Collection of Arabidopsis thalianaMorphological Insertion Mutants

A collection of transgenic Arabidopsis thalianaplants has been obtained by Agrobacterium-mediated transformation. The genomes of the transgenic plants contain insertions of T-DNA of the vector plasmids pLD3 or pPCVRN4. Genes bearing T-DNA insertions were shown to constitute 12–18% of the total number of A. thalianagenes. Seventy-five lines have been chosen from the collection and subjected to genetic and molecular-genetic analysis. Of these, 5 were dominant mutants, and 70, recessive insertion mutants with various morphological defects. Identification of mutant phenotypes and genetic characterization of the transgenic lines have been performed with the use of nutrient media supplemented with exogenous hormones, which revealed five recessive lethal mutants and one dominant sterile mutant.     

Repair of bleomycin-induced damage to Escherichia coli DNA. II. Participation of inducible processes

The role of inducible cell functions in repair and mutagenesis after bleomycin-induced DNA damages was studied in Escherichia coli. Influence on these processes of some rec genes as well as sbcB, the structural gene for exonuclease I, was investigated. The data obtained suggest that this enzyme plays a negative role in the repair of DNA damaged by bleomycin. The hypersensitivity of recA mutant to bleomycin and recAlexA-dependence of bleomycin-induced mutagenesis do not suggest any principal differences between UV-induced pyrimidine dimers and apyrimidinic sites in the case of post-replication repair.     

Induction of SOS function in Escherichia coli after exposure to various types of chemical mutagens

On the basis of the SOS-chromotest which was developed by the authors earlier, the minimum time required for expression of the SOS-response is shown to be 15 min, the maximum being recorded 2 h later. An assay of induction of the SOS-response to the mutagens which act on DNA via various mechanisms (e. g., UV-irradiation, mitomycin C, nalidixic acid, nitroso-methylurea and acridine orange) revealed that all the mutagens under study caused induction of the SOS-response. Analysis of efficiency of SOS induction under the action of a mixture of formaldehyde with various amino acids has shown that arginine, asparagine and, especially, cysteine decrease the level of the SOS-response induction. This fact suggests an opportunity for using the SOS-chromotest not only to identify the mutagens and cancerogens, but also to screen the agents for their antimutagenic activity. The study of the SOS-response in the cells which are deficient in genes for repair and recombination has shown that induction is significantly suppressed in the mutants recA, lexA and recF; it is not modified in sbcB mutants and is significantly increased in the mutant lines recBC, uvrB and, particularly, in the double mutant recBCsbcB.     

Analysis of the Avifauna Structure in the Alpine Belt of the Northwestern Putorana Plateau,Central Siberia

Biology Bulletin - Ecological patterns of the spatial differentiation of bird fauna and populations in the alpine belt of the northwestern Putorana Plateau were analyzed at 730–1412 m above...