Repair of methyl methane sulfonate-damaged phage by Haemophilus influenzae

Seven mutants of Haemophilus influenzae strain Rd (mmsA-) have been isolated that are more sensitive to methyl methane sulfonate (mms) than recombination-deficient (recA-) mutants. The mutations cotransformed about 25% with the strA locus while the five studied clustered tightly; they are all probably allelic. The mutants are not sensitive to ultraviolet radiation, X-rays, or nitrous acid. Mms-damaged phage HP1 plated very inefficiently on these mutants, indicating that they lack the first step in the excision repair of the lesion N3-methyladenine (m3A). Incubation of damaged phage at 30 degrees C in the absence of mms resulted in a steady decline of viability when the phage were plated on the wild mmsA+ host but an initial steep rise was seen when it was plated on an mmsA- mutant. The rise is explained by the assumption that m3A lesions hydrolyzed off the DNA giving rise to repairable apurinic sites by both the mmsA+ and mmsA- hosts. No decline in viability was observed when hydroxylamine was present in the medium. This compound is known to prevent or slow down beta-elimination. The delayed decline in viability is therefore explained by assuming that apurinic sites give rise to beta-elimination-induced single strand breaks in the phage DNA that cannot be repaired by either host. Marker rescue experiments indicated that these breaks did not interrupt injection of phage DNA.     

A hex mutant of Haemophilus influenzae.

Summary A mutant of Haemophilus influenzae which does not discriminate between low efficiency (LE) and high efficiency (HE) markers has been isolated. The mutant does not differ wild type in its sensitivity to ultraviolet radiation, methyl methanesulfonate (MMS) mitomycin C, and nitrous acid. Spontaneous mutation frequencies for three loci studied are 10-to 30-fold higher in the mutant than in the wild type strain. Low- and high-efficiency transforming markers are equally UV-resistant when assayed on this mutant. This mutant is thus similar to the hex mutant of Streptococcus pneumoniae.     

SHLD2/FAM35A co‐operates with REV7 to coordinate DNA double‐strand break repair pathway choice

DNA double‐strand breaks (DSBs) can be repaired by two major pathways: non‐homologous end‐joining (NHEJ) and homologous recombination (HR). DNA repair pathway choice is governed by the opposing activities of 53BP1, in complex with its effectors RIF1 and REV7, and BRCA1. However, it remains unknown how the 53BP1/RIF1/REV7 complex stimulates NHEJ and restricts HR to the S/G2 phases of the cell cycle. Using a mass spectrometry (MS)‐based approach, we identify 11 high‐confidence REV7 interactors and elucidate the role of SHLD2 (previously annotated as FAM35A and RINN2) as an effector of REV7 in the NHEJ pathway. FAM35A depletion impairs NHEJ‐mediated DNA repair and compromises antibody diversification by class switch recombination (CSR) in B cells. FAM35A accumulates at DSBs in a 53BP1‐, RIF1‐, and REV7‐dependent manner and antagonizes HR by limiting DNA end resection. In fact, FAM35A is part of a larger complex composed of REV7 and SHLD1 (previously annotated as C20orf196 and RINN3), which promotes NHEJ and limits HR. Together, these results establish SHLD2 as a novel effector of REV7 in controlling the decision‐making process during DSB repair.     

Morphological,karyological and palynological investigation of endemic Centaurea kurdica Reichardt from Turkey

The purpose of this study was to determine the morphological, morphometrical, karyological and palynological features of the endemic Centaurea kurdica Reichardt species from East Anatolian region. Some morphological features of the species like morphology of capitula, involucra, involucral leaves (phyllaries) and achene have been investigated. The chromosome number of Centaurea kurdica was found as 2n = 18 and haploid karyotype formula 6m+2sm+1M. Metaphase chromosome length ranged from 5.81 to 3.91 μm and the total haploid chromosome length was 41.09 μm. The results of the light microscope investigation of pollen revealed that it is radially symmetrical, isopolar tricolporate and has spheroid-type pollen, and exine ornamentation was also determined as scabrate.     

A multivariate statistical approach to Centaurea classification using essential oil composition data of some species from Turkey

The composition of the essential oils of ten Centaurea species from Turkey, Centaurea aladaghensis, C. antiochia var. prealta, C. antitauri, C. babylonica, C. balsamita, C. cheirolepidoides, C. deflexa, C. iconiensis, C. lanigera, C. ptosimopappoides have been studied. Multivariate statistical analyses (Principal Component Analysis, Multidimensional Scaling, Hierarchical Cluster Analysis) applied to GC-MS data, seem to be very useful to investigate and establish the natural taxonomic delimitation of this very difficult genus. The groupings resulted independent from the ecological similarities (i.e. plants that live in the same habitats or share similar morphological characteristics), so it seems that the environment has no influence on the biosynthesis of the volatiles of these plants.     

Silicon increases boron tolerance and reduces oxidative damage of wheat grown in soil with excess boron

The effect of silicon on the growth, boron concentrations, malondialdehyde (MDA) content, lipoxygenase (LOX) activity, proline (PRO) and H₂O₂ accumulation, and the activities of major antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] and non-enzymatic antioxidants (AA) of wheat grown in soil originally with toxic B concentrations were investigated. Applied of 5.0 and 10.0 mM Si to the B toxic soil significantly increased Si concentration of the wheat and counteracted the deleterious effects of B on shoot growth. The contents of PRO, H₂O₂, MDA, and LOX activity of wheat grown in B toxic soil were significantly reduced by Si treatments. Compared with control plants, the activities of SOD, CAT, APX and content of AA were decreased by applied Si. Based on the present work, it can be concluded that Si alleviates B toxicity of wheat by preventing oxidative membrane damage and also translocation of B from root to shoot and/or soil to plant.     

Fatty acid and tocochromanol patterns of some Salvia L. species

In the course of our investigations of new sources of higher plant lipids, seed fatty acid compositions and the tocochromanol contents of Salvia bracteata, S. euphratica var. euphratica, S. aucherii var. canascens, S. cryptantha, S. staminea, S. limbata, S. virgata, S. hypargeia, S. halophylla, S. syriaca and S. cilicica were investigated using GLC and HPLC systems. Some of the species are endemic to Turkey. All the Salvia sp. showed the same pattern of fatty acids. Linoleic, linolenic and oleic acid were found as the abundant components. Tocochromanol derivatives of the seed oil showed differences between Salvia species. gamma-Tocopherol was the abundant component in most of the seed oils except of S. cilicica. The total tocopherol contents of the seed oils were determined to be more than the total of tocotrienols.