2,037 research outputs found
In Italy the new Government was sworn in but a question comes up from the shadow: did the “Government of Change” start out by prompting a constitutional change?
La rappresentanza territoriale nel sistema parlamentare italiano dal disegno del Costituente al presente processo di riforma: quali prospettive dopo il referendum?
Emergenza e tutela ambientale nel sistema delle fonti tra problemi definitori e rapporto tra ordinamenti
Genotypic Characterization of Azotobacteria Isolated from Argentinean Soils and Plant-Growth-Promoting Traits of Selected Strains with Prospects for Biofertilizer Production
The genetic diversity among 31 putative Azotobacter isolates obtained from agricultural and non-agricultural soils was assessed using rep-PCR genomic fingerprinting, and identified to species level by ARDRA and partial 16S rRNA gene sequence analysis. High diversity was found among the isolates, identified as A. chroococcum, A. salinestris and A. armeniacus. Selected isolates were characterized on the basis of phytohormone biosynthesis, nitrogenase activity, siderophore production and phosphate solubilization. Indole-3 acetic-acid (IAA), gibberellin (GA3)and zeatin (Z) biosynthesis, nitrogenase activity and siderophore production were found in all evaluated strains, with variation among them, but no phosphate solubilization was detected. Phytohormones excreted to the culture medium ranged the following concentrations: 2.2-20 µg IAA ml-1, 0.3-0.7 µg GA3 ml-1, 0.5-1.2 µg Z ml-1. Seed inoculations with further selected Azotobacter strains and treatments with their cell-free cultures increased the number of seminal roots and root hairs in wheat seedlings. This latter effect was mimicked by treatments with IAA-pure solution but it was not related with bacterial root colonization. Our survey constitutes a first approach to the knowledge of Azotobacter species inhabiting Argentinean soils, in three contrasting geographical regions. Moreover, this phenotypic characterization constitutes an important contribution to the selection of Azotobacter strains for biofertilizer formulations.Fil: Rubio, Esteban Julio. Instituto Nacional de TecnologĂa Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de InvestigaciĂłn de Ciencias Veterinarias y AgronĂłmicas. Instituto de MicrobiologĂa y ZoologĂa AgrĂcola; Argentina;Fil: Montechia, Marcela Susana. Universidad de Buenos Aires. Facultad de AgronomĂa. Departamento de BiologĂa Aplicada y Alimentos. Cátedra de Microbiologia AgrĂcola; Argentina;Fil: Tosi, Micaela. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico - CONICET - Parque Centenario. Instituto de Investigaciones en Biociencias AgrĂcolas y Ambientales; Argentina; Universidad de Buenos Aires. Facultad de AgronomĂa. Departamento de BiologĂa Aplicada y Alimentos. Cátedra de Microbiologia AgrĂcola; Argentina;Fil: Cassan, Fabricio Dario. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Departamento de Cs.naturales. Laboratorio de Fisiologia Vegetal y de la Interaccion Planta-microorganismo; Universidad Nacional de RĂo Cuarto. Facultad de Ciencias Exactas FisicoquĂmicas y Naturales. Departamento de Ciencias Naturales; Argentina;Fil: Perticari, Alejandro. Instituto Nacional de TecnologĂa Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de InvestigaciĂłn de Ciencias Veterinarias y AgronĂłmicas. Instituto de MicrobiologĂa y ZoologĂa AgrĂcola; Argentina;Fil: Correa, Olga Susana. Universidad de Buenos Aires. Facultad de AgronomĂa. Departamento de BiologĂa Aplicada y Alimentos. Cátedra de Microbiologia AgrĂcola; Argentina
Conditional knockout of RAD51-related genes in Leishmania major reveals a critical role for homologous recombination during genome replication
Homologous recombination (HR) has an intimate relationship with genome replication, both during repair of DNA lesions that might prevent DNA synthesis and in tackling stalls to the replication fork. Recent studies led us to ask if HR might have a more central role in replicating the genome of Leishmania, a eukaryotic parasite. Conflicting evidence has emerged regarding whether or not HR genes are essential, and genome-wide mapping has provided evidence for an unorthodox organisation of DNA replication initiation sites, termed origins. To answer this question, we have employed a combined CRISPR/Cas9 and DiCre approach to rapidly generate and assess the effect of conditional ablation of RAD51 and three RAD51-related proteins in Leishmania major. Using this approach, we demonstrate that loss of any of these HR factors is not immediately lethal but in each case growth slows with time and leads to DNA damage and accumulation of cells with aberrant DNA content. Despite these similarities, we show that only loss of RAD51 or RAD51-3 impairs DNA synthesis and causes elevated levels of genome-wide mutation. Furthermore, we show that these two HR factors act in distinct ways, since ablation of RAD51, but not RAD51-3, has a profound effect on DNA replication, causing loss of initiation at the major origins and increased DNA synthesis at subtelomeres. Our work clarifies questions regarding the importance of HR to survival of Leishmania and reveals an unanticipated, central role for RAD51 in the programme of genome replication in a microbial eukaryote
Genome duplication in Leishmania major relies on persistent subtelomeric DNA replication
DNA replication is needed to duplicate a cell’s genome in S phase and segregate it during cell division. Previous work in Leishmania detected DNA replication initiation at just a single region in each chromosome, an organisation predicted to be insufficient for complete genome duplication within S phase. Here, we show that acetylated histone H3 (AcH3), base J and a kinetochore factor co-localise in each chromosome at only a single locus, which corresponds with previously mapped DNA replication initiation regions and is demarcated by localised G/T skew and G4 patterns. In addition, we describe previously undetected subtelomeric DNA replication in G2/M and G1-phase-enriched cells. Finally, we show that subtelomeric DNA replication, unlike chromosome-internal DNA replication, is sensitive to hydroxyurea and dependent on 9-1-1 activity. These findings indicate that Leishmania’s genome duplication programme employs subtelomeric DNA replication initiation, possibly extending beyond S phase, to support predominantly chromosome-internal DNA replication initiation within S phase
Atomic Undercoordination in Ag Islands on Ru(0001) Grown via Size-Selected Cluster Deposition: An Experimental and Theoretical High-Resolution Core-Level Photoemission Study
The possibility of depositing precisely mass-selected Ag clusters (Ag-1, Ag-3, and Ag-7) on Ru(0001) was instrumental in determining the importance of the in-plane coordination number (CN) and allowed us to establish a linear dependence of the Ag 3d(5/2) core-level shift on CN. The fast cluster surface diffusion at room temperature, caused by the low interaction between silver and ruthenium, leads to the formation of islands with a low degree of ordering, as evidenced by the high density of low-coordinated atomic configurations, in particular CN = 4 and 5. On the contrary, islands formed upon Ag-7 deposition show a higher density of atoms with CN = 6, thus indicating the formation of islands with a close-packed atomic arrangement. This combined experimental and theoretical approach, when applied to clusters of different elements, offers the perspective to reveal nonequivalent local configurations in two-dimensional (2D) materials grown using different building blocks, with potential implications in understanding electronic and reactivity properties at the atomic level
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