No abstract

Genetic variability among 122 Rhynchosporium secalis isolates collected from barley in three regions of Tunisia was investigated using host differentials, amplified fragment length polymorphism (AFLP), and microsatellite markers. The isolates were collected from a widely grown scald-susceptible barley cultivar Rihane and a range of local landrace cultivars in geographically distinct regions with different agroclimatic conditions. Pathotypic diversity (the proportion of unique pathotypes) was high in R. secalis populations from the high (100% diversity), moderate (95%), and low (100%) rainfall areas of Tunisia, and from both Rihane (which is the sole variety grown in the high rainfall region) and local landraces (which predominate in the low rainfall area). This may reflect a general adaptability for aggressiveness and suggests that the widely grown cultivar Rihane has exerted little or no selection pressure on the pathogen population since its release in 1983. Genotypic diversity (GD), defined as the probability that two individuals taken at random had different genotypes, was high for populations from Rihane, local landraces, and different agro-ecological zones (GD = 0.96-0.99). There was low genetic differentiation among pathogen populations from different host populations (G(ST) < or = 0.08, theta < or = 0.12) and agro-ecological zones (G(ST) < or = 0.05, theta < or = 0.04), which may be partly explained by gene flow due to the movement of infected stubble around the country. There was no correlation (r = 0.06, P = 0.39) between virulence phenotype and AFLP haplotype. A phenetic tree revealed groups with low bootstrap values that did not reflect the grouping of isolates based on host, pathotype, or agro-ecological region. The implications of these findings for R. secalis evolutionary potential and scald-resistance breeding in Tunisia are discussed.

Since the number of patients studied is limited, further studies are needed with a larger series of patients to evaluate the potential utility of GNG11, AREG and CP as molecular markers for AML subtype classification. Our study is the first to analyze these genes in AML, B-ALL, T-ALL and chronic leukemia (myeloid and lymphoid) patients by RT-PCR. This rapid and sensitive method could be used to screen these genes in different types of leukemia.

The hypothesis of optimal host species selection predicts that when a parasitoid has the choice between two host species, it will choose the species that gives the best survival chances for its progeny. We confirmed this hypothesis by laboratory experiments with Leptopilina boulardi Barb. et al., a cynipid parasitoid which prefers Drosophila melanogaster Meigen (the host species most suitable for parasitoid survival) above D. simulans Sturt. As far as fitness parameters are concerned, the fertility of L. boulardi is higher with D. melanogaster, the egg laying can be spread out over a long period when this host is relatively scarce. This does not occur with D. simulans in which parasitic oviposition stops soon when this host is not abundant. Investigations of this foraging strategy were done under more complex natural conditions. We found that L. boulardi has a type III functional response with D. melanogaster only; furthermore, it seems that a switching effect may exist with this host. Parasitoid females appear to distribute their eggs more regularly on D. melanogaster, thus avoiding superparasitism. This seems to be independent of the relative frequency of this host. However, superparasitism of D. simulans did occur more frequently when this host was scarce. Résumé Stratégie de ponte de Leptopilina boulardi (Hyménoptère parasite de drosophiles) dans les conditions naturelles Le concept de réponse optimale d'un parasite vis‐à‐vis de l'hǒte le plus favorable pour son développement demeure surtout théorique et n'a pu ětre vérifié que dans les conditions de laboratoire. Nous avons montré que Drosophila melanogaster s'avère ětre, par rapport à D. simulans, l'hǒte le plus favorable pour le développement du cynipide parasite Leptopilina boulardi. Une étude sur le terrain a démontré que ce parasite présente une réponse fonctionnelle densité dépendante vis‐à‐vis de D. melanogaster et non vis‐à‐vis de D. simulans, avec un effet de bascule. D'autre part, il s'avère que ce parasite exploite beaucoup mieux son hǒte, en évitant le superparasitisme, ceci étant démontré au laboratoire et dans la nature. Enfin, il apparaǐt qu'il est capable d'allonger sa période de ponte lorsque cet hǒte est rare, ce qui ne se produit pas avec D. simulans.

The heterogeneity of acute myeloid leukemia (AML) with respect to biology and clinical course resides in the fact that patients belonging to the same group show marked differences in their response to chemotherapy, which would necessitate a refinement of AML classification. In order to contribute to define molecular markers for AML we realized microarray assays on two M5 AMLs and selected four differentially expressed genes to validate their expression by RQ-PCR. We have shown that two down-regulated genes in AML, Guanine nucleotide binding protein (G protein) gamma 11 (GNG11) and Amphiregulin are also down-regulated in B-ALL and T-ALL patients. We have found a gene, Ceruloplasmin, which is up-regulated in AML but not in B-ALL and T-ALL. The level of expression of these genes varies from one patient to another. Since the group of patients studied is limited, further studies must carry on with a larger series of patients to be able to make subdivision according to the expression of GNG11, Amphiregulin and Ceruloplasmin. Our study is the first to analyze these genes in AML, B-ALL, T-ALL and CL patients by quantitative real time PCR. This rapid and sensitive method could be used to screen these genes in different types of leukemia.