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31.
参照植物根尖细胞学研究的方法标准,对香薷属3种(5个居群)植物进行核形态学分析。结果表明:(1)从染色体数目看,密花香薷2居群染色体数目2n=16;野苏子2居群染色体数目2n=20,染色体数目和倍性与前人报道的一致;毛穗香薷染色体数目2n=10为首次报道。(2)聚类分析结果显示,3种(5居群)植物中野苏子和密花香薷亲缘关系较近;结合现有报道数据分析表明,该属植物仅有2种倍性(二倍体和四倍体),且二倍体占主导地位。(3)核型参数分析表明:密花香薷的稻城无名山居群1核型公式为2n=2x=16=14m+2sm,居群2为2n=2x=16=16m,着丝粒指数(CI)分别为39.57和42.32,不对称系数AI值分别为2.75和2.87,核型不对称性都为1A型;毛穗香薷的核型公式为2n=2x=10=10m,着丝粒指数(CI)为41.76,不对称系数AI值为5.25,核型不对称性为1B型;野苏子的昆明西山居群核型公式为2n=2x=20=14m+6sm,聂拉木樟木沟居群为2n=2x=20=16m+4sm,着丝粒指数(CI)分别为38.49和40.97,不对称系数AI值为4.20和4.30,核型不对称性为1B型和2B型。 相似文献
32.
本研究针对红托竹荪干品在储藏过程中易发生褐变、降低商品性问题,探究了不同储藏条件(温度、气体微环境)对红托竹荪干品储藏品质的影响。以红托竹荪干品为原材料,考察了在气体微环境(空气、N2、CO2和脱氧)和不同储藏温度(5、25和45 ℃)下红托竹荪干品储藏品质的动态变化。在60 d的储藏期内,所有样品的褐变指数、剪切力、多酚氧化酶、过氧化氢酶、总酚、还原糖和5-羟甲基糠醛含量均增加,游离氨基酸、白度值、复水比均降低。与25、45 ℃相比,以上指标在5 ℃条件下均表现最优,5 ℃储藏条件下呈味氨基酸和挥发性成分指标更接近于0 d;在不同气体微环境比较下,CO2储藏环境下干品品质保持最好,通过综合评分得出5 ℃低温结合CO2充气条件下干品品质最优,其次为N2结合5 ℃低温。结合经济成本,5 ℃低温结合CO2或N2充气可以作为红托竹荪干品延长货架期的推荐储藏技术。 相似文献
33.
为揭示中国西藏高原河流浮游纤毛虫群落结构特征及与水环境的关系,于2015—2016年的8月和11月,利用25号浮游生物网,分别在拉萨河中上游共8个代表性采样点,共采集64个水样。物种鉴定采用活体观察和固定染色相结合的方法。共鉴定出纤毛虫91种,夏季49种,各样点物种数由小到大依次为:S2S4S8S5S1S3=S7S6。秋季64种,各样点物种数由小到大依次为:S4S3=S1=S2=S5S8S6=S7。夏季各样点丰度为1.2×10~4—5.6×10~5个/L,秋季各样点丰度在1.2×10~4—2.6×10~5个/L之间。夏、秋季的优势种均为12种且优势种组成与分布不同,表现该流域纤毛虫存在明显的时空差异;群落结构分析显示:纤毛虫群落结构简单,物种组成多样性低而分布均匀;纤毛虫营养功能结构分析表明,夏季B、S类群的物种丰富度低于秋季;相关分析表明,总磷和总氮是影响夏季纤毛虫物种多样性的主要环境因子,并且浊度、NH_4-N和NO_3-N是影响秋季纤毛虫的主要环境因子。 相似文献
34.
Identifying genomic locations that have experienced selective sweeps is an important first step toward understanding the molecular basis of adaptive evolution. Using statistical methods that account for the confounding effects of population demography, recombination rate variation, and single-nucleotide polymorphism ascertainment, while also providing fine-scale estimates of the position of the selected site, we analyzed a genomic dataset of 1.2 million human single-nucleotide polymorphisms genotyped in African-American, European-American, and Chinese samples. We identify 101 regions of the human genome with very strong evidence (p < 10−5) of a recent selective sweep and where our estimate of the position of the selective sweep falls within 100 kb of a known gene. Within these regions, genes of biological interest include genes in pigmentation pathways, components of the dystrophin protein complex, clusters of olfactory receptors, genes involved in nervous system development and function, immune system genes, and heat shock genes. We also observe consistent evidence of selective sweeps in centromeric regions. In general, we find that recent adaptation is strikingly pervasive in the human genome, with as much as 10% of the genome affected by linkage to a selective sweep. 相似文献
35.
巴特 《现代生物医学进展》2007,7(12):1824-1828
目的:表达纯化hPRL-1重组蛋白,分析其理化性质及酶学特性。方法:热激法将重组pET15b质粒转化入E.coli BL21中,IPTG诱导表达出His-tagged hPRL-1蛋白。使用Ni-NTA亲和层析法结合Mono Q离子交换层析法纯化。用SDS-PAGE法和Western Blot法进行表达情况的定性定量分析,并使用HPLC法鉴定蛋白纯度,计算出蛋白分子量,圆盘等电聚焦电泳分析重组蛋白等电点。比较分析以pNPP、4-MUP和DiFMUP为底物时的酶促反应动力学。同时以pNPP为底物测定酶的最适pH值;以4-MUP为底物测定酶的最适温度,分析探讨缓冲液离子强度与蛋白酪氨酸酶通用抑制剂钒酸钠对酶活力的影响。结果:以亲和层析和离子交换层析结合,可以纯化得到纯度约为95%的蛋白。测得蛋白分子量为24.54kD,等电点为9.11。以pNPP、4-MUP和DiFMUP为底物时Km分别为3720μmol/L,130μmol/L和50μmol/L。酶的最适pH值为7.6,最适温度为34℃。结论:纯化所得蛋白为目的蛋白hPRL-1;两步纯化相结合可以得到纯度较高的蛋白;三种底物特异性依次为DiFMUP>4-MUP>pNPP。 相似文献
36.
MyD88是IL-1R/TLR受体超家族向细胞内转导胞外信号时募集到受体胞浆尾部的重要接头蛋白．由TIR结构域介导的MyD88分子同源二聚化是它招募到受体胞浆尾部的前提,然后二聚化的MyD88再募集下游信号分子,传递信号,引发促炎基因的表达．本研究旨在建立一种模型,以实现活细胞原位的、基于荧光信号变化的MyD88二聚化抑制物的高通量筛选．我们分别构建了MyD88 TIR与GFP和RFP的融合蛋白表达质粒,瞬时转染HeLa细胞,在488 nm激发光下,转染GFP-MyD88 TIR和RFP-MyD88 TIR细胞,检测到绿色荧光与红色荧光间的共振能量转移(FRET)．而当细胞转染GFP-MyD88 TIR和RFP或RFP-MyD88 TIR和GFP,因TIR二聚化不能实现,FRET效率受到严重影响．实验结果提示,依赖双阳性表达GFP-MyD88 TIR和RFP-MyD88 TIR的细胞株,检测不同化合物对于荧光FRET效率的影响,可以建立MyD88 TIR二聚化抑制药物的筛选模型．此外,我们构建了原核表达质粒,利用纯化的His-MyD88 TIR分别与GST或GST-MyD88 TIR蛋白进行体外结合实验,发现GST-MyD88 TIR(而非GST)可以与His-MyD88 TIR相互结合．结果的差异性提示,利用His-MyD88 TIR和GST-MyD88 TIR体外结合实验分析,可以进一步确定抑制物是否直接阻断了TIR的相互作用．结合真核细胞的荧光FRET阻断结果和原核表达的重组蛋白相互作用分析,可确定MyD88 TIR二聚化的抑制物．利用这一模型可以对商品化的小分子库、自行制备的天然产物组分进行广泛的筛选,从中获得有效抑制MyD88二聚化的化合物,参与对MyD88信号通路依赖的慢性炎症、自身免疫性疾病的药物治疗． 相似文献
37.
报道中国鳖甲族1新纪录属及1新种:异颚弗鳖甲Freudeia heteromaxillaria sp.nov.,描述了新种的形态特征并附鉴别特征图和整体照片.新种模式标本保存于中国科学院西北高原生物研究所和河北大学博物馆. 相似文献
38.
报道中国鳖甲族1新纪录属及1新种:异颚弗鳖甲Freudeia heteromaxillaria sp.nov.,描述了新种的形态特征并附鉴别特征图和整体照片。新种模式标本保存于中国科学院西北高原生物研究所和河北大学博物馆。 相似文献
39.
GRAHAM E. ROTHERAY MARIA‐ANGELES MARCOS‐GARCÍA GEOFF HANCOCK CELESTE PÉREZ‐BAÑÓN CHRIS T. MAIER 《Zoological Journal of the Linnean Society》2009,156(4):697-749
We studied 42 species of saprophagous, Neotropical Copestylum (Diptera, Syrphidae) reared from decaying Cactaceae and Agavaceae. Thirty‐three species were reared during fieldwork in Bolivia, Costa Rica, Ecuador, Mexico, Peru, and Trinidad from 1998–2007. Nine species came from museum and private collections. Seven were new species. We describe these new species and the third stage larva and/or puparium and breeding sites of 40 species. Not described are two apparent species related to Copestylum apicale (Loew, 1866) reared from Cactaceae. Resolution of their status was beyond the scope of this paper but reference is made to their distinctive larval morphology. Based on early stage characters all reared species can be placed in ten species groups, all but three of which have been recognized previously on the basis of adult characters. A high level of congruence was found between adult and larval characters in terms of these species groups. Eight of the groups appear to be related closely and may represent a monophyletic lineage within Copestylum that has diversified in xeric habitats. Early stage morphology varied within and amongst groups but two trends in functional morphology are recognizable. One trend is towards feeding in watery decay and the other towards feeding in firmer decay. The latter trend is characterized by species that scoop food and use grinding mills in their head skeletons to break it up. They also have armoured thoraces with varying arrangements of sclerotized spicules or stiffened setae for gripping and protection during tunnelling, a short anal segment, and a short posterior breathing tube for protecting the openings. The former trend is characterized by species with opposite and contrasting features. They filter food and have well‐developed pre‐oral setal filters but they lack grinding mills or only have poorly developed grinding mills. They have reduced thoracic armature, elongate anal segments, and posterior breathing tubes which facilitates simultaneous feeding and respiration. Comparison with 23 Copestylum species reared from bromeliads (Bromeliaceae) suggests a common pattern of diversification in that species groups with the largest body sizes are more specialized. 相似文献
40.
We used a large panel of pedigreed, genetically admixed house mice to study patterns of recombination rate variation in a leading mammalian model system. We found considerable inter-individual differences in genomic recombination rates and documented a significant heritable component to this variation. These findings point to clear variation in recombination rate among common laboratory strains, a result that carries important implications for genetic analysis in the house mouse.THE rate of recombination—the amount of crossing over per unit DNA—is a key parameter governing the fidelity of meiosis. Recombination rates that are too high or too low frequently give rise to aneuploid gametes or prematurely arrest the meiotic cell cycle (Hassold and Hunt 2001). As a consequence, recombination rates should experience strong selective pressures to lie within the range defined by the demands of meiosis (Coop and Przeworski 2007). Nonetheless, classical genetic studies in Drosophila (Chinnici 1971; Kidwell 1972; Brooks and Marks 1986), crickets (Shaw 1972), flour beetles (Dewees 1975), and lima beans (Allard 1963) have shown that considerable inter-individual variation for recombination rate is present within populations. Recent studies examining the transmission of haplotypes in human pedigrees have corroborated these findings (Broman et al. 1998; Kong et al. 2002; Coop et al. 2008).Here, we use a large panel of heterogeneous stock (HS) mice to study variation in genomic recombination rates in a genetic model system. These mice are genetically admixed, derived from an initial generation of pseudorandom mating among eight common inbred laboratory strains (DBA/2J, C3H/HeJ, AKR/J, A/J, BALB/cJ, CBA/J, C57BL/6J, and LP/J), followed by >50 generations of pseudorandom mating in subsequent hybrid cohorts (Mott et al. 2000; Demarest et al. 2001). The familial relationships among animals in recent generations were tracked to organize the mice into pedigrees. In total, this HS panel includes ∼2300 animals comprising 85 families, 8 of which span multiple generations. The remainder consists of nuclear families (sibships) that range from 1 to 34 sibs, with an average of 9.6 sibs (Valdar et al. 2006) (Mott et al. 2000; Demarest et al. 2001; Shifman et al. 2006).
Open in a separate windowaThis family was composed of two sibships sharing a common mother but with different fathers.With the exception of several founding individuals, most of these HS mice have been genotyped at 13,367 single nucleotide polymorphisms (SNPs) across the genome (available at http://gscan.well.ox.ac.uk/). Although the publicly available HS genotypes have passed data quality filters (Shifman et al. 2006), we took several additional measures to ensure the highest possible accuracy of base calls. First, data were cleansed of all non-Mendelian inheritances, and genotypes with quality scores <0.4 were removed. Genotypes that resulted in tight (<10 cM in sex-specific distance) double recombinants were also omitted because strong positive crossover interference in the mouse renders such closely spaced crossovers biologically very unlikely (Broman et al. 2002). A total of 10,195 SNPs (including 298 on the X chromosome) passed these additional quality control criteria; the results presented below consider only this subset of highly accurate (>99.98%) and complete (<0.01% missing) genotypes. The cleaned data are publicly available (at http://cgd.jax.org/mousemapconverter/).We used the chrompic program within CRI-MAP (Lander and Green 1987; Green et al. 1990) to estimate the number of recombination events in parental meioses. The algorithm implemented in chrompic first phases parent and offspring genotypes using a maximum-likelihood approach. Next, recombination events occurring in the parental germline are identified by comparing parent and offspring haplotypes across the genome (Green et al. 1990). For example, a haplotype that first copies from one maternal chromosome and then switches to copying from the other maternal chromosome signals a recombination event in the maternal germline.chrompic is very memory intensive and cannot handle the multigenerational pedigrees and the large sibships included in the HS panel. To circumvent these computational limitations, several modifications to the data were implemented. First, the eight multigenerational pedigrees were split into 102 nonoverlapping sibships, retaining grandparental information when available (Cox et al. 2009). Finally, large sibships were subdivided: sibships with >13 progeny were split into two groups: those with >26 progeny were split into three groups and those with >39 sibs were split into four groups. Partitioning large sibships by units of 10, 11, or 12, rather than 13, had no effect on the estimation of crossover counts, suggesting that the estimates were robust to the unit of subdivision. These subdivided families were used only for haplotype inference; all other analyses treated whole sibships as focal units. In total, we analyzed 132 nonoverlapping sibships, ranging in size from 2 to 48 sibs (mean = 13.9). This data set encompassed 3640 meioses—300–2000% more meioses than previously studied human pedigrees (Broman et al. 1998; Kong et al. 2002; Coop et al. 2008)—providing excellent power to detect recombination rate variation among individuals.The recombination rate for the maternal (or paternal) parent of a given sibship was estimated as the average number of recombination events in the haploid maternal (or paternal) genomes transmitted to her (or his) offspring. Our analyses treat males and females separately, as previous observations in mice (Murray and Snell 1945; Mallyon 1951; Reeves et al. 1990; Dietrich et al. 1996; Shifman et al. 2006; Paigen et al. 2008), along with findings from this study, point to systematically higher recombination rates in female than in male mice (this study: P < 2.2 × 10−16, Mann–Whitney U-Test comparing autosomal crossover counts in the 131 HS females to those in the 131 HS males).There is considerable recombination rate heterogeneity among the 131 mothers and 131 fathers in the HS pedigrees (Figure 1). The female with the highest recombination rate had an average of nearly twice as many crossovers per meiosis compared with the lowest (female range: 9.0–17.3; mean = 13.3; SD = 3.28). Similarly, the least actively recombining male had only 55% the amount of recombination as the male with the highest recombination rate (male range: 7.7–14.7; mean = 11.7; SD = 2.76). These average values are similar to previously reported recombination counts in house mice, determined using both cytological (Dumas and Britton-Davidian 2002; Koehler et al. 2002) and genetic (Dietrich et al. 1996) approaches. Note that the recombination rates that we report reflect the number of exchange events visible in genetic data. Under the assumption of no chromatid interference, the expected number of crossovers that occur at meiosis is equal to twice these values.Open in a separate windowFigure 1.—Variation in recombination frequency in HS mice. The mean number of recombination events per transmitted gamete in each mother (A; n = 131) and father (B; n = 131) was inferred by comparing parent and offspring genotypes at >10,000 autosomal and X-linked markers using the CRIMAP chrompic computer program. Error bars span ±2 SEs.To test for variation in recombination within the HS females and within the HS males, we performed a one-way ANOVA using parental identity as the factor and the recombination count for a single haploid genome transmission on the pedigree as the response variable. Significance of the resultant F-statistic was empirically assessed by randomizing parental identity with respect to individual recombination counts, recomputing the F-statistic on the permuted data set, and determining the quantile position of the observed F-statistic along the distribution of 106 F-statistics derived from randomization. There is highly significant variation for genomic recombination rate among HS females (F = 1.7842, P < 10−6; Figure 1A) and males (F = 2.3103, P < 10−6; Figure 1B).We next examined patterns of recombination rate inheritance using the eight complex families to test for heritability of this trait. We fit a polygenic model of inheritance using the polygenic command within SOLAR v.4, accounting for the uneven relatedness among individuals through a matrix of pairwise coefficients of relatedness (Almasy and Blangero 1998). Sex was included as a covariate in the model to account for the well-established differences between male and female recombination rates in mice (Murray and Snell 1945; Mallyon 1951; Reeves et al. 1990; Dietrich et al. 1996; Shifman et al. 2006; Paigen et al. 2008). Recombination rates show significant narrow-sense heritability (h2 = 0.46; SE = 0.20; P = 0.008), indicating that variation for recombination rate among HS mice is partly attributable to additive genetic variation. This result agrees with previous evidence for genetic effects on recombination rate variation in the house mouse (Reeves et al. 1990; Shiroishi et al. 1991; Koehler et al. 2002).In summary, we have shown that HS mice differ significantly in their genomic recombination rates and have demonstrated that this variation is heritable. These findings indicate that interstrain variation for genomic average recombination rate exists among at least two of the eight progenitor strains of the HS stock, mirroring observations of significant variation among inbred laboratory strains for many other quantitative characters (Grubb et al. 2009). Indeed, cytological analyses have already revealed significant differences in recombination frequencies between A/J and C57BL/6J males (Koehler et al. 2002), two of the HS founding strains.This interstrain variation in genomic recombination rate carries important practical implications for genetic analysis in the house mouse. Most notably, crosses using inbred mouse strains with high recombination rates will provide higher mapping resolution than crosses using strains with reduced recombination rates. However, the strategic use of high-recombination-rate strains will not necessarily expedite the fine mapping of loci. The distribution of recombination events in mice is not uniform across chromosomes and appears to be strain specific (Paigen et al. 2008; Grey et al. 2009; Parvanov et al. 2009).The history of the classical inbred mouse strains as inferred from pedigrees (Beck et al. 2000), sequence comparisons to wild mice (Salcedo et al. 2007), and genomewide phylogenetic analyses (Frazer et al. 2007; Yang et al. 2007) suggests that much of the interstrain variation for recombination rate arises from genetic polymorphism among Mus domesticus individuals in nature. However, many other factors have likely shaped recombination rate variation among the classical strains, including inbreeding, artificial selection, and hybridization with closely related species (Wade and Daly 2005). These aspects of the laboratory mouse''s history challenge comparisons between recombination rate variation in the HS panel and human populations and provide strong motivation for studies of recombination rate variation in natural populations of house mice.Although we find a strong genetic component to inter-individual variation in recombination rate, a large fraction (∼54%) of the phenotypic variation for recombination is not explained by additive genetic variation alone. Sampling error and other forms of genetic variation (e.g., dominance and epistasis) likely combine to account for some of the residual variation. In addition, micro-environmental differences within the laboratory setting (Koren et al. 2002) and life history differences among families, including parental age (Koehler et al. 2002; Kong et al. 2004), might contribute to variation in recombination rates among the HS mice.Identifying the genetic loci that underlie recombination rate differences among the HS mice (and hence in the eight founding inbred strains) presents a logical next step in the research program initiated here. The complicated pedigree structure, relatively small number of animals with recombination rate estimates (n = 262), and potentially sex-specific genetic architecture of this trait (Kong et al. 2008; Paigen et al. 2008) will pose challenges to this analysis. Nonetheless, dissecting the genetic basis of recombination rate variation is a pursuit motivated by its potential to lend key insights into several enduring questions. Why do males and females differ in the rate and distribution of crossover events? What are the evolutionary mechanisms that give rise to intraspecific polymorphism and interspecific divergence for recombination rate? What are the functional consequences of recombination rate variation? Alternative experimental approaches, including those that combine the power of QTL mapping with immunocytological assays for measuring recombination rates in situ (Anderson et al. 1999), promise to offer additional clues onto the genetic mechanisms that give rise to variation in this important trait. 相似文献
TABLE 1
Heterogeneous stock mouse pedigrees| Pedigree | Pedigree class | No. of nonoverlapping sibships in the pedigree | No. of retained sibships | No. of meioses |
|---|---|---|---|---|
| 1 | Multigenerational | 17 | 17 | 464 |
| 2 | Multigenerational | 27 | 20 | 728 |
| 3 | Multigenerational | 23 | 19 | 602 |
| 4 | Multigenerational | 14 | 9 | 254 |
| 5 | Multigenerational | 11 | 9 | 242 |
| 6 | Multigenerational | 5 | 3 | 68 |
| 7 | Multigenerational | 4 | 3 | 100 |
| 8 | Multigenerational | 2 | 1 | 16 |
| 9 | Sibshipa | 2 | 1 | 20 |
| 32–85 | Sibship | 51 | 1146 | |
| Total | 180 | 132 | 3640 |