Search

Purpose: To assess the unique biological effects of different forms of ionizing radiation causing DNA double-strand breaks (DSBs), we compared the killing effect, mutagenesis frequency, and mutation type spectrum using the model filamentous fungus Neurospora. Materials and methods: Asexual spores of wild-type Neurospora and two DSB repair-deficient strains [one homologous recombination- and the other non-homologous end-joining (NHEJ) pathway-deficient] were irradiated with argon (Ar)-ion beams, ferrous (Fe)-ion beams, or X-rays. Relative biological effectiveness (RBE), forward mutation frequencies at the ad-3 loci, and mutation spectra at the ad-3B gene were determined. Results: The canonical NHEJ (cNHEJ)-deficient strain showed resistance to higher X-ray doses, while other strains showed dose-dependent sensitivity. In contrast, the killing effects of Ar-ion and Fe-ion beam irradiation were dose-dependent in all strains tested. The rank order of RBE was Ar-ion > Fe-ion > C-ion. Deletion mutations were the most common, but deletion size incremented with the increasing value of linear energy transfer (LET). Conclusions: We found marked differences in killing effect of a cNHEJ-deficient mutant between X-ray and high-LET ion beam irradiations (Ar and Fe). The mutation spectra also differed between irradiation types. These differences may be due to the physical properties of each radiation and the repair mechanism of induced damage in Neurospora crassa. These results may guide the choice of irradiation beam to kill or mutagenize fungi for agricultural applications or further research.

We previously used heavy-ion beam irradiation to generate a self-incompatible mutant of Verbena×hybrida ‘Temari Coral Pink’ (SC), which exhibits a late-acting self-incompatibility system. In the present study, the behavior of pollen tubes and seed productivity after self-pollination were comparatively investigated in SC and wild species Verbena peruviana (VP), one of the parental species of Verbena×hybrida. Although reciprocal cross-pollination between VP and SC produced seeds with high frequencies, namely 57.1% for SC×VP and 59.7% for VP×SC, self-pollinated VP flowers produced no seeds. In the latter, almost all of the pollen germinated on the stigma, but further growth of the pollen tube was inhibited at the upper part of the style. These observations of pollen tube behavior may indicate that the SI system of VP was different from that of SC. VP may possess a homomorphic gametophytic SI system, which is characterized by the inhibition of pollen tube growth at style. We propose a set of SC and VP as a novel model plants for genetic analysis of the SI mechanism in the Verbenaceae family.

A simple amphiphilic low-molecular-weight gelator based on L -lysine, N α -acetyl- N e -lauroyl- L -lysine ( 1 ), its alkali metal salts [Na ( 2 ) and K ( 3 )], and two-component gelators [ 1 and 2 and 1 and 3 ] were synthesized. Compound 1 had a good hydrogelation ability that formed a pure water gel at 2 g L −1 (0.2 wt.%) and a saline gel at 4 g L −1 (0.4 wt.%). Two-component compounds were able to form hydrogels in aqueous solutions containing alkali metal and alkali earth metal ions in addition to pure water and saline. Although 1 formed organogels in a few organic solvents, two-component compounds also functioned as a good organogelator. The FT-IR study indicated that the driving forces for the formation of supramolecular gels were hydrogen-bonding and hydrophobic interactions. Furthermore, the thermal properties of the hydrogels are discussed.

The electrical, optical and structural properties of Al0.5In0.5P and Ga0.5In0.5P layers grown on (001) GaAs substrates by gas source molecular beam epitaxy (GSMBE) using phosphine (PH3) gas have been studied. For heavy Be doping, the electrical activity was found to be unity up to atomic Be concentration of 2 × 1018 cm-3 in Al0.5In0.5P and 3 × 1019 cm-3 in Ga0.5In0.5P. The maximum hole concentrations achieved are 3.5 × 1018 cm-3 in Al0.5In0.5P and 4 × 1019 cm-3 in Ga0.5In0.5P. 20 K photoluminescence (PL) measurements for heavily Be-doped Al0.5In0.5P showed that the decrease in electrical activity is due to deep levels resulting possibly from Al-Be related defects. An ordered structure and a compositional modulated structure were first observed in Ga0.5In0.5P grown by GSMBE. The degree of ordering was found to be less perfect than that for metalorganic vapor phase epitaxy (MOVPE) due to the lower growth temperature. Typical 300 K PL energy was found to be 1.88 eV which was 20 meV lower than the “normal” energy (1.9 eV).