Rapid cold-hardening increases membrane fluidity and cold tolerance of insect cells

The rapid cold-hardening (RCH) response not only confers dramatic protection against cold-shock (non-freezing) injury, but also "instantaneously" enhances organismal performance. Since cold-shock injury is associated with damage to the cell membrane, we investigated the relationship between RCH and changes in cold tolerance and membrane fluidity at the cellular level. None of the adult flies (Sarcophaga bullata) in the cold-shocked treatment group survived direct transfer to -8 degrees C for 2 h; in contrast, 64.5% of flies in the RCH group survived exposure to -8 degrees C. Differences between the treatment groups also were reflected at the cellular level; only 21.3% of fat body cells in the cold-shocked group survived compared to 68.5% in the RCH group. Using 31P solid-state NMR spectroscopy, we determined that membrane fluidity increased concurrently with rapid cold-hardening of fat body cells. This result suggests that membrane characteristics may be modified very rapidly to protect cells against cold-shock injury.     

Chill sensitivity of honey bee, Apis mellifera, embryos

Improved methods for preservation of honey bee, Apis mellifera L., germplasm would be very welcome to beekeeping industry queen breeders. The introduction of two parasites and the emergence of an antibiotic resistant disease have increased demands for resistant stock. Techniques for artificial insemination of queens are available, and semen has been cryopreserved with limited success. However, cryopreservation of embryos for rearing queens would mesh well with current practices and also provide drones (haploid males). Eggs at five ages between twenty-four hours and sixty-two hours were exposed to 0, -6.6, and/or -15 degrees C for various times, and successful hatch measured. Honey bee embryos show chill sensitivity as do other insect embryos, and the rate of chill injury increases dramatically with decrease in holding temperature. The 48 h embryos in both groups showed the greatest tolerance to chilling, although 44 h embryos were only slightly less so.     

The evolution of female mating preferences: differentiation from species with promiscuous males can promote speciation

Females of many species are frequently courted by promiscuous males of their own and other closely related species. Such mating interactions may impose strong selection on female mating preferences to favor trait values in conspecific males that allow females to discriminate them from their heterospecific rivals. We explore the consequences of such selection in models of the evolution of female mating preferences when females must interact with heterospecific males from which they are completely postreproductively isolated. Specifically, we allow the values of both the most preferred male trait and the tolerance of females for males that deviate from this most preferred trait to evolve. Also, we consider situations in which females base their mating decisions on multiple male traits and must interact with males of multiple species. Females will rapidly differentiate in preference when they sometimes mistake heterospecific males for suitable mates, and the differentiation of female preference will select for conspecific male traits to differentiate as well. In most circumstances, this differentiation continues indefinitely, but slows substantially once females are differentiated enough to make mistakes rare. Populations of females with broader preference functions (i.e., broader tolerance for males with trait values that deviate from females' most preferred values) will evolve further to differentiate if the shape of the function cannot evolve. Also, the magnitude of separation that evolves is larger and achieved faster when conspecific males have lower relative abundance. The direction of differentiation is also very sensitive to initial conditions if females base their mate choices on multiple male traits. We discuss how these selection pressures on female mate choice may lead to speciation by generating differentiation among populations of a progenitor species that experiences different assemblages of heterospecifics. Opportunities for differentiation increase as the number of traits involved in mate choice increase and as the number of species involved increases. We suggest that this mode of speciation may have been particularly prevalent in response to the cycles of climatic change throughout the Quaternary that forced the assembly and disassembly of entire communities on a continentwide basis.     

Yarrowia lipolytica possesses two plasma membrane alkali metal cation/H+ antiporters with different functions in cell physiology

The family of Nha antiporters mediating the efflux of alkali metal cations in exchange for protons across the plasma membrane is conserved in all yeast species. Yarrowia lipolytica is a dimorphic yeast, phylogenetically very distant from the model yeast Saccharomyces cerevisiae. A search in its sequenced genome revealed two genes (designated as YlNHA1 and YlNHA2) with homology to the S. cerevisiae NHA1 gene, which encodes a plasma membrane alkali metal cation/H+ antiporter. Upon heterologous expression of both YlNHA genes in S. cerevisiae, we showed that Y. lipolytica antiporters differ not only in length and sequence, but also in their affinity for individual substrates. While the YlNha1 protein mainly increased cell tolerance to potassium, YlNha2p displayed a remarkable transport capacity for sodium. Thus, Y. lipolytica is the first example of a yeast species with two plasma membrane alkali metal cation/H+ antiporters differing in their putative functions in cell physiology; cell detoxification vs. the maintenance of stable intracellular pH, potassium content and cell volume.     

Conferring cadmium resistance to mature tobacco plants through metal-adsorbing particles of tomato mosaic virus vector

Tomato mosaic virus vectors were designed that produced, by a translational readthrough, a fusion protein consisting of coat protein and metal-binding peptide, as a result of which particles were expected to present the metal-binding peptides on their surface. When inoculated in plants, they were expected to replicate and form a metal-adsorbing artificial sink in the cytoplasm, so as to reduce metal toxicity. Vectors were constructed harbouring sequences encoding various lengths of polyhistidine as a metal-binding peptide. One of the vectors, TLRT6His, which contains a 6 x histidine sequence, moved systemically in tobacco plants, and its particles were shown to retain cadmium ions by an in vitro assay. When a toxic amount of cadmium was applied, the toxic effect was much reduced in TLRT6His-inoculated tobacco plants, probably as a result of cadmium adsorption by TLRT6His particles in the cytosol. This shows the possible use of an artificial sink for metal tolerance and the advantage of employing a plant viral vector for phytoremediation.     

Using essential oils to overcome bacterial biofilm formation and their antimicrobial resistance

The increase of resistant bacteria puts a huge pressure on the antimicrobials in current use. Antimicrobial resistance (AMR) results from antibiotic misuse and abuse over many years and is a global financial burden. New polices must be developed for the use of antimicrobials and to continue research efforts to mitigate AMR. It is essential to target the most harmful bacteria and concentrate on their mechanisms of resistance to develop successful antimicrobials. Essential oils (EOs) are occur naturally in plants and have long been used as antimicrobials, but most have not been researched. This review explores EOs as alternative antimicrobials, investigating their ability to decrease or inhibit biofilm formation, and assess their ability to contribute to AMR control. Low concentrations of EOs can inhibit Gram-positive and Gram-negative pathogenic bacteria. Some EOs have demonstrated strong anti-biofilm activities. If EOs are successful against biofilm formation, particularly in bacteria developing AMR, they could be incorporated into new antimicrobials. Therefore, there is a need to investigate these EOs’ potential, particularly for surface disinfection, and against bacteria from food, clinical and non-clinical environments.     

蜜蜂抗狄斯瓦螨机制的研究进展

狄斯瓦螨Varroa destructor已蔓延至世界各地,给养蜂生产带来巨大挑战,被认为是世界养蜂业的主要威胁。因此,抗螨机制的研究和抗螨蜂种的培育显得尤为重要,而掌握蜜蜂的抗螨机制则是成功培育抗螨蜂种的前提条件。本文从行为、生理及分子机制等多个不同角度对国内外蜜蜂抗狄斯瓦螨机制研究的最新进展进行了详细的阐述。尤其是从分子水平研究蜜蜂的抗螨机制对选育抗螨蜂种具有重要意义,将为利用分子遗传辅助标记筛选方法和先进的生物工程技术并结合传统的育种手段成功培育出具有抗螨性能的优良蜜蜂品系奠定基础。     

外源水杨酸和茉莉酸对荞麦幼苗耐盐生理特性的效应

以盐敏感荞麦品种‘TQ-0808’幼苗为材料,采用100mmol·L^（-1）NaCl并添加不同浓度水杨酸（sA）和茉莉酸（JA）的处理方法,测定荞麦耐盐生理指标,确定外源SA和JA对荞麦耐盐生理特性的效应。结果表明,外源SA和JA均能明显降低盐胁迫下荞麦叶片质膜透性和丙二醛（MDA）含量,外源SA降低的幅度略高于JA,外源SA最适浓度为0．6mmol·L^（-1）外源SA和JA均能明显增加盐胁迫下荞麦叶片超氧化物歧化酶（SOD）和抗坏血酸过氧化物酶（APX）活性及叶片净光合速率,外源JA增加的幅度明显大于SA,外源JA最适浓度为40gmol·L^（-1）。外源sA和JA明显改善盐胁迫下荞麦的生理特性,对盐胁迫具有较好的缓解作用,说明通过适当浓度的外源SA和JA处理来提高荞麦耐盐性是可行的。