Embryonic lethality leads to hybrid male inviability in hybrids between Drosophila melanogaster and D. santomea

The study of the morphological defects unique to interspecific hybrids can reveal which developmental pathways have diverged between species. Drosophila melanogaster and D. santomea diverged more than 10 million years ago, and when crossed produce sterile adult females. Adult hybrid males are absent from all interspecific crosses. We aimed to determine the fate of these hybrid males. To do so, we tracked the development of hybrid females and males using classic genetic markers and techniques. We found that hybrid males die predominantly as embryos with severe segment‐specification defects while a large proportion of hybrid females embryos hatch and survive to adulthood. In particular, we show that most male embryos show a characteristic abdominal ablation phenotype, not observed in either parental species. This suggests that sex‐specific embryonic developmental defects eliminate hybrid males in this interspecific cross. The study of the developmental abnormalities that occur in hybrids can lead to the understanding of cryptic molecular divergence between species sharing a conserved body plan.     

贵州马比木内生真菌的多样性研究

为了解贵州省马比木内生真菌的多样性,通过采集贵阳修文、遵义播州、铜仁万山3个县区的不同季节的健康马比木植物不同组织部位样本进行内生真菌的分离,分析分离菌ITS rDNA序列,采用分子系统学方法,对3个地区的不同季节马比木植物不同组织部位的内生真菌进行鉴定、归类,并进行多样性评价。结果表明,从1 444个马比木组织块中分离出1 037株内生真菌,分别隶属于30个属,其中间壳座属Diaporthe为优势属,分离率与分离频率分别为40.24%与57.58%;夏季内生真菌的多样性指数最高,4个季节的相似度在0.40-0.71之间,贵阳的相似性指数最高,三地的相似性指数在0.42-0.55之间,果实的多样性指数最高,各个组织部位的相似性指数在0.00-0.54之间。表面植株生长环境及部位对内生真菌的组成和多样性均有影响。     

Landscape distribution of food and nesting sites affect larval diet and nest size,but not abundance of Osmia bicornis

Habitat fragmentation is a major threat for beneficial organisms and the ecosystem services they provide. Multiple‐habitat users such as wild bees depend on both nesting and foraging habitat. Thus, they may be affected by the fragmentation of at least two habitat types. We investigated the effects of landscape‐scale amount of and patch isolation from both nesting habitat (woody plants) and foraging habitat (specific pollen sources) on the abundance and diet of Osmia bicornis L. Trap‐nests of O. bicornis were studied in 30 agricultural landscapes of the Swiss Plateau. Nesting and foraging habitats were mapped in a radius of 500 m around the sites. Pollen composition of larval diet changed as isolation to the main pollen source, Ranunculus, increased, suggesting that O. bicornis adapted its foraging strategy in function of the nest proximity to main pollen sources. Abundance of O. bicornis was neither related to isolation or amount of nesting habitat nor to isolation or abundance of food plants. Surprisingly, nests of O. bicornis contained fewer larvae in sites at forest edge compared to isolated sites, possibly due to higher parasitism risk. This study indicates that O. bicornis can nest in a variety of situations by compensating scarcity of its main larval food by exploiting alternative food sources.     

Bioremediation of DDT in soil by genetically improved strains of soil fungus Fusarium solani

Bioremediation of DDT in soil by genetically improved recombinants of the soil fungus Fusarium solani was studied. The parent strains were isolated from soil enriched with DDD or DDE (immediate anaerobic and aerobic degradation products of DDT), as further degradation of these products are slow processes compared to the parent compound. These naturally occurring strains isolated from soil, however, are poor degraders of DDT and differed in their capability to degrade its metabolites such as DDD, DDE, DDOH and DBP and other organochlorine pesticides viz. kelthane and lindane. Synergistic effect was shown by some of these strains, when grown together in the medium containing DDD and kelthane under mixed culture condition. No synergism in DDE degradation was observed with the strains isolated from enriched soil. DDD-induced proteins extracted from individual culture filtrate (exo-enzyme) when subjected to SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed complementary polypeptide bands in these strains i.e., each strain produced distinct DDD degrading polypeptide bands and the recombinant or hybrid strains produced all of the bands of the two parents and degraded DDD better than the parental strains. Recombinant hybrid strains with improved dehalogenase activity were raised by parasexual hybridisation of two such complementary isolates viz. isolate 1(P-1) and 4(P-2) showing highest complementation and are compatible for hyphal fusion inducing heterokaryosis. These strains are genetically characterised as Kel⁺Ben^RDBP^-Lin^- and Kel^-Ben^rDBP⁺Lin⁺ respectively.Recombinants with mixed genotype, i.e., Kel⁺Ben^RDBP⁺Lin⁺ showing superior degradation quality for DDT were selected for bioremediation study. Recombination was confirmed by polypeptide band analysis of DDD induced exo-proteins from culture filtrate usingSDS-Polyacrylamide Gel Electrophoresis (PAGE) and RAPD (Random Amplified Polymorphic DNA) of genomic DNA using PCR (Polymerase Chain Reaction) technique. SDS-PAGE showed combination of DDD induced polypeptide bands characteristic of both the parents in the recombinants or the hybrids. PCR study showed the parent specific bands in the recombinant strains confirming gene transformation.     

Ready-to-use DNA extracted with a CTAB method adapted for herbarium specimens and mucilaginous plant tissue

This report summarizes major changes in previously published protocols for DNA extraction to improve the quality of DNA extracted from plants. Here, we highlight the critical modifications in the original protocols. The efficiency of these changes results in high-quality DNA ready to use in a variety of phytogenetically distant plant families, in particular species with mucopolysaccharides. The DNA obtained can be used without further purification in various molecular biology assays, including direct sequencing and AFLP and RAPD (random-amplified polymorphic DNA) analyses. The effectiveness of this method is proven by the amplification and sequencing of PCR products of up to 1 kb with DNA extracted from herbarium tissue ≥60 years old. This versatility is not usually found in DNA extraction protocols. In addition, this method is quick, adaptable to standard laboratories, and most important, safer and more cost-effective.     

Genetic population structure of the endemic fourline wrasse (Larabicus quadrilineatus) suggests limited larval dispersal distances in the Red Sea

The connectivity among marine populations is determined by the dispersal capabilities of adults as well as their eggs and larvae. Dispersal distances and directions have a profound effect on gene flow and genetic differentiation within species. Genetic homogeneity over large areas is a common feature of coral reef fishes and can reflect high dispersal capability resulting in high levels of gene flow. If fish larvae return to their parental reef, gene flow would be restricted and genetic differentiation could occur. Larabicus quadrilineatus (Labridae) is considered as an endemic fish species of the Red Sea and Gulf of Aden. The juveniles of this species are cleaner fish that feed on ectoparasites of other fishes. Here, we investigated the genetic population structure and gene flow in L. quadrilineatus among five locations in the Red Sea to infer connectivity among them. To estimate genetic diversity, we analysed 369 bp of 237 mitochondrial DNA control region sequences. Haplotype and nucleotide diversities were higher in the southern than in the northern Red Sea. Analysis of molecular variance (amova) detected the highest significant genetic variation between northern and central/southern populations (Phi(CT) = 0.01; P < 0.001). Migration analysis revealed a several fold higher northward than southward migration, which could be explained by oceanographic conditions and spawning season. Even though the Phi(ST) value of 0.01 is rather low and implies a long larval dispersal distance, estimates based on the isolation-by-distance model show a very low mean larval dispersal distance (0.44-5.1 km) compared to other studies. In order to enable a sustainable ornamental fishery on the fourline wrasse, the results of this study suggest that populations in the northern and southern Red Sea should be managed separately as two different stocks. The rather low larval dispersal distance of about 5 km needs to be considered in the design of marine protected areas to enable connectivity and self-seeding.     

The isolation of Saccharomyces cerevisiae nuclear membranes with nuclease and high-salt treatment

Saccharomyces cerevisiae nuclear membranes were prepared from isolated nuclei by digesting chromatin with deoxyribonuclease and ribonuclease, washing of residual nuclei with 0.5 M MgCl₂, and discontinuous gradient centrifugation in buffered Ficoll solutions. Electron microscopic examination of the preparations showed single membrane and double membrane vesicles and membrane sheets. Pores or residual pores were often visible. In double membrane profiles the two unit membranes were often separated by the remains of the perinuclear cistern. The nuclear membrane fragments contained 58% protein, 23.8% phospholipid, 6% sterols, 7.1% neutral acylglycerols, 4.8% RNA, and 0.3% DNA. The phospholipid content of the membrane preparations was influenced by a phospholipase activity with acidic pH optimum.     

Isolation and characterization of plasma membrane from lactating bovine mammary gland

Plasma membranes were isolated from lactating bovine mammary gland. Two crude membrane fractions; medium/d 1.033 (light membrane) and 1.033/1.053 interfaces (heavy membrane), were obtained by Ficoll density gradient centrifugation of osmotically washed microsomal fraction. Two crude membranes were further purified separately by sucrose density gradient centrifugation. Both light and heavy membranes banded at a sucrose density of 1.14. The purified membranes appeared as heterogeneous smooth membrane vesicles on electron microscopy. The contaminating suborganelles were not detected. The yield of the purified membranes relative to the homogenate was 1.2%. The degree of purity of the membranes was shown by a great increase in the specific activity of 5′-nucleotidase over the homogenate of 20-fold for light membrane and of 16-fold for heavy membrane. The relative activities of Mg²⁺-ATPase, (Na⁺ + K⁺)-ATPase, γ-glutamyl transpeptidase, phosphodiesterase I, akaline phosphatase and xanthine oxidase were also high (12–18-times) and nearly 20% of these enzymes was recovered. The activity of marker enzyme for mitochondria, endoplasmic reticulum and Golgi apparatus was very low, while that of acid phosphatase for lysosome was relatively high (5-times). DNA and RNA contents were very low. The major polypeptides rich in other suborganelles were not detected profoundly in the membrane fraction and the polypeptide compositions in both light and heavy membranes were similar upon SDS-polyacrylamide gel electrophoresis.     

Progress in leaf protoplast isolation and culture from virus-free axenic shoot cultures of Vitis vinifera L.

Axenic shoot cultures of virus-free Vitis vinifera L. cv. Soultanina were a highly efficient source for isolation of viable protoplasts. Optimum results were obtained with leaves of 50–100 mg fresh weight, leaf discs of 0.7 cm in diameter, 100 and 15 U ml^-1 Cellulase R-10 and Macerozyme R-10, respectively, and 18 h reaction time in either light or in darkness. Protoplast yield was approx. 25×10⁶ viable protoplasts per g fresh weight and their size ranged from 12 to 44 m. During a 20-day culture period, the maximum survival rate obtained was approx. 40%. A plating density of 10×10⁵ protoplasts per ml resulted in increased survival rates. Various growth regulators and glutamine did not significantly improve survival rates of protoplasts, whereas extract from coconut added to the culture medium caused an increase in the survival rates of protoplasts. Cell elongation at a significant rate and divisions were observed. [¹⁴C]glucose uptake was studied as an index of cell membrane integrity and functioning. Uptake rate of glucose by protoplasts was linear for up to 60 min, fully inhibited by NaN₃, with an optimum pH of 4.8. Protoplasts 24 h old exhibited significantly lower rates of glucose uptake.     

A comparison of individual‐based genetic distance metrics for landscape genetics

A major aim of landscape genetics is to understand how landscapes resist gene flow and thereby influence population genetic structure. An empirical understanding of this process provides a wealth of information that can be used to guide conservation and management of species in fragmented landscapes and also to predict how landscape change may affect population viability. Statistical approaches to infer the true model among competing alternatives are based on the strength of the relationship between pairwise genetic distances and landscape distances among sampled individuals in a population. A variety of methods have been devised to quantify individual genetic distances, but no study has yet compared their relative performance when used for model selection in landscape genetics. In this study, we used population genetic simulations to assess the accuracy of 16 individual‐based genetic distance metrics under varying sample sizes and degree of population genetic structure. We found most metrics performed well when sample size and genetic structure was high. However, it was much more challenging to infer the true model when sample size and genetic structure was low. Under these conditions, we found genetic distance metrics based on principal components analysis were the most accurate (although several other metrics performed similarly), but only when they were derived from multiple principal components axes (the optimal number varied depending on the degree of population genetic structure). Our results provide guidance for which genetic distance metrics maximize model selection accuracy and thereby better inform conservation and management decisions based upon landscape genetic analysis.