用抗性筛选法选育γ—亚麻酸（GLA）高产菌株

以深黄被孢霉（Mortierella isabellina）为出发菌株,经紫外线诱变处理,采用抗性筛选法,直接在梯度平板上挑选取抗脂肪酸脱氢酶抑制物抑芽丹（maleic hydrazide）的菌株进行初筛,然后经摇瓶发酵法测定相关性能指标进行得筛,获得一株生产性能比出发菌株显提高的突变株M80,其菌体收率达25.10g/L、油脂产率达12.35g/L、γ-亚麻酸（GLA）产率达771.88mg/L。     

Horizontal transmission, vertical inactivation, and stochastic loss of mariner-like transposable elements

Horizontal transmission has been well documented as a major mechanism for the dissemination of mariner-like elements (MLEs) among species. Less well understood are mechanisms that limit vertical transmission of MLEs resulting in the "spotty" or discontinuous distribution observed in closely related species. In this article we present evidence that the genome of the common ancestor of the melanogaster species subgroup of Drosophila contained an MLE related to the mellifera (honey bee) subfamily. Horizontal transmission, approximately 3-10 MYA, is strongly suggested by the observation that the sequence of the MLE in Drosophila erecta is 97% identical in nucleotide sequence with that of an MLE in the cat flea, Ctenocephalides felis. The D. erecta MLE has a spotty distribution among species in the melanogaster subgroup. The element has a high copy number in D. erecta and D. orena, a moderate copy number in D. teissieri and D. yakuba, and was apparently lost ("stochastic loss") in the lineage leading to D. melanogaster, D. simulans, D. mauritiana, and D. sechellia. In D. erecta, most copies are concentrated in the heterochromatin. Two copies from D. erecta, denoted De12 and De19, were cloned and sequenced, and they appear to be nonfunctional ("vertical inactivation"). It therefore appears that the predominant mode of MLE evolution is vertical inactivation and stochastic loss balanced against occasional reinvasion of lineages by horizontal transmission.      

Complement component C3: molecular basis of the C3*S025 variant and evidence for molecular heterogeneity of other variants

Complement component 3 (C3) is the central molecule of the complement system. It displays a number of polymorphic variants with, as yet, unclear functional consequences. We have investigated a number of rare C3 variants by PCR-SSCP (polymerase chain reaction-single strand conformation polymorphism) analysis and could identify the molecular basis of a C3^*S025 variant. The decreased electrophoretic mobility of this protein is caused by the exchange of a neutral serine residue to an arginine residue (positively charged). This exchange is unlikely to have functional consequences as it maps to the C-terminus of the -chain. C3 variants appear to have originated from various independent mutations as we could not detect this mutation in different allotypes.     

The mouse C1q genes are clustered on chromosome 4 and show conservation of gene organization

Mouse complement component C1q is a serum glycoprotein which consists of six A chains, six B chains and six C chains. The three polypeptides are 223, 228, and 217 residues long, respectively, and are encoded by three genes. DNA probes for mouse C1q A, B, and C chains were hybridized to Southern blots of DNA obtained from various inbred mouse strains. On the basis of fragment length polymorphisms, two different alleles of each of the genes could be identified. The distribution of these alleles was determined in the BXD and LXPL recombinant inbred strain series. Comparison with previously reported strain distribution patterns shows that the genes encoding mouseClq map to the same locus on distal chromosome 4. Overlapping clones spanning the entire gene cluster ofClq were isolated from genomic libraries using specific cDNA probes. The three genesClqA, ClqB, andClqC are closely arranged on a 19 kilobase stretch of DNA in the 5 to 3 orientation A-C-B. Each gene consists of two exons separated by one intron. Sequence comparison of Clq from three different species have shown that the B chains have the strongest similarity. Southern blot analysis of chromosomal DNA from 14 vertebrate species demonstrated highest similarity between theClqB genes, followed byClqC and finallyClqA.The nucleotide sequence data reported in this paper have been submitted to the EMBL, GenBank, and DDBJ nucleotide sequence databases and have been assigned the accession numbers X92958 (ClqA), X92959 (ClqB), and X92960 (ClqC)     

Small steps or giant leaps for male-killers? Phylogenetic constraints to male-killer host shifts

Background  

Arthropods are infected by a wide diversity of maternally transmitted microbes. Some of these manipulate host reproduction to facilitate population invasion and persistence. Such parasites transmit vertically on an ecological timescale, but rare horizontal transmission events have permitted colonisation of new species. Here we report the first systematic investigation into the influence of the phylogenetic distance between arthropod species on the potential for reproductive parasite interspecific transfer.     

Physiological responses of spring rapeseed (Brassica napus) to red/far‐red ratios and irradiance during pre‐ and post‐flowering stages

Early shade signals promote the shade avoidance syndrome (SAS) which causes, among others, petiole and shoot elongation and upward leaf position. In spite of its relevance, these photomorphogenic responses have not been deeply studied in rapeseed (Brassica napus). In contrast to other crops like maize and wheat, rapeseed has a complex developmental phenotypic pattern as it evolves from an initial rosette to the main stem elongation and an indeterminate growth of floral raceme. In this work, we analyzed (1) morphological and physiological responses at individual level due to low red/far‐red (R/FR) ratio during plant development, and (2) changes in biomass allocation, grain yield and composition at crop level in response to high R/FR ratio and low irradiance in two modern spring rapeseed genotypes. We carried out pot and field experiments modifying R/FR ratios and irradiance at vegetative or reproductive stages. In pot experiments, low R/FR ratio increased the petiole and lamina length, upward leaf position and also accelerated leaf senescence. Furthermore, low R/FR ratio reduced main floral raceme and increased floral branching with higher remobilization of soluble carbohydrates from the stems. In field experiments, low irradiance during post‐flowering reduced grain yield, harvest index and grain oil content, and high R/FR ratio reaching the crop partially alleviated such effects. We conclude that photomorphogenic signals are integrated early during the vegetative growth, and irradiance has stronger effects than R/FR signals at rapeseed crop level.