RESUMO
The landraces are considered important sources of valuable germplasm for breeding activities to face climatic changes as well as to satisfy the requirement of new varieties for marginal areas. Runner bean (Phaseolus coccineus L.) is one of the most cultivated Phaseolus species worldwide, but few studies have been addressed to assess the genetic diversity and structure within and among landrace populations. In the present study, 20 different populations of a runner bean landrace from Central Italy named "Fagiolone," together with 41 accessions from Italy and Mesoamerica, were evaluated by using 14 nuclear SSRs to establish its genetic structure and distinctiveness. Results indicated that "Fagiolone" landrace can be considered as a dynamic evolving open-pollinated population that shows a significant level of genetic variation, mostly detected within populations, and the presence of two main genetic groups, of which one distinguished from other Italian runner bean landraces. Results highlighted also a relevant importance of farmers' management practices able to influence the genetic structure of this landrace, in particular the seed exchanges and selection, and the past introduction in cultivation of landraces/cultivars similar to seed morphology, but genetically rather far from "Fagiolone." The most suitable on-farm strategies for seed collection, conservation and multiplication will be defined based on our results, as a model for threatened populations of other allogamous crop species. STRUCTURE and phylogenetic analyses indicated that Mesoamerican accessions and Italian landraces belong to two distinct gene pools confirming the hypothesis that Europe could be considered a secondary diversification center for P. coccineus.
Assuntos
Variação Genética , Genética Populacional , Phaseolus/genética , Agricultura , Análise por Conglomerados , Evolução Molecular , Geografia , Itália , Repetições de Microssatélites , Phaseolus/anatomia & histologia , Fenótipo , Filogenia , Característica Quantitativa Herdável , Sementes/genéticaRESUMO
The event chain leading to germination blockage in durum wheat (Triticum turgidum ssp. durum Desf.) seeds exposed to the allelochemical coumarin (2H-chromen-2-one) was studied. The physiological and biochemical aspects thought to be critical for a successful seed germination were measured. At concentrations above 200 microM: , coumarin inhibited seed germination in a concentration-dependent manner. Inhibition occurred early during seed imbibition (phase I), was rapid, and irreversible. During phase I, coumarin inhibited water uptake, electrolyte retention capacity, and O(2) consumption. Later on, coumarin delayed the reactivation of peroxidases, enhanced the activity of superoxide dismutase, decreased the activities of selected marker enzymes for metabolic resumption, and repressed the transcription of molecular chaperones involved in secretory pathways. Insufficient and/or late seed rehydration caused by coumarin could have delayed membrane stabilization or decreased respiratory O(2) consumption, both of which are conducive to an overproduction of reactive O(2) species. Being unbalanced by an adequate upsurge of antioxidant defense systems, the resulting oxidative stress might have ultimately interfered with the germination program.
Assuntos
Cumarínicos/farmacologia , Triticum/efeitos dos fármacos , Antioxidantes/metabolismo , Germinação/efeitos dos fármacos , Oxigênio/metabolismo , Sementes/efeitos dos fármacos , Sementes/fisiologia , Triticum/fisiologia , Água/metabolismoRESUMO
The genomic and cDNA sequences of three PDI homoeologous genes located on chromosomes 4A, 4B and 4D of bread wheat and their promoters were cloned and sequenced. The three sequences showed a very high conservation of the coding region and of the exon/intron structure, which consisted of ten exons. The comparison of wheat sequences with those of rice and Arabidopsis showed a significant conservation of the exon/intron structure across the three species. The expression of each gene was analysed by RT-PCR in different plant tissues (roots, coleoptiles, spikelets, leaves and developing caryopses). All the genes showed a higher expression in developing caryopses than in other analysed tissues, wherein some differences were detected. The promoter sequences of the three genes possessed some regulatory motifs typical of endosperm specific expression.
Assuntos
Cromossomos de Plantas/genética , Regulação da Expressão Gênica de Plantas/genética , Proteínas de Plantas/genética , Regiões Promotoras Genéticas/genética , Isomerases de Dissulfetos de Proteínas/genética , Triticum/genética , Arabidopsis/enzimologia , Arabidopsis/genética , Éxons/genética , Íntrons/genética , Dados de Sequência Molecular , Especificidade de Órgãos/genética , Oryza/enzimologia , Oryza/genética , Análise de Sequência de DNA/métodos , Homologia de Sequência do Ácido Nucleico , Triticum/enzimologiaRESUMO
The organisation of the durum wheat genomic sequence (3.5 kb) coding for protein disulfide isomerase (PDI), deduced by comparison between genomic fragments and cDNA sequences (1.5 kb) isolated from immature caryopses, is described. The gene structure consists of ten exons and nine introns. The presence of consensus sequences involved in splicing, such as intron-exon junctions and branchpoint, has been observed and discussed. Although the deduced wheat PDI amino acid sequence exhibited an overall identity of only 31% to that of human PDI, their modular architecture in terms of number, size, location and secondary structure-propensities of the constituent domains are remarkably similar. The comparison of the amino acid sequences with the eight available plant PDI-like sequences showed a high identity with four of them and low with the remaining ones. Analyses of transcription levels showed that the PDI mRNA was present in all analysed tissues, with much higher expression in immature caryopses.
Assuntos
Genes de Plantas/genética , Isomerases de Dissulfetos de Proteínas/genética , Triticum/genética , Sequência de Aminoácidos , Sequência de Bases , Northern Blotting , Clonagem Molecular , DNA Complementar/química , DNA Complementar/genética , DNA Complementar/isolamento & purificação , DNA de Plantas/química , DNA de Plantas/genética , DNA de Plantas/isolamento & purificação , Éxons , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Íntrons , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Distribuição Tecidual , Triticum/enzimologiaRESUMO
Foliar antioxidants were measured in adult individuals of holm oak (Quercus ilex L.) and white oak (Q. pubescens Willd.) growing in the field either within the vicinity of natural CO2 springs or at a nearby control site under ambient CO2, which had been previously exposed to either daily irrigation or no irrigation. In oak trees permanently exposed to elevated CO2 the activities of antioxidant enzymes tended to be lower and the ascorbate pool was larger and more in reduced form, suggesting an attenuation of the oxidative risk in the CO2-enriched trees. In the enriched individuals of both species. the imposition of water shortage significantly increased the size of the glutathione pool and the total superoxide dismutase activity in a species-specific manner. Moreover, water-stressed trees exposed to elevated CO2 tended to have higher catalase and ascorbate peroxidase activities than water-stressed control trees. Such changes may reflect the need for an enhanced compensatory effort when trees acclimated to elevated CO2 are exposed to oxidative stress-promoting environmental factors, such as water shortage.