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In the cypress improvement programme for resistance against canker disease, caused by Seiridium cardinale, controlled crosses among cypress species were done by the IPP. The hybrids Cupressus sempervirens (as female) x C. dupreziana (as male) aroused great interest, becuase some morphological traits of hybrids were always identical to those of the paternal tree, C. dupreziana. A team, constituted by Italian and French biologists, geneticists and sylviculturists, examined six 15-year-old families obtained by controlled crosses of 6 different clones of C. sempervirens (as female) and C. dupreziana (as male). C. dupreziana is native to the Tassili N’Ajjer (figure 1) desert of Algeria and is one of the most threatened trees in the world. The following morphological characteristics distintive of the parental species were measured for the hybrids and the parents:
Image - Figure 1
Industrialized nations' passing flirtation with asbestos has left a nasty legacy. Exposure to airborne asbestos fibrils causes in fact asbestosis and malignancies such as bronchogenic carcinoma and pleural mesothelioma. Although extraction and use of asbestos have been banned in many countries, substantial amounts of fibres have remained on sites previously occupied by dismissed asbestos industries. Cleaning up contaminated soil around defunct asbestos mines and factories is a lot harder than removing asbestos sheets from buildings, and the widely-dispersed fibres can easily become airborne if disturbed. The toxic effects of inhaled asbestos fibres rely on both physical and chemical factors. The surface properties of asbestos fibres, and in particular iron, play a role in pathogenicity ( ). Crocidolite, one of the most potently carcinogenic forms of asbestos, contains up to 29 % iron, that originates highly reactive centres when occurring at the surface in poorly co-ordination state. This can cause the formation of highly reactive free radicals that damage DNA and eventually trigger cancers. Experiments in vitro demonstrate that iron removal makes the asbestos considerably less hazardous by reducing their potential to generate radicals and to damage DNA ( ). Most soil microorganisms need iron for their own metabolism, so some have very effective ways of scavenging it from their environment. Plants, bacteria and fungi can release potent chelators such as siderophores and polycarboxylic acids, that grab hold of iron atoms in soil minerals and bring it into soluble forms.
Document - titolo
Cyclic environmental changes have occurred during the last two million years. Living organisms react to changing phases through adaptation strategies, otherwise they get extinct. Forest trees are among the most ancient living organisms and in many cases they symbolise the last representatives of taxonomic units that underwent severe selection and/or extinction. The present distribution of trees in the forest landscape is the result of population dynamics experienced during the last millennia. In order to understand the mechanisms determining the evolution and the diversity of forest tree populations, it is important to consider historical factors, such as climatic and geological events, and evidences provided by fossil pollen records. The availability of fossil pollen records is restricted to few taxa, i.e., those producing large amount of pollen and characterised by wind pollination. Recently, the application of molecular markers to population genetics has provided additional research tools.
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Document - Estremi del lavoro pubblicato
Arbuscular mycorrhizal fungi (AM) are indeed mysterious and still surprising organisms. Plenty of papers have recently provided new insights on these organisms. The classification of AM fungi has been reviewed even if it's still under debate. The phosphate transporters in AM fungi and their impact on the phosphate transfer in plant is giving new exciting glances to a crucial step of plant physiology. Other fundamental aspects, such as lipids and carbohydrates metabolism and C translocation, have been clarified by means of NMR experiments. However, the mother of all the questions is still unsolved: what about the genome in AM fungi? There are two levels hidden behind this same question: i) the organization and the complexity of the fungal genome (genome size, ploidy, repeated sequences and so on) and ii) the affordability of a genome sequencing project like those already available for Saccharomyces cerevisiae or Neurospora crassa. The first level is a priority to understand the accomplishment of the AM life cycle, the genetic polymorphisms, as well as the variability which has already been reported at least in ribosomal genes. All these data have so far supported the concept that heterokaryosis, the coexistence of different nuclei in cells, occurs troughout the AM fungal life. Very recent results opened the way to the alternative hypothesis of homokaryosis. The second level will be crucial to compare AM fungi with saprotrophic or pathogenic fungi and to understand how they impact on plant development. Recently it was demonstrated that Glomus intraradices is haploid and has a small genome size in the lower limit for eukaryotes. It will be very important to see whether low values are confirmed also for other AM species: this will allow us to understand whether there is a relationship between biotrophism and genome size. The genomics and functional genomics of mycorrhizal plants are currently important tools to investigate the influence of the fungus in comparison to non-mycorrhizal plants. It has been successfully demonstrated that EST-based approaches are effective in monitoring the interaction between symbionts, but information is mostly about the plant or the mycorrhiza taken as a whole, rather than about the fungus itself. Fungal transcripts coming from mycorrhizal roots are evaluated as not more than the 5%. Therefore, a more direct way is to study the fungus alone, by sequencing the genome and collecting ESTs. In the last months the proposal to sequencing G. intraradices genome has been approved, and this project will be carried out during 2004. In addition to the extraordinary possibility of having a global genetic blueprint for an AM fungus, we can expect to have some answers to one of the basic questions we have: is there a genetic basis for biotrophy? By comparing the genome of G. intraradices with that of a saprobic fungus, we will be able to see whether some genes, crucial for an independent life, are missing and whether the host plant complements the missing functions.Document - Fig 1
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