黄孢原毛平革菌抗营养阻遏产漆酶诱变育种及其产酶特性

【目的】筛选能抗营养阻遏产漆酶的黄孢原毛平革菌,论证其产漆酶的确定性及抗营养阻遏产木质素酶的可行性,为白腐菌产酶代谢调控、木质素降解机理的研究奠定基础。【方法】利用重复紫外诱变法,以愈创木酚富氮鉴别培养基筛选目标菌株;比较不同营养条件下菌体生长与产酶动力学差异研究产酶营养调控机理;通过热处理、排除锰离子和加入过氧化氢酶等不同措施论证黄孢原平毛平革菌能否产生漆酶。【结果】3种不同方法均证实选育到的pcR5305和pcR5324菌株在限氮与富氮条件下均能产生漆酶,pcR5305和pcR5324在限氮条件下产漆酶分别达到203.5、187.6 U/L;在富氮条件下为220.6、183.9 U/L,而原菌株pc530在两种条件下都基本不产生漆酶。二菌株产漆酶调控方式不同,pcR5305漆酶产生与菌体生长同步,而pcR5324漆酶产生却受营养氮阻遏。二菌株同时具有抗营养阻遏高产木质素过氧化物酶(LiP)和锰过氧化物酶(MnP)(分别为LiP 1343.2、MnP 252.2 U/L;LiP 1169.5、MnP 172.4 U/L)的能力。【结论】筛选到的黄孢原毛平革菌变异菌株能产漆酶,同时表现了抗营养阻遏产漆酶、木质素过氧化物酶和锰过氧化物酶的能力,具有重要的生产应用与理论研究价值,为白腐菌产酶代谢调控机理研究提供了原始菌株并奠定了良好的基础。     

Demographic History and Genomic Response to Environmental Changes in a Rapid Radiation of Wild Rats

For organisms to survive and prosper in a harsh environment, particularly under rapid climate change, poses tremendous challenges. Recent studies have highlighted the continued loss of megafauna in terrestrial ecosystems and the subsequent surge of small mammals, such as rodents, bats, lagomorphs, and insectivores. However, the ecological partitioning of these animals will likely lead to large variation in their responses to environmental change. In the present study, we investigated the evolutionary history and genetic adaptations of white-bellied rats (Niviventer Marshall, 1976), which are widespread in the natural terrestrial ecosystems in Asia but also known as important zoonotic pathogen vectors and transmitters. The southeastern Qinghai-Tibet Plateau was inferred as the origin center of this genus, with parallel diversification in temperate and tropical niches. Demographic history analyses from mitochondrial and nuclear sequences of Niviventer demonstrated population size increases and range expansion for species in Southeast Asia, and habitat generalists elsewhere. Unexpectedly, population increases were seen in N. eha, which inhabits the highest elevation among Niviventer species. Genome scans of nuclear exons revealed that among the congeneric species, N. eha has the largest number of positively selected genes. Protein functions of these genes are mainly related to olfaction, taste, and tumor suppression. Extensive genetic modification presents a major strategy in response to global changes in these alpine species.     

Breaking the 10% Efficiency Barrier in Organic Photovoltaics: Morphology and Device Optimization of Well‐Known PBDTTT Polymers

With the advances in organic photovoltaics (OPVs), the invention of model polymers with superior properties and wide applicability is of vital importance to both the academic and industrial communities. The recent inspiring advances in OPV research have included the emergence of poly(benzodithiophene‐co‐thieno[3,4‐b]thiophene) (PBDTTT)‐based materials. Through the combined efforts on PBDTTT polymers, over 10% efficiencies have been realized recently in various types of OPV devices. This review attempts to critically summarize the recent advances with respect to five well‐known PBDTTT polymers and their design considerations, basic properties, photovoltaic performance, as well as device application in conventional, inverted, tandem solar cells. These PBDTTT polymers also make great contributions to the rapid advances in the field of emerging ternary blends and fullerene‐free OPVs with top performances. Addtionally, new challenges in developing novel photovoltaic polymers with more superior properties are prospected. More importantly, the research of highly efficient PBDTTT‐based polymers provides useful insights and builds fundamentals for new types of OPV applications with various architectures.     

Multispecies coexistence of trees in tropical forests: spatial signals of topographic niche differentiation increase with environmental heterogeneity

Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites. We interpret this pattern as evidence of pervasive niche differentiation, which increases in importance with increasing environmental heterogeneity.     

Formation of Adeno-Associated Virus Circular Genomes Is Differentially Regulated by Adenovirus E4 ORF6 and E2a Gene Expression

A central feature of the adeno-associated virus (AAV) latent life cycle is persistence in the form of both integrated and episomal genomes. However, the molecular processes associated with episomal long-term persistence of AAV genomes are only poorly understood. To investigate these mechanisms, we have utilized a recombinant AAV (rAAV) shuttle vector to identify circular AAV intermediates from transduced HeLa cells and primary fibroblasts. The unique structural features exhibited by these transduction intermediates included circularized monomer and dimer virus genomes in a head-to-tail array, with associated specific base pair alterations in the 5′ viral D sequence. In HeLa cells, the abundance and stability of AAV circular intermediates were augmented by adenovirus expressing the E2a gene product. In the absence of E2a, adenovirus expressing the E4 open reading frame 6 gene product decreased the abundance of AAV circular intermediates, favoring instead the linear replication form monomer (Rf_m) and dimer (Rf_d) structures. In summary, the formation of AAV circular intermediates appears to represent a new pathway for AAV genome conversion, which is consistent with the head-to-tail concatemerization associated with latent-phase persistence of rAAV. A better understanding of this pathway may increase the utility of rAAV vectors for gene therapy.     

Crystallization and preliminary X-ray crystallographic analysis of spruce budworm antifreeze protein.

Antifreeze proteins have the ability to bind to ice with high affinity and inhibit further crystal growth. The insect antifreeze protein from spruce budworm exhibits very high thermal hysteresis activity and is implicated in the protection of overwintering larvae from freezing. This protein has been crystallized in 20-25% polyethylene glycol (Mr 6000), 0.4 M NaCl, 0.1 M Tris-HCl, pH 8.5, by vapor diffusion using the hanging drop method. The resulting crystals are very thin (typically <0.01 mm in the shortest dimension), and only after repeated seeding could crystals be grown large enough for data collection using synchrotron radiation. The crystals belong to the monoclinic space group C2, with cell dimensions a = 82.28 A, b = 62.29 A, c = 63.63 A, and beta = 113.7 degrees. Molecules in the asymmetric unit are related by a twofold axis of symmetry with two molecules present. Native data to a resolution of 2.6 A have been collected with 90.3% completeness and a Rsym of 6.9%.     

The use of next generation sequencing technology to study the effect of radiation therapy on mitochondrial DNA mutation

The human mitochondrial genome has an exclusively maternal mode of inheritance. Mitochondrial DNA (mtDNA) is particularly vulnerable to environmental insults due in part to an underdeveloped DNA repair system, limited to base excision and homologous recombination repair. Radiation exposure to the ovaries may cause mtDNA mutations in oocytes, which may in turn be transmitted to offspring. We hypothesized that the children of female cancer survivors who received radiation therapy may have an increased rate of mtDNA heteroplasmy mutations, which conceivably could increase their risk of developing cancer and other diseases. We evaluated 44 DNA blood samples from 17 Danish and 1 Finnish families (18 mothers and 26 children). All mothers had been treated for cancer as children and radiation doses to their ovaries were determined based on medical records and computational models. DNA samples were sequenced for the entire mitochondrial genome using the Illumina GAII system. Mother's age at sample collection was positively correlated with mtDNA heteroplasmy mutations. There was evidence of heteroplasmy inheritance in that 9 of the 18 families had at least one child who inherited at least one heteroplasmy site from his or her mother. No significant difference in single nucleotide polymorphisms between mother and offspring, however, was observed. Radiation therapy dose to ovaries also was not significantly associated with the heteroplasmy mutation rate among mothers and children. No evidence was found that radiotherapy for pediatric cancer is associated with the mitochondrial genome mutation rate in female cancer survivors and their children.