197,037 research outputs found
A Prize To Give For: An Experiment on Public Good Funding Mechanisms
No full textThis article investigates fund-raising mechanisms based on a prize as a way to overcome free riding in the private provision of public goods. We focus on an environment characterised by income heterogeneity and incomplete information about income levels. Our analysis compares experimentally the performance of a lottery, an all-pay auction and a benchmark voluntary contribution mechanism. We find that prize-based mechanisms perform better than voluntary contribution in terms of public good provision. Contrary to the theoretical predictions, contributions are significantly higher in the lottery than in the all-pay auction, both overall and by individual income types. Copyright � The Author(s). Journal compilation � Royal Economic Society 2009.
Modification of protein synthesis in barley shoots as a response to a temperature step-down (cold shock).
No full textHaplotype characterization and markers at the barley Mlo powdery mildew resistance locus as tools for marker-assisted selection
No full textRecessive mlo alleles of the barley Mlo gene confer resistance to almost all known isolates of the powdery mildew fungal pathogen targeting barley (Hordeum vulgare). To characterize haplotypes present in the Mlo chromosomal region of cultivated Mlo and mlo barley genotypes, weconducted a polymorphism search in 3 predicted low-copy sequence regions adjacent to the Mlo gene by examining a sample of 4 Mlo and 3 mlo cultivars. Eight singlenucleotide polymorphisms (SNPs) and 1 insertion–deletion (indel) were detected, and easy to use PCR-based markers were developed for typing the SNPs. The PCR markers were used to characterize a collection of 46 Mlo and 25 mlo barley cultivars, identifying 3 distinct mlo-11 haplotypes, 1 mlo-9 haplotype, and 4 Mlo haplotypes. We summarized the haplotype and marker information obtained here and in a previous study to help breeders identify strategies for mlo marker-assisted selection. The ability of the markers to identify mlo-resistant genotypes in segregating populations was demonstrated using 2 resistance-characterized F2 populations derived by 3-way crosses.G Tacconi, V Baldassarre, N C Collins, D Bulgarelli, A M Stanca, G Val
The CC-NB-LRR-Type Rdg2a resistance gene confers immunity to the seed-borne barley leaf stripe pathogen in the absence of hypersensitive cell death
No full textBACKGROUND: Leaf stripe disease on barley (Hordeum vulgare) is caused by the seed-transmitted hemi-biotrophic fungus Pyrenophora graminea. Race-specific resistance to leaf stripe is controlled by two known Rdg (Resistance to Drechslera graminea) genes: the H. spontaneum-derived Rdg1a and Rdg2a, identified in H. vulgare. The aim of the present work was to isolate the Rdg2a leaf stripe resistance gene, to characterize the Rdg2a locus organization and evolution and to elucidate the histological bases of Rdg2a-based leaf stripe resistance. PRINCIPLE FINDINGS: We describe here the positional cloning and functional characterization of the leaf stripe resistance gene Rdg2a. At the Rdg2a locus, three sequence-related coiled-coil, nucleotide-binding site, and leucine-rich repeat (CC-NB-LRR) encoding genes were identified. Sequence comparisons suggested that paralogs of this resistance locus evolved through recent gene duplication, and were subjected to frequent sequence exchange. Transformation of the leaf stripe susceptible cv. Golden Promise with two Rdg2a-candidates under the control of their native 5′ regulatory sequences identified a member of the CC-NB-LRR gene family that conferred resistance against the Dg2 leaf stripe isolate, against which the Rdg2a-gene is effective. Histological analysis demonstrated that Rdg2a-mediated leaf stripe resistance involves autofluorescing cells and prevents pathogen colonization in the embryos without any detectable hypersensitive cell death response, supporting a cell wall reinforcement-based resistance mechanism. CONCLUSIONS: This work reports about the cloning of a resistance gene effective against a seed borne disease. We observed that Rdg2a was subjected to diversifying selection which is consistent with a model in which the R gene co-evolves with a pathogen effector(s) gene. We propose that inducible responses giving rise to physical and chemical barriers to infection in the cell walls and intercellular spaces of the barley embryo tissues represent mechanisms by which the CC-NB-LRR-encoding Rdg2a gene mediates resistance to leaf stripe in the absence of hypersensitive cell death.Davide Bulgarelli, Chiara Biselli, Nicholas C. Collins, Gabriella Consonni, Antonio M. Stanca, Paul Schulze-Lefert and Giampiero Val
Protein synthesis during cold shock in barley tissues. Comparison of two genotypes with winter and spring growth habit.
No full textIn barley (Hordeum vulgare L.) seedlings, a temperature step-down from 24 °C to 6°C (cold shock) determined a reduction in the incorporation of labeled aminoacids and modified the electrophoretic pattern of total proteins. At 6 °C some new proteins appeared and others were intensified (cold shock-induced proteins= CSPs); meantime, few proteins disappeared or were curtailed (cold-repressed proteins=CRPs). The majority of the proteins of the seedlings were labeled at about the same rate both at 6 °C and 24 °C, whereas at 0 °C only the cold shock proteins and a few others were detectable. The cold shock-induced variations of the protein profile differed in roots and in seed remnants which showed only some of the CSPs detected in roots. Total protein synthesis of barley genotypes lsquoOnicersquo and lsquoGeorgiersquo, which have respectively a winter and spring growth habit, were similarly inhibited by a temperature drop. The two genotypes, however, showed some differences in the CSPs and CRPs pattern. Because lsquoOnicersquo and lsquoGeorgiersquo have also a different thermotolerance, the hypothesis can be made that in barley specific CSPs are involved in conferring various degrees of cold resistance
Una «certa tiritera di parole» : genesi, forma e funzione dell'anapesto in "Lavorare stanca"
No full textL’uso insistito di strutture ritmiche anapestiche nei versi di Cesare Pavese è dato critico da sempre sottolineato, ma raramente approfondito, in particolare in relazione al suo aspetto genetico. Questo studio si presenta quindi come un’analisi del progressivo affermarsi dell’elemento prosodico anapestico nella poesia pavesiana a partire dalle sue prime occorrenze, individuabili addirittura all’interno delle liriche del 1923 che inaugurano la raccolta "Sfoghi". L’evoluzione delle forme metriche è quindi seguita lungo tutte le composizioni che anticipano "Lavorare stanca", fino ad arrivare a "Frasi all’innamorata", necessario antecedente stilistico de "I mari del Sud". L’analisi di tutte le varianti prosodiche e metriche presenti nella raccolta del 1936 porta infine ad una serie di considerazioni circa le funzionalità dell’anapesto all’interno della produzione pavesiana: precisi riferimenti riportati ne "Il mestiere di vivere" spingono a ricollegare il «monotono ritmo» della poesia di Pavese alla ricerca di un «filtro» che permetta al poeta di ottenere un «condensato racconto», finalmente libero dalla precedente poesia di sfogo
Histological and molecular analysis of Rdg2a barley resistance to leaf stripe
No full textJournal compilation © 2008 Blackwell Publishing LtdBarley (Hordeum vulgare L.) leaf stripe is caused by the seed-borne fungus Pyrenophora graminea. We investigated microscopically and molecularly the reaction of barley embryos to leaf stripe inoculation. In the resistant genotype NIL3876-Rdg2a, fungal growth ceased at the scutellar node of the embryo, while in the susceptible near-isogenic line (NIL) Mirco-rdg2a fungal growth continued past the scutellar node and into the embryo. Pathogen-challenged embryos of resistant and susceptible NILs showed different levels of UV autofluorescence and toluidine blue staining, indicating differential accumulation of phenolic compounds. Suppression subtractive hybridization and cDNA amplified fragment-length polymorphism (AFLP) analyses of embryos identified P. graminea-induced and P. graminea-repressed barley genes. In addition, cDNA-AFLP analysis identified six pathogenicity-associated fungal genes expressed during barley infection but at low to undetectable levels during growth on artificial media. Microarrays representing the entire set of differentially expressed cDNA-AFLP fragments and 100 barley homologues of previously described defence-related genes were used to study gene expression changes at 7 and 14 days after inoculation in the resistant and susceptible NILs. A total of 171 significantly modulated barley genes were identified and assigned to four groups based on timing and genotype dependence of expression. Analysis of the changes in gene expression during the barley resistance response to leaf stripe suggests that the Rdg2a-mediated response includes cell-wall reinforcement, signal transduction, generation of reactive oxygen species, cell protection, jasmonate signalling and expression of plant effector genes. The identification of genes showing leaf stripe inoculation or resistance-dependent expression sets the stage for further dissection of the resistance response of barley embryo cells to leaf stripe.Anita Haegi, Vera Bonardi, Elena Dall'Aglio, David Glissant, Giorgio Tumino, Nicholas Collins, Davide Bulgarelli, Alessandro Infantino, A. Michele Stanca, Massimo Delledonne and Giampiero Val
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