Construction of an Aspergillus nidulans multicopy transformant for the xlnB gene and its use in purifying the minor X24 xylanase

 Using recombinant DNA techniques, an Aspergillus nidulans multicopy transformant for the gene xlnB coding for the minor X₂₄ xylanase has been constructed. When grown on glucose as sole carbon source this transformant secretes 114 U of xylanase (mg protein)^-1. In this culture condition, X₂₄ is the only xylanase secreted and the predominant protein in the culture filtrate. This strategy has been used to purify the X₂₄ enzyme to homogeneity. The purified xylanase showed a single band on sodium dodecyl sulphate/ polyacrylamide gel electrophoresis with a molecular mass of 24 kDa and had an isoelectric point of approximately 3.5. The enzyme was a non-debranching endo-1,4-β-xylan xylanohydrolase highly specific for xylans and showed optimal activity at pH 5.5 and 52°C. The X₂₄ xylanase had a Michaelis constant, K _m, of 12.43 mg oat spelt xylan ml^-1 and a V _max of 1639 μmol min^-1 (mg protein)^-1. Received: 17 May 1995/Received last revision: 25 September 1995/Accepted: 29 September 1995     

Relationship between abundance of N2-fixing cyanobacteria and environmental features of Spanish rice fields

In order to estimate the potential utilization of N₂-fixing (heterocystous) cyanobacteria as natural biofertilizers in the Valencian rice fields (Spain), the distribution and seasonal variation of these microorganisms in water and sediment samples were evaluated, and the relationships among cyanobacterial abundance and physical and chemical characteristics of soil and water were investigated. N₂-fixing cyanobacteria were present in all the samples analyzed (25 sampling points sampled three times per year during two years). The relative cyanobacterial abundance in soil and water followed contrasting patterns, maximum presence in soil coincided with minimum abundance in water. Correlation analysis showed that cyanobacterial abundance in the two phases (water and sediment) was influenced more by water than by soil properties. Salinity, mineralization variables, and soluble reactive phosphate (SRP) correlated positively with heterocystous cyanobacteria presence. Furthermore, dissolved inorganic nitrogen (DIN) and the ratio DIN: SRP correlated negatively with cyanobacterial abundance. However DIN: SRP ratio better described the cyanobacterial distribution, with a threshold effect: below the Redfield ratio value (7.2 in mass units) cyanobacterial abundance was clearly higher. Correspondence to: A. Quesada.     

Interactions between migratory endoparasitic nematodes and arbuscular mycorrhizal fungi in perennial crops: A review

The root-lesion nematodes are important pests attacking stone and pome fruit crops throughout the world. They play an important role in the development of orchard replant problems. Host resistance toPratylenchus vulnus, the nematode of concern in mediterranean environments, has been difficult to find, and even more, to transmit into commercial rootstocks. Alternative management measures using early mycorrhizal infection that would confer protection against the nematode at a stage when plants are most vulnerable are currently being explored. These measures are considered important, taking into account a widespread change towards production systems that use in vitro material propagated in treated substrates free of mycorrhizal and other beneficial microorganisms. The prophylactic effect against root-lesion nematodes would be linked to mycorrhizal dependency of the host plant. Increase in tolerance would seem to be related to mycorrhiza assisted nutrition rather than to a direct suppressive effect of AM over the root-lesion nematode. InCitrus, Prunus, Malus andCydonia rootstocks, the nematode has shown to have a negative effect over AM colonization in the root.     

Pairing and recombination between individual chromosomes of wheat and rye in hybrids carrying the ph1b mutation

Wheat-rye chromosome associations at metaphase I studied by Naranjo and Fernández-Rueda (1991) in ph1b ABDR hybrids have been reanalysed to establish the frequency of pairing between individual chromosomes of wheat and rye. Wheat chromosomes, except for 2A and 2D, and their arms were identified by C-banding. Diagnostic C-bands and other cytological markers such as telocentrics or translocations were used to identify each one of the rye chromosomes and their arms. Both the amount of telomeric C-heterochromatin and the structure of the rye chromosomes relative to wheat affected the level of wheatrye pairing. The degree to which rye chromosomes paired with their wheat homoeologues varied with each of the three wheat genomes; in most groups, the B-R association was more frequent than the A-R or D-R associations. Recombination between arms 1RL and 2RL and their homoeologues of wheat possessing a different telomeric C-banding pattern was detected and quantified at anaphase I. The frequency of recombinant chromosomes obtained supports the premise that recombination between wheat and rye chromosomes may be estimated from wheat-rye pairing.     

Complete sequence of a new HLA-B35 allele found in a tribe of Mapuche Indians in the south of Argentina

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number U17107. The nameB*3509 was officially assigned by the WHO Nomenclature Committee in December 1994     

Relationship between the levels of wheat-rye metaphase I chromosomal pairing and recombination revealed by GISH

The metaphase I and anaphase I stages of meiosis of wheat×rye hybrids carrying the ph1b mutation were analyzed by genomic in situ hybridization. This technique allows distinction between three different types of wheat-rye associations in metaphase I configurations as well as detection of wheat-rye recombinant chromosomes in anaphase I cells. The frequency of associations between wheat and rye chromosomes greatly exceeded the level of wheat-rye recombination found in the three hybrids examined. Extremely distal associations, which account for about 50% of the total wheat-rye metaphase I chromosomal pairing, can explain such a discrepancy between metaphase I and anaphase I data. It is further discussed whether these associations reflect very distally located chiasmata or nonchiasmatic pairing. The sizes of the segments exchanged in wheat-rye recombinant chromosomes provide cytological evidence that wheat-rye recombination is restricted to the distal chromosomal regions. Received: 24 August 1995; in revised form: 27 February 1996 / Accepted: 28 March 1996     

Genetics and gibberellin production inGibberella fujikuroi

Gibberella fujikuroi (Fusarium moniliforme) is a complex group of plant pathogens. Some strains produce gibberellic acid and other gibberellins that promote growth and regulate various stages in plant development.The paper describes the research effort directed to development of genetic tools for this species. Furthermore the main features of the gibberellin biosynthetic pathway as established in Gibberella are described.Abbreviations AMO 1618 2-isopropyl-4-(trimethylammonium chloride)-5-methylphenylpiperidine-1-carboxylate - hydroxykaurenoic acid ent-kaur-16-en-7-ol-19-oic acid - kaurenal ent-kaur-16-en-19-al - kaurene ent-kaur-16-ene - kaurenoic acid ent-kaur-16-en-19-oic acid - kaurenol ent-kaur-16-en-19-ol - paclobutrazol 1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-lyl)pentan-3-ol - pefurazoate pent-4-enyl-N-furfuryl-N-imidazol-1-ylcarbonyl-DL-homoa laninate - tetcyclacis 5-(4-chlorophenyl)-3,4,5,9,10-pentaazatetracyclo-5,4,10^2.6,O^8.11-dodeca-3,9-diene - triarimol -(2,4-dichlorophenyl)--phenyl-5-pyrimidine methyl alcohol     

Effect of morphine and abstinence syndrome on [3H]bromoxidine binding to α2-adrenoreceptors in rat brain

At 4 days after the implantation of two subcutaneous 75 mg morphine pellets in the back skin, rats were morphine-dependent. In the three layers studied in the occipital cortex we found that the values of the ₂-adrenergic agonist [³H]bromoxidine binding increased with respect to animals implanted with placebo pellets. Typical behavioral and physiological symptoms of the abstinence syndrome appeared 30 minutes after administration of naloxone, [³H]bromoxidine binding values being similar to those obtained in animals implanted with placebo pellets. The pattern of response of the [³H]bromoxidine binding was similar in the hippocampus and the superficial gray layer of the superior colliculus of the mesencephalon, but the differences were not statistically significant in these areas. This paper concludes that exist brain regional differences in the ₂-adrenoreceptors response under morphine-treatment and possibly under naloxone-induced morphine abstinence syndrome.     

Toxicity of and mutagenesis by chlorate are independent of nitrate reductase activity in Chlamydomonas reinhardtii

Summary Spontaneous chlorate-resistant (CR) mutants have been isolated from Chlamydomonas reinhardtii wildtype strains. Most of them, 244, were able to grow on nitrate minimal medium, but 23 were not. Genetic and in vivo complementation analyses of this latter group of mutants indicated that they were defective either at the regulatory locus nit-2, or at the nitrate reductase (NR) locus nit-1, or at very closely linked loci. Some of these nit-1 or nit-2 mutants were also defective in pathways not directly related to nitrate assimilation, such as those of amino acids and purines. Chlorate treatment of wild-type cells resulted in both a decrease in cell survival and an increase in mutant cells resistant to a number of different chemicals (chlorate, methylammonium, sulphanilamide, arsenate, and streptomycin). The toxic and mutagenic effects of chlorate in minimal medium were not found when cells were grown either in darkness or in the presence of ammonium, conditions under which nitrate uptake is drastically inhibited. Chlorate was also able to induce reversion of nit ^– mutants of C. reinhardtii, but failed to produce His ⁺ revertants or Ara^r mutants in the BA-13 strain of Salmonella typhimurium. In contrast, chlorate treatment induced mutagenesis in strain E1F1 of the phototrophic bacterium Rhodobacter capsulatus. Genetic analyses of nitrate reductase-deficient CR mutants of C. reinhardtii revealed two types of CR, to low (1.5 mM) and high (15 mM) chlorate concentrations. These two traits were recessive in heterozygous diploids and segregated in genetic crosses independently of each other and of the nit-1 and nit-2 loci. Three her loci and four lcr loci mediating resistance to high (HC) and low (LC) concentrations of chlorate were identified. Mutations at the nit-2 locus, and deletions of a putative locus for nitrate transport were always epistatic to mutations responsible for resistance to either LC or HC. In both nit ⁺ and nit ^– chlorate-sensitive (CS) strains, nitrate and nitrite gave protection from the toxic effect of chlorate. Our data indicate that in C. reinhardtii chlorate toxicity is primarily dependent on the nitrate transport system and independent of the existence of an active NR enzyme. At least seven loci unrelated to the nitrate assimilation pathway and mediating CR are thought to control indirectly the efficiency of the nitrate transporter for chlorate transport. In addition, chlorate appears to be a mutagen capable of inducing a wide range of mutations unrelated to the nitrate assimilation pathway.     

Alpha-neo-endorphin-like immunoreactivity in the cat brain stem

This paper examines the distribution of fibers and cell bodies containing alpha-neo-endorphin in the cat brain stem by using an indirect immunoperoxidase technique. A high or moderate density of immunoreactive cell bodies was found in the superior central nucleus, nucleus incertus, dorsal tegmental nucleus, nucleus of the trapezoid body, and in the laminar spinal trigeminal nucleus, whereas a low density of such perikarya was observed in the inferior colliculus, nucleus praepositus hypoglossi, dorsal nucleus of the raphe, nucleus of the brachium of the inferior colliculus, and in the nucleus of the solitary tract. The highest density of immunoreactive fibers was found in the substantia nigra, dorsal motor nucleus of the vagus, nucleus coeruleus, lateral tegmental field, marginal nucleus of the brachium conjunctivum, and in the inferior and medial vestibular nuclei. These results indicate that alpha-neo-endorphin is widely distributed in the cat brain stem and suggest that the peptide could play an important role in several physiological functions, e.g., those involved in respiratory, cardiovascular, auditory, and motor mechanisms.