Stand dynamics modulate water cycling and mortality risk in droughted tropical forest

Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long‐term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought‐related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality.     

Preconditioning of Caenorhabditis elegans to anoxic insult by inactivation of cholinergic,GABAergic and muscle activity

For most metazoans, oxygen deprivation leads to cell dysfunction and if severe, death. Sublethal stress prior to a hypoxic or anoxic insult (“preconditioning”) can protect cells from subsequent oxygen deprivation. The molecular mechanisms by which sublethal stress can buffer against a subsequent toxic insult and the role of the nervous system in the response are not well understood. We studied the role of neuronal activity preconditioning to oxygen deprivation in Caenorhabditis elegans. Animals expressing the histamine gated chloride channels (HisCl1) in select cell populations were used to temporally and spatially inactivate the nervous system or tissue prior to an anoxic insult. We find that inactivation of the nervous system for 3 h prior to the insult confers resistance to a 48-h anoxic insult in 4th-stage larval animals. Experiments show that this resistance can be attributed to loss of activity in cholinergic and GABAergic neurons as well as in body wall muscles. These observations indicate that the nervous system activity can mediate the organism's response to anoxia.     

Trehalose-6-phosphate synthase as an intrinsic selection marker for plant transformation

Insertion of foreign DNA into plant genomes occurs randomly and with low frequency. Hence, a selectable marker is generally required to identify transgenic plants. Until now, all selection systems have been based on the use of non-plant genes, derived from microorganisms and usually conferring antibiotic or herbicide resistance. The use of microorganism-derived genes however has raised biosafety concerns. We have developed a novel selection system based on enhancing the expression of a plant-intrinsic gene and the use of a harmless selection agent. Selection takes advantage of the reduced glucose sensitivity of seedlings with enhanced expression of AtTPS1, a gene encoding trehalose-6-P synthase. As a result, transformants can be identified as developing green seedlings amongst the background of small, pale non-transformed plantlets on high glucose medium. In addition, vegetative regeneration of tobacco leaf explants is very sensitive to high external glucose. Overexpression of AtTPS1 in tobacco allows selecting glucose insensitive transgenic shoots.     

Gag cytotoxic T lymphocyte escape mutations can increase sensitivity of HIV-1 to human TRIM5alpha, linking intrinsic and acquired immunity

Although laboratory-adapted HIV-1 strains are largely resistant to the human restriction factor TRIM5α (hTRIM5α), we have recently shown that some viruses carrying capsid (CA) sequences from clinical isolates can be more sensitive to this restriction factor. In this study we evaluated the contribution to this phenotype of CA mutations known to be associated with escape from cytotoxic T lymphocyte (CTL) responses. Recombinant viruses carrying HIV-1 CA sequences from NL4-3 and three different clinical isolates were prepared, along with variants in which mutations associated with CTL resistance were modified by site-directed mutagenesis, and the infectivities of these viruses in target cells expressing hTRIM5α and cells in which TRIM5α activity had been inhibited by overexpression of TRIM5γ were compared. For both hTRIM5α-sensitive viruses studied, CTL-associated mutations were found to be responsible for this phenotype. Both CTL resistance mutations occurring within HLA-restricted CA epitopes and compensatory mutations occurring outside CTL epitopes influenced hTRIM5α sensitivity, and mutations associated with CTL resistance selected in prior hosts can contribute to this effect. The impact of CTL resistance mutations on hTRIM5α sensitivity was context dependent, because mutations shown to be responsible for the TRIM5α-sensitive phenotype in viruses from one patient could have little or no impact on this parameter when introduced into another virus. No fixed relationship between changes in hTRIM5α sensitivity and infectivity was discernible in our studies. Taken together, these findings suggest that CTL mutations may influence HIV-1 replication by modifying both viral infectivity and sensitivity to TRIM5α.     

Monophyly, divergence times, and evolution of host plant use inferred from a revised phylogeny of the Drosophila repleta species group

We present a revised molecular phylogeny of the Drosophila repleta group including 62 repleta group taxa and nine outgroup species based on four mitochondrial and six nuclear DNA sequence fragments. With ca. 100 species endemic to the New World, the repleta species group represents one of the major species radiations in the genus Drosophila. Most repleta group species are associated with cacti in arid or semiarid regions. Contrary to previous results, maximum likelihood and Bayesian phylogenies of the 10-gene dataset strongly support the monophyly of the repleta group. Several previously described subdivisions in the group were also recovered, despite poorly resolved relationships between these clades. Divergence time estimates suggested that the repleta group split from its sister group about 21millionyears ago (Mya), although diversification of the crown group began ca. 16Mya. Character mapping of patterns of host plant use showed that flat leaf Opuntia use is common throughout the phylogeny and that shifts in host use from Opuntia to the more chemically complex columnar cacti occurred several times independently during the history of this group. Although some species retained the use of Opuntia after acquiring the use of columnar cacti, there were multiple, phylogenetically independent instances of columnar cactus specialization with loss of Opuntia as a host. Concordant with our proposed timing of host use shifts, these dates are consistent with the suggested times when the Opuntioideae originated in South America. We discuss the generally accepted South American origin of the repleta group.     

Robotics of human movements

The construction of robotic systems that can move the way humans do, with respect to agility, stability and precision, is a necessary prerequisite for the successful integration of robotic systems in human environments. We explain human-centered views on robotics, based on the three basic ingredients (1) actuation; (2) sensing; and (3) control, and formulate detailed examples thereof.     

Fetal toxicity of valsartan and possible reversible adverse side effects

BACKGROUND: Published cases suggest that the use of angiotensin II receptor antagonists is fetotoxic during the third trimester, but not in early pregnancy. CASE: We report a case in which the adverse fetal effect of angiotensin II receptor antagonist treatment was reversed. A woman with chronic hypertension was treated with valsartan until gestation week (GW) 20, when a complete anhydramnios was observed. Six days after interruption of the treatment, amniotic fluid reappeared. It reached a normal level at GW 23.5. The plasmatic creatinine level and the renal ultrasound examination were within normal limits at the six-month follow-up. CONCLUSIONS: Whereas angiotensin-II-receptor antagonist generates a severe renal toxicity, this case suggests that, at least in the first half of pregnancy, these effects can be reversed.     

Genetic evidence of recent migration among isolated-by-sea populations of the freshwater blenny (<Emphasis Type="Italic">Salaria fluviatilis</Emphasis>)

Genetic diversity is the raw material for evolutionary change, so a species’ capacity to maintain its genetic diversity is a major concern in conservation genetics. Although genetic diversity within a population is reduced through time by genetic drift, gene flow among populations can act to recover or add new genetic variants. The goal of this study was to infer potential connectivity among isolated-by-sea populations of the vulnerable freshwater blenny (Salaria fluviatilis) and to determine if gene flow could contribute to maintaining genetic diversity in connected populations. Four genetic clusters (one small at the North, one large at the South for both East and West coasts) were detected with different clustering methods (FLOCK, STUCTURE, UPGMA, AMOVA). The two larger genetic clusters with higher migration-rate estimates among localities had higher genetic diversity and allelic richness and lower relatedness between individuals, compared to isolated localities found in smaller clusters. Our results also suggest that sea currents may facilitate fish movements among neighbouring rivers. Overall, gene flow among isolated-by-sea but close rivers could maintain the evolutionary potential of freshwater blenny populations. This finding should be considered when elaborating a conservation program for this species.