Distribution of mobile dispersed genes (mdg-1 and mdg-3) in the chromosomes of Drosophila melanogaster

The localization of mobile dispersed genes (mdg-1 and mdg-3) was studied by in situ hybridization with the polytene chromosomes of 20 laboratory stocks of Drosophila melanogaster. The average number of sites was 20 for mdg-1 and 12 for mdg-3, but the actual number varied from stock to stock (14–27 for mdg-1 and 5–18 for mdg-3). A total of 182 possible sites have been detected for mdg-1 and 123 sites for mdg-3. In spite of the individual and interstock variation, the distribution over chromosomes was found to be nonrandom for mdg-3 and especially for mdg-1. Frequently occurring sites of mdg-1 hybridization were revealed, most of which coincided with regions of intercalary heterochromatin, especially in chromosome 2.     

Consequences of selection in highly inbred <Emphasis Type="Italic">Drosophila</Emphasis> strains

The results of three long-term breeding and genetic experiments with Drosophila melanogaster performed at different times are summarized. Selections for different fitness components led to similar results. The data on the concentration of viability mutations in the inbred strains LA, LA⁺, and LA^? after 400 generations of selection and the strain ULA during its breeding are presented for the first time. The results of studying the genetic heterogeneity and spontaneous mutational process in Drosophila inbred strains comply with the idea of M.E. Lobashev that “a change in the direction of selection or acceleration of its rate is always accompanied by a concurrent increase in mutational variation.”     

Mdg-1 mobile element polymorphism in selected Drosophila melanogaster populations

The changes in mdg-1 mobile element polymorphism that followed artificial selection for either high or low egg-to-adult viability in a Drosophila melanogaster population were investigated. The two selected subpopulations were thus characterized for fecundity, wing length, and number and location of the mdg-1 mobile element by in situ hybridization of the biotinylated-DNA on salivary gland chromosomes. The selected populations that differed greatly in egg-to-adult viability showed the same mean fecundity and identical values for intra and inter components of variances, intraclass correlation coefficient, and fluctuating asymmetry estimated on the wing length measurement. This indicates a non-correlated effect between deleterious mutations affecting viability and other fitness components. However, the two selected populations differed in their pattern of mdg-1 location, although the mean number of insertions per genome was not different from that of the initial population hence, the number of insertions of the mdg-1 mobile element was independent of the effective population size. These results suggest that the mdg-1 copy number was regulated, and that during the selection process, drift and inbreeding made up new insertion patterns of the mdg-1 element in the selected populations. The results are discussed in the light of some recent theoretical models of the population dynamics of transposable elements.     

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Ecdysone-dependent changes in the activity of ontogenetic puffs in the salivary glands of Drosophila cultivated in vitro as regards the effect of heterosis and selection of adaptively significant characters]

Regression of 4 intermolt and induction of 14 early ecdysone puffs in two inbred stocks of Drosophila with high (HA) and low (LA) activity and hybrid F1 HA x LA were studied. Experiments were performed in vitro with ecdysone-containing media. Differences in developmental rate and fitness of stocks HA, LA and their hybrid were shown to correlate with the rate of change in polythene chromosomes puffing activity. Adaptive heterosis and ontogenetic homeostasis mechanisms are under discussion in connection with the results obtained.     

The influence of hypotonic treatment on the morphology of meiotic stages II. Prophase of the first meiotic division of female mice up to dictyotene

The copy number of the mdg-1 mobile element was determined by biotinylated-DNA hybridization, in salivary gland chromosomes of inbred Drosophila melanogaster larvae from sib progenies. It appears that the lower the egg-to-adult survival (viability), the higher the mdg-1 copy number in the surviving larvae. This suggests a common regulation of the mdg-1 copy number and the viability under inbreeding.     

The functional significance of amylase polymorphism in Drosophila melanogaster VI. Duration of development and amylase activity in larvae when starch is a limiting factor

Two stocks homozygous for the amylase alleles Amy ¹ and Amy ^{4, 6} were compared for amylase activity during larval development and duration of larval development on a food medium on which addition of starch promotes survival. The two stocks have the same development time when reared under optimal food conditions. Then, the higher amylase activity which characterizes the Amy ^{4, 6} stock appears far into the third instar. On the food used in the present experiments in which starch is a limiting factor for survival, the activity difference appears already in the 2nd instar. Moreover, Amy ^{4, 6} has a duration of larval development which is almost one day shorter than the Amy ¹ stock. This would result in a large selective advantage for the Amy ^{4, 6} stock when brought in competition on this food with the Amy ¹ stock.These rrsults support the explanation given for the results of earlier competition experiments between the Amy ¹ and the Amy ^{4, 6} stock, that the relative fitness of the stock with the high amylase activity improves when starch is added to a food medium in which it is a limiting factor for survival because the Amy ^{4, 6} stock by virtue of its higher amalyse activity utilizes starch better than its competitor.     

Differences in the number of nucleolus organizers in Chironomus tepperi shown by in situ hybridization

Two stocks of Chironomus tepperi could be isolated. One stock, N(IV)⁺, contains nucleolus organizers in chromosome I and IV, whereas the other one, N(IV)^–, shows only one nucleolus in chromosome I. It is demonstrated by in situ hybridization with radioactive rRNA that the absence of the nucleolus in chromosome IV of stock N(IV)^– is not related to an inactivation of the nucleolar DNA, as might have been suggested, but is due to the lack of ribosomal cistrons.     

Detection and Molecular Characterization of Two FAD3 Genes Controlling Linolenic Acid Content and Development of Allele-Specific Markers in Yellow Mustard (Sinapis alba)

Development of yellow mustard (Sinapis alba L.) with superior quality traits (low erucic and linolenic acid contents, and low glucosinolate content) can make this species as a potential oilseed crop. We have recently isolated three inbred lines Y1127, Y514 and Y1035 with low (3.8%), medium (12.3%) and high (20.8%) linolenic acid (C18∶3) content, respectively, in this species. Inheritance studies detected two fatty acid desaturase 3 (FAD3) gene loci controlling the variation of C18∶3 content. QTL mapping revealed that the two FAD3 gene loci responsible for 73.0% and 23.4% of the total variation and were located on the linkage groups Sal02 and Sal10, respectively. The FAD3 gene on Sal02 was referred to as SalFAD3.LA1 and that on Sal10 as SalFAD3.LA2. The dominant and recessive alleles were designated as LA¹ and la¹ for SalFAD3.LA1, and LA² and la² for SalFAD3.LA2. Cloning and alignment of the coding and genomic DNA sequences revealed that the SalFAD3.LA1 and SalFAD3.LA2 genes each contained 8 exons and 7 introns. LA¹ had a coding DNA sequence (CDS) of 1143 bp encoding a polypeptide of 380 amino acids, whereas la¹ was a loss-of-function allele due to an insertion of 584 bp in exon 3. Both LA² and la² had a CDS of 1152 bp encoding a polypeptide of 383 amino acids. Allele-specific markers for LA¹, la¹, LA² and la² co-segregated with the C18∶3 content in the F₂ populations and will be useful for improving fatty acid composition through marker assisted selection in yellow mustard breeding.     

Selection on Viability of Individuals Heterozygous for the Temperature-Sensitive Lethal Mutation l(2)M167DTS in Experimental Populations of Drosophila melanogaster

In experiments on introduction of mutation l(2)M167 ^DTS in Drosophila melanogaster populations, larval and pupal viability and developmental rate are limiting factors determining the intensity of selection on the l(2)M167 ^DTS mutation. Notwithstanding the rapid elimination of the mutation from the population, positive selection for viability was shown, which increased fitness of the mutation carriers in generations. The fitness component viability was estimated in individuals l(2)M167 ^DTS /+; relative to that of wild-type individuals, it varied from 0.5 to 1.0. Factors affecting this trait in overcrowded populations were found.__________Translated from Genetika, Vol. 41, No. 6, 2005, pp. 759–766.Original Russian Text Copyright © 2005 by Kulikov, Marec, Mitrofanov.     

Variation in the post‐mating fitness landscape in fruit flies

Sperm competition is pervasive and fundamental to determining a male's overall fitness. Sperm traits and seminal fluid proteins (Sfps) are key factors. However, studies of sperm competition may often exclude females that fail to remate during a defined period. Hence, the resulting data sets contain fewer data from the potentially fittest males that have most success in preventing female remating. It is also important to consider a male's reproductive success before entering sperm competition, which is a major contributor to fitness. The exclusion of these data can both hinder our understanding of the complete fitness landscapes of competing males and lessen our ability to assess the contribution of different determinants of reproductive success to male fitness. We addressed this here, using the Drosophila melanogaster model system, by (i) capturing a comprehensive range of intermating intervals that define the fitness of interacting wild‐type males and (ii) analysing outcomes of sperm competition using selection analyses. We conducted additional tests using males lacking the sex peptide (SP) ejaculate component vs. genetically matched (SP⁺) controls. This allowed us to assess the comprehensive fitness effects of this important Sfp on sperm competition. The results showed a signature of positive, linear selection in wild‐type and SP⁺ control males on the length of the intermating interval and on male sperm competition defence. However, the fitness surface for males lacking SP was distinct, with local fitness peaks depending on contrasting combinations of remating intervals and offspring numbers. The results suggest that there are alternative routes to success in sperm competition and provide an explanation for the maintenance of variation in sperm competition traits.     

Characteristics of antibody inhibition of rat kidney (Na+−K+)-ATPase

Summary Antibodies which were raised against highly purified membrane-bound (Na⁺–K⁺)-ATPase from the outer medulla of rat kidneys inhibit the (Na⁺–K⁺)-ATPase activity up to 95%. The antibody inhibition is reversible. The time course of enzyme inhibition and reactivation is biphasic in semilogarithmic plots.In the purified membrane-bound (Na⁺–K⁺)-ATPase negative cooperativity was observed (a) for the ATP dependence of the (Na⁺–K⁺)-ATPase activity (n=0.86), (b) for the ATP binding to the enzyme (n=0.58), and (c) for the ouabain inhibition of the (Na⁺–K⁺)-ATPase activity (n=0.77). By measuring the Na⁺ dependence of the (Na⁺–K⁺-ATPase reaction, a positive homotropic cooperativity (n=1.67) was found.As reactivation of the antibody-inhibited enzyme proceeds very slowly (t _0.5=5.2hr), it was possible to measure characteristics of the antibody-(Na⁺–K⁺)-ATPase complex: The antibodies exerted similar effects on the ATP dependence of the (Na⁺–K⁺)-ATPase reaction and on the ATP binding of the enzyme.V _max of the (Na⁺–K⁺)-ATPase reaction and the number of ATP binding sites were reduced whileK _{0.5 ATP} for the (Na⁺–K⁺)-ATPase activity and for the ATP binding were increased by the antibodies. The Hill coefficients for the ATP binding and for the ATP dependence of the enzyme activity were not significantly altered by the antibodies. The antibodies increased theK _0.5 value for the Na⁺ stimulation of the (Na⁺–K⁺)-ATPase activity, but they did not alter the homotropic interactions between the Na⁺-binding sites. The negative cooperativity which was observed for the ouabain inhibition of the (Na⁺–K⁺)-ATPase activity was abolished by the antibodies.The data are tentatively explained by the following model: The antibodies bind to the (Na⁺–K⁺)-ATPase from the inner membrane side, reduce the ATP binding symmetrically at the ATP binding sites and reduce thereby also the (Na⁺–K⁺)-ATPase activity of the enzyme. The antibodies may inhibit the ATP binding by a direct interaction or by means of a conformational change at the ATP binding sites. This may possibly also lead to the alteration of the Na⁺ dependence of the (Na⁺–K⁺)-ATPase activity and to the observed alteration of the dose response to the ouabain inhibition.     

Effects of leaf position and nitrogen supply on the expansion of leaves of field grown sunflower (Helianthus annuus L.)

Leaf growth responses to N supply and leaf position were studied using widely-spaced sunflower plants growing under field conditions. Both N supply (range 0.25 to 11.25 g added N per plant) and leaf position significantly (p=0.001) affected maximum leaf area (LA_max) of target leaves through variations in leaf expansion rate (LER); effects on duration of expansion were small. Specific leaf nitrogen (SLN, g N m^-2) fell quite rapidly during the initial leaf expansion phase (LA < 35% LA_max) but leveled off during the final 65% increase of leaf area. This pattern held across leaf positions and N supply levels. Leaf nitrogen accumulation after 35% LA_max continued up to achievement of LA_max; reductions in the higher SLN characteristic of the initial phase were insufficient to cover the nitrogen requirements for expansion during the final phase. LER in the quasi-linear expansion phase (35 to 100% of LA_max) was strongly associated with SLN above a threshold that varied with leaf position (mean 1.79±0.225 g N m^-2). This contrasts with the response of photosynthesis at high irradiance to SLN, which has previously been shown to have a threshold of 0.3 g N m^-2; in the present work saturation of photosynthetic rate was evident when SLN reached 1.97 g N m^-2. Thus, once the area of a leaf exceeds 35% of LA_max, expansion proceeds provided SLN values are close to the levels required for maximum photosynthesis. However, growth of leaves during the initial expansion phase ensures a minimum production of leaf area even at low N supply levels.     

Gene transfer in Drosophila melanogaster: cytological alterations in the salivary chromosomes of transformed stocks

Cytological abnormalities are observed in salivary chromosomes of stocks of Drosophila melanogaster possessing DNA-induced, v ⁺ transformations mapping either at 10.0 or 133.0. In initial studies, the untransformed control stock and six transformed stocks were assigned code numbers prior to cytological examination. Salivary chromosome regions 1B9 · 10—1C2 · 3 and 10A1 · 2—10B1 · 2 were carefully examined in each of the coded stocks. (Band 1B11 is tentatively identified as the site of the suppressor-of-sable locus at 10.0 and band 10A1 is the site of the vermilion locus at 133.0.) When cytological studies were complete each of the stocks was identified. In every transformed stock examined, anomalies had been scored in association with the chromosome region corresponding to the map position of the DNA-induced alteration. In the control stock, anomalies were observed at neither position. — Approximately 10–15% of the nuclei in transformed stocks exhibit significant departure from normality in the pertinent chromosome region. The perturbations range from minor alterations of banding pattern to apparent pieces of extra chromatin in the most extreme cases. In stocks with v⁺ transformations mapping at 133.0, apparent extra chromatin is observed with frequencies varying from 0.05 to 0.02. In these cases the abnormal structures are associated with salivary band 10A1 · 2, forming a band-like structure, frequently an almost perfect doublet (open or closed), often lying in an abnormal position, and with fine chromatin threads connecting to the chromosomal doublet. In stocks with v⁺ transformations mapping at 10.0, apparent extra chromatin is observed with a frequency of about 0.001. These abnormal structures are frequently thread-like, lying to the side or off the tip of the chromosome, with compact regions which sometimes resemble chromomeres, and with fine threads connecting to the chromosomal 1B11 region.     

Genetics of esterases in Drosophila. VII. Genetic control of the activity level of juvenile hormone (JH)-esterase and heat resistance in D. virilis at high temperatures

The heat-resistant subline 147S was obtained in Drosophila virilis by selecting for viability individuals of heat-sensitive stock 147. It was shown that in the heat-treated 147S pupae the activity of juvenile hormone (JH)-esterase is decreased and, consequently, the titer of juvenile hormone is increased compared with those in the control pupae. These changes are consistent with those observed earlier for resistant stock 101. Heat-resistant stocks 101 and 147S were crossed with heat-sensitive stock 147, whose heat-treated larvae show earlier activation and higher activity of JH-esterase than control larvae. The viability and electrophoretic esterase patterns were analyzed in the F₁ and F₂ hybrids at different temperatures. It was found that the F₁ hybrid is resistant to the effect of high temperature and its activity level of JH-esterase is lower compared with controls. In the F₂ hybrid, there was a 3:1 segregation of viability and a 1:2:1 segregation of the activity level of JH-esterase at high temperatures. It is concluded that the activity level of JH-esterase and heat resistance in D. virilis are monogenically controlled at high temperatures.     

The effect of trait type and strength of selection on heritability and evolvability in an island bird population

The heritability (h²) of fitness traits is often low. Although this has been attributed to directional selection having eroded genetic variation in direct proportion to the strength of selection, heritability does not necessarily reflect a trait's additive genetic variance and evolutionary potential (“evolvability”). Recent studies suggest that the low h² of fitness traits in wild populations is caused not by a paucity of additive genetic variance (V_A) but by greater environmental or nonadditive genetic variance (V_R). We examined the relationship between h² and variance‐standardized selection intensities (i or β_σ), and between evolvability (I_A:V_A divided by squared phenotypic trait mean) and mean‐standardized selection gradients (β_μ). Using 24 years of data from an island population of Savannah sparrows, we show that, across diverse traits, h² declines with the strength of selection, whereas I_A and I_R (V_R divided by squared trait mean) are independent of the strength of selection. Within trait types (morphological, reproductive, life‐history), h², I_A, and I_R are all independent of the strength of selection. This indicates that certain traits have low heritability because of increased residual variance due to the age at which they are expressed or the multiple factors influencing their expression, rather than their association with fitness.     

Initial soil C and land‐use history determine soil C sequestration under perennial bioenergy crops

In the UK and other temperate regions, short rotation coppice (SRC) and Miscanthus x giganteus (Miscanthus) are two of the leading ‘second‐generation’ bioenergy crops. Grown specifically as a low‐carbon (C) fossil fuel replacement, calculations of the climate mitigation provided by these bioenergy crops rely on accurate data. There are concerns that uncertainty about impacts on soil C stocks of transitions from current agricultural land use to these bioenergy crops could lead to either an under‐ or overestimate of their climate mitigation potential. Here, for locations across mainland Great Britain (GB), a paired‐site approach and a combination of 30‐cm‐ and 1‐m‐deep soil sampling were used to quantify impacts of bioenergy land‐use transitions on soil C stocks in 41 commercial land‐use transitions; 12 arable to SRC, 9 grasslands to SRC, 11 arable to Miscanthus and 9 grasslands to Miscanthus. Mean soil C stocks were lower under both bioenergy crops than under the grassland controls but only significant at 0–30 cm. Mean soil C stocks at 0–30 cm were 33.55 ± 7.52 Mg C ha^?1 and 26.83 ± 8.08 Mg C ha^?1 lower under SRC (P = 0.004) and Miscanthus plantations (P = 0.001), respectively. Differences between bioenergy crops and arable controls were not significant in either the 30‐cm or 1‐m soil cores and smaller than for transitions from grassland. No correlation was detected between change in soil C stock and bioenergy crop age (time since establishment) or soil texture. Change in soil C stock was, however, negatively correlated with the soil C stock in the original land use. We suggest, therefore, that selection of sites for bioenergy crop establishment with lower soil C stocks, most often under arable land use, is the most likely to result in increased soil C stocks.     

Transposition of mobile dispersed genes (MDG) after substitution of various chromosome pairs in inbred Drosophila melanogaster strains

Transpositions of MDG-1, MDG-3 and copia were detected as a result of crosses of the inbred maladaptive LA stock with laboratory stocks, in order to construct the genomes carrying different combinations of the LA or non-La chromosomal pairs. Changes of the mobile gene distributions were revealed in chromosomes of hybrid genotypes, as compared to parental chromosomal pairs. A trivial source of variability of chromosomal molecular structure ensured by crossing over was excluded by inversions which serve as suppressors of crossing over in corresponding crosses. Multiple transpositions of mobile genes in definite chromosomal sites were detected in genotypes carrying chromosomal pair 2 originated from the LA stock. No such transpositions were observed, when the pair 2 was substituted by the chromosome 2 originated from the Swedish-b line or in control crosses, where the LA stock was not involved. Both LA chromosomes 2 and 3 were shown to be the targets of transpositions. Comparison of hot spot transposition sites of MDG-1, as a result of crosses, with the earlier described rare events of spontaneous transpositions in the LA stock, coupled with its fitness increase, revealed that the hot spot sites were shared in both series of experiments. The data obtained show that transpositions of mobile genetic elements may change the genetic and molecular structure of the chromosome involved in crosses, in spite of suppression of crossing over by inversions usually suggested as a tool for keeping chromosomal genetic structure intact.     

Biochemical selection of immature,haploid embryos of Zea mays L.

Summary A method was devised for the biochemical selection of immature, haploid Zea mays embryos using Adh1 ^– and either the Stock 6 or indeterminate gametophyte (ig in W23) high haploid-inducing systems. Haploid (Adh1 ^–) embryos survived exposure to levels of allyl alcohol which killed diploid (Adh1 ⁺/Adh1 ^–) embryos. Of the total surviving embryos which were examined cytologically 15% (using ig) and 22% (using Stock 6) were haploid. In two experiments with Stock 6, 100% of the surviving embryos were haploid. To obtain maximum effectiveness of Stock 6 and ig, Adh1 ^– was transferred to stock 6 and W23 backgrounds. Immature, haploid embryos are being used to develop haploid, morphogenic tissue cultures of Zea mays.     

The protective effect of alpha lipoic acid against traumatic brain injury in rats

Traumatic brain injury (TBI) was induced by a weight-drop device using 300 g–1 m weight-height impact. The study groups were: control, alpha-lipoic acid (LA) (100 mg/kg, po), TBI, and TBI + LA (100 mg/kg, po). Forty-eight hours after the injury, neurological scores were measured and brain samples were taken for histological examination or determination of thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) levels, myeloperoxidase (MPO) and Na⁺-K⁺ ATPase activities, whereas cytokines (TNF-α, IL-1β) were determined in blood. Brain oedema was evaluated by wet–dry weight method and blood–brain barrier (BBB) permeability was evaluated by Evans Blue (EB) extravasation. As a result, neurological scores mildly increased in trauma groups. Moreover, TBI caused a significant decrease in brain GSH and Na⁺-K⁺ ATPase activity, which was accompanied with significant increases in TBARS level, MPO activity and plasma proinflammatory cytokines. LA treatment reversed all these biochemical indices as well as histopathological alterations. TBI also caused a significant increase in brain water content and EB extravasation which were partially reversed by LA treatment. These findings suggest that LA exerts neuroprotection by preserving BBB permeability and by reducing brain oedema probably by its anti-inflammatory and antioxidant properties in the TBI model.