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The task of working group 4 was to examine the relationship between ecosystem functioning and biodiversity in marine systems. The definition of biodiversity used by the working group is the biological variability in ecosystems as the genetic, species and habitat level. The inventory of marine life is much closer to completion in Europe than in many other areas but some geographic areas, such as the Mediterranean Sea, and specific taxa, mostly in the small size range (viruses, bacteria and protists), require more exploration. Also required is a European synthesis, including studies of both horizontal and vertical gradients of biodiversity, as well as the relationship between diversity and environmental data. The most efficient manner to investigate how species impact ecosystem functioning is to understand the role of the relatively few key organisms. These species should be identified and preferentially attract the attention of ecologists and biological oceanographers. Their study would provide a functional understanding that could be used to model and predict the response of marine ecosystems to global environmental change. In addition to global issues, working group 4 also examined a large range of regional and local issues that also require attention because it is at these scales that most burning societal questions occur. The working group identified a need for additional support to strengthen existing large-scale research infrastructures and establish new ones. In the Mediterranean and on the Atlantic coast. These are invaluable tools to investigate the interactions between biodiversity and ecosystem functioning. Finally, the loss of taxonomic expertise due to the declining number of marine systematists should be a matter of great concern to Europe, which must be dealt with urgently.

Les ADN kinétoplastiques de Phytomonas associés à la maladie du Hartrot en Guyane Française (P.Hart 1) comportent majoritairement (90%) de minicercles à séquences de bases homogènes. L'étude à permis de déterminer la moitié de la séquence nucléotidique du minicercle P.Hart 1 (749 bp) et rechercher les blocs de séquence (CSB) commun a plusieurs espèces de Trypanosomes

We have extracted and compared the kinetoplast DNA (kDNA) of thirteen #Phytomonas# isolates obtained from different plants originating from various countries and cultured #in vitro#. The kDNA structure from all the isolates appeared as a large network of interlocked minicircles with some maxicircles extruding from the network. The sizes of the minicircles varied from 1.3 to 2.8 kb according to #Phytomonas# isolates. The electrophoretic analysis of the minicircles digested with various restriction endonucleases permified to characterize each #Phytomonas# isolate. Cross hybridization experiments were perfomed by Southern blot techniques using minicircles from different isolates as probes. A high sequence homology was found between minicircles from #Phytomonas# isolated from crude sap of coconut trees affected with Hartrot disease in French Guyana and Brazil. The overall results show that kDNA analysis could be used for distinguishing #Phytomonas# isolates and thus for identifying the infection of plant by pathogenic strain.

The aim of the study was to assess, in a group of nonselected patients with neuroblastoma, the prognostic value of both N-myc gene amplification and DNA ploidy index, taking into account potential confounding factors such as age and stage. Of 59 patients studied, 23 were younger than 1 year at diagnosis, 31 presented with stage IV, 10 with stage III, 5 with stage II, 8 with stage I, and 4 with stage IV-S. N-myc genomic content was analyzed by Southern blot hybridization technique and N-myc amplification (greater than or equal to 3 copies/haploid genome) was present in 6 stage IV, 2 stage III, and 1 stage IV-S. The DNA ploidy index was analyzed by flow cytometry. Of the 59 neuroblastomas, 26 were diploid (DNA index, 1) and 33 were aneuploid (DNA index, greater than 1). The majority of the aneuploid tumors (28 of 33) were near-triploid with DNA indexes between 1.25 and 1.68, 4 were near-diploid (DNA index up to 1.18), and 1 was hypotetraploid (DNA index, 1.85). The proportion of near-triploid tumors was significantly greater among patients under 1 year of age and among patients presenting with stages I, II, and IV-S. Interestingly, 0 of 28 near-triploid neuroblastomas exhibited N-myc gene amplification, compared to 9 of 31 in the group of diploid, near-diploid, and hypotetraploid tumors (Fisher's exact test, P less than 0.001). Four factors were significantly related to a high risk of relapse in univariate analysis, i.e., age, stage, DNA index, and N-myc amplification. In multivariate analysis, only N-myc amplification and the DNA index remained significantly associated with a high risk of relapse. The 2-year disease-free survival rate was 94% (95% confidence interval, 77-98%) for patients with near-triploid neuroblastoma, compared to 45 and 11% (95% confidence interval, 32-70 and 4-23%) for patients with diploid or near-diploid tumors, without and with N-myc amplification, respectively. We concluded that the combination of N-myc and DNA index should be included in routine management of neuroblastoma.

The kinetoplast DNA (kDNA) was purified from ten #Phytomonas# isolates originating from various countries and recently cultured #in vitro#. Topoisomerase II lesolved the huge kDNA network in free minicircles which were then analyzed by electron microscopy, restriction endonucleases and southern blot hybridization. The sizes of the #Phytomonas# minicircles varied from,1.3 to 2.8 kilobase pairs (kb). Restriction endonuclease analysis showed that they were heterogeneous in base sequences and that heterogeneity could be elevated in certain isolates. However most minicircles from two isolates were homogeneously deaved with a variety of endonucleases, allowing to map the restriction sites. Moreover restriction endonuclease cleavage permitted to separate after electrophoresis maxicircles usually present in low proportion (