortly reviewed, with major focus on the technologies developed in our group. The two general strategies lie, on one side, in the oxidative ring expansion of 3-hydroxy-lactams toN-carboxy-amino acid anhydrides or Leuch's anhydrides and subsequent coupling with-amino acid esters and, on the other side, in the nucleophilic ring opening ofN-Boc--lactams. Both approaches have been successfully applied to the synthesis of,-diamino acid,-amino--hydroxy acid, polyhydroxylated-amino acid,,-disubstituted-amino acid,-amino acid,-amino--hydroxy acid and,-disubstituted-amino acid derived peptides. Because of the mild reaction conditions needed for the above transformations and the highly stereoselective procedures employed for the construction of the starting-lactam ring, the whole process allows the production of optically pure final products.     

Novel prebiotic systems: Nucleotide oligomerization in surfactant entrapped water pools

Summary Oligomerization of 5-TMP in water pools entrapped by dodecyl-ammonium chloride surfactant aggregates in benzene: hexane in the presence of dicyanodiimide at temperatures ranging from 21°–72° resulted in the formation of linear and cyclic oligonucleotides containing up to pentamers. Effects of temperature, time and surfactants have been examined. Rate constants for the formation of oligomers have been determined at five different temperatures. These data afforded values of H = 11.8 ± 1.9 Kcal mole^–1, S=–53 6 e.u. and G = 27.4 4.0 Kcal mole^–1. Prebiotic significance of these results are discussed.     

11 S seed storage proteins fromHelianthus species (Compositae): Biochemical,size and charge heterogeneity

The seeds of 19 sunflower species were compared on the basis of their protein contents and the relative proportions of their protein fractions. The globulin content varied from 50% to about 70% and the albumin content from 18% to 35% according to the species. The level of intermediateMr polypeptides showed a great variability (9.6 to 24.3%). Comparative studies onMr polymorphism were carried out by means of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of non reduced and/or reduced samples using both mono- and bidimensional procedures. Polypeptide constituents of helianthinin were compared including both number and molecular size (cultivatedH. annuus was used as a standard). Studies focused on differences observed between the major two (Mr 38 000), (Mr 32 000) and (Mr 25 500), (21 000) polypeptides families constituting the main A, B, and C subunits. and polypeptides analyses permit to discriminate easilyH. petiolaris from the other species. Charge polymorphism was studied using isoelectric focusing (IEF) and IEF-PAGE in mono and bidimensional procedures in the presence or absence of 2-mercaptoethanol (2-ME). Only a specific ₄ polypeptide enables an easy discrimination betweenH. petiolaris and all the other species. Detailed nomenclature of the , and , polypeptides constituting the different helianthinin globulin subunits is given via the results of pI andMr analyses. Monodimensional IEF patterns of the more basic albumins (pI > 8.0) appear to provide a more valuable approach to identifying specific protein markers.     

Local helix content in an alanine-rich peptide as determined by the complete set of 3JHNα coupling constants

Summary Alanine-rich peptides serve as models for exploring the factors that control helix structure in peptides and proteins. Scalar CH-NH couplings (³J_HN) are an extremely useful measure of local helix content; however, the large alanine content in these peptides leads to significant signal overlap in the CH region of ¹H 2D NMR spectra. Quantitative determination of all possible ³J_HN values is, therefore, very challenging. Szyperski and co-workers [(1992) J. Magn. Reson., 99, 552–560] have recently developed a method for determining ³J_HN from NOESY spectra. Because ³J_HN may be determined from 2D peaks outside of the CH region, there is a much greater likelihood of identifying resolved resonances and measuring the associated coupling constants. It is demonstrated here that ³J_HN can be obtained for every residue in the helical peptide Ac-(AAAAK)₃A-NH₂. The resulting ³J_HN profile clearly identifies a helical structure in the middle of the peptide and further suggests that the respective helix termini unfold via distinct pathways.Abbreviations ³J_HN three-bond CH-NH scalar coupling constant - NOE nuclear Overhauser enhancement - NOESY two-dimensional nuclear Overhauser spectroscopy - COSY two-dimensional correlated spectroscopy - DQF-COSY two-dimensional double-quantum-filtered correlated spectroscopy - TOCSY two-dimensional total correlation spectroscopy To whom correspondence should be addressed.Deceased March 5, 1996.     

Phytochrome action in Oryza sativa L.

Summary In-vivo phytochrome determinations in totally etiolated rice seedlings with a dual-wavelength spectrophotometer showed that on a fresh weight basis phytochrome concentration was highest in the coleoptile apex (0.175 of mean) ( O.D.) g^-1 (fresh weight). The age of the seedlings had little effect on the pattern of phytochrome distribution in the coleoptiles.The extent of growth inhibition observed 2 days after the irradiations was proportional to the logarithm of P _fr amount in the coleoptiles at the time of initial exposure to either red or blue light. Ultraviolet irradiation, however, did not induce either reversible growth inhibition or optically detectable phytochrome changes in vivo.After the conversion of P _r to P _fr bya brief red irradiation, non-photochemical transformation of phytochrome was observed in intact coleoptile tissues. Most of the optically measurable P _fr disappeared within 6 hours at 27°, when the total ( O.D.) decreased to about one fifth of the original level. The optical data did not agree with the fact that 50% of the initial physiological reversibility was still observed 9 hours later. No significant difference in dark transformation rate was seen between intact and excised coleoptile tissues.Abbreviations P _r red light absorbing form of phytochrome - P _fr far-red light absorbing form of phytochrome - ( O.D.) the change in the optical density difference reading at two wavelengths, following irradiation of the sample with actinic sources of red and far-red light - UV ultraviolet light     

Geometry of the dry-state oligomerization of 2′,3′-cyclic phosphates

Summary Evaporation of a solution of thymidine plus either theexo or theendo diastereomer of uridine cyclic 2,3-O, O-phosphorothioate (U > p(S) in 1,2-diaminoethane hydrochloride buffer gave the 2,5 and 3,5 isomers of (P-thio) uridylylthymidine (Up(S)dT) in a ratio of 1:2 with a combined yield of about 20%. These isomers were re-converted to U > p(S) and dT by a reaction that is known to proceed by an in-line mechanism. Both the 2,5 and 3,5 isomers gave as product the same diastereomer of U > p(S) that had been used originally in their formation. These dry-state prebiotic reactions (Verlander, Lohrmann, and Orgel 1973) are thus shown to be stereospecific, and both the 2,5 and 3,5 internucleotide bonds are formed by an in-line mechanism.Abbreviations DAE 1,2-diaminoethane - HPLC high pressure liquid chromatography - RNase bovine pancreatic ribonuclease A, EC 3.1.4.22 - TEAB triethylammonium bicarbonate - tris tris(hydroxymethyl)aminomethane - UMP(S) uridine monophosphorothioate - U > p uridine cyclic 2,3-phosphate - U > p(S) uridine cyclic 2,3-O, O-phosphorothioate - Up(S)dT (P-thio)uridylylthymidine - U2p(R_p-S)5dT (P-thio)uridylylthymidine with theR configuration at phosphorous, and a 2,5 internucleotide linkage     

On the appropriateness of use of a continuous formulation for the modelling of discrete multireactant systems following Michaëlis–Menten kinetics

The possibility of solving the mass balances to a multiplicity of substrates within a CSTR in the presence of a chemical reaction following Michaelis-Menten kinetics using the assumption that the discrete distribution of said substrates is well approximated by an equivalent continuous distribution on the molecular weight is explored. The applicability of such reasoning is tested with a convenient numerical example. In addition to providing the limiting behavior of the discrete formulation as the number of homologous substrates increases, the continuous formulation yields in general simpler functional forms for the final distribution of substrates than the discrete counterpart due to the recursive nature of the solution in the latter case.List of Symbols C{N. M} mol/m³ concentration of substrate containing N monomer residues each with molecular weight M - {N, M} normalized value of C{N. M} - C {M} mol/m³ da concentration of substrate of molecular weight M - _in normalized value of C {M} at the i-th iteration of a finite difference method - {M} normalized value of C {M} - C ₀{N.M} mol/m³ inlet concentration of substrate containing N monomer residues each with molecular weight M - {N ·M} normalized value of C₀{N. M} - _{0 i} normalized value of C ₀ {M} at the i-th iteration of a finite difference method - C ₀ {M} mol/m³ da initial concentration of substrate of molecular weight M - C _tot mol/m³ (constant) overall concentration of substrates (discrete model) - C _tot mol/m³ (constant) overall concentration of substrates (continuous model) - D deviation of the continuous approach relative to the discrete approach - i dummy integer variable - I arbitrary integration constant - j dummy integer variable - k dummy integer variable - K _m mol/m³ Michaëlis-Menten constant for the substrates - l dummy integer variable - M da molecular weight of substrate - M normalized value of M - M da maximum molecular weight of a reacting substrate - N number of monomer residues of a reacting substrate - N maximum number of monomer residues of a reacting substrate - N total number of increments for the finite difference method - Q m³/s volumetric flow rate of liquid through the reactor - S inert product molecule - S _i substrate containing i monomer residues - V m³ volume of the reactor - v _max mol/m³ s reaction rate under saturating conditions of the enzyme active site with substrate - v _max{N. M} mol/m³ s reaction rate under saturating conditions of the enzyme active site with substrate containing N monomer residues with molecular weight M - _max{N · M} dimensionless value of v_max{N. M} (discrete model) - _max{M} dimensionless value of v _max {M} (continuous model) - mol/m³ s molecular weight-averaged value of v_max (discrete model) - mol.da/m³s molecular weight-averaged value of v_max (continuous model) - v _max {M} mol.da/m³s reaction rate under saturating conditions of the enzyme active site with substrate with molecular weight M - _max {M} dimensionless value of v_max{M} - _{max, (i)} dimensionless value of v_max{M} at the i-th iteration of a finite difference method - v _max mol/m³ s reference constant value of v _max Greek Symbols dimensionless operating parameter (discrete distribution) - dimensionless operating parameter (continuous distribution) - M da (average) molecular weight of a monomeric subunit - M selected increment for the finite difference method - auxiliary corrective factor (discrete model)     

Action of light on accumulation of carotenoids and chlorophylls in the milo shoot (Sorghum vulgare Pers.)

We have performed a comprehensive study on the mechanism of regulation of carotenogenesis by light in the shoot of Sorghum vulgare. Our work shows that carotenoid accumulation is simultaneously controlled by phytochrome (P_fr) and by the availability of chlorophyll. Throughout plastidogenesis light dependent chlorophyll and carotenoid accumulation are interdependent processes: Accumulation of chlorophyll in natural light requires the presence of carotenoids; likewise, accumulation of considerable amount of carotenoids depends on the availability of chlorophyll. However, in both cases the efficiency of the biosynthetic pathway, the potential biosynthetic rates (capacities) are determined by phytochrome. A push and pull model of carotenogenesis advanced previously (Frosch and Mohr 1980, Planta 148, 279) to explain carotenogenesis in the mustard (Sinapis alba) seedling also applies to the monocotyledonous milo (Sorghum vulgare) seedling. Therefore, we suggest that the model applies to carotenogenesis in higher plants in general.Abbreviations Chl chlorophyll(s) - PChl protochlorophyll(ide) - HIR High irradiance response (of phytochrome) - P_fr far-red absorbing, physiologically active form of phytochrome - P red absorbing physiologically inactive form of phytochrome - P_tot total phytochrome - i.e. [P_r]+[P_fr] =[P_fr]+[P_tot], wavelength dependent photoequilibrium of the phytochrome system - RL red light - FR far-red light     

Using stable hydrogen and oxygen isotope measurements of feathers to infer geographical origins of migrating European birds

Successful application of stable-hydrogen isotope measurements (D_f) of feathers to track origins of migratory birds and other wildlife requires a fundamental understanding of the correlation between D_f and deuterium patterns in rainfall (D_p) over continental scales. A strong correlation between D_p and D_f has been confirmed for birds and insects in North America, but not yet for other continents. Here, we compare D_f data from resident European birds to new D_p basemaps for Europe. Three maps, representing growing-season and mean annual D_p estimates from an elevation-explicit, detrended interpolation model and growing-season D_p estimates from simple Kriging, all indicate that strong isotope gradients occur across Europe with a general depletion occurring in a northeast direction. The feather data, representing 141 individuals of 25 avian species from 38 sites, ranged from –131 to –38. Regression analysis showed that strong correlations existed between both mean annual and growing-season D_p estimated by detrended interpolation and D_f of non-aquatic and non-corvid birds (r²=0.66 and 0.65, respectively). We also examined mean annual and growing-season ¹⁸O_p vs. ¹⁸O_f for our samples. Both oxygen regressions were similar (r²=0.56 and 0.57, respectively) but poorer than for deuterium. Our study reveals that D measurements of feathers from migratory birds in Europe may be used to track their origin and movements, and so provide a powerful investigative tool for avian migration research in Europe.