Responses of potential hosts of Asian cuckoos to experimental parasitism

In the arms race between avian brood parasites and their hosts, several adaptations and counter‐adaptations have evolved. The most prominent host defence is rejection of parasitic eggs. We experimentally parasitized nests of 10 potential host species breeding in sympatry with four different cuckoo species in an area in Bangladesh using differently coloured model eggs to test host responses. In four species we introduced both mimetic and non‐mimetic eggs. Black Drongos Dicrurus macrocercus, hosts of the Indian Cuckoo Cuculus micropterus, rejected all model eggs. Common Mynas Acridotheres tristis and Jungle Babblers Turdoides striata accepted all eggs regardless of mimicry. These two species are parasitized by Asian Koels Eudynamys scolopaceus, Common Hawk‐cuckoo Hierococcyx varius and, in the case of Jungle Babblers, Jacobin Cuckoos Clamator jacobinus. Pied Mynas Gracupica contra, with no records of parasitism in our study area, also accepted all eggs regardless of mimicry. In the six remaining species, all of which lay spotted eggs, we introduced only non‐mimetic eggs. Black‐hooded Orioles Oriolus xanthornus rejected all model eggs, even though we have found no records of natural parasitism. Long‐tailed Shrikes Lanius schach and House Crows Corvus splendens, hosts of Asian Koels, rejected 75 and 9.1% of model eggs, respectively. Large‐billed Crows Corvus macrorhynchos, apparently not used as hosts in our study area, accepted all blue but rejected all brown model eggs. Oriental Magpie‐Robins Copsychus saularis and Red‐vented Bulbuls Pycnonotus cafer accepted all non‐mimetic model eggs. In Black Drongos, Long‐tailed Shrikes and Black‐hooded Orioles, all model eggs were ejected within 24 h of introduction. The results show considerable variation in egg rejection rates among various species, providing baseline data for further investigation of co‐evolutionary interactions between brood parasites and hosts in this region.     

Widespread hybridization between the Greater Spotted Eagle Aquila clanga and the Lesser Spotted Eagle Aquila pomarina (Aves: Accipitriformes) in Europe

Hybridization is a significant threat for endangered species and could potentially even lead to their extinction. This concern applies to the globally vulnerable Greater Spotted Eagle Aquila clanga, a species that co‐occurs, and potentially interbreeds, with the more common Lesser Spotted Eagle Aquila pomarina in a vast area of Eastern Europe. We applied single nucleotide polymorphism (SNP) and microsatellite markers in order to study hybridization and introgression in 14 European spotted eagle populations. We detected hybridization and/or introgression in all studied sympatric populations. In most regions, hybridization took place prevalently between A. pomarina males and A. clanga females, with introgression to the more common A. pomarina. However, such a pattern was not as obvious in regions where A. clanga is still numerous. In the course of 16 years of genetic monitoring of a mixed population in Estonia, we observed the abandonment of A. clanga breeding territories and the replacement of A. clanga pairs by A. pomarina, whereby on several occasions hybridization was an intermediate step before the disappearance of A. clanga. Although the total number of Estonian A. clanga × A. pomarina pairs was twice as high as that of A. clanga pairs, the number of pairs recorded yearly were approximately equal, which suggests a higher turnover rate in interbreeding pairs. This study shows that interspecific introgressive hybridization occurs rather frequently in a hybrid zone at least 1700‐km wide: it poses an additional threat for the vulnerable A. clanga, and may contribute to the extinction of its populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 725–736.     

A Genome-Wide Gene Function Prediction Resource for Drosophila melanogaster

Predicting gene functions by integrating large-scale biological data remains a challenge for systems biology. Here we present a resource for Drosophila melanogaster gene function predictions. We trained function-specific classifiers to optimize the influence of different biological datasets for each functional category. Our model predicted GO terms and KEGG pathway memberships for Drosophila melanogaster genes with high accuracy, as affirmed by cross-validation, supporting literature evidence, and large-scale RNAi screens. The resulting resource of prioritized associations between Drosophila genes and their potential functions offers a guide for experimental investigations.     

RELT induces cellular death in HEK 293 epithelial cells

RELT is a recently identified Tumor Necrosis Factor Receptor that possess two homologues in humans named RELL1 and RELL2. We investigated whether RELT and its homologues could induce cellular death when transiently transfected into HEK 293 epithelial cells. Transfection of RELT family members into HEK 293 epithelial cells induced cell death characterized by rounding and lifting of cells accompanied by DNA fragmentation, characteristics that are consistent with the activation of an apoptotic pathway. Overexpression of RELT in COS-7 cells resulted in cell rounding and lifting without DNA fragmentation, suggesting that the effects of RELT signaling may vary among different cell types. In summary, we report that overexpression of RELT or its homologues RELL1 and RELL2 in HEK 293 epithelial cells results in cell death with morphological characteristics consistent with the activation of an apoptotic pathway.     

Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers

It has been forecast that the challenge of meeting increased food demand and protecting environmental quality will be won or lost in maize, rice and wheat cropping systems, and that the problem of environmental nitrogen enrichment is most likely to be solved by substituting synthetic nitrogen fertilizers by the creation of cereal crops that are able to fix nitrogen symbiotically as legumes do. In legumes, rhizobia present intracellularly in membrane-bound vesicular compartments in the cytoplasm of nodule cells fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound vesicular compartments, rhizobia are supplied with energy derived from plant photosynthates and in return supply the plant with biologically fixed nitrogen, usually as ammonia. This minimizes or eliminates the need for inputs of synthetic nitrogen fertilizers. Recently we have demonstrated, using novel inoculation conditions with very low numbers of bacteria, that cells of root meristems of maize, rice, wheat and other major non-legume crops, such as oilseed rape and tomato, can be intracellularly colonized by the non-rhizobial, non-nodulating, nitrogen fixing bacterium, Gluconacetobacter diazotrophicus that naturally occurs in sugarcane. G. diazotrophicus expressing nitrogen fixing (nifH) genes is present in symbiosome-like compartments in the cytoplasm of cells of the root meristems of the target cereals and non-legume crop species, somewhat similar to the intracellular symbiosome colonization of legume nodule cells by rhizobia. To obtain an indication of the likelihood of adequate growth and yield, of maize for example, with reduced inputs of synthetic nitrogen fertilizers, we are currently determining the extent to which nitrogen fixation, as assessed using various methods, is correlated with the extent of systemic intracellular colonization by G. diazotrophicus, with minimal or zero inputs.     

Genotyping of pantophysin I (Pan I) of Atlantic cod (Gadus morhua L.) by allele‐specific PCR

The two main allelic variants of the Atlantic cod (Gadus morhua L.) pantophysin I (Pan I) locus have different frequencies within different cod stocks. The Dra I polymorphism which distinguishes the two alleles can thus be used for discrimination of coastal and offshore cod populations. We present a new method for Pan I genotyping using fluorescent allele‐specific duplex polymerase chain reaction (PCR). This method is more rapid, reliable and cost‐effective than the previously published method and it is not affected by DNA source and quality. This improvement is important for studies demanding high throughput and accuracy of Pan I genotyping