小麦植物铁载体分泌基因的染色体定位

采用室内控制生长条件的营养液培养技术,通过检测缺铁条件下２０个中国春的Ｈｏｐｅ染色体代换系及其亲本中国春和Ｈｏｐｅ小麦植物铁载本分泌的动态变化规律以及植物铁载体分泌高峰期内５次测定值的汇总资料,对六倍体小麦ＰＳ分泌基因进行染色体定位。ＰＳ分泌率通过根分泌物对新形成的Ｆｅ（ＯＨ）３的活化能力进行测定,在缺铁症出现时每隔２,３天测定１次,随着缺铁失绿症严重程度的增加,ＰＳ分泌率呈现迅速增高再逐渐降低的     

Heritability estimates from genomewide relatedness matrices in wild populations: Application to a passerine,using a small sample size

Genomic developments have empowered the investigation of heritability in wild populations directly from genomewide relatedness matrices (GRM). Such GRM‐based approaches can in particular be used to improve or substitute approaches based on social pedigree (PED‐social). However, measuring heritability from GRM in the wild has not been widely applied yet, especially using small samples and in nonmodel species. Here, we estimated heritability for four quantitative traits (tarsus length, wing length, bill length and body mass), using PED‐social, a pedigree corrected by genetic data (PED‐corrected) and a GRM from a small sample (n = 494) of blue tits from natural populations in Corsica genotyped at nearly 50,000 filtered SNPs derived from RAD‐seq. We also measured genetic correlations among traits, and we performed chromosome partitioning. Heritability estimates were slightly higher when using GRM compared to PED‐social, and PED‐corrected yielded intermediate values, suggesting a minor underestimation of heritability in PED‐social due to incorrect pedigree links, including extra‐pair paternity, and to lower information content than the GRM. Genetic correlations among traits were similar between PED‐social and GRM but credible intervals were very large in both cases, suggesting a lack of power for this small data set. Although a positive linear relationship was found between the number of genes per chromosome and the chromosome heritability for tarsus length, chromosome partitioning similarly showed a lack of power for the three other traits. We discuss the usefulness and limitations of the quantitative genetic inferences based on genomic data in small samples from wild populations.     

干旱环境中褐家鼠的种群数量动态研究

动物种群数量动态研究是种群生态学研究的主要对象之一．借用Leslei矩阵建立数学模型对分布在新疆北部干旱环境中的褐家鼠种群数量动态进行了预测．同时经计算得新疆北部干旱环境中褐家鼠种群的特征根(λ),及其对应的特征向量(ns)．结果表明,12年后雌体总数达到29 801．686 28,同时根据褐家鼠种群增长曲线,发现该种群的增长属于稳定型的指数增长类型．     

Study of the deactivation of β-galactosidase entrapped in alginate-carrageenan gels

The stability of β-galactosidase entrapped in Ca-alginate–K-κ-carrageenan gels under operation conditions was studied. The thermal deactivation of the immobilised enzyme and the biocatalyst protein loss due to gel swelling were taken into account in the mass balance of the enzymatic reaction rate expression.

Time-temperature effect was the most important factor in the biocatalyst deactivation reaction. However, results showed that the enzyme entrapped in gels was partially lost by gel swelling, which was a source of error in predicting results in continuous processes. The enzyme loss determined in this work showed a non-linear behaviour and it depended on mixing conditions of the reactor.

Values of protein loss were used in the modelling of a fixed-bed reactor with similar flow conditions to reduce the error in predicting the operation conditions to maintain a constant conversion.

For reaction conditions similar to those analysed in this work, the β-galactosidase was well entrapped in alginate-carrageenan matrices.     

Expected Relationship Between the Silent Substitution Rate and the GC Content: Implications for the Evolution of Isochores

The relationship between the silent substitution rate (K _s) and the GC content along the genome is a focal point of the debate about the origin of the isochore structure in vertebrates. Recent estimation of the silent substitution rate showed a positive correlation between K _s and GC content, in contradiction with the predictions of both the regional mutation bias model and the selection or biased gene conversion model. The aim of this paper is to help resolve this contradiction between theoretical studies and data. We analyzed the relationship between K _s and GC content under (1) uniform mutation bias, (2) a regional mutation bias, and (3) mutation bias and selection. We report that an increase in K _s with GC content is expected under mutation bias because of either nonequilibrium of the isochore structure or an increasing mutation rate from AT toward GC nucleotides in GC-richer isochores. We show by simulations that CpG deamination tends to increase the mutation rate with GC content in a regional mutation bias model. We also demonstrate that the relationship between K _s and GC under the selectionist or biased gene conversion model is positive under weak selection if the mutation selection equilibrium GC frequency is less than 0.5. Received: 28 March 2001 / Accepted: 16 May 2001     

Pairwise null model analyses of temporal patterns of bird assemblages contradict the assumptions of competition theory

Compensatory dynamics assume inverse patterns of population dynamics of species with similar ecological resource requirements (temporal segregation). The objective of this study was to test this hypothesis on temporal samples (10–57 years) of 19 breeding bird assemblages of various habitats. We used presence/absence null model (SIM2) in combination with the C-score and Sørensen indices. The C-score index estimates the average number of checkerboards for two species, while the Sørensen index measures the qualitative similarity of co-occurrence between two species in a time series. We used pairwise null model analysis to select significant species pairs based on three selection criteria: the standard confidence interval criterion, conservative empirical Bayes mean based criterion and confidence limit based criterion. Altogether, 21 402 species pairs were analysed. The SIM2 algorithm detected from 157 to 7 segregated pairs depending on the selection criterion. The number of significant negative pairs with possible biological significance (foraging guild membership, predator–prey interactions) was far lower and represented approximately 0.0–0.3% (4–65) of pairs in a matrix. Indeed, the number of detected negative associations depended on the selection criterion. Moreover, the number of segregated pairs was negatively related to the area of the census plots and fill of the species matrix. Our results underline the minor importance of interspecific competitive interactions in temporal patterns of bird assemblages. Instead, we suggest that stochastic factors, climate or heterospecific social information may lead to more or less synchronous dynamics of bird pairs.     

Phylogenies based on combined mitochondrial and nuclear sequences conflict with morphologically defined genera in the eimeriid coccidia (Apicomplexa)

Partial mitochondrial (mt) cytochrome c oxidase subunit I (COI) and near-complete nuclear (nu) 18S rDNA sequences were obtained from various eimeriid coccidia infecting vertebrates. New and published sequences were used in phylogenetic reconstructions based on nu 18S rDNA, mt COI and concatenated sequence datasets. Bayesian analyses of nu 18S rDNA sequences used secondary structure-based alignments with a doublet nucleotide substitution model; the codon nucleotide substitution model was applied to COI sequences. Although alignment of the mt COI sequences was unambiguous, substitution saturation was evident for comparisons of COI sequences between ingroup (eimeriid) and outgroup (sarcocystid) taxa. Consequently, a combined dataset applying partition-specific analytical and alignment improvements was used to generate a robust molecular phylogeny. Most eimeriid parasites that infect closely related definitive hosts were found in close proximity on the resulting tree, frequently in a single clade. Whether this represents coevolution or co-accommodation or a combination remains an open point. Unlike host associations, basic oocyst configuration (number of sporocysts per oocyst and sporozoites per sporocyst) was not correlated with phylogeny. Neither ‘Eimeria-type’ nor ‘Isospora-type’ oocyst morphotypes formed monophyletic groups. In the combined dataset tree (representing only a tiny fraction of described eimeriid coccidia), at least 10 clades of Eimeria spp. would need to be re-assigned to nine distinct genera to resolve their paraphyly. The apparent lack of congruence between morphotype and genotype will require taxonomists to balance nomenclatural stability and diagnostic ease against the ideal of monophyletic genera. For now, recognition of paraphyletic eimeriid genera defined by basic oocyst configuration may be necessary for reasons of taxonomic stability and diagnostic utility. Future taxonomic revisions to produce monophyletic eimeriid genera will ultimately require the identification of reliable phenotypic characters that agree with the molecular phylogeny of these parasites or, less optimally, acceptance that genotyping may be needed to support monophyletic supraspecific taxonomic groups.     

用分子原位杂交（GISH）鉴定小麦－簇毛麦双倍体、附加系、代换系和易位系

用生物素标记的簇毛麦（Ｈａｙｎａｌｄｉａｖｉｌｌｏｓａ）染色体组ＤＮＡ（ｔｏｔａｌｇｅｎｏｍｉｃＤＮＡ）作探针,以普通小麦染色体组ＤＮＡ作遮盖（用量１：２００左右）,进行有丝分裂中期和减数分裂中期Ｉ染色体的分子原位杂交（ＧＩＳＨ）,经抗生物素蛋白－辣根过氧化物酶复合物（ｂｉｏ－ｓｔｒｅｐｔａｖｉｄｉｎ－ｈｏｒｓｅｒａｄｉｓｈｐｅｒｏｘｉｄａｓｅ）和联苯胺四盐酸（ＤＡＢ）检测显色后,小麦－簇毛麦双倍体、附加系、代换系和易位系中的簇毛麦染色体及染色体片段显棕色,与显浅蓝色的小麦染色体可明显区分。用ＧＩＳＨ不仅可以检测导入小麦中的簇毛麦染色质,而且可以清楚地显示出易位染色体断裂点的确切位置。将ＧＩＳＨ用于减数分裂期染色体配对分析,还可以清晰形象地显示出同源和非同源染色体之间的配对和分离情况。