The Srs2 Suppressor of Rad6 Mutations of Saccharomyces Cerevisiae Acts by Channeling DNA Lesions into the Rad52 DNA Repair Pathway

rad6 mutants of Saccharomyces cerevisiae are defective in the repair of damaged DNA, DNA damage induced mutagenesis, and sporulation. In order to identify genes that can substitute for RAD6 function, we have isolated genomic suppressors of the UV sensitivity of rad6 deletion (rad6 delta) mutations and show that they also suppress the gamma-ray sensitivity but not the UV mutagenesis or sporulation defects of rad6. The suppressors show semidominance for suppression of UV sensitivity and dominance for suppression of gamma-ray sensitivity. The six suppressor mutations we isolated are all alleles of the same locus and are also allelic to a previously described suppressor of the rad6-1 nonsense mutation, SRS2. We show that suppression of rad6 delta is dependent on the RAD52 recombinational repair pathway since suppression is not observed in the rad6 delta SRS2 strain containing an additional mutation in either the RAD51, RAD52, RAD54, RAD55 or RAD57 genes. Possible mechanisms by which SRS2 may channel unrepaired DNA lesions into the RAD52 DNA repair pathway are discussed.     

Flanking Microsatellite Markers for Breeding Varieties Against Asian Rice Gall Midge

The Asian rice gall midge, Orseolia oryzae Wood-Mason (Cecidomyiidae: Diptera) is a serious pest of wet season rice in South and Southeast Asia. Due to internal feeding habit and presence of biotypes of the pest, the most feasible way to control is breeding varieties resistant against multiple biotypes through marker-assisted breeding (MAB). But very few versatile co-dominant markers linked to the gall midge resistance genes are available. We used a set of F₉ recombinant inbred lines (RILs) of the cross TN1/PTB10 and identified microsatellite markers for the gall midge resistance gene in cv. PTB10 on short arm of rice chromosome 8. Markers RM22550 and RM547 flank the gene at a distance of 0.9 and 1.9 cM, respectively. Amplification of the markers in gall midge resistant and susceptible cultivars showed that these markers can be successfully used in MAB for development of gall midge resistant varieties.     

LRRK2 A419V is not associated with Parkinson's disease in different Chinese populations

It has been suggested that a common LRRK2 polymorphic variant (A419V (rs34594498 C >T)) may be a risk factor among Asians (especially in Taiwan). In this study, we examined this variant in a larger and independent Taiwan cohort. We found the frequency of the variant (A419V) to be very rare in our Taiwan PD and controls (?0.6%). Further studies were conducted in two other Chinese populations (Singapore and China), comprising of a total of 3004 subjects including 1517 PD patients and 1487 control subjects. However, our multi-center Chinese study revealed that the frequency of the variant was rare (?0.4%) and was not associated with risk of PD, suggesting that the variant is not a major risk factor for PD among Chinese, at least in our study population.     

Rank order of success favors longer duration of imidazole-based therapy for Helicobacter pylori in duodenal ulcer disease: a randomized pilot study

Background. Studies on eradication therapy in developing countries have shown a success rate of 70–85%, which is suboptimal. Duration of therapy may be an important factor dictating eradication success in such regions. Aim. The study was undertaken to evaluate the effect of increasing the treatment period on eradication of Helicobacter pylori in duodenal ulcer disease. Methods. A randomized trial was carried out in which 64 consecutive H. pylori‐infected patients with duodenal ulcer disease were enrolled. The patients were randomized to one of the three trial arms. Therapy consisted of lansoprazole 30 mg twice a day (b.i.d.), amoxycillin 1 g b.i.d. and tinidazole 500 mg b.i.d. The treatment period was 1 week in group I, 2 weeks in group II and 3 weeks in group III. At inclusion, patients underwent endoscopy and the presence of H. pylori was documented by a positive urease test and C14 urea breath test. Four weeks after completion of eradication therapy, the patients were subjected to repeat endoscopy to assess ulcer healing and tests for H. pylori infection. Results. Sixty‐four patients (55 male and nine female; mean age 35.5 years) were enrolled in each group. The H. pylori eradication rate for group I (1 week of therapy) was 47.6%, that for group II (2 weeks of therapy) was 80%, and that for group III (3 weeks of therapy) was 91.3% (p = .003). The ulcer healing rates were 71.4, 80 and 95.6% in groups I, II and III, respectively (p = .09). Conclusion. The 3‐week regimen significantly improved the eradication rate as compared with the 1‐week regime. Increasing the duration of therapy significantly improved the chances of eradication of H. pylori in duodenal ulcer disease.     

Specific PCR-based detection of Alternaria helianthi: the cause of blight and leaf spot in sunflower

Alternaria helianthi is an important seed-borne pathogenic fungus responsible for blight disease in sunflower. The current detection methods, which are based on culture and morphological identification, are time-consuming, laborious and are not always reliable. A PCR-based diagnostic method was developed with species-specific primers designed based on the sequence data of a region consisting of the 5.8S RNA gene and internal transcribed spacers—ITS 1 and ITS 2 of nuclear ribosomal RNA gene (rDNA) repeats of A. helianthi. The specificity of the primer pairs AhN1F and AhN1R designed was verified by PCR analysis of DNA from 18 Alternaria helianthi strains isolated from India, 14 non-target Alternaria spp. and 11 fungal isolates of other genera. A single amplification product of 357-bp was detected from DNA of A. helianthi isolates. No cross-reaction was observed with any of the other isolates tested. The detection limit of the PCR method was of 10?pg from template DNA. The primers could also detect the pathogen in infected sunflower seed. This species-specific PCR method provides a quick, simple, powerful and reliable alternative to conventional methods in the detection and identification of A. helianthi. This is the first report of an A. helianthi-specific primer set.     

Influence of salt stress on biochemical processes in chickpea,Cicer arietinum L.

Summary Soybean plants were grown in pots with or without vesicular-arbuscular myocorrhizal (VAM) fungi in three soils of low plant-available P content, different texture and different water-holding capacities. Mineral nutrients, except P, were provided in a complete nutrient solution. The biomass of non-VAM plants was positively and fungal colonization negatively correlated with increasingly coarse soil texture. There was no correlation of soil P with host or endophyte growth. Plant growth enhancement was positively correlated with soil water content at −1.5 MPa. These observations suggest soil water status and the mycorrhizal condition interact in influencing plant growth.     

Symbiotically defective histidine auxotrophs of Bradyrhizobium japonicum

Four histidine auxotrophs of Bradyrhizobium japonicum strain USDA 122 were isolated by random transposon Tn5 mutagenesis. These mutants arose from different, single transposition events as shown by the comparison of EcoRI and XhoI-generated Tn5 flanking sequences of genomic DNA. The mutants grew on minimal medium supplemented with l-histidine or l-histidinol but failed to grow with l-histidinol phosphate. While two of the muants were symbiotically defective and did not form nodules on Glycine max cvs. Lee and Peking and on Glycine soja, the other two mutants were symbiotically competent. Reversion to prototrophy occurred at a frequency of about 10^-7 on growth medium without added antibiotics, but prototrophs could not be isolated from growth medium containing 200 g/ml kanamycin and streptomycin. The prototrophic revertants formed nodules on all the soybean cultivars examined. When histidine was supplied to the plant growth medium, both nodulation deficient mutants formed effective symbioses. On histidine unamended plants, nodules were observed infrequently. Three classes of bacterial colonies were isolated from such infrequent nodules: class 1 were kanamycin resistant-auxotrophs; class 2 were kanamycin sensitive-prototrophs; and class 3 were kanamycin-sensitive auxotrophs. Our results suggest that two Tn5 insertion mutations in B. japonicum leading to histidine auxotrophy, affect nodulation in some way. These mutations are in regions that show no homology to the Rhizobium meliloti common nodulation genes.     

8-anilino-1-naphthalene sulfonic acid (ANS) induces folding of acid unfolded cytochrome c to molten globule state as a result of electrostatic interactions.

Hydrophobic interaction of 8-anilino-1-naphthalene sulfonic acid (ANS) with proteins is one of the widely used methods for characterizing/detecting partially folded states of proteins. We have carried out a systematic investigation on the effect of ANS, a charged hydrophobic fluorescent dye, on structural properties of acid-unfolded horse heart cytochrome c at pH 2.0 by a combination of optical methods and electrospray ionization mass spectroscopy (ESI MS). ANS was found to induce, a secondary structure similar to native protein and quenching of fluorescence of tryptophan residue, in the acid-unfolded protein. However, the tertiary structure was found to be disrupted thus indicating that ANS stabilizes a molten globule state in acid-unfolded protein. To understand the mechanism of ANS-induced folding of acid-unfolded cytochrome c, comparative ESI MS, soret absorption, and tryptophan fluorescence studies using nile red, a neutral hydrophobic dye, and ANS were carried out. These studies suggested that, at low pH, electrostatic interactions between negatively charged ANS molecules and positively charged amino acid residues present in acid-unfolded cytochrome c are probably responsible for ANS-induced folding of acid-unfolded protein to partially folded compact state or molten globule state. This is the first experimental demonstration of ANS induced folding of unfolded protein and puts to question the usefulness of ANS for characterization/determination of partially folded intermediates of proteins observed under low pH conditions.