转几丁质酶和葡聚糖酶双价基因棉花对土壤细菌种群多样性的影响

以转几丁质酶和葡聚糖酶双价基因棉花为研究对象,非转基因受体棉花为对照,通过比较可培养细菌数量和基于16S rRNA克隆文库细菌种群分析,评价外源双价基因的导入在苗期、蕾期、花铃期和吐絮期对棉花根际细菌群落多样性的影响。结果表明,可培养细菌的数量不受外源双价基因的影响,随着棉花生育期的交替而变化,以代谢旺盛的花铃期最多。构建的转基因和非转基因不同生育期根际土壤细菌16S rRNA文库容量为2400个克隆,涵盖了细菌的283个属。其中,Acidobacterium是最大优势类群,共包括624个克隆,其次为未知细菌种群和Flavisolibacter。比较转基因和非转基因棉花根际土壤细菌的种群结构,结果显示,同一生育期内前者种群的多样性显著低于后者,二者的共有类群随着生长发育的进行而增多。研究结果说明几丁质酶基因和葡聚糖酶基因对棉花根际细菌种群多样性有着不同程度的削减作用,但是随着种植时间的延长,该差异呈现逐渐缩小的趋势。     

Effects of C10‐ and C12‐chain length alkyl analogs of monochamol on attraction of longhorn pine sawyer Monochamus saltuarius (Coleoptera: Cerambycidae)

The aggregation pheromone of Monochamus (Coleoptera: Cerambycidae) beetles, 2‐(undecyloxy) ethanol (hereafter referred to as monochamol), has gained considerable attention because of its usefulness in monitoring and population control of pine sawyer beetles. The hydroxyether structural motif is conserved in pheromones of the subfamily Lamiinae of the Cerambycidae. In this study, we investigated the effects of C10‐ and C12‐chain length alkyl analogs of monochamol, 2‐(decyloxy) ethanol and 2‐(dodecyloxy) ethanol, on attracting M. saltuairus in Andong, Gyeongsangbuk‐do, Korea. The C10 and C12 analogs attracted M. saltuarius when used in combination with α‐pinene and ethanol, but the responses of these alkyl chain analogs were lower than those of monochamol. Furthermore, the addition of either C10 or C12 analog to the use of monochamol with α‐pinene and ethanol had no effect on attraction of M. saltuarius, indicating high sensitivity of M. saltuarius to monochanol. Taken together, the results of this study suggest that chemical communication within a Monochamus species depends not only on monochamol, but also on other semiochemicals.     

The role of short-chain fatty acids in the interplay between diet,gut microbiota,and host energy metabolism

Short-chain fatty acids (SCFAs), the end products of fermentation of dietary fibers by the anaerobic intestinal microbiota, have been shown to exert multiple beneficial effects on mammalian energy metabolism. The mechanisms underlying these effects are the subject of intensive research and encompass the complex interplay between diet, gut microbiota, and host energy metabolism. This review summarizes the role of SCFAs in host energy metabolism, starting from the production by the gut microbiota to the uptake by the host and ending with the effects on host metabolism. There are interesting leads on the underlying molecular mechanisms, but there are also many apparently contradictory results. A coherent understanding of the multilevel network in which SCFAs exert their effects is hampered by the lack of quantitative data on actual fluxes of SCFAs and metabolic processes regulated by SCFAs. In this review we address questions that, when answered, will bring us a great step forward in elucidating the role of SCFAs in mammalian energy metabolism.     

PCR-mediated screening and labeling of DNA from clones

A simplified and economical protocol for DNA library screening and nonradioactive labeling is described. Bacterial clones are lysed in 1% of Triton X-100 and subjected to polymerase chain reaction in the presence of digoxigenin-11-dUTP to screen and simultaneously to label the DNA inserts. Bacteriallysates are stable in storage at −20°C and can be used repeatedly for PCR-mediated labeling. In this protocol, very low concentrations of dNTP, digoxigenin-dUTP, and primers are used in combination with a reduced reaction volume. This will considerably reduce the expense of screening and labeling bacterial clones and facilitate the exchange of DNA probes among laboratories.     

Effects of individual Bacillus thuringiensis insecticidal crystal proteins on adult Heliothis virescens (F.) and Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae)

Bacillus thuringiensis (Bt) is a grampositive, spore forming bacterium, which is principally distinguishedfrom other bacilli by the production of large, insecticidal,protein crystals (Insecticidal Crystal Proteins, or ICPs). Theseproteins are usually thought to act only on the actively feedinglarvae of susceptible species by a mechanism which involvesconsumption and proteolytic processing of the protein followed bybinding to, and lysis of, midgut epithelial cells. However, few authorshave reported Bt toxicity to adult insects. In the followingpaper, we expand on previous reports of toxicity to adult insects andpresent data which demonstrate that: (1) proteolytically activated ICPssignificantly reduce the lifespans of adult Heliothis virescensand Spodoptera exigua at concentrations of 500 g/ml, butnot 167 or 25 g/ml, (2) individual activated ICPs are differentiallytoxic to adult H. virescens and S. exigua, and (3)adult S. exigua are sensitive to Cry1C protoxin at aconcentration of 1 mg/ml.Deceased     

A multi-generation analysis of the stability of transgenic virus resistance in doubled-haploid tobacco lines

Plants can be genetically engineered for virus resistance by transformation with a viral gene. We transformed tobacco with the tomato spotted wilt virus (TSWV) nucleocapsid gene from the Hawaiian L isolate in order to obtain TSWV resistant breeding lines. Doubled-haploid lines were produced from primary transgenic plants that were selected for resistance to the virus. Several of these lines showed very high levels of resistance and were symptomless after inoculation with the Hawaiian L isolate of TSWV. The accumulation of only low levels of full-length transgene RNA and protein observed in these lines is consistent with an RNA-mediated mechanism of resistance. The lines that were highly resistant to the Hawaiian L isolate of TSWV were also found to be highly resistant to several other isolates of TSWV, while lines that were only moderately resistant to the Hawaiian L isolate were often susceptible to the other isolates. The highly resistant lines were advanced over several generations by self-pollination. Although these lines were fully homozygous, several lines lost resistance in later generations, indicating that the resistance was unstable. Selection for resistance in these unstable lines did not prevent the occurrence of susceptible progeny in subsequent generations. Therefore, testing over several generations is required to determine the stability of resistance when breeding crops with transgenic virus resistance.     

Construction and characterization of BAC libraries for three fish species; rainbow trout, carp and tilapia

Bacterial artificial chromosome (BAC) libraries are important tools for genomic research. We have constructed seven genomic BAC libraries from three fish species, rainbow trout (Oncorhynchus mykiss), carp (Cyprinus carpio) and tilapia (Oreochromis niloticus). The two rainbow trout BAC libraries have average insert sizes of 58 and 110 kb. The average size of inserts in the carp BAC library is 160 kb. The average insert sizes of the four tilapia BAC libraries are 65, 105, 145 and 194 kb, respectively. These libraries represent good coverage of each genome (2-64 x coverage). The libraries can be screened by conventional colony hybridization and provide a starting point for the construction of high-density filtres or polymerase chain reaction (PCR) screening approaches. These BAC libraries will facilitate the positional cloning of quantitative trait loci (QTLs) for a variety of economically important traits in these species.