Vertebrate DNA transposon as a natural mutator: the medaka fish Tol2 element contributes to genetic variation without recognizable traces

DNA-based transposable elements, or DNA transposons, transpose in a cut-and-paste fashion, involving excision from the chromosome. If this process affects the function of a host gene and the excision rate is high, any gene associated with such an element would clearly be in a genetically "unstable" state, and there are many examples of unstable genes in various organisms. However, none have hitherto been reported in vertebrates. We here document the finding of an unstable mutant gene in the medaka fish, Oryzias latipes, a useful model animal for vertebrate genetics and evolutionary studies. In an inbred strain, excision of the Tol2 element inserted in a pigmentation gene occurs spontaneously, giving rise to different heritable phenotypes and new mutant genes that carry different excision footprint sequences. The phenotypic mutation rate is as high as 2% per gamete, representing a 1000-fold increase from spontaneous mutation rates so far determined with the same organism. With mutations caused by insertion, and then excision, of transposons, one can no longer recognize participation of transposons in their generation. Thus, the impact of DNA transposons on vertebrate genomes may be, and may have been, larger than commonly supposed.     

Effect of pedal rate on diurnal variations in cardiorespiratory variables

Recently, it was observed that the freely chosen pedal rate of elite cyclists was significantly lower at 06:00 than at 18:00 h, and that ankle kinematics during cycling exhibits diurnal variation. The modification of the pedaling technique and pedal rate observed throughout the day could be brought about to limit the effect of diurnal variation on physiological variables. Imposing a pedal rate should limit the subject's possibility of adaptation and clarify the influence of time of day on physiological variables. The purpose of this study was to determine whether diurnal variation in cardiorespiratory variables depends on pedal rate. Ten male cyclists performed a submaximal 15 min exercise on a cycle ergometer (50% W_max). Five test sessions were performed at 06:00, 10:00, 14:00, 18:00, and 22:00 h. The exercise bout was divided into three equivalent 5 min periods during which different pedal rates were imposed (70 rev · min^-1, 90 rev · min^-1 and 120 rev · min^-1). No significant diurnal variation was observed in heart rate and oxygen consumption, whatever the pedal rate. A significant diurnal variation was observed in minute ventilation (p=0.01). In addition, the amplitude of the diurnal variation in minute ventilation depended on pedal rate: the higher the pedal rate, the greater the amplitude of its diurnal variation (p=0.03). The increase of minute ventilation throughout the day is mainly due to variation in breath frequency (p=0.01)—the diurnal variation of tidal volume (all pedal rate conditions taken together) being non-significant—but the effect of pedal rate×time of day interaction on minute ventilation specific to the higher pedal rate conditions (p=0.03) can only be explained by the increase of tidal volume throughout the day. Even though an influence of pedal rate on diurnal rhythms in overall physiological variables was not also evidenced, high pedal rate should have been imposed when diurnal variations of physiological variables in cycling were studied.     

Spatial and temporal variation of photosynthesis in intertidal Mazzaella laminarioides (Bory)Fredericq (Rhodophyta, Gigartinales)

The red alga Mazzaella laminarioides is an economically important species with an extended latitudinal distribution along the Chilean coast. Its populations form mid-intertidal stands, several meters wide, and therefore are differentially exposed to environmental variables that result in temporal and spatial variability in productivity. We evaluated the effect of latitude and intertidal height on productivity by in situ measurement of photosynthetic performance. Daily and seasonal variations of O₂-evolution rate and maximal quantum yield (F _v/F _m) were determined in plants from the upper and lower intertidal zone at two localities 1500,km apart. Results suggest that plant responses were mainly affected by irradiation, temperature and desiccation. At local level, upper intertidal plants showed a reduced photosynthetic rate and quantum efficiency as compared to those displayed by plants from the lower intertidal, indicating their higher level of excitation energy acclimation. Stronger acclimation differences between upper and lower intertidal plants were observed in spring and summer. Differences in photosynthetic parameters between reproductive phases were recorded in autumn and winter, regardless of the position of the individuals in the intertidal zone. The effects of tidal elevation on seasonal patterns of photosynthesis were also influenced by latitude. Seasonal variation in photosynthetic efficiency was observed in plants from the northern population at both intertidal elevations, but only at the upper intertidal level in the southern population. This study shows that production variability in M. laminarioides results from differences in the intensity of environmental factors observed seasonally at local (intertidal) and latitudinal scales.     

Seasonal Variation in the Chemical Composition of Tropical Australian Marine Macroalgae

The proximate chemical composition (ash, soluble carbohydrate, lipid and protein) was determined in 30 common species of tropical Australian marine macroalgae from Darwin Harbour (12^∘26′S, 130^∘51′E), in summer (hot and wet) and winter (cool and dry). There was a wide diversity of species in both seasons (19 species in summer and 20 species in winter). In most species, the major component was soluble carbohydrate (chlorophytes range 2.5–25.8% dry weight (dw), phaeophytes range 8.4–22.2% dw, rhodophytes range 18.7–39.2% dw) with significantly higher (p < 0.05) percentages only in winter season rhodophytes. Highest percentages of protein were found in rhodophytes collected in the summer (range 4.8–12.8% dw), with significantly lower percentages (p < 0.05) during winter. All species had lipid contents within the range 1.3–7.8% dw, with highest percentages in summer phaeophytes, but no significant differences between species or season. Most species had moderate to high ash contents (24.2–89.7% dw), with the highest percentages during summer. Compared with summer samples, macroalgae collected in winter had higher energy value and slightly lower percentages of inorganic matter. The variation of algal groups and chemical composition may influence the availability of the food source for the majority of herbivores, which in turn is likely to effect their ecology and community structure.     

Genetic diversity studies of Kherigarh cattle based on microsatellite markers

We report a genetic diversity study of Kherigarh cattle, a utility draught-purpose breed of India, currently declining at a startling rate, by use of microsatellite markers recommended by the Food and Agriculture Organization. Microsatellite genotypes were derived, and allelic and genotypic frequencies, heterozygosities and gene diversity were estimated. A total of 131 alleles were distinguished by the 21 microsatellite markers used. All the microsatellites were highly polymorphic, with mean (±s.e.) allelic number of 6.24 ±1.7, ranging 4–10 per locus. The observed heterozygosity in the population ranged between 0.261 and 0.809, with mean (±s.e.) of 0.574 ±0.131, indicating considerable genetic variation in this population. Genetic bottleneck hypotheses were also explored. Our data suggest that the Kherigarh breed has not experienced a genetic bottleneck in the recent past.     

Genotyping of recombinant Pichia pastoris strains

A simplified amplified-fragment length polymorphism (AFLP) method was used to genotype Pichia pastoris strains obtained by transformation of P. pastoris strain GS115 with a single integration vector. A total of 14 transformants and 3 control strains were analyzed, which generated 16 different band patterns. A clonal variation was obtained after the transformation process due to genetic differences generated during the transformation event of the host strain. Furthermore, the cluster analysis showed that the transformants with lesser genetic differences with respect to the P. pastoris host strain are the recombinant strains with the highest level of recombinant protein production.     

Genetic Identity of Populus tremuloides Litter Influences Decomposition and Nutrient Release in a Mixed Forest Stand

Recent research has shown that genetic variation can directly impact community and ecosystem level processes. Populus tremuloides (trembling aspen) is an extremely widespread and genetically diverse tree species important to many North American forest ecosystems. Using leaf litter from five genotypes grown in a common garden under two nutrient treatments, we tracked litter decomposition in a natural aspen stand for 1 year. Here we show that aspen leaf litter decomposes and releases carbon, nitrogen, and sulfur in relation to its genetic identity. In a secondary experiment, we show that the genetic diversity of aspen litter mixtures can influence decomposition, however weakly so. Overall, nutrient treatments influenced leaf litter decomposition the most, followed by genetic identity, and then by genetic diversity (if at all in some cases). In this widespread, genetically diverse, and dominant species, genetic variation within a single species is important to ecosystem functioning. The relatively weak effect of genetic diversity on the processes measured here does not preclude its importance to ecosystem functioning, but does suggest that genetic identity and composition are more important than genetic diversity per se.     

Circadian Variation with a Diurnal Bimodal Profile on Scent-Marking Behavior in Captive Common Marmosets (Callitrhix jacchus)

Scent-marking behavior is associated with different behavioral contexts in callitrichids, including signalizing a territory, location of feeding resources, and social rank. In marmosets and tamarins it is also associated with intersexual communication. Though it appears very important for the daily routine of the individuals, very few researchers have investigated distribution through the 24-h cycle. In a preliminary report, we described a preferential incidence of this behavior 2 h before nocturnal rest in families of common marmosets. We expand the data using 8 family groups (28 subjects), 8 fathers, 6 mothers, 8 nonreproductive adults (4 sons and 4 daughters), and 6 juvenile (3 sons and 3 daughters) offspring that we kept in outdoor cages under natural environmental conditions. We recorded the frequency of anogenital scent marking for each group during the light phase, twice a wk, for 4 consecutive wks, from March 1998 to September 1999. Cosinor test detected 24- and 8-h variations in 89.3% and 85.7% of the subjects, respectively, regardless of sex or reproductive status. The 8-h component is a consequence of the 2 peaks for the behavior, at the beginning and end of the light phase. Daily distribution of scent marking is similar to that others described previously for motor activity in marmosets. The coincident rhythmical patterns for both behaviors seem to be associated with feeding behavior, as described for callitrichids in free-ranging conditions, involving an increase in foraging activities early in the morning and shortly before nocturnal rest.     

Genetic variation of ticks (Ixodes ricinus L.) in the Lithuanian and Norwegian populations

RAPD markers were used to measure the genetic diversity of 119 individuals of Ixodes ricinus collected from Lithuania and Norway. The samples were analysed within and also between the populations. We analysed 74 loci in each of 6 populations. Our results show high levels of diversity within the populations. The percentage of polymorphic loci of the six analysed populations: Birzai, Vilnius, Kretinga, Tjore, Kjosvik and Odderoya were 68.9%, 58.1%, 78.38%, 62.2%, 44.6% and 68.9%, respectively. The percentage of polymorphic loci in the Lithuanian populations was 93.2%, and in the Norwegian populations 81.08%. The genetic distance ranged from 0.019 to 0.079 within Norwegian populations and from 0.005 to 0.0967 within Lithuanian populations and between the countries from 0.022 to 0.146. The genetic variation of I. ricinus among Norwegian populations was lower than among Lithuanian populations. The highest part of genetic variation in I. ricinus ticks depends on variation within Kretinga (Lithuania) and Odderoya (Norway) populations situated in coastal areas where many migratory and sea birds are aggregated.     

Evaluation of Resistance Pattern to Fenpyroximate and Pyridaben in Tetranychus Urticae collected from Ggreenhouses and Apple Orchards using Lethal Concentration-slope Relationship

This study aimed to monitor the present and future developments of the resistance of Tetranychus urticae Koch to fenpyroximate and pyridaben, using the relationship of the LC₅₀ and slope of the concentration-mortality line in a probit model, for the provision of reliable resistance management tactics. Tetranychus urticae populations were collected from 16 commercial greenhouses, where various crops were cultivated, as well as from 10 apple orchards throughout Korea. The resistance to fenpyroximate and pyridaben of each population was estimated by calculating the median lethal concentration (LC₅₀), resistance ratio (RR) and slope of the concentration-mortality regression. Most of the greenhouse populations exhibited moderate levels of resistance, whereas the apple orchard populations showed only low levels, indicating that T. urticae populations in greenhouses were more strongly selected than those in apple orchards. Four population groups were established based on either the habitats (greenhouse and apple orchard) or acaricides (fenpyroximate and pyridaben). To test the hypothesis, “the slope is greatest at low and high levels of resistance,” the slopes were regressed as a function of the LC₅₀, and fitted to a polynomial regression. The polynomial regression model explained this relationship well for the four population groups (p < 0.05), indicating that the development of resistance toward fenpyroximate or pyridaben was consistent with the gradient. A laboratory selection study agreed with the results from both acaricide field populations. These results suggest that the gradient was a good indicator of the susceptibility of T. urticae to genetic variations, which was related to the LC₅₀. The application of these findings is also discussed in relation to the resistance management of T. urticae.