Markers for selection of the rice Xa21 disease resistance gene

Six molecular markers were mapped to a 7.4-cM region of rice chromosome 11 containing the Xa21 gene, which confers resistance to the pathogen Xanthomonas oryzae pv oryzae. Three markers, RG103, 248 and 818, co-segregated with Xa21 in a population of 1141 plants. Multiple copies of all marker loci were present within the region that was introgressed from Oryza longistaminata into O. sativa. The marker loci were cloned and primers were designed that defined sequence-tagged sites. Physical mapping of the three tightly linked central markers revealed that RG103, the marker that hybridizes to the Xa21 gene, resides on a separate DNA fragment from the other two markers.Disclaimer: Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Somatic embryogenesis,organogenesis and callus growth kinetics of flax

The effects of plant growth regulators (PGR) on calli induction, morphogenesis and somatic embryogenesis of flax were studied. The organogenic and callus formation capacity were assessed for different types of source explants. Root and shoot explants were equally good material for calli production but the former produced calli without shoot regeneration capacity. Under the experimental conditions tested, 2,4-dichlorophenoxyacetic acid (2,4-D) + zeatin was the most efficient PGR combination on calli induction and biomass production. The calli were green but with no rhizogenic capacity. In contrast, and at similar concentrations, indole-3-butyric acid (IBA) + kinetin induced white or pale green friable calli with a good root regeneration capacity (60%). A factorial experiment with different combinations of 2,4-D + zeatin + gibberellic acid (GA₃) levels revealed that the direction of explant differentiation was determined by specific PGR interactions and concentrations. The results from these experiments revealed that the morphogenetic pathway (shoot versus root differentiation) can be manipulated on flax explants by raising the 2,4-D level from 0.05 to 3.2 mg l^?1 in the induction medium. The induction and development of somatic embryos from flax explants was possible in a range of 2,4-D + zeatin concentrations surrounding 0.4 mg l^?1 2,4-D and 1.6 mg l^?1 zeatin, the most efficient growth regulator combination.     

Glycerolysis of olive oil: batch operational stability of Candida rugosa lipase immobilized in hydrophilic polyurethane foams

The operational stability of the Candida rugosa lipase immobilized in a hydrophilic polyurethane foam was evaluated in consecutive batches for the glycerolysis of olive oil in n-hexane, aimed at the production of monoglycerides.Glycerol controlled the glycerolysis in the system under study, since it is both a substrate and a powerful water binder that reduces the water activity of the reaction medium and of the microenvironment. Two sets of experiments were carried out under different glycerol/triglyceride ratios. After 345 hours of consecutive 23 hours batches no lipase inactivation was observed.List of Symbols a_w thermodynamic activity of water - DG diglyceride (s) - FAME fatty acid methyl ester (s) - FFA free fatty acid (s) - FID flame ionization detector Gly glycerol - MG monoglyceride (s) - TG triglyceride (s) - TLC thin layer chromatography The authors are grateful to Profs. P. Adlercreutz, Technical University of Lund, Sweden, and J.M.S. Cabral, Instituto Superior Técnico, Lisbon, Portugal, for inspiring discussions and advice, to Prof. Helena Pereira, Instituto Superior de Agronomia (ISA), Lisbon, Portugal, for the use of GC equipment and to Mrs. Marlene Dionísio, ISA, for invaluable help with some of the experimental work.     

Adsorption studies for the separation ofl-tryptophan froml-serine and indole in a bioconversion medium

l-tryptophan was produced froml-serine and indole by immobilized Escherichia coli cells in organic-aqueous systems. Selective adsorption was the method chosen to enable both product separation andl-serine reutilization. Amongst various adsorbents tested activated carbons and neutral polymeric resins (XAD-4 and XAD-7) showed good performance. The neutral resins could selectively concentrate thel-tryptophan from dilute aqueous solutions and adsorbed only 5% of the unconvertedl-serine. High separation factors (l-tryptophan/l-serine and indole/l-tryptophan) were obtained with these adsorbents. Despite a lower capacity, the XAD-7 resin had the advantage of desorbingl-tryptophan with basic or acidic solutions, while organic solvents were required to desorb, at the same concentration levels, this compound from XAD-4.In a packed bed column filled with XAD-4 resin or activated carbon, totall-tryptophan adsorption and recovery were achieved at linear velocities up to 5.0 cm/min and 3.2 cm/min respectively. Successive sorbent reutilization, following continuous sorption and elution steps, was carried out in packed bed columns with the neutral resins and activated carbon.Thel-form of tryptophan, after crystallization, was identified by HPTLC.List of Symbols HPLC High Performance Liquid Chromatography - HPTLC High Performance Thin Layer Chromatography - Trp tryptophan - Ser Serine - A amount of sorbent(g) - c equilibrium solute concentration in the aqueous phase (g/dm³) - c _i initial (before adding the sorbent) liquid phase concentration (g/dm³) - C _T tryptophan concentration in the inlet solution (g/dm³) - C _To tryptophan concentration in the outlet solution (g/dm³) - E _z axial dispersion coefficient (m²/s) - k experimental constant (Eq. 1, 2 and 3) - K ₁ rate constant of adsorption (min^–1) - L column length(m) - n experimental constant (eq. 1, 2 and 3) - q equilibrium solid phase concentration (g solute/g sorbent) - q _max maximum capacity of sorbent (g solute/g sorbent) - t time(s) - v liquid velocity (m/s) - V volume of liquid phase(dm³) - V _e eluted volume(dm³) - V _r volume needed to saturate the column (dm³)     

Prevalence of Colonization Factor Antigens (CFAs) and Adherence to HeLa Cells in Enterotoxigenic Escherichia coli Isolated from Feces of Children in São Paulo

Fifty-eight enterotoxigenic Escherichia coli (ETEC) strains, isolated from children with and without diarrhea in Sao Paulo, were examined for the presence of colonization factor antigens (CFAs) and their ability to adhere to HeLa cells. Antisera to CFA/I, the coli surface (CS) antigens CS1CS3, CS2CS3, and CS2 of CFA/II, CFA/III, and CS5CS6 and CS6 of CFA/IV were used. CFAs were identified in 43% of the ETEC strains: 40% of the strains with CFAs harbored CFA/I, 24% carried CFA/II (CS1CS3), 24% carried CFA/IV (CS6), and 12% carried CFA/IV (CS5CS6). CFAs occurred mainly among ETEC strains producing only heat-stable (ST-I) enterotoxin and in strains also producing heat-labile toxin (LT-I). No ETEC strains tested expressed CFA/III. A marked change in serotypes of ST-I-producing strains was found in Sao Paulo between 1979 and 1990. Adherence to HeLa cells was detected in 14% of the ETEC strains. All of them had a diffuse adherence pattern and produced only ST-I, and 88% carried CS6 antigen.     

Hydraulic properties of sphagnum peat moss and tuff (scoria) and their potential effects on water availability

The importance of macrostructure to root growth of ryegrass (L. perenne) seedlings sown on the soil surface was studied in two soils in which the macrostructure had resulted mainly from root growth and macro-faunal activity. Sets of paired soil cores were used, one of each pair undisturbed and the other ground and repacked to the field bulk density. Undisturbed and repacked soils were first compared at equal water potentials in the range −1.9 to −300 kPa. At equal water potential, the undisturbed soil always had the greater strength (penetration resistance), and root growth was always greater in the repacked soil with no macrostructure than it was in the soil with macrostructure intact. At equal high strength (low water potentials) it appeared that root growth was better when soils were structured. When strength was low (high water potentials), root growth was better in the unstructured soil. Soils were then compared during drying cycles over 21 days. The average rate at which roots grew to a depth of 60 mm, and also the final percentage of plants with a root reaching 60 mm depth, was greatest in repacked soils without macrostructure. The species of vegetation growing in the soil before the experiment affected root growth in undisturbed soil; growth was slower where annual grasses and white clover had grown compared with soil which had supported a perennial grass. It appears that relatively few roots locate and grow in the macrostructure. Other roots grow in the matrix, if it is soft enough to be deformed by roots. Roots in the matrix of a structured soil grow more slowly than roots in structureless soil of equal bulk density and water potential. The development of macrostructure in an otherwise structureless soil, of the type studied, is of no advantage to most roots. However, once a macrostructure has developed, the few roots locating suitable macropores are able to grow at low water potential when soil strength is high. The importance of macrostructure to establishing seedlings in the field lies in rapid penetration of at least a few roots to a depth that escapes surface drying during seasonal drought. ei]{gnB E}{fnClothier}     

Microbial production of xylitol from D-xylose using Candida tropicalis

Candida tropicalis DSM 7524 was used to produce xylitol from d-xylose. The fermentation conditions were optimized during continuous cultivation. The strain employed showed no great dependence upon temperature in a range between 30° C and 37° C. It achieved its best yield of xylitol from d-xylose at a pH value of 2.5. Such low pH values allow non sterile cultivation, which is a major economic factor. With an oxygen uptake rate of 0.8–1 ml oxygen per litre culture medium, the C. tropicalis produce xylitol at a yield of between 77% and 80% of the theoretical value. Higher yeast extract concentrations prevent the conversion of d-xylose into xylitol. d-xylose acts as a growth inhibitor in higher concentrations. The maximum xylitol yield was reached at a d-xylose concentration of around 100 g/l. In a non sterile batch culture with substrate shift 220 g/l xylitol were produced from 300 g/l d-xylose at a xylitol productivity rate of 0.37 g/(lh). In order to increase the specific yield, C. tropicalis was immobilised on porous glass and cultivated in a fluidized bed reactor. In a continuous non sterile cultivation with immobilised cells 155 g/l d-xylose produced 90–95% g/l xylitol with a productivity of 1.35 g/(lh).Mr. S. S. da Silva was a visiting scientist to the GBF. He was supported by a scholarship from the National Council of Scientific and Technological Development, Brasilia, Brazil (CNPq).We also would like to gratefully acknowledge the support of Prof. Dr. Michele Vitolo of the University of Sao Paulo, and the Centre for Biotechnology and Chemistry, Lorena, S. P. Brazil, in particular the Department of Fermentative Process.We are grateful to Prof. Rainer Jonas, head of the International Cooperation between Germany/Brazil for the helpful discussions and Dr. Heinrich Lönsdorf (GBF) for the Scanning electron micrographs.Dedicated to the 65th birthday of Prof. Dr. Fritz Wagner.     

Structural characterization and promoter activity analysis of the γ-kafirin gene from sorghum

A genomic clone encoding the γ-kafirin gene from sorghum was isolated and sequenced. A 2938 bp sequenced fragment includes an intronless open reading frame of 636 nucleotides encoding a putative polypeptide of 212 amino acids. Comparison of the deduced amino acid sequence of γ-kafirin with the published sequences of γ-prolamins of maize, and Coix revealed highly conserved domains. The N-terminal region of these proteins contains the conserved hexapeptide PPPVHL, which is repeated eight times in γ-zein, four times in γ-kafirin and three times in γ-coixin. The number of PPPVHL repeats accounts predominantly for the differences in the molecular weights of γ-prolamins. Several putative regulatory sequences common to the γ-kafirin and γ-zein genes were identified in both the 5′ and the 3′ flanking regions. Putative GCN4-like regulatory sequences were found at positions ?192 and ?476 in the 5′ flanking region of γ-kafirin. In the 3′ noncoding region, three putative polyadenylation signals, two AATAAT and one AATGAA, were found at positions + 658, + 716, and + 785, respectively. In order to investigate the role of the putative GCN4-like motifs and other possible cis-acting element(s) of the γ-kafirin promoter, a series of deleted and chimeric promoter constructs were introduced into maize, Coix and sorghum tissues by particle bombardment. Histochemical analysis of β-glucuronidase (GUS) activity in different tissues indicated that the element(s) responsible for tissue specificity is probably located in the 285-bp proximal region of the promoter, while the remaining promoter sequence seems to carry the element(s) responsible for the quantitative response.     

Intertidal interstitial Halicyclops from the Brazilian coast (Copepoda: Cyclopoida)

H. tageae sp. n. and Halicyclops ytororoma sp. n. are described from the intertidal interstitial water of Brazilian beaches. H. tageae is distinguished from all congeneric species by the number of setae on legs 1–4 endopodite 2 (1, 1, 2, 2) and by possessing a reduced inner spine on the leg 5 exopodite. It shares with H. brevispinosus, H. pusillus and H. canui the spine formula 2, 3, 3, 3 on exopodite 3 of swimming legs 1–4. H. ytororoma closely resembles H. gauldi and differs from this species by having 4 setae on leg 1 endopodite 3; H. gauldi has 3 setae on this segment.This is the first record of Halicyclops from marine interstitial water in Brazil.