感染松萎蔫病的葡萄牙海岸松中内生细菌的分离

葡萄牙海岸松被松材线虫感染后的迅速死亡表明有其他生物的介入。内生细菌是一类普遍存在的生物,它在大部分植物中能形成种群。松材线虫携带的细菌也有可能导致海岸松的迅速死亡。笔者通过培养分离得到的细菌分离物,利用扩增性核糖体DNA限制性酶切片段分析(ARDRA)和变性梯度凝胶电泳分析(DGGE),了解被感染的和未被感染的海岸松内生细菌的种群结构,以分析鉴定与松材线虫相关的细菌。从样树和松材线虫中分离的细菌Alphaproteobacteria、 Bacteroidetes 属仅存在于内生菌中,而Actinobacteria、Firmicutes被发现仅与松材线虫相关。 ARDRA和 DGGE 分析证明内生菌种群结构多样性的差异可能与松材线虫的入侵有关。这种细菌种群的多样性差异似乎与Burkholderia、 Pseudomonas 和Luteibacter属中的某些菌株有关。而从树中分离出来的Janthinobacterium agaricidamnosum、 P. lutea 和 Dyella yeojuensis 与松材线虫相关     

Host specificity of Lepidoptera in tropical and temperate forests

For numerous taxa, species richness is much higher in tropical than in temperate zone habitats. A major challenge in community ecology and evolutionary biogeography is to reveal the mechanisms underlying these differences. For herbivorous insects, one such mechanism leading to an increased number of species in a given locale could be increased ecological specialization, resulting in a greater proportion of insect species occupying narrow niches within a community. We tested this hypothesis by comparing host specialization in larval Lepidoptera (moths and butterflies) at eight different New World forest sites ranging in latitude from 15 degrees S to 55 degrees N. Here we show that larval diets of tropical Lepidoptera are more specialized than those of their temperate forest counterparts: tropical species on average feed on fewer plant species, genera and families than do temperate caterpillars. This result holds true whether calculated per lepidopteran family or for a caterpillar assemblage as a whole. As a result, there is greater turnover in caterpillar species composition (greater beta diversity) between tree species in tropical faunas than in temperate faunas. We suggest that greater specialization in tropical faunas is the result of differences in trophic interactions; for example, there are more distinct plant secondary chemical profiles from one tree species to the next in tropical forests than in temperate forests as well as more diverse and chronic pressures from natural enemy communities.     

The Cancer Cell Line Encyclopedia enables predictive modelling of anticancer drug sensitivity

The systematic translation of cancer genomic data into knowledge of tumour biology and therapeutic possibilities remains challenging. Such efforts should be greatly aided by robust preclinical model systems that reflect the genomic diversity of human cancers and for which detailed genetic and pharmacological annotation is available. Here we describe the Cancer Cell Line Encyclopedia (CCLE): a compilation of gene expression, chromosomal copy number and massively parallel sequencing data from 947 human cancer cell lines. When coupled with pharmacological profiles for 24 anticancer drugs across 479 of the cell lines, this collection allowed identification of genetic, lineage, and gene-expression-based predictors of drug sensitivity. In addition to known predictors, we found that plasma cell lineage correlated with sensitivity to IGF1 receptor inhibitors; AHR expression was associated with MEK inhibitor efficacy in NRAS-mutant lines; and SLFN11 expression predicted sensitivity to topoisomerase inhibitors. Together, our results indicate that large, annotated cell-line collections may help to enable preclinical stratification schemata for anticancer agents. The generation of genetic predictions of drug response in the preclinical setting and their incorporation into cancer clinical trial design could speed the emergence of 'personalized' therapeutic regimens.     

Structure of the bacteriophage phi29 DNA packaging motor

Motors generating mechanical force, powered by the hydrolysis of ATP, translocate double-stranded DNA into preformed capsids (proheads) of bacterial viruses and certain animal viruses. Here we describe the motor that packages the double-stranded DNA of the Bacillus subtilis bacteriophage phi29 into a precursor capsid. We determined the structure of the head-tail connector--the central component of the phi29 DNA packaging motor--to 3.2 A resolution by means of X-ray crystallography. We then fitted the connector into the electron densities of the prohead and of the partially packaged prohead as determined using cryo-electron microscopy and image reconstruction analysis. Our results suggest that the prohead plus dodecameric connector, prohead RNA, viral ATPase and DNA comprise a rotary motor with the head-prohead RNA-ATPase complex acting as a stator, the DNA acting as a spindle, and the connector as a ball-race. The helical nature of the DNA converts the rotary action of the connector into translation of the DNA.