A role for Sds3p, a component of the Rpd3p/Sin3p deacetylase complex, in maintaining cellular integrity in <i>Saccharomyces</i> <i>cerevisiae</i>

The SDS3 gene was identified in a suppressor screen for mutations that enhance position-effect silencing in yeast. Cells that are defective in SDS3 have pleiotropic phenotypes, similar to those seen in the absence of the histone deacetylase components Rpd3p and Sin3p, including meiotic defects and improper regulation of the HO gene. To gain further insight into SDS3 function we undertook an epistasis analysis with other SDS genes. We found that sds3 is synthetically lethal in combination with a deletion of the SWI6 (SDS11) gene, which encodes a cell-cycle regulator. sds3 swi6 double mutants do not display a specific cell-cycle arrest phenotype, but instead die due to cell lysis. Constitutive expression of the G1 cyclin gene CLN2 restores viability to an sds3 swi6 strain, as does overexpression of SKT5/CHS4, which encodes a regulatory subunit of chitin synthase III, and SSD1, a gene previously implicated in ensuring cell-cycle progression and cellular integrity. Significantly, growth in the presence of 1 M sorbitol or overexpression of PKC1 also partially suppresses the lethal phenotype of the sds3 swi6 strain. This lethality in the absence of SWI6 function most probably reflects an important or essential role for Sds3p in the Rpd3p/Sin3p histone deacetylase complex, since RPD3 and SIN3 mutations are also synthetically lethal in combination with swi6 and these phenotypes are also rescued by elevated dosage of SKT5/CHS4, SSD1, or PCK1. Taken together, these data indicate that the transcription factor Swi6p and the Rpd3p-based deacetylase complex act in parallel pathways to activate genes required for cell wall biosynthesis

DNA-end capping by the budding yeast transcription factor and subtelomeric binding protein Tbf1

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Distinct roles for yeast Stn1 in telomere capping and telomerase inhibition

The budding yeast Cdc13, Stn1 and Ten1 (CST) proteins are proposed to function as an RPA-like complex at telomeres that protects ('caps') chromosome ends and regulates their elongation by telomerase. We show that Stn1 has a critical function in both processes through the deployment of two separable domains. The N terminus of Stn1 interacts with Ten1 and carries out its essential capping function. The C terminus of Stn1 binds both Cdc13 and Pol12, and we present genetic data indicating that the Stn1-Cdc13 interaction is required to limit continuous telomerase action. Stn1 telomere association, similar to that of Cdc13, peaks during S phase. Significantly, the magnitude of Stn1 telomere binding is independent of telomere TG tract length, suggesting that the negative effect of Stn1 on telomerase action might be regulated by a modification of CST activity or structure in cis at individual telomeres. Genetic analysis suggests that the Tell kinase exerts an effect in parallel with the Stn1 C terminus to counteract its inhibition of telomerase. These data provide new insights into the coordination of telomere capping and telomerase regulation

A dynamic decision-making tool for calculating the optimal rates of N application for 40 annual crops while minimising the residual level of mineral N at harvest

Adequate nitrogen (N) fertilisation is an important component of sustainable management in agricultural systems because it reduces the environmental impacts of agriculture. However, taking into account the varied sources of soil N remains a challenge, and farmers require robust decision-making tools to manage increasingly diverse growing conditions. To address these issues, we present the AzoFert® decision support system for farmers and extension services. This tool is capable of providing N recommendations at the field scale for 40 main field crops. It is based on a full inorganic N balance sheet and integrates the dynamic modelling of N supply from soil and various organic sources. Because of the choice of formalisms and parameters and the structure and modularity of the computer design, the tool is easily adaptable to new crops and cropping systems. We illustrate the application of Azofert® through a range of N fertilisation experiments conducted on cereals, sugar beet and vegetables in Franc

Original Network of Zigzag Chains in the β Polymorph of Fe 2 WO 6 : Crystal Structure and Magnetic Ordering

International audienceThe structural and physical properties of the β polymorph of iron tungstate Fe2WO6 have been investigated by synchrotron and neutron diffraction vs temperature, combined with magnetization and dielectric properties measurements. The monoclinic P21/a crystal structure of β-Fe2WO6 has been determined and consists of an original network of zigzag chains of FeO6 and WO6 octahedra sharing trans and skew edges, connected through corners into a 3D structure. Magnetization measurements indicate an antiferromagnetic transition at TN = 264 K, which corresponds to a ↑↑↓↓ nearly collinear ordering of iron moments inside sequences of four edge-sharing FeO6 octahedra, as determined by neutron diffraction. A canting of the moments out of the ac plane is observed below 150 K, leading to a noncollinear antiferromagnetic structure, the P21/a′ magnetic space group remaining unchanged. These results are discussed in comparison with the crystal and magnetic structures of γ-Fe2WO6 and with the magnetic couplings in other iron tungstates and trirutile Fe2TeO6

Universal stripe order as a precursor of the superconducting phase in pressurized BaFe2Se3 Spin Ladder

International audienceAbstract It has been recently observed that a superconducting phase emerges under pressure in the Fe-based spin-ladders BaFe 2 X 3 (X = S, Se). The low dimensionality of the Fe spin-ladders, which simplifies the elaboration of theoretical models, should help to understand the mechanism of superconductivity. We investigate here the frontier between magnetic and superconducting (SC) phases in BaFe 2 Se 3 by performing challenging powder neutron diffraction (PND) and Fe K β x-ray emission spectroscopy (XES) under high pressure. We show that the ambient pressure ground state with a block-like magnetic order is destabilized under pressure. A pressure-induced antiferromagnetic stripe-like spin order, similar to the magnetic order of the parent superconductor BaFe 2 S 3 , is observed above 3-4 GPa. Our discovery shows that the stripe magnetic order is a key phase close to the SC dome and its particular magnetic fluctuations could be involved in the stabilization of superconductivity in Fe-based spin ladders

Crystal chemistry and magnetism of iron-tungsten mixed oxide

Iron tungstate Fe2WO6 attracts interest due to its photoelectrochemical and magnetic properties. On the one hand, Fe2WO6 is studied either as a photocatalyst for degradation of environmental pollutants [1,2] or as a photoanode for water oxidation in tandem devices [3-4]. On the other hand, some magneto-dielectric properties [5] have been reported, confirming that further work is needed to investigate the magnetic and electric properties. Indeed, Fe2WO6 iron tungstate exists as three crystal structures with different organizations of the FeO6 and WO6 octahedra [6-8]. In the present work, we have clarified the conditions of polymorphism using a complete set of the three polymorphs as single-phase products. In particular, a spray-drying route from aqueous solution had to be developed for the synthesis of the low temperature α polymorph. We have revised the structural model for this α-polymorph, solved the heretofore-unknown structure of the β-polymorph and compared magnetic properties through bulk magnetic measurements and preliminary neutron diffraction results. We also report on the influence of the Fe/W ratio using a combination of X-Ray diffraction, 57Fe Mossbauer spectroscopy, scanning electron microscopy and ICP-OES quantification