Sustained Photosynthetic Performance of Coffea spp. under Long-Term Enhanced [CO2]

Coffee is one of the world’s most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but these studies have not anticipated possible mitigating effects of the elevated atmospheric [CO₂] because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m^-2 s^-1), RH (75%) and 380 or 700 μL CO₂ L^-1 for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high [CO₂] treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth [CO₂], the net rate of CO₂ assimilation increased (34-49%) when measured at 700 than at 380 μL CO₂ L^-1. This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory) components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated [CO₂], although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to [CO₂] supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated [CO₂] were observed. Overall, as no apparent sign of photosynthetic down-regulation was found, our data suggest that Coffea spp. plants may successfully cope with high [CO₂] under the present experimental conditions.     

A 3D-Video-Based Computerized Analysis of Social and Sexual Interactions in Rats

A large number of studies have analyzed social and sexual interactions between rodents in relation to neural activity. Computerized video analysis has been successfully used to detect numerous behaviors quickly and objectively; however, to date only 2D video recording has been used, which cannot determine the 3D locations of animals and encounters difficulties in tracking animals when they are overlapping, e.g., when mounting. To overcome these limitations, we developed a novel 3D video analysis system for examining social and sexual interactions in rats. A 3D image was reconstructed by integrating images captured by multiple depth cameras at different viewpoints. The 3D positions of body parts of the rats were then estimated by fitting skeleton models of the rats to the 3D images using a physics-based fitting algorithm, and various behaviors were recognized based on the spatio-temporal patterns of the 3D movements of the body parts. Comparisons between the data collected by the 3D system and those by visual inspection indicated that this system could precisely estimate the 3D positions of body parts for 2 rats during social and sexual interactions with few manual interventions, and could compute the traces of the 2 animals even during mounting. We then analyzed the effects of AM-251 (a cannabinoid CB1 receptor antagonist) on male rat sexual behavior, and found that AM-251 decreased movements and trunk height before sexual behavior, but increased the duration of head-head contact during sexual behavior. These results demonstrate that the use of this 3D system in behavioral studies could open the door to new approaches for investigating the neuroscience of social and sexual behavior.     

Thrombin inhibitors built on an azaphenylalanine scaffold

A series of azaphenylalanine derivatives were investigated as novel thrombin inhibitors based on the prodrug principle. By systematic structural modifications we have identified optimal groups for this series that led us to potent inhibitors of thrombin incorporating the benzamidine fragment at the P1 position, and their potentially orally active benzamidoxime prodrugs. The binding modes in the thrombin active site of two representative compounds were identified by X-ray crystallographic analysis.     

Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy

Araújo, T.H., Faria, F.P., Katchburian, E. and Freymüller, E. (2009). Ultrastructural changes in skeletal muscle of the tail of the lizard Hemidactylus mabouia immediately following autotomy. —Acta Zoologica (Stockholm) 91 : 440–446. Although autotomy and subsequent regeneration of lizard tails has been extensively studied, there is little information available on ultrastructural changes that occur to the muscle fibers at the site of severance. Thus, in the present study, we examine the ultrastructure of the musculature of the remaining tail stump of the lizard Hemidactylus mabouia immediately after autotomy. Our results show that exposed portions of the skeletal muscle fibers of the stump that are unprotected by connective tissue bulge to produce large mushroom‐like protrusions. These exposed portions show abnormal structure but suffer no leakage of cytoplasmic contents. Many small and large vesicular structures appeared between myofibrils in the interface at this disarranged region (distal) and the other portion of the fibers that remain unchanged (proximal). These vesicles coalesce, creating a gap that leads to the release of the mushroom‐like protrusion. So, our results showed that after the macroscopic act of autotomy the muscular fibers release part of the sarcoplasm as if a second and microscopic set of autotomic events takes place immediately following the macroscopic act of autotomy. Presumably these changes pave the way for the formation of a blastema and the beginning of regeneration.     

Novel 3'-phosphoadenosine-5'-phosphatases from extremely halotolerant Hortaea werneckii reveal insight into molecular determinants of salt tolerance of black yeasts

The 3'-phosphoadenosine-5'-phosphatase encoded by HAL2 gene, is a ubiquitous enzyme required for the removal of the cytotoxic 3'-phosphoadenosine-5'-phosphate produced during sulfur assimilation in eukaryotes. Salt toxicity in yeast and plants results from Hal2 inhibition by sodium or lithium ions. Two novel HAL2-like genes, HwHAL2A and HwHAL2B, have been cloned from saltern-inhabited extremely halotolerant black yeast Hortaea werneckii. Expression of both HwHAL2 isoforms was differentially inducible upon salt. When the HwHAL2 genes were transferred from such a halotolerant species into the salt sensitive Saccharomyces cerevisiae, the resulting organism can tolerate 1.8M NaCl or 0.8M LiCl, the highest reported salt concentrations at which S. cerevisiae can grow. With genetic and biochemical validation we demonstrated the critical HwHal2B sequence motif--the META sequence--common only to Dothideales fungi, with evident effect on the HwHal2B-dependent salt tolerance. These results may have significance for biosaline agriculture in coastal environments.     

Higher frequency of legitimate pollinators and fruit set of autotetraploid trees of Libidibia ferrea (Leguminosae) compared to diploids in a mixed tropical urban population

Journal of Plant Research - In mixed-ploidy populations, newly formed polyploids initially occur at low frequencies when compared to diploids. However, polyploidy may lead to morphological and...     

The dynamics of coexistence: habitat sharing versus segregation patterns among three sympatric montane vipers

Contact zones of closely related and ecologically similar species constitute rare opportunities to study the evolutionary consequences of past speciation processes. They represent natural laboratories in which strong competition could lead to the exclusion of one species, or the various species may switch into distinct ecological niches. Alternatively, if reproductive isolation has not yet been achieved, they may hybridize. We elucidate the degree of taxon integrity by comparing genetics and habitat use of three similar‐sized congeneric viper species, Vipera ammodytes, Vipera aspis, and Vipera berus, of Nadiza Valley in western Slovenia. No hybridization was detected for either mitochondrial or nuclear genomes. Similarly, external intermediacy by a single prestudy viper (probably V. ammodytes × V. aspis) indicates that hybridization occasionally occurs, but should be very rare. Populations of the three related viperids are partially allopatric in Nadiza Valley, but they also coexist in a narrow contact zone in the montane grassland along the south‐exposed slope of Mount Stol (1673 m a.s.l.). Here, the three species that occupy areas in or near patches of rocky microhabitats (e.g. stone piles, slides, and walls) live in syntopy. However, fine‐scale measurements of structural components show partial habitat segregation, in which V. berus becomes more dominant at elevations above 1400 m and occupies mostly the mountain ridge and north‐exposed slopes of Mount Stol, V. aspis occurs below 1300 m and is the only species to inhabit stoneless patches of grass and bushes around 1000 m and lower, and V. ammodytes occurs at all elevations up to 1500 m, but is restricted to a rocky microhabitat. We suggest that a high degree of microstructure divergence, slightly different environmental niches, and a generally favourable habitat for all three viper species, keep the pressure for mis‐mating and hybridization low, although mechanisms such as reduced hybrid inferiority and temporal mating segregation cannot yet be excluded.     

Type II restriction modification systems of Prevotella bryantii TC1-1 and Prevotella ruminicola 23 strains and their effect on the efficiency of DNA introduction via electroporation

The restriction endonucleases PbrTI and Pru2I, isoschizomers of Sau3AI and HaeIII, were partially purified and characterized from anaerobic rumen bacteria Prevotella bryantii TC1-1 and Prevotella ruminicola 23, respectively. These are the first type II restriction endonucleases discovered in strains of the genus Prevotella, and they represent one of the barriers hindering gene transfer in these microorganisms. Heterologous DNA was protected against the action of the PbrTI or Pru2I by incubation in a cell-free extract of the respective strain which contained 20 mM EDTA. This led to the development of a protocol enabling successful electrotransformation of the P. bryantii TC1-1 strain with a pRH3 Bacteroides--Escherichia coli shuttle vector containing up to 7-kb long DNA inserts. Plasmid DNA isolated from the transformed strain facilitated the transfer with further increased efficiency and made possible the introduction of ligation reaction products directly to P. bryantii TC1-1 without passing them first through E. coli.     

Color Vision in <Emphasis Type="Italic">Leontopithecus chrysomelas</Emphasis>: A Behavioral Study

We assessed the color discriminations by golden-headed lion tamarins (Leontopithecus chrysomelas) via a series of tasks involving a behavioral paradigm that maximizes the naturalness of the stimuli. The stimuli were pairs of Munsell color chips used in earlier experiments with human dichromats. We tested 3 male and 3 female monkeys with stimuli of random brightness values in order to assure that discriminations were based on color rather than brightness cues. Results indicate that each male and one female presented random performances for stimuli resembling hue conditions under which tamarins forage: oranges vs. greens. Two females exhibited discriminations consistent with allelic trichromacy. Findings indicate the presence of an M/L cone opsin polymorphism, a condition of most platyrrhines that is characterized by dichromatic and/or trichromatic females and dichromatic males. Interspecific differences in allelic frequency among lion tamarins raises the possibility that habitat fragmentation is affecting heterozygous frequencies, a trend that could impact tamarin foraging efficiency.