Dolomitic vegetation of South Spain

Large areas of rather sandy dolomites are to be found in the Betic ranges. In these soils appears a very specialized xerophilous vegetation with a high percentage of endemic species. These communities, grouped into a particular order, Convolvuletalia boissieri, are fully reviewed here and consist of the following syntaxa: ROSMARINETEA Br. Bl. 1947 em. Rivas et al. 1991

CONVOLVULETALIA BOISSIERI Rivas Martínez, Pérez Raya & Molero Mesa in Pérez Raya 1987 (syn. Pterocephaletalia spathulati Rivas Martínez, Pérez Raya & Molero Mesa in Rivas Martínez, A. Molina & G. Navarro 1988).

Andryalion agardhii Rivas Martínez 1961

Andryalo agardhii-Convolvuletum boissieri Quézel 1953 nom. inv. convolvuletosum boissieri centaureetosum bombycinae subass. nova centaureetosum funkii subass. nova Hippocrepido eriocarpae-Pterocephaletum spathulati (Quézel 1953) Rivas Goday & Mayor 1966 em. Mota & Valle 1992 Arenario delaguardiae-Centaureetum bombycinae ass. nova Galio batici-Thymetum granatensis Mota & Valle 1992 Helianthemo frigiduli-Pterocephaletum spathulatae Martínez Parras & Peinado 1987 Scorzonero albicantis-Pterocephaletum spathulatae Martínez Parras & Peinado 1987 Com. de Jasione crispa subsp. segurensis Thymo granatensis-Arenarietum tomentosae Mota & Valle 1991 arenarietosum tomentosae pterocephaletosum-spathulatae Mota & Valle 1992 Com. of Brassica almeriensis and Pterocephalus spathulatus     

Bacteriophage λ-mediated transposon mutagenesis of phytopathogenic and epiphytic Erwinia species is strain dependent

Summary Using transformation and conjugal mobilization, plasmids carrying the lamB gene of Escherichia coli were transferred to a range of Erwinia strains. The resultant strains were infected with 467, and kanamycin resistant transductants were screened for various mutant phenotypes including auxotrophy and altered extracellular enzyme activities. Reversion analysis suggested that most mutant phenotypes were due to Tn5 insertion. The applicability of the techniques was highly strain dependent. However a rapid and simple route to mutant isolation was obtained, which could allow the use of other -related genetic techniques in several important species which, to date, have not been genetically manipulated.     

Glutamine-synthetase isoforms appearing in sunflower cotyledons during germination

Ion-exchange chromatography has been used to separate the isoforms of glutamine synthetase (GS; EC 6.3.1.2) appearing in sunflower (Helianthus annuus L. cv. Peredovic) cotyledons during seedling growth under different light and nitrogen conditions. Both in dry and imbibed seeds, only a single form of GS (GS_s) was detected. Upon seed germination, the GS_s isoform was gradually replaced by cytosolic (GS₁) and plastidic (GS₂) isoforms. Light and nitrate decreased the levels of GS₁. In contrast, the appearance of GS₂ was greatly stimulated by light. Nitrate also had a positive effect, particularly in the light. Light and nitrate acted synergistically on the appearance of GS₂. The GS₂:GS₁ ratio in cotyledons of 9-d-old seedlings ranged from about 2, in darkness and nitrate-deprivation conditions, to 16 under light and nitrate application. The possible physiological roles of the distinct GS isoforms appearing in the epigeal cotyledons of sunflower during germination, and their differential regulation by light and nitrate, are discussed.Abbreviations GS glutamine synthetase - GS₁ cytosolic GS - GS₂ plastidic GS - GS_s GS from seeds This work was supported by a grant from Dirección General de Investigatión Científica y Técnica (PB90-0777) and Plan Andaluz de Investigación (3261), Spain. P.C. gratefully acknowledges receipt of a scholarship from Junta de Andalucía. The valuable technical assistance of Mrs. G. Alcalá is greatly appreciated. We are also grateful to Eurosemillas (Córdoba) for supplying us with sunflower seeds.     

Replication Region Fragments Cloned from Flac+ Are Identical to EcoRI Fragment f5 of F

The replication region fragments from Flac⁺ cloned in plasmids pSC138 and pML31 are identical with each other and with EcoRI fragment 5 of plasmid F.     

Cloning and characterization of EcoRI and HindIII restriction endonuclease-generated fragments of antibiotic resistance plasmids R6-5 and R6

Summary DNA fragments generated by the EcoRI or HindIII endonucleases from the low copy number antibiotic resistance plasmids R6 and R6-5 were separately cloned using the high copy number ColEl or pML21 plasmid vectors and the insertional inactivation procedure. The hybrid plasmids that were obtained were used to determine the location of the EcoRI and HindIII cleavage sites on the parent plasmid genomes by means of electron microscope heteroduplex analysis and agarose gel electrophoresis. Ultracentrifugation of the cloned fragments in caesium chloride gradients localized the high buoyant density regions of R6-5 to fragments that carry the genes for resistance to streptomycin-spectinomycin, sulfonamide, and mercury and a low buoyant density region to fragments that carry the tetracycline resistance determinant. Functional analysis of hybrid plasmids localized a number of plasmid properties such as resistances to antibiotics and mercury and several replication functions to specific regions of the R6-5 genome. Precise localisation of the genes for resistance to chloramphenicol, kanamycin, fusidic acid and tetracycline was possible due to the presence of identified restriction endonuclease cleavage sites within these determinants.Only one region competent for autonomous replication was identified on the R6-5 plasmid genome and this was localized to EcoRI fragment 2 and HindIII fragment 1. However, two additional regions of replication activity designated RepB and RepC, themselves incapable of autonomous replication but capable of supporting replication of a linked ColE1 plasmid in polA^– bacteria, were also identified.     

Haplotype distribution of and linkage disequilibrium between four polymorphic markers near the CFTR locus in Brazilian cystic fibrosis patients

To contribute to a better understanding of the origin and distribution of CFTR mutations in the Brazilian population, we have investigated the linkage between four polymorphic markers (XV2c, KM19, GATT, and TUB9) within or near the CFTR locus. The distribution of alleles for each polymorphism for both parental and cystic fibrosis (CF) chromosomes from Rio de Janeiro CF families were ascertained using a maximum-likelihood method. This same method was applied to study the distribution of the haplotypes defined by these markers. There was no significant association between the XV2c and KM19 loci on the parental and CF chromosomes. On the other hand, a strong association between GATT and TUB9 loci was observed on both CF and parental chromosomes, and striking linkage disequilibrium between the GATT-TUB9 pair and deltaF508 was observed (chi2 = 26.48, p < 0.0001). Remarkable linkage disequilibrium between the GATT-TUB9 marker pair and non-deltaF508 was also found (chi2 = 17.05, p < 0.0001). Our finding of a linkage disequilibrium between GATT-TUB9 and the CFTR locus could suggest that gene flow between different ethnic groups, mainly sub-Saharan and Mediterranean populations, with Brazilian populations could have resulted in some CF mutations originating on chromosomes that carried the GATT-TUB9 marker haplotype 7-2 (OR = 1.34 < 2.83 < 6.00; p = 0.0066).