The lizard Psammodromus algirus (Squamata: Lacertidae) is darker at high altitudes

Altitudinal gradients offer a good opportunity to study organisms' adaptations to clinal environmental variables. Regarding altitude, the most influential variables on organisms are temperature and ultraviolet (UV) solar radiation, the first decreasing and the second increasing with altitude. Both variables affect ectotherms' biology, as ectotherms depend on environmental temperature for thermoregulation, frequently being heliotherms. Here, we studied dorsal coloration in the lizard Psammodromus algirus (Linnaeus, 1758) along a wide altitudinal gradient (2200 m) in Sierra Nevada (south‐east Spain). We hypothesize that the skin will be darker with altitude, i.e. in environments with lower temperatures and higher UV radiation intensity. Results show that individual dorsal colorations became darker at high altitude. We propose two non‐mutually exclusive explanations for this result: (1) darker dorsal surface would favour faster warming at high altitudes, where temperature is lower, and (2) darker dorsal surface would protect against UV radiation, stronger at high altitudes. We found significant relationships between both temperature and UV radiation and population dorsal darkness, giving mixed support for the two explanations. Moreover, dorsal hue was positively correlated with substrate hue, suggesting that hue evolved to maximize crypsis. Our study therefore suggests that geographical variation in dorsal coloration in this lizard is adaptive, and darkness coloration might have evolved in response to adverse conditions (low temperature and high UV radiation) at high altitudes. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 132–141.     

Possible nonconductive role of Geobacter sulfurreducens pilus nanowires in biofilm formation

Geobacter sulfurreducens required expression of electrically conductive pili to form biofilms on Fe(III) oxide surfaces, but pili were also essential for biofilm development on plain glass when fumarate was the sole electron acceptor. Furthermore, pili were needed for cell aggregation in agglutination studies. These results suggest that the pili of G. sulfurreducens also have a structural role in biofilm formation.     

Noctiluca scintillans may act as a vector of toxigenic microalgae

Noctiluca scintillans food vacuoles containing toxigenic microalgae of the genera Dinophysis and Pseudo-nitzschia are reported in samples from the Galician Rías Baixas (NW Spain). N. scintillans may play an important role in the population dynamics of toxigenic microalgae blooms, and may act as a vector of phycotoxins to higher trophic levels. The harmful effects of Noctiluca in natural shellfish beds and/or aquaculture sites may be magnified if cells are loaded with toxigenic microalgal prey.     

Sperm Storage in the Yellow Dung Fly Scathophaga stercoraria: Identifying the Sperm of Competing Males in Separate Female Spermathecae

We examined the effects of male and female behaviour and morphology on the process of sperm storage in the yellow dung fly Scathophaga (Scatophaga) stercoraria. The larger of two males was more successful in transferring sperm to females' spermathecae the greater the difference in weight to his smaller competitor, as expected from previous studies by other authors. Sperm length, which is not correlated to body size, affected sperm access to the spermathecae, the female storage organs; longer sperm were more likely to be found in the spermathecae. A female typically had a singlet spermatheca and two spermathecae arranged as a pair, a doublet. However, there was variation from this pattern, which influenced the pattern of sperm storage. We measured the proportion of sperm from two competing males in females' singlet and doublet spermathecae. When the larger male's sperm were longer than his competitor's, they were more often in a female's singlet when he was her first mate and equally likely to be in the singlet or doublet when he was her second mate. When the larger male's sperm were shorter than his competitor's, the pattern was more complicated, principally because his sperm were not as successful at entering the female's doublet when he was her second mate. Counts of sperm, made using the same experimental procedure, showed that these effects were due to greater numbers of sperm entering the females' doublets when the larger male mated second. Sperm length was thus the factor with the largest single influence on the pattern of sperm storage. However, our most important result is that it was the interactions between male and female characters that were significant. Males mostly determine the early, especially precopulatory, events and females strongly influence the later ones.     

Cytotoxic T lymphocyte lysis of HTLV-1 infected cells is limited by weak HBZ protein expression,but non-specifically enhanced on induction of Tax expression

Background

Immunogenetic evidence indicates that cytotoxic T lymphocytes (CTLs) specific for the weak CTL antigen HBZ limit HTLV-1 proviral load in vivo, whereas there is no clear relationship between the proviral load and the frequency of CTLs specific for the immunodominant antigen Tax. In vivo, circulating HTLV-1-infected cells express HBZ mRNA in contrast, Tax expression is typically low or undetectable. To elucidate the virus-suppressing potential of CTLs targeting HBZ, we compared the ability of HBZ- and Tax-specific CTLs to lyse naturally-infected cells, by co-incubating HBZ- and Tax-specific CTL clones with primary CD4⁺ T cells from HLA-matched HTLV-1-infected donors. We quantified lysis of infected cells, and tested whether specific virus-induced host cell surface molecules determine the susceptibility of infected cells to CTL-mediated lysis.

Results

Primary infected cells upregulated HLA-A*02, ICAM-1, Fas and TRAIL-R1/2 in concert with Tax expression, forming efficient targets for both HTLV-1-specific CTLs and CTLs specific for an unrelated virus. We detected expression of HBZ mRNA (spliced isoform) in both Tax-expressing and non-expressing infected cells, and the HBZ_26–34 epitope was processed and presented by cells transfected with an HBZ expression plasmid. However, when coincubated with primary cells, a high-avidity HBZ-specific CTL clone killed significantly fewer infected cells than were killed by a Tax-specific CTL clone. Finally, incubation with Tax- or HBZ-specific CTLs resulted in a significant decrease in the frequency of cells expressing high levels of HLA-A*02.

Conclusions

HTLV-1 gene expression in primary CD4⁺ T cells non-specifically increases susceptibility to CTL lysis. Despite the presence of HBZ spliced-isoform mRNA, HBZ epitope presentation by primary cells is significantly less efficient than that of Tax.

     

Alleviation of water and osmotic stress-induced changes in nitrogen metabolizing enzymes in <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. cultivars by potassium

Present communication reports laboratory and pot experiments conducted to study the influence of water and osmotic stress on nitrogen uptake and metabolism in two wheat (Triticum aestivum L) cultivars with and without potassium supplementation. Polyethylene glycol 6000-induced osmotic stress/restricted irrigation caused a considerable decline in the activity of nitrate reductase, glutamate synthase, alanine and aspartate aminotransferases, and glutamate dehydrogenase. Potassium considerably improved nitrogen metabolism under normal water supply conditions and also resulted in amelioration of the negative impact of water and osmotic stresses indicating that potassium supplementation can be used as a potential tool for enhancing the nitrogen use efficiency in wheat for exploiting its genetic potential.     

HLA Genes in Mayos Population from Northeast Mexico

HLA class I and class II alleles have been studied in 60 unrelated people belonging to Mayos ethnic group, which lives in the Mexican Pacific Sinaloa State. Mayos HLA profile was compared to other Amerindians and worldwide populations’ profile. A total of 14,896 chromosomes were used for comparisons. Genetic distances between populations, Neigbour-Joining dendrograms and correspondence analyses were performed to determine the genetic relationship among population. The new specific Mayo HLA haplotypes found are: HLA-A*02-B*35-DRB1*1406-DQB1*0301; HLA-A*02-B*48-DRB1*0404-DQB1*0302; HLA-A*24-B*51-DRB1*0407-DQB1*0302 and HLA-A*02-B*08-DRB1*0407-DQB1*0302. However, the typical Meso American HLADRB1*0407 represents a 40% of all DRB1 alleles. While common HLA characteristics are found in Amerindian distant ethnic groups, still new group specific HLA haplotypes are being found, suggesting that a common founder effect (i.e. high DRB1*0407) is noticed. Moreover, new HLA haplotypes are almost certainly appearing along time probably due to specific pathogen (?) selection for diversity. Mayo language is close to the Tarahumara one (another geographically close group); notwithstanding both groups are not genetically close according to our results, showing again the different evolution of genes and languages, which do not correlate. Finally, Sinaloa is one of the Mexican States in which more European genes are found. However, the results presented in this paper, where no European HLA genes are seen in Mayos, should have a bearing in establishing transplant programs and in HLA and disease studies.Key Words: Amerindians, HLA, mayos, mexica, nahua, transplant.