The role of low soil temperature in the inhibition of growth and PSII function during dark chilling in soybean genotypes of contrasting tolerance

Dark chilling affects growth and yield of warm-climate crops such as soybean [ Glycine max (L.) Merr.]. Several studies have investigated chilling-stress effects on photosynthesis and other aspects of metabolism, but none have compared effects of whole-plant chilling (WPC; shoots and roots) with that of aboveground chilling in legumes. This is important because low root temperatures might induce additional constraints, such as inhibition of N₂ fixation, thereby aggravating chilling-stress symptoms. Effects of dark chilling on PSII, shoot growth, leaf ureide content and photosynthetic capacity were studied in two soybean genotypes, Highveld Top (chilling tolerant) and PAN809 (chilling sensitive), in experiments comparing effects of WPC with that of shoot chilling (SC). Both treatments inhibited shoot growth in PAN809 but not Highveld Top. Also, WPC in PAN809 caused a decrease in leaf ureide content followed by severe chlorosis and alterations in O-J-I-P fluorescence-rise kinetics, distinct from SC. A noteworthy difference was the appearance of a ΔK peak in the O-J-I-P fluorescence rise in response to WPC. These genotypic and treatment differences also reflected in the degree of inhibition of CO₂ assimilation rates. The appearance of a ΔK peak, coupled with growth inhibition, reduced ureide content, chlorosis and lower CO₂ assimilation rates, provides mechanistic information about how WPC might have aggravated chilling-stress symptoms in PAN809. We introduce a model explaining how chilling soil temperatures might trigger N-limitation in sensitive genotypes and how characteristic changes in O-J-I-P fluorescence-rise kinetics are linked to changes in carbon and nitrogen metabolism.     

Dynamic expression of ancient and novel molluscan shell genes during ecological transitions

Background  

The Mollusca constitute one of the most morphologically and ecologically diverse metazoan phyla, occupying a wide range of marine, terrestrial and freshwater habitats. The evolutionary success of the molluscs can in part be attributed to the evolvability of the external shell. Typically, the shell first forms during embryonic and larval development, changing dramatically in shape, colour and mineralogical composition as development and maturation proceeds. Major developmental transitions in shell morphology often correlate with ecological transitions (e.g. from a planktonic to benthic existence at metamorphosis). While the genes involved in molluscan biomineralisation are beginning to be identified, there is little understanding of how these are developmentally regulated, or if the same genes are operational at different stages of the mollusc's life.     

Combinations of SNPs related to signal transduction in bipolar disorder

Any given single nucleotide polymorphism (SNP) in a genome may have little or no functional impact. A biologically significant effect may possibly emerge only when a number of key SNP-related genotypes occur together in a single organism. Thus, in analysis of many SNPs in association studies of complex diseases, it may be useful to look at combinations of genotypes. Genes related to signal transmission, e.g., ion channel genes, may be of interest in this respect in the context of bipolar disorder. In the present study, we analysed 803 SNPs in 55 genes related to aspects of signal transmission and calculated all combinations of three genotypes from the 3×803 SNP genotypes for 1355 controls and 607 patients with bipolar disorder. Four clusters of patient-specific combinations were identified. Permutation tests indicated that some of these combinations might be related to bipolar disorder. The WTCCC bipolar dataset were use for replication, 469 of the 803 SNP were present in the WTCCC dataset either directly (n = 132) or by imputation (n = 337) covering 51 of our selected genes. We found three clusters of patient-specific 3×SNP combinations in the WTCCC dataset. Different SNPs were involved in the clusters in the two datasets. The present analyses of the combinations of SNP genotypes support a role for both genetic heterogeneity and interactions in the genetic architecture of bipolar disorder.     

Modification of sialic acids by 9-O-acetylation is detected in human leucocytes using the lectin property of influenza C virus

Influenza C virus spike glycoprotein HEF specifically recognizesglycoconjugates containing 9-O-acetyl-N-acetylneuraminic acid.The same protein also contains an esterase activity. Takingadvantage of these two properties, influenza C virus was usedas a very sensitive probe for the detection of traces of 9-O-acetyl-N-acetylneuraminicacid in human leucocytes. The binding of influenza C virus toleucocyte glycoproteins and gangliosides separated by sodiumdodecyl sulphate–polyacrylamide gel electrophoresis andthin-layer chromatography, respectively, was assayed using achromogenic esterase substrate. In this way, glycoproteins ofB-lymphocytes and T-lymphocytes were found to contain 9-O-acetylatedsialic acids. Of the various 9-O-acetylated gangliosides detected,one had the characteristics of 9-O-acetylated G^D3. The identificationof 9-O-acetylated sialic acids on distinct glycoproteins andglycolipids should be helpful in assigning a physiological roleto this sugar. O-acetylation gangliosides influenza C virus lymphocytes sialic acids     

Interaction of nitric oxide with the oxygen evolving complex of photosystem II and manganese catalase: a comparative study

Thermus thermophilus catalase. Flash fluorescence studies indicate that the S₃ state of the OEC in the presence of ca. 0.6 mM NO is reduced to the S₁ with an apparent halftime of ca. 0.4 s at about 18 °C, compared with a biphasic decay, with approximate halftimes of 28 s for S₃ to S₂ and 140 s for S₂ to S₁ in the absence of NO. Under similar conditions the S₂ state is reduced by NO to the S₁ state with an approximate halftime of 2 s. These results extend a recent study indicating a slow reduction of the S₁ state at −30°C, via the S₀ and S₋₁ states, to a Mn(II)-Mn(III) state resembling the corresponding state in catalase. The reductive mode of action of NO is repeated with the di-Mn cluster of catalase: the Mn(III)-Mn(III) redox state is reduced to the Mn(II)-Mn(II) state via the intermediate Mn(II)-Mn(III) state. The kinetics of this reduction suggest a decreasing reduction potential with decreasing oxidation state, similar to what is observed with the active states of the OEC. What is unique about the OEC is the rapid interaction of NO with the S₃ state of the OEC, which is compatible with a metalloradical character of this state. Received: 16 June 1999 / Accepted: 28 February 2000     

Molecular species of oxidized phospholipids in brain differentiate between learning- and memory impaired and unimpaired aged rats

Amino Acids - Loss of cognitive function is a typical consequence of aging in humans and rodents. The extent of decline in spatial memory performance of rats, assessed by a hole-board test, reaches...     

A novel circulating tamiami mammarenavirus shows potential for zoonotic spillover

A detailed understanding of the mechanisms underlying the capacity of a virus to break the species barrier is crucial for pathogen surveillance and control. New World (NW) mammarenaviruses constitute a diverse group of rodent-borne pathogens that includes several causative agents of severe viral hemorrhagic fever in humans. The ability of the NW mammarenaviral attachment glycoprotein (GP) to utilize human transferrin receptor 1 (hTfR1) as a primary entry receptor plays a key role in dictating zoonotic potential. The recent isolation of Tacaribe and lymphocytic choriominingitis mammarenaviruses from host-seeking ticks provided evidence for the presence of mammarenaviruses in arthropods, which are established vectors for numerous other viral pathogens. Here, using next generation sequencing to search for other mammarenaviruses in ticks, we identified a novel replication-competent strain of the NW mammarenavirus Tamiami (TAMV-FL), which we found capable of utilizing hTfR1 to enter mammalian cells. During isolation through serial passaging in mammalian immunocompetent cells, the quasispecies of TAMV-FL acquired and enriched mutations leading to the amino acid changes N151K and D156N, within GP. Cell entry studies revealed that both substitutions, N151K and D156N, increased dependence of the virus on hTfR1 and binding to heparan sulfate proteoglycans. Moreover, we show that the substituted residues likely map to the sterically constrained trimeric axis of GP, and facilitate viral fusion at a lower pH, resulting in viral egress from later endosomal compartments. In summary, we identify and characterize a naturally occurring TAMV strain (TAMV-FL) within ticks that is able to utilize hTfR1. The TAMV-FL significantly diverged from previous TAMV isolates, demonstrating that TAMV quasispecies exhibit striking genetic plasticity that may facilitate zoonotic spillover and rapid adaptation to new hosts.     

A novel method for assessing the 3-D orientation accuracy of inertial/magnetic sensors

A novel method for assessing the accuracy of inertial/magnetic sensors is presented. The method, referred to as the “residual matrix” method, is advantageous because it decouples the sensor's error with respect to Earth's gravity vector (attitude residual error: pitch and roll) from the sensor's error with respect to magnetic north (heading residual error), while remaining insensitive to singularity problems when the second Euler rotation is close to ±90°. As a demonstration, the accuracy of an inertial/magnetic sensor mounted to a participant's forearm was evaluated during a reaching task in a laboratory. Sensor orientation was measured internally (by the inertial/magnetic sensor) and externally using an optoelectronic measurement system with a marker cluster rigidly attached to the sensor's enclosure. Roll, pitch and heading residuals were calculated using the proposed novel method, as well as using a common orientation assessment method where the residuals are defined as the difference between the Euler angles measured by the inertial sensor and those measured by the optoelectronic system. Using the proposed residual matrix method, the roll and pitch residuals remained less than 1° and, as expected, no statistically significant difference between these two measures of attitude accuracy was found; the heading residuals were significantly larger than the attitude residuals but remained below 2°. Using the direct Euler angle comparison method, the residuals were in general larger due to singularity issues, and the expected significant difference between inertial/magnetic sensor attitude and heading accuracy was not present.