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Ziolkowski, Piotr A.,Underwood, Charles J.,Lambing, Christophe,Martinez-Garcia, Marina,Lawrence, Emma J.,Ziolkowska, Liliana,Griffin, Catherine,Choi, Kyuha,Franklin, F. Chris H.,Martienssen, Robert A. Cold Spring Harbor Laboratory Press 2017 Genes & development Vol.31 No.3
<P>Here, Ziolkowski et al. combine high-throughput fluorescence methods to measure crossovers with natural <I>Arabidopsis</I> ecotypes in order to identify the first <I>trans</I>-acting modifier of meiotic recombination in plants. The authors found that HEI10, which encodes a conserved ubiquitin E3 ligase, naturally limits <I>Arabidopsis</I> crossovers and has the potential to influence the response to selection.</P><P>During meiosis, homologous chromosomes undergo crossover recombination, which creates genetic diversity and balances homolog segregation. Despite these critical functions, crossover frequency varies extensively within and between species. Although natural crossover recombination modifier loci have been detected in plants, causal genes have remained elusive. Using natural <I>Arabidopsis thaliana</I> accessions, we identified two major recombination quantitative trait loci (<I>rQTL</I>s) that explain 56.9% of crossover variation in Col×Ler F<SUB>2</SUB> populations. We mapped <I>rQTL1</I> to semidominant polymorphisms in <I>HEI10</I>, which encodes a conserved ubiquitin E3 ligase that regulates crossovers. Null <I>hei10</I> mutants are haploinsufficient, and, using genome-wide mapping and immunocytology, we show that transformation of additional <I>HEI10</I> copies is sufficient to more than double euchromatic crossovers. However, heterochromatic centromeres remained recombination-suppressed. The strongest <I>HEI10</I>-mediated crossover increases occur in subtelomeric euchromatin, which is reminiscent of sex differences in <I>Arabidopsis</I> recombination. Our work reveals that HEI10 naturally limits <I>Arabidopsis</I> crossovers and has the potential to influence the response to selection.</P>
HUA ZHANG,YOLANDA LEUNG,DANIEL LOUDEN,ROCKY DE NYS,ROBERT LAMB 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2008 NANO Vol.3 No.4
The intrinsic and extrinsic toxicity of SiO2 nanoparticles (Aerosil OX50, φ ∼ 40 nm) are investigated with a comparison to the particles in micron size (SiO2 gel, φ ∼ 1.5 μm). Nanoparticles potentially functioned as a carrier of harmful substances transfer was assessed by examining the surface adsorption behavior of the nanoparticles towards γ-picoline (4-methylpyridine), recognized as one type of the marine pollutants, as well as the penetration behavior of the nanoparticles towards a typical marine macro-organism (Caulerpa taxifolia). Silica nanoparticle surface can take up to 2.6 molecules/nm2 of γ-picoline in an aqueous solution comparable to the marine environment. These nanoparticles can further travel onto the surface and into the bulk of the algae (Caulerpa taxifolia) with a depth of ∼ 1 μm while carrying toxic γ-picoline. The integrated intrinsic and extrinsic toxicity of SiO2 nanoparticles has a significant effect on the growth of the algae. The large surface area of the silica nanoparticles results in a high adsorption capability and allows the particles to participate in possible toxic carrier activities in water medium towards marine organisms.