Living in the city: can anyone become an ‘urban exploiter'?

Aim As urban landscapes expand, shifts in biodiversity are occurring. This is leading biogeographers and ecologists to consider human‐dominated landscapes in their current work. One question that arises is: what characterizes those species that are widespread in the most highly urban environments compared with those restricted to less urbanized areas in the city? Here, we aim to identify the traits that enable species to become urban exploiters, i.e. to dominate highly urbanized surroundings. Identifying these traits may help us better predict and possibly mitigate the biotic homogenization occurring in these areas. Location Israel in general, with special focus on the city of Jerusalem. Methods Combining literature and field‐based data for birds in Israel we compared phenotypic, behavioural and life‐history traits between urban exploiters and urban adapters. The latter occur in urban landscapes, but are characteristic of the less urbanized parts of the city. We then examined the trends along a finer field‐sampled gradient of increasing urbanization from sub‐natural to downtown areas within the city of Jerusalem. Results Urban exploiters and adapters differed primarily in social structure and migratory status: exploiters were significantly more social and sedentary than urban adapters. Clear trends were also seen for dietary preferences along a gradient of increasing urbanization in Jerusalem, such that, with increasing urbanization, the proportion of granivorous species increased whereas the proportion of species feeding on invertebrates declined. In contrast, neither relative brain size nor behavioural flexibility, as measured by feeding innovations, differed significantly among urban exploiters and adapters in Israel or along the urbanization gradient in Jerusalem specifically. Main conclusions The results of our study suggest that being successful in more vs. less urbanized environments in the city is not necessarily a factor of brain size nor of how flexible and behaviourally innovative the species is; rather, it depends on a combination of traits, including diet, degree of sociality, sedentariness and preferred nesting sites.     

Bidirectional communication system in katydids: the effect on chorus structure

Unlike most acoustic systems evolved for pair formation whereonly males signal, the katydidPhaneroptera nana has a bidirectional communication system where both males and females sing. Despiteextensive study on male chorusing behavior in different communicationsystems, this behavior has rarely been explored in duettingspecies. I examined how this bidirectional communication systemaffects the collective pattern of male signaling.P. nana malesalternate their songs, and in response to synthetic stimulidelay their calls, according to the phase of stimulation. Pairsof synthetic calls (simulating alternating males) presentedto females elicited equal female response, as long as the intercallinterval was 200 ms. Thus, male alternation is imposed by thefemale's responsiveness and may be interpreted as a "jammingavoidance reaction." Further evidence suggests that chorusstructure is not merely constrained by the female sensory temporalresolution, but rather is adaptively related to female choicein this species.     

Axoplasmic importins enable retrograde injury signaling in lesioned nerve

Axoplasmic proteins containing nuclear localization signals (NLS) signal retrogradely by an unknown mechanism in injured nerve. Here we demonstrate that the importin/karyopherin alpha and beta families underlie this process. We show that importins are found in axons at significant distances from the cell body and that importin beta protein is increased after nerve lesion by local translation of axonal mRNA. This leads to formation of a high-affinity NLS binding complex that traffics retrogradely with the motor protein dynein. Trituration of synthetic NLS peptide at the injury site of axotomized dorsal root ganglion (DRG) neurons delays their regenerative outgrowth, and NLS introduction to sciatic nerve concomitantly with a crush injury suppresses the conditioning lesion induced transition from arborizing to elongating growth in L4/L5 DRG neurons. These data suggest a model whereby lesion-induced upregulation of axonal importin beta may enable retrograde transport of signals that modulate the regeneration of injured neurons.     

An Arabidopsis thaliana gene for methylsalicylate biosynthesis, identified by a biochemical genomics approach, has a role in defense

Emission of methylsalicylate (MeSA), and occasionally of methylbenzoate (MeBA), from Arabidopsis thaliana leaves was detected following the application of some forms of both biotic and abiotic stresses to the plant. Maximal emission of MeSA was observed following alamethicin treatment of leaves. A gene (AtBSMT1) encoding a protein with both benzoic acid (BA) and salicylic acid (SA) carboxyl methyltransferase activities was identified using a biochemical genomics approach. Its ortholog (AlBSMT1) in A. lyrata, a close relative of A. thaliana, was also isolated. The AtBSMT1 protein utilizes SA more efficiently than BA, whereas AlBSMT1 catalyzes the methylation of SA less effectively than that of BA. The AtBSMT1 and AlBSMT1 genes showed expression in leaves under normal growth conditions and were more highly expressed in the flowers. In A. thaliana leaves, the expression of AtBSMT1 was induced by alamethicin, Plutella xylostella herbivory, uprooting, physical wounding, and methyl jasmonate. SA was not an effective inducer. Using a beta-glucuronidase (GUS) reporter approach, the promoter activity of AtBSMT1 was localized to the sepals of flowers, and also to leaf trichomes and hydathodes. Upon thrip damage to leaves, AtBSMT1 promoter activity was induced specifically around the lesions.     

A Novel Functional Human Eukaryotic Translation Initiation Factor 4G

Mammalian eukaryotic translation initiation factor 4F (eIF4F) is a cap-binding protein complex consisting of three subunits: eIF4E, eIF4A, and eIF4G. In yeast and plants, two related eIF4G species are encoded by two different genes. To date, however, only one functional eIF4G polypeptide, referred to here as eIF4GI, has been identified in mammals. Here we describe the discovery and functional characterization of a closely related homolog, referred to as eIF4GII. eIF4GI and eIF4GII share 46% identity at the amino acid level and possess an overall similarity of 56%. The homology is particularly high in certain regions of the central and carboxy portions, while the amino-terminal regions are more divergent. Far-Western analysis and coimmunoprecipitation experiments were used to demonstrate that eIF4GII directly interacts with eIF4E, eIF4A, and eIF3. eIF4GII, like eIF4GI, is also cleaved upon picornavirus infection. eIF4GII restores cap-dependent translation in a reticulocyte lysate which had been pretreated with rhinovirus 2A to cleave endogenous eIF4G. Finally, eIF4GII exists as a complex with eIF4E in HeLa cells, because eIF4GII and eIF4E can be purified together by cap affinity chromatography. Taken together, our findings indicate that eIF4GII is a functional homolog of eIF4GI. These results may have important implications for the understanding of the mechanism of shutoff of host protein synthesis following picornavirus infection.