Genetic control of “natural” killer lymphocytes in the mouse

Spleens from normal young mice contain lymphocytes that can kill certain in vitro grown Moloney lymphoma lines in a⁵¹Cr-release cytotoxicity test. A lymphoid cell without detectable T- or B-cell markers was previously shown to be responsible. Killing activity shows a marked dependence on the genotype of the donor mouse. When tested against a YAC line of strain A origin maintained in vitro spleens of A, A.CA, and A.SW mice had low activity, whereas CBA, C3H, C57L, and C57Bl spleens were highly active. In semisyngeneic F₁ crosses with strain A as one parent, reactivity resembled the opposite parental strain. Thus, (A×CBA)F₁, (A×C3H)F₁, (A×C57L)F₁, and (A×C57Bl)F₁ were reactive, whereas A×A.CA showed no significant activity. Analysis of the reactivity in (A×C57Bl)F₁×A backcross mice suggests that multiple genes are involved. Preliminary linkage analysis suggests at least oneH-2 linked factor. Another gene appears to be linked to theB (black) locus.     

乌蕨孢子萌发研究

用随机区组试验和方差分析方法, 研究了培养温度、贮藏温度、GA 处理和光照强度对乌蕨( Sphenomeris chinensis) 孢子萌发的影响。与室温(20～25℃ ) 相比, 培养温度在28℃时, 孢子最大萌发率相近而萌发速率明显较高。贮藏温度(A) 极显著( P < 0 . 01 ) 影响孢子萌发率, - 20℃ 贮藏降低萌发率; GA (B) 对孢子萌发率无显著影响。光照强度(C) 极显著( P < 0.01) 影响孢子萌发率, 充足光照和弱光照无显著差异, 黑暗处理降低萌发率。A×B, A×C, B×C 及A×B×C 交互效应不显著。     

鄂尔多斯半日花提取物的杀线虫作用

为全面了解濒危植物半日花的价值,测定并比较半日花不同浓度的6种提取物药液对松材线虫的生物活性,选出有较强杀线虫活性的甲醇、乙醇及水提取物,系统研究了提取物种类、浓度和处理时间对松材线虫死亡率的影响。三因素方差分析表明,提取物种类(A)、处理浓度(B)和处理时间(C),三因素的互作效应(A×B×C)和双因素互作效应(A×B、A×C、B×C)对线虫的校正死亡率都有极显著影响。最佳药液处理为:水提取物在6mg.L-1浓度时与1d的作用组合和乙醇提取物在3mg.L-1浓度时与5d的组合,以上两种组合的校正死亡率均达到100%。比较水、乙醇提取物5d中的LC50值,确定水是提取活性物质的首选溶剂。     

Amyloid beta-derived neuroplasticity in bone marrow-derived mesenchymal stem cells is mediated by NPY and 5-HT2B receptors via ERK1/2 signalling pathways

Objective:  In Alzheimer's disease, toxic soluble and insoluble forms of amyloid beta (Aβ) cause synaptic dysfunction and neuronal loss. Given its potential role in producing a toxic host microenvironment for transplanted donor stem cells, we investigated the interaction between Aβ and proliferation, survival, and differentiation of bone marrow-derived mesenchymal stem cells (BM-MSC) in culture.
Materials and methods:  We used BM-MSC that had been isolated from mouse bone marrow and cultured, and we also assessed relevant reaction mechanisms using gene microarray, immunocytochemistry, and inhibitors of potential signalling molecules, such as mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK)1/2 and tyrosine protein kinase.
Results and conclusions:  Interestingly, we found that treatment with aggregated (1–40 or 1–42) and oligomeric (1–42) Aβ promoted neuronal-like differentiation of BM-MSC without toxic effects. This was not dependent on soluble factors released from BM-MSC progeny nor solely on formation of Aβ fibrils. The effect of Aβ is mediated by G-protein coupled receptors, neuropeptide Y1 (NPY1R) and serotonin (5-hydroxytryptamine) receptor 2B, via phosphatidylinositol-3-OH kinase-dependent activation of the MAPK/ERK1/2. Our results lend support to the idea that reciprocal donor stem cell–host interactions may promote a regenerative response that can be exploited by epigenetic modulation of NPY/serotonergic gene expression, for stem cell therapy, in Alzheimer's disease.     

Linkage disequilibrium in two European F<Subscript>2</Subscript> flint maize populations under modified recurrent full-sib selection

According to quantitative genetic theory, linkage disequilibrium (LD) can hamper the short- and long-term selection response in recurrent selection (RS) programs. We analyzed LD in two European flint maize populations, KW1265 × D146 (A × B) and D145 × KW1292 (C × D), under modified recurrent full-sib selection. Our objectives were to investigate (1) the decay of initial parental LD present in F₂ populations by three generations of intermating, (2) the generation of new LD in four (A × B) and seven (C × D) selection cycles, and (3) the relationship between LD changes and estimates of the additive genetic variance. We analyzed the F₂ and the intermated populations as well as all selection cycles with 104 (A × B) and 101 (C × D) simple sequence repeat (SSR) markers with a uniform coverage of the entire maize genome. The LD coefficient D and the composite LD measure Δ were estimated and significance tests for LD were performed. LD was reduced by intermating as expected from theory. A directional generation of negative LD between favorable alleles could not be observed during the selection cycles. However, considerable undirectional changes in D were observed, which we attributed to genetic sampling due to the finite population size used for recombination. Consequently, a long-term reduction of the additive genetic variance due to negative LD was not observed. Our experimental results support the hypothesis that in practical RS programs with maize, LD generated by selection is not a limiting factor for obtaining a high selection response.     

桔小实蝇和番石榴实蝇对6种寄主果实的产卵选择适应性

植食性昆虫对寄主植物的选择适应性是研究昆虫和植物协同进化关系的核心内容之一。评估寄主植物对植食性昆虫种群的适合度,需要综合分析昆虫对寄主的产卵选择性和寄主对昆虫的取食适合性。以桔小实蝇和番石榴实蝇为研究对象,分别测定了这两种实蝇对6种寄主果实:番石榴、香蕉、杨桃、木瓜、甜橙、番茄的产卵选择性以及幼虫取食后对其生长发育的影响。寄主产卵选择性实验分别采用完整寄主果实直接供试产卵和块状寄主果实气味引诱产卵两种处理方式;在生长发育适应性实验中,以幼虫和蛹的存活和生长发育等相关参数作为评价指标。实验结果表明,寄主的供试方式不同,两种实蝇的选择性均有明显差异;对寄主气味选择性强的寄主更适合于两种实蝇后代的生长发育。两种实蝇对6种寄主果实的产卵选择性和后代发育适合性两者相关性不显著,与许多文献报道单一地采用发育适合性(如发育历期、存活率或蛹重等)作为评价寄主选择性的结果不一致。两种实蝇之间对6种寄主果实的产卵选择和幼虫取食适合性既具相似性也具差异性,表明这两种实蝇在寄主生态位上既有重叠性又有分化性。     

Comparative QTL mapping of resistance to Ustilago maydis across four populations of European flint-maize

 We mapped and characterized quantitative trait loci (QTLs) for resistance to Ustilago maydis and investigated their consistency across different flint-maize populations. Four independent populations, comprising 280 F₃ lines (A×B^I), 120 F₅ lines (A×B^II), 131 F₄ lines (A×C) and 133 F₄ lines (C×D), were produced from four European elite flint inbreds (A, B, C, D) and genotyped at 89, 151, 104, and 122 RFLP marker loci, respectively. All F_n lines were evaluated in field trials with two replications in five German environments. Genotypic variances were highly significant for the percentage of U. maydis infected plants (UST) in all populations, and heritabilities exceeded 0.69. Between five and ten QTLs were detected in individual populations by composite interval mapping, explaining between 39% and 58% of the phenotypic variance. These 19 different QTLs were distributed over all ten chromosomes without any clustering on certain chromosomes. In most cases, gene action was dominant or overdominant. Fourteen pairs of the detected QTLs for UST displayed significant digenic epistatic interactions, but only two of them did so after arcsin √UST/100 transformation. Significant QTL× environment interactions occurred frequently. Between two to four QTLs were common between pairs of populations. Population C×D was also grown in Chartres, a location with a high U. maydis incidence. Two out of six QTLs identified for Chartres were in common with QTLs detected across five German environments for C×D. Consequently, marker-assisted or phenotypic selection based on results from natural infection seem to be suitable breeding strategies for improving the resistance of maize to U. maydis. Received: 3 July 1998 / Accepted: 24 July 1998     

Effect of gut bacteria on fitness of the Chinese citrus fly, <Emphasis Type="Italic">Bactrocera minax</Emphasis> (Diptera: Tephritidae)

A likely symbiotic association between tephritid fruit flies and gut bacteria has been recognized since the beginning of the last century. However, direct evidence for a link between gut bacteria and fruit fly fitness is still limited or absent for many species. Similar to other tephritids, the gut of Bactrocera minax (Enderlein) (Diptera: Tephritidae) is known to contain bacteria throughout the life stage, but what, if any, impact these bacteria have on B. minax fitness is entirely unknown. In order to elucidate the effects of bacteria on the fitness of B. minax, resident bacteria were isolated from the adult gut using culture-dependent techniques. Adult fly diets were subsequently supplemented with three bacterial isolates (Klebsiella pneumonia, Citrobacter braakii and Pantoea dispersa), or bacteria were removed from flies by antibiotics treatment: untreated adults provided a control. Adult fitness parameters (male and female longevity, female fecundity, male copulation number) were measured for the two treatments and one control group. Results were complex depending on the fitness parameter measured and the bacterial species. Compared to the controls, antibiotic treated B. minax had significantly decreased fecundity, but male and female longevity was increased. When flies were fed diets supplemented with any of the three bacterial isolates, female fecundity was significantly enhanced. However, only Citrobacter braakii significantly increased male mating frequency than control males. The results show that gut bacteria directly influence fitness of B. minax, but impacts are dependent on the bacterial species and the fitness parameters measured.     

Micro-coevolution of host genetics with gut microbiome in three Chinese ethnic groups

Understanding the micro-coevolution of the human gut microbiome with host genetics is challenging but essential in both evolutionary and medical studies. To gain insight into the interactions between host genetic variation and the gut microbiome, we analyzed both the human genome and gut microbiome collected from a cohort of 190 students in the same boarding college and representing 3 ethnic groups, Uyghur, Kazakh, and Han Chinese. We found that differences in gut microbiome were greater between genetically distinct ethnic groups than those genetically closely related ones in taxonomic composition, functional composition, enterotype stratification, and microbiome genetic differentiation. We also observed considerable correlations between host genetic variants and the abundance of a subset of gut microbial species. Notably, interactions between gut microbiome species and host genetic variants might have coordinated effects on specific human phenotypes. Bacteroides ovatus, previously reported to modulate intestinal immunity, is significantly correlated with the host genetic variant rs12899811 (meta-P = 5.55 × 10⁻⁵), which regulates the VPS33B expression in the colon, acting as a tumor suppressor of colorectal cancer. These results advance our understanding of the micro-coevolution of the human gut microbiome and their interactive effects with host genetic variation on phenotypic diversity.     

Distribution of frit flies (Chloropidae: Meromyza Mg.) in Vologda oblast and East Poland

Species diversity and abundance of frit flies from the genus Meromyza have been assessed in coastal biotopes, grasslands, and agro-ecosystems of Vologda oblast (Russia) and Warsaw province (Poland). The Jaccard quotient of similarity (IG) of frit fly abundance has shown a uniformity between coastal banks and grasslands along these banks, as well as between cultivated cereals (except for oats) and field boundaries, cultivated fields, and some reach-in-herbs grasslands, including hayfields. Considerable heterogeneity of species composition of the flies has been revealed in similar biotopes. The biotopes studied have been found to be dominated by one species of frit flies. It has been discovered that cereal rotation in agro-ecosystem results in change in the dominant species of frit fly. The cereal height has been found to influence the abundance and diversity of frit flies. No regularities have been observed in the correlation between the abundances of frit flies in different biotopes. It has been pointed out that M. nigriseta Fed. and M. variegata Mg. can feed on cultivated cereals.     

Persistent postmating,prezygotic reproductive isolation between populations

Studying reproductive barriers between populations of the same species is critical to understand how speciation may proceed. Growing evidence suggests postmating, prezygotic (PMPZ) reproductive barriers play an important role in the evolution of early taxonomic divergence. However, the contribution of PMPZ isolation to speciation is typically studied between species in which barriers that maintain isolation may not be those that contributed to reduced gene flow between populations. Moreover, in internally fertilizing animals, PMPZ isolation is related to male ejaculate—female reproductive tract incompatibilities but few studies have examined how mating history of the sexes can affect the strength of PMPZ isolation and the extent to which PMPZ isolation is repeatable or restricted to particular interacting genotypes. We addressed these outstanding questions using multiple populations of Drosophila montana. We show a recurrent pattern of PMPZ isolation, with flies from one population exhibiting reproductive incompatibility in crosses with all three other populations, while those three populations were fully fertile with each other. Reproductive incompatibility is due to lack of fertilization and is asymmetrical, affecting female fitness more than males. There was no effect of male or female mating history on reproductive incompatibility, indicating that PMPZ isolation persists between populations. We found no evidence of variability in fertilization outcomes attributable to different female × male genotype interactions, and in combination with our other results, suggests that PMPZ isolation is not driven by idiosyncratic genotype × genotype interactions. Our results show PMPZ isolation as a strong, consistent barrier to gene flow early during speciation and suggest several targets of selection known to affect ejaculate‐female reproductive tract interactions within species that may cause this PMPZ isolation.     

An operating cost of learning in Drosophila melanogaster

Although the fitness benefits of learning are well understood, we know little about its costs; yet both are essential to understand the evolution of animal learning. We tested the hypothesis that learning has an operating cost, such that an animal repeatedly forced to use its learning ability would show a reduction in some fitness component(s), relative to an animal of the same genotype that does not have to learn. Five ‘High-learning’ lines of Drosophila melanogaster, which had been selected for improved learning ability, were exposed to 12 consecutive 48-h cycles of alternating conditioning treatment under mild nutritional stress. Their learning score first increased, reaching a maximum around day 12 (i.e. the sixth conditioning cycle), and then progressively declined. These changes were not due to ageing, as they were not observed in flies from the same lines maintained under standard conditions. From around day 12, the productivity (egg-laying rate) of the flies in the conditioning treatment became progressively reduced, relative to flies from the same lines not exposed to conditioning, but otherwise kept under the same food-limited conditions. This reduction in productivity was not observed when these treatments were applied to five ‘Low-learning’ lines, which had not been exposed to selection, and which show no detectable response to conditioning under our experimental conditions. Furthermore, exposure to repeated cycles of conditioning revealed an apparent trade-off between the learning score and productivity among the ‘High-learning’ lines. These results indicate an operating cost of learning, paid only by genotypes that show learning, rather than general effects of stress caused by the conditioning regime. Potential proximate explanations include (1) the impairment of oviposition decisions caused by the accumulation of memory interference and (2) energy costs of collecting, processing and storing information.     

银额果绳(Drosophila albomicans)B染色体对繁殖的影响

利用遗传背景一致的３类含有不同Ｂ染色体数目的银额果蝇（Ｄｒｏｓｏｐｈｉｌａ ａｌｂｏｍｉｃａｎｓ）品系,对繁殖的２个参数,即净繁殖量和性比进行了比较研究。结果表明Ｂ染色体对净繁殖量有着显著的影响,其影响依赖于Ｂ染色体数目的不同而不同;低数目增加其携带者的净繁殖量,而在高含量时有使其携带者净繁殖量下降的趋势。Ｂ染色体对繁殖的影响还具有一定的时间分布特征,即３类品系净繁殖量的差异主要集中在雌蝇繁殖的早期。因为雌蝇繁殖的后期产生的后代数占总后代数的比例很低且对种群发展贡献较小,Ｂ染色体的这种时间效应使得其携带者在自然界的生存竞争中更具优势。这些结果支持关于Ｂ染色体的杂合优势模型,但不支持目前占主导地位的寄生模型。     

Drosophila Adaptation to Viral Infection through Defensive Symbiont Evolution

Microbial symbionts can modulate host interactions with biotic and abiotic factors. Such interactions may affect the evolutionary trajectories of both host and symbiont. Wolbachia protects Drosophila melanogaster against several viral infections and the strength of the protection varies between variants of this endosymbiont. Since Wolbachia is maternally transmitted, its fitness depends on the fitness of its host. Therefore, Wolbachia populations may be under selection when Drosophila is subjected to viral infection. Here we show that in D. melanogaster populations selected for increased survival upon infection with Drosophila C virus there is a strong selection coefficient for specific Wolbachia variants, leading to their fixation. Flies carrying these selected Wolbachia variants have higher survival and fertility upon viral infection when compared to flies with the other variants. These findings demonstrate how the interaction of a host with pathogens shapes the genetic composition of symbiont populations. Furthermore, host adaptation can result from the evolution of its symbionts, with host and symbiont functioning as a single evolutionary unit.     

Reticulate evolution in the apogamous Dryopteris varia complex (Dryopteridaceae,subg. Erythrovariae,sect. Variae) and its related sexual species in Japan

Apogamous fern species are often difficult to distinguish from related species because of their continuous morphological variations. To clarify the genetic relationships among the members of the Dryopteris varia complex, we analyzed the nucleotide sequences of the plastid gene rbcL and the nuclear gene PgiC. We also analyzed the diploid sexual species D. caudipinna and D. chinensis, which have not been included in the complex, but were recently shown to be closely related to the complex in a molecular phylogenetic study. The PgiC sequences of the diploid sexual species, D. varia, D. saxifraga, D. sp. ‘protobissetiana’ (undescribed diploid sexual species), D. caudipinna, and D. chinensis, were well differentiated and hence designated A, B, C, D, and E, respectively. Thus, the PgiC constitution of apogamous species in the complex was as follows: D. bissetiana, B + C; D. kobayashii, B + C + E); D. pacifica, A + C, A + B + C, or A + C + D; D. sacrosancta, A + C + E; and D. saxifragivaria, B + C. These results suggest that these apogamous species are formed by hybridizations of species including not only the three diploid sexual species of the D. varia complex (A, B, and C) but also the two diploid sexual species D. caudipinna (D) and D. chinensis (E), which do not belong to the complex.     

Characterization of the peptidases of Calliphora: Many features allow the utilization of small peptides as an amino acid reservoir

Electrophoretic separation of whole flies and of haemolymph indicates the presence of four peptidases, named dipeptidase A, B and C (Dip A, B and C) and leucine amino peptidase (LAP) after enzymes of similar substrate specificities and electrophoretic mobilities found in Drosophila (Laurie-Ahlberg, Biochem. Genet.20, 407–424, 1982; Walker et al., Insect Biochem.10, 535–541, 1980). Prominent in both tissues and haemolymph, dipeptidase A and B together hydrolyse a variety of dipeptides in vitro and probably most of the fly's small peptide component in vivo. Though Dip A and Dip B hydrolyse many of the same substrates, their activities differ in at least several respects. Dip A's K_ms are higher than Dip B's K_ms and hence in vivo the two enzymes together are likely to provide peptide hydrolysis through a wide range of substrate concentration. Dip A's unique hydrolyses are of peptides with biosynthesized amino acids in the N-terminal position and Dip B's unique hydrolyses are of peptides with essential amino acids in the N-terminal position. Dip B, but not Dip A, is inhibited by free amino acid. It is inhibited non-competitively and most strongly by essential amino acids. In cell-free haemolymph Dip B's activity is more stable than Dip A's. The accumulation and maintenance of small peptides in times of dietary sufficiency and the utilization of the small peptides as a source of amino acid in times of dietary scarcity (Collett, Insect Biochem.6, 179–185, 1976a; J. Insect Physiol.22, 1433–1440, 1976b) may be attributed to these features.     

EFFECTS ON FITNESS COMPONENTS OF P-ELEMENT INSERTS IN DROSOPHILA MELANOGASTER: ANALYSIS OF TRADE-OFFS

We analyzed the trade-offs between fitness components detected in four experiments in which traits were manipulated by inserting small (control) and large (treatment) P-elements into the Drosophila melanogaster genome. Treatment effects and the interactions of treatment with temperature, experiment, and line were caused by the greater length and different positions of the treatment insert. In inbred flies, the treatment decreased early and total fecundity. Whether it increased the lifespan of mated females depended upon adult density. Analysis of line-by-treatment-by-temperature interactions revealed hidden trade-offs that would have been missed by other methods. They included a significant trade-off between lifespan and early fecundity. At 25°C high early fecundity was associated with decreased reproductive rates and increased mortality rates 10–15 days later and persisting throughout life, but not at 29.5°C. Correlations with Gompertz coefficients suggested that flies that were heavier at eclosion also aged more slowly and that flies that aged more slowly had higher fecundity late in life at 25°C. The results support the view that lifespan trades off with fecundity and that late fecundity trades off with rate of aging in fruitflies. Genetic engineering is an independent method for the analysis of trade-offs that complements selection experiments.     

Mapping the Fitness Landscape of Gene Expression Uncovers the Cause of Antagonism and Sign Epistasis between Adaptive Mutations

How do adapting populations navigate the tensions between the costs of gene expression and the benefits of gene products to optimize the levels of many genes at once? Here we combined independently-arising beneficial mutations that altered enzyme levels in the central metabolism of Methylobacterium extorquens to uncover the fitness landscape defined by gene expression levels. We found strong antagonism and sign epistasis between these beneficial mutations. Mutations with the largest individual benefit interacted the most antagonistically with other mutations, a trend we also uncovered through analyses of datasets from other model systems. However, these beneficial mutations interacted multiplicatively (i.e., no epistasis) at the level of enzyme expression. By generating a model that predicts fitness from enzyme levels we could explain the observed sign epistasis as a result of overshooting the optimum defined by a balance between enzyme catalysis benefits and fitness costs. Knowledge of the phenotypic landscape also illuminated that, although the fitness peak was phenotypically far from the ancestral state, it was not genetically distant. Single beneficial mutations jumped straight toward the global optimum rather than being constrained to change the expression phenotypes in the correlated fashion expected by the genetic architecture. Given that adaptation in nature often results from optimizing gene expression, these conclusions can be widely applicable to other organisms and selective conditions. Poor interactions between individually beneficial alleles affecting gene expression may thus compromise the benefit of sex during adaptation and promote genetic differentiation.