The plant heat stress transcription factor (Hsf) family: structure, function and evolution

Ten years after the first overview of a complete plant Hsf family was presented for Arabidopsis thaliana by Nover et al. [1], we compiled data for 252 Hsfs from nine plant species (five eudicots and four monocots) with complete or almost complete genome sequences. The new data set provides interesting insights into phylogenetic relationships within the Hsf family in plants and allows the refinement of their classification into distinct groups. Numerous publications over the last decade document the diversification and functional interaction of Hsfs as well as their integration into the complex stress signaling and response networks of plants. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress.     

Subcellular expression pattern and role of IL-15 in pneumococci induced lung epithelial apoptosis

Streptococcus pneumoniae is the leading causative agent of community-acquired pneumonia. Induction of apoptosis in pulmonary epithelial cells by bacteria during pneumonia might be harmful to the host. Interleukin-15 (IL-15) has been demonstrated as an effective inhibitor of apoptosis and is expressed in lung epithelium on the mRNA and protein level. Therefore, we characterized the sub-cellular expression pattern of the short and long IL-15 isoforms in lung epithelial cells in vitro as well as its role in pneumococci-related lung epithelial cell apoptosis. We found an expression pattern for both IL-15 signal peptides in the pulmonary epithelial cell lines A549 and Beas-2B. Moreover, a strong co-localization of IL-15 and IL-15Ralpha was detected on cell surfaces. Compared to pro-inflammatory cytokine stimulation, neither IL-15 nor its trimeric receptor complex was up-regulated after pneumococcal infection. However, overexpression of IL-15 isoforms revealed IL-15LSP and IL-15Vkl as inhibitors of pneumococci induced apoptosis in pulmonary epithelial cells. Thus, IL-15 may act as an anti-apoptotic molecule in pneumococci infection, thereby suggesting IL-15 as a benefical cytokine in pulmonary host defense against infection.     

Symposium review: biology,ecology and life history of bluefish

Reviews in Fish Biology and Fisheries -     

Chronic intermittent hypoxia increases sympathetic responsiveness to hypoxia and hypercapnia

We sought to determine whether chronic exposure tointermittent hypoxia (CIH) increases sympathetic responsiveness tosubsequent chemoreflex stimulation. Sprague-Dawley rats were exposed to30 days of CIH: exposure chamber%O₂ [fractionalconcentration of chamber O₂(Fc_O2)]nadir 6.5-7% with return to 21% each minute for 8 h/day duringthe diurnal sleep period (Exp group). Sham controls (SC group) weresimilarly handled but kept at 21%Fc_O2 andcompared with unhandled controls (UC group). Rats were then anesthetized with urethan, and preganglionic cervical sympathetic activity (CSA), diaphragm electromyogram, arterial pressure, and electrocardiogram were recorded while the rats were spontaneously breathing 100% O₂, room air, 10%O₂, 12%CO₂, and 10%O₂-12%CO₂. CSA and heart rate were alsorecorded during phenylephrine infusion to assess baroreceptor function.Mean arterial pressure was significantly greater in Exp than in SC andUC rats during all conditions (P < 0.05). A vasopressor response to 10%O₂-12%CO₂ was observed only in Exp rats.CSA was greater in Exp than in SC and UC rats during 10%O₂, 12%CO₂, and 10%O₂-12%CO₂ but not during room-air exposure. A significant increase in CSA compared with room air wasnoted during 10% O₂, 12%CO₂, and 10%O₂-12%CO₂ in Exp but not in SC or UCrats. No differences in baroreceptor function were observed amonggroups. We conclude that CIH leads to increased sympatheticresponsiveness to chemoreflex stimulation.

     

Plants and Animals as Concept Generators for the Development of Biomimetic Cable Entry Systems

Many animals and plants have high potential to serve as concept generators for developing biomimetic materials and structures. We present some ideas based on structural and functional properties of plants and animals that led to the development of two types ofbiomimetic cable entry systems. Those systems have been realized on the level of functional demonstrators.     

The value of spatial experience and group size for ant colonies in direct competition

Animals often search for food more efficiently with experience. However, the contribution of experience to foraging success under direct competition has rarely been examined. Here we used colonies of an individually foraging desert ant to investigate the value of spatial experience. First, we trained worker groups of equal numbers to solve either a complex or a simple maze. We then tested pairs of both groups against one another in reaching a food reward. This task required solving the same complex maze that one of the groups had been trained in, to determine which group would exploit better the food reward. The worker groups previously trained in the complex mazes reached the food reward faster and more of these workers fed on the food than those trained in simple mazes, but only in the intermediate size group. To determine the relative importance of group size versus spatial experience in exploiting food patches, we then tested smaller trained worker groups against larger untrained ones. The larger groups outcompeted the smaller ones, despite the latter's advantage of spatial experience. The contribution of spatial experience, as found here, appears to be small, and depends on group size: an advantage of a few workers of the untrained group over the trained group negates its benefits.     

A covariotide model explains apparent phylogenetic structure of oxygenic photosynthetic lineages

The aims of the work were (1) to develop statistical tests to identify whether substitution takes place under a covariotide model in sequences used for phylogenetic inference and (2) to determine the influence of covariotide substitution on phylogenetic trees inferred for photosynthetic and other organisms. (Covariotide and covarion models are ones in which sites that are variable in some parts of the underlying tree are invariable in others and vice versa.) Two tests were developed. The first was a contingency test, and the second was an inequality test comparing the expected number of variable sites in two groups with the observed number. Application of these tests to 16S rDNA and tufA sequences from a range of nonphotosynthetic prokaryotes and oxygenic photosynthetic prokaryotes and eukaryotes suggests the occurrence of a covariotide mechanism. The degree of support for partitioning of taxa in reconstructed trees involving these organisms was determined in the presence or absence of sites showing particular substitution patterns. This analysis showed that the support for splits between (1) photosynthetic eukaryotes and prokaryotes and (2) photosynthetic and nonphotosynthetic organisms could be accounted for by patterns arising from covariotide substitution. We show that the additional problem of compositional bias in sequence data needs to be considered in the context of patterns of covariotide/covarion substitution. We argue that while covariotide or covarion substitution may give rise to phylogenetically informative patterns in sequence data, this may not always be so.