Mutations in a plastid-localized elongation factor G alter early stages of plastid development in Arabidopsis thaliana

<p>Abstract</p> <p>Background</p> <p>Proper development of plastids in embryo and seedling tissues is critical for plant development. During germination, plastids develop to perform many critical functions that are necessary to establish the seedling for further growth. A growing body of work has demonstrated that components of the plastid transcription and translation machinery must be present and functional to establish the organelle upon germination.</p> <p>Results</p> <p>We have identified <it>Arabidopsis thaliana </it>mutants in a gene that encodes a plastid-targeted elongation factor G (<it>SCO1</it>) that is essential for plastid development during embryogenesis since two T-DNA insertion mutations in the coding sequence (<it>sco1-2 </it>and <it>sco1-3</it>) result in an embryo-lethal phenotype. In addition, a point mutation allele (<it>sco1-1</it>) and an allele with a T-DNA insertion in the promoter (<it>sco1-4</it>) of <it>SCO1 </it>display conditional seedling-lethal phenotypes. Seedlings of these alleles exhibit cotyledon and hypocotyl albinism due to improper chloroplast development, and normally die shortly after germination. However, when germinated on media supplemented with sucrose, the mutant plants can produce photosynthetically-active green leaves from the apical meristem.</p> <p>Conclusion</p> <p>The developmental stage-specific phenotype of the conditional-lethal <it>sco1 </it>alleles reveals differences in chloroplast formation during seedling germination compared to chloroplast differentiation in cells derived from the shoot apical meristem. Our identification of embryo-lethal mutant alleles in the Arabidopsis elongation factor G indicates that <it>SCO1 </it>is essential for plant growth, consistent with its predicted role in chloroplast protein translation.</p

Effect of confined electrolyte volumes on galvanic corrosion kinetics in statically loaded materials

This work investigates the effects that the confined volume of atmospheric electrolytes has on the galvanic corrosion kinetics of martensitic stainless steel alloys coupled with UNS A97075 in simulated atmospheric environments at relative humidity values that span the range of operational exposures. Restricted volumes found in thin films and droplets have been shown to control reduction reaction kinetics and are an ongoing challenge to characterize and standardize . This, along with the dynamic and high concentration of aggressive ions found in confined electrolytes, creates a unique corrosion system that requires a multifaceted approach to evaluate varied conditions, compare them with traditional measurements and more accurately predict galvanic atmospheric corrosion. In this work, corrosion currents in galvanic couples were obtained under three environmental conditions: Please click Additional Files below to see the full abstract

Relationship between electrochemical reaction processes and environment-assisted crack growth under static and dynamic atmospheric conditions

Environment-assisted cracking (EAC) of aluminum alloys in corrosive atmospheres is an important maintenance and safety issue for aerospace structures. EAC initiation and propagation are influenced by the interaction of load, environment, and alloy properties. For atmospheric corrosion, environmental conditions are dynamic; where temperature, relative humidity, and surface contaminants interact to control thin film electrolyte properties. Recent studies have determined that stage II stress corrosion crack (SCC) propagation, under atmospheric conditions is strongly dependent on humidity. SCC propagation in AA5083 and AA7075 alloys is a maximum during drying processes at intermediate humidity levels at or below the deliquescence relative humidity (DRH) for the applied corrosive salt. An improved understanding of the dependence of cracking on atmospheric conditions is important to testing material performance, establishing durable designs, and managing structural integrity. Please click Additional Files below to see the full abstract

Preferred Basis in a Measurement Process

The effect of decoherence is analysed for a free particle, interacting with an environment via a dissipative coupling. The interaction between the particle and the environment occurs by a coupling of the position operator of the particle with the environmental degrees of freedom. By examining the exact solution of the density matrix equation one finds that the density matrix becomes completely diagonal in momentum with time while the position space density matrix remains nonlocal. This establishes the momentum basis as the emergent 'preferred basis' selected by the environment which is contrary to the general expectation that position should emerge as the preferred basis since the coupling with the environment is via the position coordinate.Comment: Standard REVTeX format, 10 pages of output. Accepted for publication in Phys. Rev