Restorer-of-Fertility Mutations Recovered in Transposon-Active Lines of S Male-Sterile Maize

Mitochondria execute key pathways of central metabolism and serve as cellular sensing and signaling entities, functions that depend upon interactions between mitochondrial and nuclear genetic systems. This is exemplified in cytoplasmic male sterility type S (CMS-S) of Zea mays, where novel mitochondrial open reading frames are associated with a pollen collapse phenotype, but nuclear restorer-of-fertility (restorer) mutations rescue pollen function. To better understand these genetic interactions, we screened Activator-Dissociation (Ac-Ds), Enhancer/Suppressor-mutator (En/Spm), and Mutator (Mu) transposon-active CMS-S stocks to recover new restorer mutants. The frequency of restorer mutations increased in transposon-active stocks compared to transposon-inactive stocks, but most mutants recovered from Ac-Ds and En/Spm stocks were unstable, reverting upon backcrossing to CMS-S inbred lines. However, 10 independent restorer mutations recovered from CMS-S Mu transposon stocks were stable upon backcrossing. Many restorer mutations condition seed-lethal phenotypes that provide a convenient test for allelism. Eight such mutants recovered in this study included one pair of allelic mutations that were also allelic to the previously described rfl2-1 mutant. Targeted analysis of mitochondrial proteins by immunoblot identified two features that consistently distinguished restored CMS-S pollen from comparably staged, normal-cytoplasm, nonmutant pollen: increased abundance of nuclear-encoded alternative oxidase relative to mitochondria-encoded cytochrome oxidase and decreased abundance of mitochondria-encoded ATP synthase subunit 1 compared to nuclear-encoded ATP synthase subunit 2. CMS-S restorer mutants thus revealed a metabolic plasticity in maize pollen, and further study of these mutants will provide new insights into mitochondrial functions that are critical to pollen and seed development

Радиационная стойкость нитевидных кристаллов SiGe, используемых для сенсоров физических величин

Приведены результаты исследования влияния облучения γ-квантами дозами до 1·10¹⁸ см⁻² и магнитного поля с индукцией до 14 Тл на электропроводность нитевидных кристаллов Si1-xGex в интервале температуры 4,2-300 К.Вивчено вплив опромінення γ-квантами (випромінювання Co⁶⁰) з дозами до 1·10¹⁸ см⁻² та магнітного поля з індукцією до 14 Тл на електропровідність ниткоподібних кристалів Si1-xGex (х = 0,03) з питомим опором 0,08,0,025 Ом·см в інтервалі температур 4,2 .300 К. Встановлено, що опір кристалів слабо змінюється в процесі опромінення дозами до 2·10¹⁷ см⁻², в той же час спостерігаються істотні зміни магнітоопору. На основі проведених досліджень запропоновано умови створення радіаційно стійких сенсорів деформації, дієздатних в умовах сильних магнітних полів.An influence of γ-irradiation (Co⁶⁰) with doze up to 1·10¹⁸ cm⁻² and magnetic field with induction up to 14 T on conduction of Si1-xGex (x = 0,03) whisker crystals with resistivity of 0,08-0,025 Ohm·cm in temperature range 4,2-300 K have been studied. It is shown that whisker crystals resistance faintly varies under irradiation with doze 2·10¹⁷ cm⁻², while their magnetoresistance substantially changes. The strain sensors stable to irradiation action operating in high magnetic fields on the base of the whiskers have been designed