Tolerance to the fungal pathogen Rhizoctonia solani AG4 of transgenic tobacco expressing the maize ribosome-inactivating protein b-32

The maize b-32 protein is a functional ribosome-inactivating protein (RIP), inhibiting in vitro translation in the cell-free reticulocyte-derived system and having specific N-glycosidase activity on 28S rRNA. Previous results indicated that opaque-2 (o2) mutant kernels, lacking b-32, show an increased susceptibility to fungal attack and insect feeding and that ectopic expression in plants of a barley and a pokeweed RIP leads to increased tolerance to fungal and viral infection. This prompted us to test whether b-32 might functi on as a protectant against pathogens. The b32.66 cDNA clone under the control of the potato wun1 gene promoter was introduced into tobacco by Agrobacterium tumefaciens-mediated transformation. Out of 23 kanamycin resistant regenerated shoots, 16 contained a PCR fragment of the corrrect size spanning the boundary between the promoter used and the coding region of the b-32 gene. Eight independently transformed tobacco lines were randomly chosen for protein analysis: all of them expressed b-32 protein. The data presented indicate that transgenic tobacco plants expressing b-32 show an increased tolerance against infection by the soil-borne fungal pathogen Rhizoctonia solani Kuhn     

Macrogeographic population structuring in the cosmopolitan agricultural pest Bactrocera cucurbitae (Diptera: Tephritidae)

The macrogeographic population structure of the agricultural pest Bactrocera cucurbitae (Diptera: Tephritidae) was investigated in order to identify the geographic origin of the species and reconstruct its range expansion. Individuals of B. cucurbitae were collected from 25 worldwide‐distributed localities (n = 570) and genotyped at 13 microsatellite loci. The Bayesian clustering reveals that B. cucurbitae can be subdivided into five main groups corresponding to populations from (i) the African continent, (ii) La Réunion, (iii) Central Asia, (iv) East Asia and (v) Hawaii. The proportions of inter‐regional assignments and the higher values of genetic diversity in populations from Pakistan, India and Bangladesh suggest that B. cucurbitae originated in Central Asia and expanded its range to East Asia and Hawaii on one hand and to Africa and the islands of the Indian Ocean on the other. A number of outliers (10–19 specimens according to different clustering algorithms) show high levels of admixture (Q > 0.70) with populations from different regions and reveal complex patterns of inter‐regional gene flow. Anthropogenic transport is the most plausible promoter of this large‐scale dispersal. The introduction of individuals from geographically distant sources did not have a relevant role in the most recent African invasions, which originated from the expansion of local populations. These results could provide a useful background to better evaluate invasion risks and establish priorities for the management of this cosmopolitan agricultural pest.     

Systematic planning for river rehabilitation: integrating multiple ecological and economic objectives in complex decisions

1. Owing to intensive human use, freshwaters are among the most seriously threatened and modified environments on the planet. Their poor condition and the risk to services that humans need from these ecosystems make their rehabilitation a priority. However, many previous studies have reported the poor performance of many rehabilitation activities. 2. Here, we analyse reasons for this poor performance, focussing on the planning of rehabilitation activities, and propose a new approach. We argue that the failure to include driving factors at a scale adequate to capture the ecological processes involved, together with an insufficient incorporation of socio‐economic aspects, is a key factor leading the poor performance of many rehabilitation activities. 3. We propose a new approach, ‘systematic rehabilitation planning’, that brings together advances made in conservation planning (cost‐effectiveness analysis) and ecosystem science (understanding the complexity of ecosystem processes). This enables planning to be done at the catchment scale, and the trade‐offs between various rehabilitation actions to be integrated and prioritised. 4. Finally, it is important, given the constraints imposed by a lack of knowledge, that the planning process is part of an adaptive cycle where it can benefit from and consolidate the experience gained during the implementation and monitoring stages.     

Ultrastructure of dental hard tissues of Gondwanatherium and Sudamerica (Mammalia, Gondwanatheria)

Sigogneau-Russell, D., Bonaparte, J. F., Frank. R. M. & Escribano. V. 1991 01 15: Ultrastructure of dental hard tissues of Gondwanatherium and Sudamerica (Mammalia, Gondwanathcria). Lethaia. Vol. 24, pp. 27–38. Oslo. ISSN 0024–1164. The ultrastructural study of small dental fragments of the South American mammals Gondwanarherium Bonaparte, 1986 (late Cretaceous) and Sudamerica Scillato-Yané & Pascual. 1985 (middlc Paleocene). tentatively classified in the Paratheria, his shown the same structural characteristics. In the first genus one notes the presence of a thick, well differentiated, prismatic enamel with prisms of pattcrn I of Boyde and interprismatic substance. In places, lines of apposition are visible. The most internal zone of the enamel is very rich in tubules, which become rarer in the peripheral enamel. The dentinc presents numerous parallel tubules, sometimes continuing into the enamel. The presence of enamel over the whole height of the tooth fragment indicates that the hypsodonty here would be due almost entirely to lengthening of the crown. While structurally resembling the specimen of Gondwunarherium, the dental fragment of Sudamerica differs in its enamel locally constituted of open prisms. In spite of the further differences in lobation and enamel folding, the similar kind of hypsodonty met with in both genera studied tends to support their grouping in the order Gondwanatheria Moncs, 1987. an order which may well be situated outside the Tribosphenida. On the contrary, the abscnce. in thc fragments under study. of the dental specializations seen in typical Xenarthra, such as enamel rcduction. suggest that the morphologic resemblance observed between these genera of the Gondwanatheria and Xenarthra might be a phenomenon of convergence rather than of phyletic relationship. However. diversity within Gondwanathcria, and our poor knowledge of the carliest stages of the complex superorder Xenarthra, do not permit at the moment any definitive statement as to their phylogenetic relationships. Teeth, ultrastructure, Gondwanarheria. Xenarthra.     

Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations

Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance ( kdr ) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F kdr alleles were found in the S-form with overall frequencies of 14% and 42% respectively. Only the 1014F allele was found in the M-form at lower frequency (11%). Analysis of a 455 bp region of intron-1 upstream the kdr locus revealed four independent mutation events originating kdr alleles, here named MS1 -1014F, S1-1014S and S2-1014S kdr- intron-1 haplotypes in S-form and MS3-1014F kdr- intron-1 haplotype in the M-form. Furthermore, there was evidence for mutual introgression of kdr 1014F allele between the two molecular forms, MS1 and MS3 being widely shared by them. Although no M/S hybrid was observed in analysed samples, this wide distribution of haplotypes MS1 and MS3 suggests inter-form hybridizing at significant level and emphasizes the rapid diffusion of the kdr alleles in Africa. The mosaic of genetic events found in Cameroon is representative of the situation in the West–Central African region and highlights the importance of evaluating the spatial and temporal evolution of kdr alleles for a better management of insecticide resistance.