A unigene catalogue of 5700 expressed genes in cassava

Two economically important characters, starch content and cassava bacterial blight resistance, were targeted to generate a large collection of cassava ESTs. Two libraries were constructed from cassava root tissues of varieties with high and low starch contents. Other libraries were constructed from plant tissues challenged by the pathogen Xanthomonas axonopodis pv.manihotis. We report here the single pass sequencing of 11 954 cDNA clones from the 5’ ends, including 111 from the 3’ ends. Cluster analysis permitted the identification of a unigene set of 5700 sequences. Sequence analyses permitted the assignment of a putative functional category for 37% of sequences whereas ~ 16% sequences did not show any significant similarity with other proteins present in the database and therefore can be considered as cassava specific genes. A group of genes belonging to a large multigene family was identified. We characterize a set of genes detected only in infected libraries putatively involved in the defense response to pathogen infection. By comparing two libraries obtained from cultivars contrasting in their starch content a group of genes associated to starch biosynthesis and differentially expressed was identified. This is the first large cassava EST resource developed today and publicly available thus making a significant contribution to genomic knowledge of cassava.     

Biotelemetry: a mechanistic approach to ecology

Remote measurement of the physiology, behaviour and energetic status of free-living animals is made possible by a variety of techniques that we refer to collectively as 'biotelemetry'. This set of tools ranges from transmitters that send their signals to receivers up to a few kilometers away to those that send data to orbiting satellites and, more frequently, to devices that log data. They enable researchers to document, for long uninterrupted periods, how undisturbed organisms interact with each other and their environment in real time. In spite of advances enabling the monitoring of many physiological and behavioural variables across a range of taxa of various sizes, these devices have yet to be embraced widely by the ecological community. Our review suggests that this technology has immense potential for research in basic and applied animal ecology. Efforts to incorporate biotelemetry into broader ecological research programs should yield novel information that has been challenging to collect historically from free-ranging animals in their natural environments. Examples of research that would benefit from biotelemetry include the assessment of animal responses to different anthropogenic perturbations and the development of life-time energy budgets.     

Developmental mechanism and evolutionary origin of vertebrate left/right asymmetries

The systematically 'handed', or directionally asymmetrical way in which the major viscera are packed within the vertebrate body is known as situs. Other less obvious vertebrate lateralisations concern cognitive neural function, and include the human phenomena of hand-use preference and language-associated cognitive partitioning. An overview, rather than an exhaustive scholarly review, is given of recent advances in molecular understanding of the mechanism that ensures normal development of 'correct' situs. While the asymmetry itself and its left/right direction are clearly vertebrate-conserved characters, data available from various embryo types are compared in order to assess the likelihood that the developmental mechanism is evolutionarily conserved in its entirety. A conserved post-gastrular 'phylotypic' stage, with left- and right-specific cascades of key, orthologous gene expressions, clearly exists. It now seems probable that earlier steps, in which symmetry-breaking information is reliably transduced to trigger these cascades on the correct sides, are also conserved at depth although it remains unclear exactly how these steps operate. Earlier data indicated that the initiation of symmetry-breaking had been transformed, among the different vertebrate classes, as drastically as has the anatomy of pre-gastrular development itself, but it now seems more likely that this apparent diversity is deceptive. Ideas concerning the functional advantages to the vertebrate lifestyle of a systematically asymmetrical visceral packing arrangement, while untestable, are accepted because they form a plausible adaptationist 'just-so' story. Nevertheless, two contrasting beliefs are possible about the evolutionary origins of situs. Major recent advances in analysis of its developmental mechanism are largely due not to zoologists, comparative anatomists or evolutionary systematists, but to molecular geneticists, and these workers have generally assumed that the asymmetry is an evolutionary novelty imposed on a true bilateral symmetry, at or close to the origin of the vertebrate clade. A major purpose of this review is to advocate an alternative view, on the grounds of comparative anatomy and molecular systematics together with the comparative study of expressions of orthologous genes in different forms. This view is that situs represents a co-optation of a pre-existing, evolutionarily ancient non-bilaterality of the adult form in a vertebrate ancestor. Viewed this way, vertebrate or chordate origins are best understood as the novel imposition of an adaptively bilateral locomotory-skeletal-neural system, around a retained non-symmetrical 'visceral' animal. One component of neuro-anatomical asymmetry, the habenular/parapineal one that originates in the diencephalon, has recently been found (in teleosts) to be initiated from the same 'phylotypic' gene cascade that controls situs development. But the function of this particular diencephalic asymmetry is currently unclear. Other left-right partitionings of brain function, including the much more recently evolved, cerebral cortically located one associated with human language and hand-use, may be controlled entirely separately from situs even though their directionality has a particular relation to it in a majority of individuals. Finally, possible relationships are discussed between the vertebrate directional asymmetries and those that occur sporadically among protostome bilaterian forms. These may have very different evolutionary and molecular bases, such that there may have been constraints, in protostome evolution, upon any exploitation of left and right for complex organismic, and particularly cognitive neural function.     

Protein trafficking in Plasmodium falciparum-infected red blood cells

Plasmodium falciparum inhabits a niche within the most highly terminally differentiated cell in the human body--the mature red blood cell. Life inside this normally quiescent cell offers the parasite protection from the host's immune system, but provides little in the way of cellular infrastructure. To survive and replicate in the red blood cell, the parasite exports proteins that interact with and dramatically modify the properties of the host red blood cell. As part of this process, the parasite appears to establish a system within the red blood cell cytosol that allows the correct trafficking of parasite proteins to their final cellular destinations. In this review, we examine recent developments in our understanding of the pathways and components involved in the delivery of important parasite-encoded proteins to their final destination in the host red blood cell. These complex processes are not only fundamental to the survival of malaria parasites in vivo, but are also major determinants of the unique pathogenicity of this parasite.     

Phosphoinositides: older than we first thought?

Despite nearly 50 years of study, it is good to see that phosphoinositides are still capable of springing the odd surprise. Signaling by the second messenger phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) was thought to be absent in yeast, but a recent paper now describes the presence of PtdIns(3,4,5)P(3) in Schizosaccharomyces pombe.     

Cell volume increase and extracellular Ca2+ are needed for hyposmotically induced prolactin release in tilapia

In thetilapia (Oreochromis mossambicus), as in many euryhalineteleost fish, prolactin (PRL) plays a central role in freshwater adaptation, acting on osmoregulatory surfaces to reduce ion and waterpermeability and increase solute retention. Consistent with theseactions, PRL release is stimulated as extracellular osmolality isreduced both in vivo and in vitro. In the current experiments, aperfusion system utilizing dispersed PRL cells was developed forpermitting the simultaneous measurement of cell volume and PRL release.Intracellular Ca²⁺ was monitored using fura 2-loaded cellsunder the same conditions. When PRL cells were exposed to hyposmoticmedium, an increase in PRL cell volume preceded the increase in PRLrelease. Cell volume increased in proportion to decreases of 15 and30% in osmolality. However, regulatory volume decrease was clearlyseen only after a 30% reduction. The hyposmotically induced PRLrelease was sharply reduced in Ca²⁺-deleted hyposmoticmedium, although cell volume changes were identical to those observedin normal hyposmotic medium. In most cells, a rise in intracellularCa²⁺ concentration ([Ca²⁺]_i)during hyposmotic stimulation was dependent on the availability ofextracellular Ca²⁺, although small transient increases in[Ca²⁺]_i were sometimes observed uponintroduction of Ca²⁺-deleted media of the same or reducedosmolality. These results indicate that an increase in cell size is acritical step in the transduction of an osmotic signal into PRL releaseand that the hyposmotically induced increase in PRL release is greatlydependent on extracellular Ca²⁺.

     

NOS inhibition accelerates atherogenesis: reversal by exercise

In this study, we assessed the effects of chronic exercise training (12 wk) on atherosclerotic lesion formation in hypercholesterolemic apolipoprotein E-deficient mice (n = 31). At the age of 9 wk, mice were assigned to the following groups: sedentary (Sed; n = 9); exercise (Ex; n = 12); sedentary and oral NG-nitro-L-arginine (L-NNA, Sed-NA; n = 4), or exercise and oral L-NNA (Ex-NA; n = 6). Chronic exercise training was performed on a treadmill for 12 wk (6 times/wk and twice for 1 h/day) at a final speed of 22 m/min, and an 8 degrees grade. L-NNA was discontinued 5 days before final treadmill testing. The farthest distance run to exhaustion was observed in Ex-NA mice (Sed: 306 +/- 32 m; Ex: 640 +/- 87; Sed-NA: 451 +/- 109 m; Ex-NA: 820 +/- 49 m; all P < 0.05). Lesion formation was assessed in the proximal ascending aorta by dissection microscopy after oil red O staining. The aortas of Sed-NA mice manifested a threefold increase in lesion formation compared with the other groups. This L-NNA-induced lesion formation was reduced by chronic exercise training (Sed, 786 +/- 144; Ex, 780 +/- 206; Sed-NA, 2,147 +/- 522; Ex-NA, 851 +/- 253; Sed-NA vs. all other groups: P < 0.001). In conclusion, treatment with oral L-NNA (an nitric oxide synthase antagonist) leads to accelerated atherogenesis in genetically determined hypercholesterolemic mice. This adverse effect can be overcome by chronic exercise training.     

Fitness reduction and potential extinction of wild populations of Atlantic salmon, Salmo salar, as a result of interactions with escaped farm salmon

The high level of escapes from Atlantic salmon farms, up to two million fishes per year in the North Atlantic, has raised concern about the potential impact on wild populations. We report on a two-generation experiment examining the estimated lifetime successes, relative to wild natives, of farm, F(1) and F(2) hybrids and BC(1) backcrosses to wild and farm salmon. Offspring of farm and "hybrids" (i.e. all F(1), F(2) and BC(1) groups) showed reduced survival compared with wild salmon but grew faster as juveniles and displaced wild parr, which as a group were significantly smaller. Where suitable habitat for these emigrant parr is absent, this competition would result in reduced wild smolt production. In the experimental conditions, where emigrants survived downstream, the relative estimated lifetime success ranged from 2% (farm) to 89% (BC(1) wild) of that of wild salmon, indicating additive genetic variation for survival. Wild salmon primarily returned to fresh water after one sea winter (1SW) but farm and 'hybrids' produced proportionately more 2SW salmon. However, lower overall survival means that this would result in reduced recruitment despite increased 2SW fecundity. We thus demonstrate that interaction of farm with wild salmon results in lowered fitness, with repeated escapes causing cumulative fitness depression and potentially an extinction vortex in vulnerable populations.