Comparative analysis of mitochondrial DNA variation in four species of Far Eastern redfins of the genus Tribolodon (Pisces, Cyprinidae)

The variability of mtDNA in four Far Eastern endemic species of the genus Tribolodon was studied in the significant part of their areas. There was no close relationship between the lifetime and the level of mtDNA variability. The relation between the population genetic structure and the level of amphidromic species was revealed. The presence of mtDNA phylogroup differed in three of the four species shows that there was a long period of independent intraspecific divergent evolution in the history of these species. This period falls on aproximately the same historical age, and, apparently, is caused by one and the same factors. The period was not enough long and ended in the integration of genetically independent units into a single species.     

Tremorgenic mycotoxins produced by strains of Penicillium spp. isolated from toxic Poa huecu parodi

Seventeen strains of Penicillium spp. have been isolated from Poa huecu Parodi from the Zapala zone, exhibiting toxicity to sheet. The following strains have been identified: P. crustosum, cyclopium, notatum, palitans, puberulum, verrucosum, viridicatum and Penicillium spp. The toxigenic capacity of the strains was studied after growing them under suitable conditions. Toxins produced were analysed by thin layer chromatography (TLC). Penitrem A (PA) and Penitrem B (PB) neurotoxins were identified and quantitated in twelve strains; verruculogen (VERR) and fumitremorgen B (FTB) being present in one of them. The effect of these mycotoxins was studied in mice. Neurological symptoms characteristic of the intoxication by tremorgenic toxins and similar to those observed in sheep suffering from huecu's disease were observed. The possible role of these toxins as causative agents of huecu's disease is discussed.     

Comparison of the reversibility of locipet23 andlys2 after UV irradiation in the standard and UV-sensitive strains ofSaccharomyces cerevisiae

Reversibility of the respiration-deficient locuspet23 and auxotrophic locuslys2 was followed in the standard (RAD1) and UV sensitive (rad1–2) strains ofSaccharomyces cerevisiae, both after identical doses of UV radiation and at identical survival. When comparing the reversibility after the treatment with identical doses of UV radiation a much higher reversibility of both loci in strainrad1–2 could be detected. When comparing the reversibility of the loci in question at identical survival of both strains it could be found that the reversibility of thepet23 locus is again much higher in strainrad1–2, whereas the reversibility of thelys2 locus is roughly identical in the two strains. Thus, the function of geneRAD1 in repair processes is apparently associated with the “error-free” repair, both at low and high doses of ultraviolet radiation.     

Physical map of the bacteriophage L (Salmonella typhimurium)

Abstract A circular restriction map of the genome of the phage L ( Salmonella typhimurium ) has been constructed with five restriction endonucleases, Eca I, Eco RI, Bam HI, Bgl I, and Pst I. The Eco RI fragments of phage-L DNA were cloned into pACYC184, and the resulting recombinant plasmids pL1, pL2,…,pL7 were introduced into Salmonella typhimurium . The genes present on the fragments cloned were identified by the marker rescue experiments with the L-phage amber mutants. A physical gene map of the L genome obtained in this way was compared with that of P22.     

UV-induced mutability in repair-deficientrad6-1 strains ofSaccharomyces cerevisiae is caused by a suppressor gene

TheRAD6 gene is a multifunctional gene required for DNA repair, induced mutagenesis and sporulation. The survival and revertibility of two loci in fourrad6-1 mutant strains of different origin after UV irradiation were followed. As expected, all therad6-1 strains tested were more sensitive to UV radiation in comparison withRAD6 strains. The reversion frequency per survivor intrpl-289 andarg4–17 alleles was significantly higher in all fourrad6-1 mutant strains than in wild-type strains after equal doses of UV radiation. On the basis of genetic analysis we suggest that the phenomenon of increased frequency of induced mutagenesis is caused by a suppressor gene.     

Role of UV-inducible proteins in repair of various wild-type Escherichia coli cells

3 wild-type strains of E. coli, namely K12 AB2497, B/r WP2 and 15 555-7v proficient in excision and post-replication repair, differ markedly in their UV resistance. To elucidate this difference, the influence was investigated of induction by application of inducing fluence (IF) before lethal fluence (LF) on repair processes after LF. In cells distinguished by low UV resistance (E. coli 15 555-7; E. coli B/r WP2), dimer excision was less complete in cultures irradiated with IF + LF than in cultures irradiated with LF only. The highly resistant E. coli K12 AB2497 performed complete excision both after IF + LF or after LF alone. All 3 types of cell survived better after IF + LF than after LF only. Because, in most strains so far investigated, the application of IF reduced dimer excision and increased survival, dimer excision per se does not appear important for survival.We conclude that the rate and completeness of dimer excision can serve as a measure of efficiency of the excision system whose action is necessary for repair of another lesion. Cells of all investigated strains could not resume DNA replication and died progressively when irradiated with LF and post-incubated with chloramphenicol (LF CAP⁺). Thus, it appears that inducible proteins are necessary for repair in all wild-type E. coli cells give with potentially lethal doses of UV irradiation.     

Starch degradation by glucoamylase Glm from Saccharomycopsis fibuligera IFO 0111 in the presence and absence of a commercial pullulanase

This study describes the course of enzymatic hydrolysis of the native corn starches Maritena 100 and Maritena 300. Hydrolyses were carried out with glucoamylase Glm produced by Saccharomycopsis fibuligera IFO 0111, which degrades also native starch, with the purpose to substitute a two-step hydrolysis (amylase followed by glucoamylase) by a one-step process (glucoamylase only). Hydrolysis generally became more effective by adding the pullulanase Promozyme D, which cleaves alpha-1,6-glycosidic bonds more effectively than glucoamylase Glm does. The time course (kinetics) of hydrolysis was followed by determination of the glucose concentration and calculation of dextrose equivalents.     

Effects of abscisic acid on the contents of polyamines and proline in common bean plants under salt stress

The effects of ABA treatment on the contents of polyamines (PAs) and proline (Pro) in the glycophyte Phaseolus vulgaris L. during plant adaptation to salt stress were studied. Two-week-old common bean seedlings grown in the phytotron chamber on the Jonson nutrient medium were subjected to salinity for 6 days by one-time NaCl addition to medium up to final concentrations of 50 and 100 mM. During first three days of salinity, the root system was daily treated with ABA (1, 5, 10, or 50 μM) for 30 min. Salt stress (100 mM NaCl) elevated the level of endogenous ABA, increased the content of Pro 14-fold, reduced sharply the content of free PAs (putrescine, spermidine, spermine, and cadaverine), and the accumulation of 1,3-diaminopropan, a product of oxidation of high-molecular PAs. Common bean plant treatment with 1 μM ABA weakened the adverse effects of salt stress (100 mM NaCl), which was manifested in the maintenance of plant growth, stimulation of chlorophyll (a and b) and carotenoid accumulation, a stabilization of water and Na⁺ balance. Seedling treatment with ABA suppressed NaCl-induced Pro and intracellular ABA accumulation and restored the levels of putrescine and spermidine. The content of spermine in the leaves of plants subjected to salt stress and treated with ABA was approximately threefold higher than in control plants, whereas the content of cadaverine increased under similar conditions more than fivefold. Simultaneously, the contents of 1,3-diaminopropan and malondialdehyde as well as activity of superoxide dismutase were reduced, which indicates a weakening of oxidative stress, one of the possible causes of defensive ABA effects against salt stress. In addition, the suppression by exogenous ABA of Pro accumulation and stimulation of PA content under salt stress confirm indirectly our hypothesis that ABA is involved in the coordinated regulation of two biosynthetic pathways, Pro and PA formation, which use a common precursor, glutamate, and play an important protective role during stress in plants.