浅析入侵植物加拿大一枝黄花的入侵机理

从影响加拿大一枝黄花入侵的内因,如生物学特性、分子遗传学特性、化感效应,外部因素,如气候特征、生态位、天敌缺乏以及人类活动影响等几方面综述了其成功入侵的机理。认为生物入侵是一个涉及多个营养级的复杂生物学过程,是多种机制综合作用的结果,它们共同促成了入侵的后果。     

No evidence of facilitation between invasive Rhamnus cathartica (European buckthorn) and invasive earthworms in west central Minnesota

Biological invaders are seen as a real and growing threat to biodiversity, and there is much interest in the role that positive interactions among invasive species may play in promoting further invasions. Both the invasive tree Rhamnus cathartica (European buckthorn) and invasive Eurasian earthworms are reported to alter forest dynamics across large parts of the northern portion of the eastern deciduous forest of North America. Some evidence suggests that the two invaders may be aided by mutual facilitation, and it has recently been hypothesized that interactions between the two organisms may form the basis of a larger multi-species “invasional meltdown.” We examined covariance among R. cathartica and earthworm distributions over a seven year period at six forested sites near the prairie-forest border in west central Minnesota and found no evidence to support facilitation. In fact, the correlation between R. cathartica and earthworm abundance and biomass was weak: 95% confidence intervals for Kendall's tau correlation coefficients in some cases indicated a negative association among the two organism types, often suggesting no association, and never allowing for a positive association greater than τ = 0.38. Individual earthworm species varied in their correlation with R. cathartica, but most correlations were negative and none were substantially positive. We thus suggest that the relationship between these invaders may be more complicated than previously thought and question whether earthworms and R. cathartica can be seen as the foundation of an invasional meltdown.     

The role of ammonium oxidizing communities in mediating effects of an invasive plant on soil nitrification

Invasive plants often benefit from changes that they impose on soil microbes via positive plant–soil feedback, but the mechanisms that underlie these changes, and the legacy of their effects, remain poorly quantified. We investigated the impacts of an invasive annual grass, Microstegium vimineum, on the structure and functioning of soil microbial communities in a multi-year, field-based common garden experiment. Given previous reports that M. vimineum can both elevate nitrification rates in soil and benefit from enhanced nitrate availability, we sought to answer the following questions: 1) Does M. vimineum alter the abundance or composition of soil nitrifying microbial communities (ammonia oxidizing archaea and bacteria, AOA and AOB, respectively)? 2) Are such effects reversible or do soil legacy effects persist after M. vimineum is no longer present? After three years, invaded plots had greater AOA abundances than uninvaded native dominated plots, as well as different AOA community structure. However, after seven years, and following a period of M. vimineum replacement by native plants in the invaded plots, AOA abundances and nitrification rates declined toward levels found in uninvaded plots. Collectively, our results suggest that while the impacts of M. vimineum invasions on nitrogen cycling likely relate to their association with AOA, these effects may not persist if M. vimineum declines over time and native plants and their associated microbes are able to re-establish.     

Elevated CO2 differentially alters belowground plant and soil microbial community structure in reed canary grass-invaded experimental wetlands

Several recent studies have indicated that an enriched atmosphere of carbon dioxide (CO₂) could exacerbate the intensity of plant invasions within natural ecosystems, but little is known of how rising CO₂ impacts the belowground characteristics of these invaded systems. In this study, we examined the effects of elevated CO₂ and nitrogen (N) inputs on plant and soil microbial community characteristics of plant communities invaded by reed canary grass, Phalaris arundinacea L. We grew the invasive grass under two levels of invasion: the invader was either dominant (high invasion) at >90% plant cover or sub-dominant (low invasion) at <50% plant cover. Experimental wetland communities were grown for four months in greenhouses that received either 600 or 365 μl l⁻¹ (ambient) CO₂. Within each of three replicate rooms per CO₂ treatment, the plant communities were grown under high (30 mg l⁻¹) or low (5 mg l⁻¹) N. In contrast to what is often predicted under N limitation, we found that elevated CO₂ increased native graminoid biomass at low N, but not at high N. The aboveground biomass of reed canary grass did not respond to elevated CO₂, despite it being a fast-growing C3 species. Although elevated CO₂ had no impact on the plant biomass of heavily invaded communities, the relative abundance of several soil microbial indicators increased. In contrast, the moderately invaded plant communities displayed increased total root biomass under elevated CO_2, while little impact occurred on the relative abundance of soil microbial indicators. Principal components analysis indicated that overall soil microbial community structure was distinct by CO₂ level for the varying N and invasion treatments. This study demonstrates that even when elevated CO₂ does not have visible effects on aboveground plant biomass, it can have large impacts belowground.     

苹果蠹蛾入侵的影响因素及检疫调控措施

苹果蠹蛾是世界性重要的果树害虫之一,适应性广,危害严重,成为许多国家重要的检疫对象。为了更有效地防止苹果蠹蛾入侵中国主要水果产区,借鉴更安全环保的检疫处理和苹果蠹蛾发生区的控制措施,分析了苹果蠹蛾的传播途径和成功入侵的影响因素如寄主植物、温度、湿度、降雨和光周期等,并重点介绍了溴甲烷熏蒸、低氧空气或混合气体处理和高温低氧低温冷藏处理等检疫处理,以及性诱剂、苹果蠹蛾颗粒病毒和利用赤眼蜂等田间生物防治措施。苹果蠹蛾的成功入侵与寄主植物的种类有直接的关系,而气候条件则是影响其种群的重要因素。3种检疫处理措施均能安全有效地杀灭水果中苹果蠹蛾的不同虫态,而田间生物防治措施则能有效地控制苹果蠹蛾成虫、卵和幼虫3个重要的虫态,从而降低水果的损失。因此,这些结果为苹果蠹蛾的内外检疫和和田间控制提供了重要的参考。     

Activity of matrix metalloproteinase-2 (MMP-2) in canine oronasal tumors

Activity of matrix metalloprotease-2 (MMP-2) and the expression of its related molecules were examined in spontaneous canine oronasal tumors. Tissue samples from melanoma and squamous cell carcinoma possessed higher MMP-2 activity, as shown in gelatin zymography, in comparison with acanthomatous epulis and nasal adenocarcinoma. Regional lymph node invasion and distant metastases were more frequently observed in the MMP-2 positive cases. There were no significant differences by RT-PCR examination in the expression of the genes encoding MMP-2, MT1-MMP and TIMP-2 among the tumor histological types. However, the MMP-2/TIMP-2 ratio showed a significantly higher level of the genes in the malignant oral melanoma and squamous cell carcinoma. The MMP-2/TIMP-2 ratio was also positively correlated with MMP-2 activity in gelatin zymography. These results indicate that the MMP-2/TIMP-2 ratio may be of value in evaluating the prognosis in canine oronasal cavity tumors.     

SigmaB基因缺失对单核细胞增生性李斯特菌毒力的影响

为了解缺失SigmaB基因对单核细胞增生性李斯特菌（LM）的毒力影响。通过体外生长试验、巨噬细胞RAW264.7的粘附与侵袭试验、小鼠肝脾载菌量试验、毒力基因转录水平试验、小鼠LD₅₀试验来研究缺失株（LM XS5 △SigmaB）的毒力变化。结果显示,与野毒株相比,缺失株体外生长能力减弱、侵袭率和粘附率降低,小鼠肝脾载菌量显著减少,毒力基因（inlA、inlB、hly、prfA、actA）的转录水平降低,而小鼠LD₅₀升高。可见,SgmaB基因对LM的毒力具有重要的调控作用,为LM基因缺失疫苗和活疫苗载体的研发可资借鉴。     

Effects of lentivirus-mediated siRNA targeting IGF-1R on migration and invasion abilities of endometrial carcinoma cells

AIM:To investigate the down-regulation of insulin-like growth factor tgpe 1 receptor(IGF-1R) on the migration and invasion abilities of human endometrial cancer cell HEC-1B. METHODS:The siRNAs targeting IGF-1R gene were synthesized, cloned into a lentivirus expression vector and transfected into endometrial cancer HEC-1B cells(HEC-1B-KD group). The control cells(without virus transfection, HEC-1B-CON group) and negative virus transfection control cells(HEC-1B-NC group) were also set up. The gene silencing effect of siRNA targeting IGF-1R was determined by real-time PCR and Western blotting at mRNA and protein levels,respectively. The proliferation rate was detected by colony formation assay. The cell migration and invasion abilities were determined by Transwell experiment. The mRNA levels of matrix metalloproteinase(MMP)-2 and MMP-9 were measured by real-time PCR. RESULTS:The mRNA and protein levels of IGF-1R in HEC-1B-KD cells were significantly reduced by 81% and 91.5%, respectively(P<0.05). In anchorage-dependent growth by colony formation assay, HEC-1B-KD cells showed much less colonies than HEC-1B-CON cells and HEC-1B-NC cells. Compared with the control cells, knockdown of IGF-1R in HEC-1B cells resulted in significant reduction of cell motility. Down-regulation of IGF-1R in HEC-1B cells also significantly reduced the invasion potential(P<0.05). Down-regulation of IGF-1R substantially reduced the expression of MMP-2 and MMP-9 compared with the control cells. CONCLUSION:Knockdown of IGF-1R reduces the migration and invasion abilities of human endometrial cancer cells in vitro accompanied with a decrease in MMP-2 and MMP-9 expression.     

Invasive potential of bacterial isolates associated with subclinical bovine mastitis

This work describes differences in the invasive ability of bacterial isolates associated with mastitis. Invasion ability was determined by the uptake and survival in a primary culture of bovine mammary epithelial cells (BMEC). BMEC were isolated from a healthy lactating cow and characterized by their morphology, immunostaining for cytokeratin and the detection of beta- and kappa-casein mRNAs. Ten bacterial isolates comprising the staphylococcal species Staphylococcus aureus (3), Staphylococcus epidermidis (1), Staphylococcus haemolyticus (1), Staphylococcus equorum (2), Staphylococcus xylosus (1) and Brevibacterium stationis (2) obtained from raw milk of cows with mastitis from backyard farms were assayed for their ability to invade BMEC. Only two S. aureus and one S. epidermidis isolates were able to invade BMEC, at similar levels to the S. aureus control strain ATCC 27543. In conclusion, using the in vitro model of infection used in this study, differences in bacterial invasion capability may be detected.