The inositol phosphatase SHIP-1 inhibits NOD2-induced NF-κB activation by disturbing the interaction of XIAP with RIP2

SHIP-1 is an inositol phosphatase predominantly expressed in hematopoietic cells. Over the ten past years, SHIP-1 has been described as an important regulator of immune functions. Here, we characterize a new inhibitory function for SHIP-1 in NOD2 signaling. NOD2 is a crucial cytoplasmic bacterial sensor that activates proinflammatory and antimicrobial responses upon bacterial invasion. We observed that SHIP-1 decreases NOD2-induced NF-κB activation in macrophages. This negative regulation relies on its interaction with XIAP. Indeed, we observed that XIAP is an essential mediator of the NOD2 signaling pathway that enables proper NF-κB activation in macrophages. Upon NOD2 activation, SHIP-1 C-terminal proline rich domain (PRD) interacts with XIAP, thereby disturbing the interaction between XIAP and RIP2 in order to decrease NF-κB signaling.     

Genotypic variation in the response of two perennial grass species to elevated carbon dioxide

Shoot and reproductive biomass of genotypes of Bromus erectus and Dactylis glomerata grown in competition at ambient and elevated CO₂ were examined for 2 consecutive years in order to test whether genetic variation in those traits exists and whether it is maintained over time. At the species level, a positive CO₂ response of shoot biomass of both species was only found in the first year of treatment. At the genotype level, no significant CO₂2genotype interaction was found at any single harvest either for vegetative or reproductive biomass of either species. Analysis over time, however, indicated that there is a potential for evolutionary adaptation only for D. glomerata: (1) repeated measures ANOVA detected a marginally significant CO₂2genotype2time interaction for shoot biomass, because the range of the genotypes CO₂ response increased over time; (2) genotypes that displayed the highest response during the first year under elevated CO₂ also showed the highest response the second year. Null (B. erectus) or weak (D. glomerata) selective potentials of elevated CO₂ were detected in this experiment, but short time series could underestimate this potential with perennial species.     

Local expression of the ipt gene in transgenic tobacco (Nicotiana tabacum L. cv. SR1) axillary buds establishes a role for cytokinins in tuberization and sink formation

The developmental characteristics of a transgenic tobacco line (BIK62) expressing the ipt cytokinin-biosynthetic gene under the control of a tagged promoter were analysed. In situ hybridization and cytokinin immunocytochemistry revealed that the ipt gene was mainly expressed in the axillary buds after the floral transition. The ipt-expressing axillary buds presented morphological alterations such as short and narrow scale-leaflets, and swollen internodes filled with starch grains, giving rise to short and tuberized lateral branches. In addition, the modification of the endogenous cytokinin balance in the axillary meristems resulted in a fast rate of leaf initiation and cytokinins accumulated mostly in the lateral zones of the reactivated axillary meristems, suggesting a role in leaf organogenesis. Cell cycle analysis revealed that the reactivated axillary meristems were characterized by predominant S+G2 nuclei. Terminal internodes displayed low levels of hexose and sucrose concomitant with starch accumulation. Extracellular invertases (EC 3.1.26) were also present in higher amounts in the tuberizing internodes compared to the axillary buds of wild-type tobacco. These results underline the role of cytokinins in cell cycle regulation and in the creation of a sink--source effect. They also provide new information about cytokinin involvement in the process of tuberization and their overproduction in axillary buds giving rise to tuberized lateral branches in a naturally non-tuberizing species.     

模拟打制实验及其在丁村角页岩石器研究中的应用

模拟打制是史前考古研究中的重要实验考古方法之一,对于正确认识考古标本的类型和技术、解读当时人类的认知水平和知识积累具有不可取代的作用。本文简要回溯了模拟打制实验的发展史,并评述其应用现状。模拟打制实验在欧美有较长的发展与应用历史,但最终趋向了不同的发展方向。传统的模拟打制实验研究在欧洲得到了更加深入的继承和发展,而美国在上世纪90年代后期逐渐发展起了以定量控制、数理统计为核心的实验方法。本文以近期在山西丁村开展的角页岩模拟打制实验为例,介绍传统的模拟打制实验的基本流程和内容,包括实验的内容设计、实施及记录和分析等。本次实验结果肯定了硬锤锤击技术在丁村角页岩石核剥片和修理中的广泛应用,并在一定程度上否定了以往对使用碰砧法的推测。文章最后对模拟打制实验存在的问题和应用前景作了讨论和展望。