Assessing genetic diversity in clonal organisms: low diversity or low resolution? Combining power and cost efficiency in selecting markers

The increasing use of molecular tools to study populations of clonal organisms leads us to question whether the low polymorphism found in many studies reflects limited genetic diversity in populations or the limitations of the markers used. Here we used microsatellite datasets for two sea grass species to provide a combinatory statistic, combined with a likelihood approach to estimate the probability of identical multilocus genotypes (MLGs) to be shared by distinct individuals, in order to ascertain the efficiency of the markers used and to optimize cost-efficiently the choice of markers to use for deriving unbiased estimates of genetic diversity. These results strongly indicate that conclusions from studies on clonal organisms derived using markers showing low polymorphism, including microsatellites, should be reassessed using appropriate polymorphic markers.     

Craniosynostosis and low middle frequency perceptive deafness in mother and son. A distinct entity?

A distinct entity?: In this report we describe the hitherto unreported association of low and middle frequency perceptive deafness and craniosynostosis in mother and son. The occurrence of hearing loss in the craniosynostosis syndromes is briefly reviewed.     

Breeding success and population trends in Adélie penguins in areas with low and high levels of human disturbance

The breeding performance and population trends of Adélie penguins (Pygoscelis adeliae) was studied at Esperanza/Hope Bay, Antarctic Peninsula, by comparing an area with low levels of human disturbance (LLD) and an area with high levels of human disturbance (HLD), close to an Argentine research station. From 1995/1996 to 2004/2005 (except for 1999/2000 and 2003/2004), the following population parameters were measured in both areas: (1) the number of breeding pairs, (2) the number of chicks in creches and (3) the number of chicks produced by breeding pairs. Counts were made for 26 breeding groups situated in the LLD area and 63 breeding groups located in the HLD area. The number of chicks per breeding pair was obtaobtained by following 100 marked nests in each area. All parameters were measured as described in the CCAMLR Monitoring Program protocols. The magnitude and direction (increasing or decreasing) of the changes in breeding population size and the number of chicks creched were similar in both areas. Overall, the number of breeding pairs decreased from 4,744 to 2,968 (37.4%) in the LLD area, and from 8,744 to 5,378 (38.6%) in the HLD area. The number of chicks fledged increased from 3,808 to 4,065 (6.7%) in the LLD area, and decreased from 6,991 to 6,712 (4%) in the HLD area. Breeding success (chicks fledged per marked nest) did not differ significantly between areas for most of the seasons compared. In 1996/1997, breeding success was significantly higher in the HLD area. Our data suggest that environmental influences currently exert greater effects than human disturbance on the penguin population at Esperanza Bay.     

Numbats and aardwolves—how low is low? A re-affirmation of the need for statistical rigour in evaluating regression predictions

Many comparative physiological studies aim to determine if a particular species differs from a prediction based on a linear allometric regression for other species. However, the judgment as to whether the species in question conforms to this allometric relationship is often not based on any formal statistical analysis. An appropriate statistical method is to compare the new species’ value with the 95% confidence limits for predicting an additional datum from the relationship for the other species. We examine the basal metabolic rate (BMR) of the termitivorous numbat (Myrmecobius fasciatus) and aardwolf (Proteles cristatus) to demonstrate the use of the 95% prediction limits to determine statistically if they have a lower-than-expected BMR compared to related species. The numbat’s BMR was 83.6% of expected from mass, but fell inside the 95% prediction limits for a further datum; a BMR < 72.5% of predicted was required to fall below the one-tail 95% prediction limits. The aardwolf had a BMR that was only 74.2% of predicted from the allometric equation, but it also fell well within the 95% prediction limits; a BMR of only 41.8% of predicted was necessary to fall below the one-tail 95% prediction limits. We conclude that a formal statistical approach is essential, although it is difficult to demonstrate that a single species statistically differs from a regression relationship for other species.     

Fast-germinating low β-glucan mutants induced in barley with improved malting quality and yield

Summary Mutation breeding has been used to improve the speed of germination in the high-yielding spring barley variety Troubadour. Five mutants were selected which combined fast germination and good agronomic performance. Two of these mutants yielded significantly more than did Troubadour over eight environments, and showed a clear improvement in their malting quality through an increase in extract yield. The improvement in malting quality appeared to be due to a decrease in the -glucan content, which seemed to enhance the germination speed and thus the starch degradation. The improvement in grain yield is postulated to be due to a better early growth caused by the enhanced germination speed. All the described changes could theoretically be explained by a single mutation event in each of the mutant genotypes, affecting the quantity of -glucans present in the endosperm.     

Meta‐analysis and candidate gene mining of low‐phosphorus tolerance in maize

Plants with tolerance to low‐phosphorus(P) can grow better under low‐P conditions, and understanding of genetic mechanisms of low‐P tolerance can not only facilitate identifying relevant genes but also help to develop low‐P tolerant cultivars. QTL meta‐analysis was conducted after a comprehensive review of the reports on QTL mapping for low‐P tolerance‐related traits in maize. Meta‐analysis produced 23 consensus QTL(cQTL), 17 of which located in similar chromosome regions to those previously reported to influence root traits. Meanwhile, candidate gene mining yielded 215 genes, 22 of which located in the cQTL regions.These 22 genes are homologous to 14 functionally characterized genes that were found to participate in plant low‐P tolerance, including genes encoding miR399s, Pi transporters and purple acid phosphatases. Four cQTL loci(cQTL2‐1,cQTL5‐3, cQTL6‐2, and cQTL10‐2) may play important roles for low‐P tolerance because each contains more original QTL and has better consistency across previous reports.     

HIF-1α involvement in low temperature and anoxia survival by a freeze tolerant insect

Protein kinases are important signalling molecules critical for normal cell growth and development. CDK11^p58 is a p34^cdc2-related protein kinase, and plays an important role in normal cell cycle progression. In this study, we mainly characterized the protein expression of CDK11^p58 during postnatal development in mouse testes and examined the cellular localization of CDK11^p58 and cyclinD3, which was associated with CDK11^p58 in mammalian cells. Western blot analysis revealed that CDK11^p58 was present in the early stages of development. It gradually increased and reached a peak in adult testes. The protein expression of CDK11^p58 was further analysed by immunohistochemistry due to its developmentally regulated expression. The variable immunostaining patterns of CDK11^p58 were visualized during different developmental periods and, in adult mouse, different stages of seminiferous tubules. CDK11^p58 expression was detected in proliferating germ cells in the early stages of developing testes. In adult testes, the protein was expressed in pachytene primary spermatocytes from stage VII to XI of spermatogenesis and in postmeiotic spermatids in all stages at different levels. The colocalization of CDK11^p58 and cyclinD3 in the adult testeis was revealed by immunofluorescence analysis. (Mol Cell Biochem 270: 99–106, 2005)     

Over-expression of ζ glutathione S-transferase in transgenic rice enhances germination and growth at low temperature

To develop a rice cultivar that would be suitable for direct-seedingcultivation in cooler temperate regions, we generated transgenic rice plants inwhich a rice encoding a -class glutathioneS-transferase (GST) under the control of a maize ubiquitinpromoter. GSTs have been suggested to be responsible for tolerance to variousstresses such as cold, salt and drought by detoxification of xenobioticcompounds and reactive oxygen species. A total of 87 R₀ transgenicrice plants harboring a chimeric GST gene were generatedusing Agrobacterium mediated transformation. ThreeR₂ lines homozygous for the transgene were assayed for GST activityand had higher GST and glutathione peroxidase activities thannon-transformants.Seedlings of the transgenic lines demonstrated greatly enhanced germination andgrowth rates at low temperature grown under submergence. The GST transgeniclines should be useful for breeding rice cultivars suitable for direct-seedingcultivation in cooler temperate regions.     

The conservative low‐phosphorus niche in Proteaceae

Plant and Soil - Intercropping cereals with legumes may achieve high crop yields at reduced input levels. Several studies have indicated that intercropping increases phosphorus use efficiency but...     

The influence of low and elevated ambient temperatures on serum prolactin and growth hormone in heifers—A review

The results of these experiments demonstrate that serum prolactin concentrations in heifers are directly related to ambient temperature. Serum prolactin concentrations were greatest when animals were exposed to 32°C and smallest when exposed to 4.5°C. Injection of 10µg of thyrotropinreleasing hormone (TRH) caused serum prolactin to increase within 5 min after treatment, and serum concentrations were related to ambient temperature. Although serum growth hormone concentrations tended to be greater in heifers exposed to higher ambient temperatures, basal concentration were not significantly influenced by temperatures of 4.5°, 21° or 32°C.Presented at the Seventh International Biometeorological Congress, 18–23 August 1975, College Park, Maryland, USA. Journal Article 3053 of the Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma.     

Gene identification and functional characterization of a Δ12 fatty acid desaturase in Tetrahymena thermophila and its influence in homeoviscous adaptation to low temperature

Homeoviscous adaptation in poikilotherms is based in the regulation of the level of desaturation of fatty acids, variation in phospholipids head groups and sterol content in the membrane lipids, in order to maintain the membrane fluidity in response to changes in environmental temperature. Increased proportion of unsaturated fatty acids is thought to be the main response to low-temperature acclimation, which is mostly achieved by fatty acid desaturases. Genome analysis of the ciliate Tetrahymena thermophila and a gene knockout approach has allowed us to identify one Δ12 FAD and to study its activity in the original host and in a yeast heterologous expression system. The “PUFA index” -relative content of polyunsaturated fatty acids compared to the sum of saturated and monounsaturated fatty acid content- was ~57% lower at 15 °C and 35 °C in the Δ12 FAD gene knockout strain (KOΔ12) compared to WT strain. We characterized the role of T. thermophila Δ12 FAD on homeoviscous adaptation and analyzed its involvement in cellular growth, cold stress response, and membrane fluidity, as well as its expression pattern during temperature shifts. Although these alterations allowed normal growth in the KOΔ12 strain at 30 °C or higher temperatures, growth was impaired at temperatures of 20 °C or lower, where homeoviscous adaptation is impaired. These results stress the importance of Δ12 FAD in the regulation of cold adaptation processes, as well as the suitability of T. thermophila as a valuable model to investigate the regulation of membrane lipids and evolutionary conservation and divergence of the underlying mechanisms.     

Contrasting cellularity and fatty acid composition in fat depots from Alentejana and Barrosã bovine breeds fed high and low forage diets

During the finishing phase of bovines, large amounts of subcutaneous and visceral fats are deposited leading to production inefficiencies with major impact on meat quality. A better understanding of the cellularity features of the main fat depots could provide strategies for adipose tissue manipulation. This study assessed the effect of feeding diets with distinct forage to concentrate ratios on the cellularity of two fat depots of beef cattle and their implications on the fatty acid profile. Thus, two phylogenetically distant Portuguese bovine breeds, Alentejana and Barrosã, were selected. The results did not show differences in subcutaneous fat deposition nor in visceral fat depots partitioning. Plasma adipokines concentration failed to show a consistent relationship with fatness, as leptin remained constant in all experimental groups, whereas interleukin-6 was influenced by breed. Fat depot seems to determine the area and number of adipocytes, with larger adipocytes and a lower number of cells in subcutaneous fat than in mesenteric fat. Neither breed nor diet influenced adipocytes area and number. The contents of total fatty acids, partial sums of fatty acids and conjugated linoleic acid isomeric profile were affected by breed and fat depot. The incorporation of saturated fatty acids (SFA), trans fatty acids, polyunsaturated fatty acids (PUFA) and branched chain fatty acids (BCFA) was higher in mesenteric fat depot, whereas subcutaneous fat depot had greater percentages of monounsaturated fatty acids (MUFA). In addition, SFA and MUFA proportions seem to be breed-related. In spite of the less relevant role of diet, the percentages of PUFA and BCFA were influenced by this factor. Under these experimental conditions, the effect of fat depot on cellularity and fatty acid composition prevails over breed or diet, as reinforced by the principal component analysis.     

Increase in CD14+HLA-DR−/low myeloid-derived suppressor cells in hepatocellular carcinoma patients and its impact on prognosis

Myeloid-derived suppressor cells (MDSCs) are known as key immune regulators in various human malignancies, and it is reported that CD14⁺HLA-DR^?/low MDSCs are increased in hepatocellular carcinoma (HCC) patients. However, the host factors that regulate the frequency and the effect on the prognosis of HCC patients are still unclear. We investigated these issues and clarified the relationships between a feature of MDSCs and host factors in HCC patients. We examined the frequency of MDSCs in 123 HCC patients, 30 chronic liver disease patients without HCC, and 13 healthy controls by flow cytometric analysis. The relationships between the clinical features and the frequency of MDSCs were analyzed. In 33 patients who received curative radiofrequency ablation (RFA) therapy, we examined the impact of MDSCs on HCC recurrence. The frequency of MDSCs in HCC patients was significantly increased. It was correlated with tumor progression, but not with the degree of liver fibrosis and inflammation. In terms of serum cytokines, the concentrations of IL-10, IL-13, and vascular endothelial growth factor were significantly correlated with the frequency of MDSCs. In HCC patients who received curative RFA therapy, the frequency of MDSCs after treatment showed various changes and was inversely correlated with recurrence-free survival time. The frequency of MDSCs is correlated with tumor progression, and this frequency after RFA is inversely correlated with the prognosis of HCC patients. Patients with a high frequency of MDSCs after RFA should be closely followed and the inhibition of MDSCs may improve the prognosis of patients.     

Independent localization of MAP2, CaMKIIα and β-actin RNAs in low copy numbers

Messenger RNA localization involves the assembly of ribonucleoprotein particles (RNPs) and their subsequent transport along the cytoskeleton to their final destination. Here, we provide new evidence that microtubule-associated protein 2 (MAP2), calcium/calmodulin-dependent protein kinase II (CaMKIIα) and β-actin RNAs localize to dendrites in distinct RNPs, which contain--unexpectedly--very few RNA molecules. The number of MAP2 molecules per particle is affected by synaptic activity and Staufen 2, indicating that RNP composition is tightly controlled. Our data suggest that the independent localization of individual RNAs in low copy numbers could contribute to tighter temporal and spatial control of expression in neurons and synapse-specific plasticity.     

Ammonium formation and assimilation in P(SARK)∷IPT tobacco transgenic plants under low N

Wild Type (WT) and transgenic tobacco plants expressing isopentenyltransferase (IPT), a gene encoding the enzyme regulating the rate-limiting step in cytokinins (CKs) synthesis, were grown under limited nitrogen (N) conditions. We analyzed nitrogen forms, nitrogen metabolism related-enzymes, amino acids and photorespiration related-enzymes in WT and P_SARK∷IPT tobacco plants. Our results indicate that the WT plants subjected to N deficiency displayed reduced nitrate (NO₃⁻) assimilation. However, an increase in the production of ammonium (NH₄⁺), by the degradation of proteins and photorespiration led to an increase in the glutamine synthetase/glutamate synthase (GS/GOGAT) cycle in WT plants. In these plants, the amounts of amino acids decreased with N deficiency, although the relative amounts of glutamate and glutamine increased with N deficiency. Although the transgenic plants expressing P_SARK∷IPT and growing under suboptimal N conditions displayed a significant decline in the N forms in the leaf, they maintained the GS/GOGAT cycle at control levels. Our results suggest that, under N deficiency, CKs prevented the generation and assimilation of NH₄⁺ by increasing such processes as photorespiration, protein degradation, the GS/GOGAT cycle, and the formation of glutamine.