CO2 stimulation and response mechanisms vary with light supply in boreal conifers

北方针叶树CO₂ 的刺激和响应机制随光强而变化 黑云杉(Picea mariana [Mill.] B.S.P.)和白云杉(Picea glauca [Moench] Voss.)是同属物种,两者都是适度耐阴,并且在北美北方针叶林中广泛分布。为了了解光照对CO₂ 浓度升高的生理生态反应的影响,在三种光照条件下(温室中光照设置为100%、50%和30%)将一年生的两种幼苗暴露在360和720 µmol mol^–1 浓度的CO₂环境中,测定了其中后期叶面气体交换量。研究结果表明,CO₂的浓度升高提高了净光合速率 (P_n)和光合水分利用效率,但降低了气孔导度和蒸腾作用。CO₂对光合作用的刺激在50%光照下最大, 在100%光照下最小。光合作用、最大羧化速率(V_cmax)和光饱和电子传递速率(J_max)均随光照强度的 降低而降低。升高的CO₂在所有光照处理中显著降低了V_cmax,在生长季节中期,两种云杉的V_cmax均显著 降低,但在生长季节后期,当光照达到30%时,这一影响变得不明显,而且黑云杉的响应大于白云杉。CO₂ 浓度升高也降低了白云杉的J_max,但在生长季后期30%光照时,这种影响变得不显著。但CO₂ 浓度升高对 黑云杉的影响随时间而变化。在所有光照处理中,CO₂ 浓度升高降低了黑云杉生长中期的J_max,且在生长后 期30%光照时影响不显著,但在100%和50%光照时,J_max升高。这些研究结果表明,两个树种植物都受益于CO₂ 浓度的升高,但它们的响应机制随着光照的增加而变化：即在100%和50%光照下,它们的响应主要是生理上的,而在30%光照下,它们的响应主要是形态上的。     

High-altitude tree growth responses to climate change across the Hindu Kush Himalaya

兴都库什喜马拉雅地区高海拔树木生长对气候变化的响应 高海拔地区快速升温可能导致树木对温度响应更为敏感,而限制高海拔地区树木生长的关键气候因子以及气候变化对树木生长产生多大程度的影响尚不清楚。本研究在兴都库什喜马拉雅地区收集了73 个样点的树轮数据,包括3个优势属的树种(Abies属、Juniperus属和Picea属),样点海拔均在3000 m以上。 将时间动态规整(dynamic time warping)的方法用于建立亚区域年表,以考虑不同站点年表之间变化的同步 性。同时,定量分析了气候因子对树木生长的贡献以及树木生长与气候因子关系的时空动态。研究结果发现,73个站点年表可以聚为3类,且与其所处的生物气候区相对应,即西喜马拉雅地区,中东喜马拉雅地区和藏东南地区。在干旱的西喜马拉雅地区,树木生长与冬、春两季的降水呈正相关关系,而在湿润的藏东南地区,树木生长与冬季温度和春季降水呈正相关关系。树木生长受最低温度的影响最大,特别是冬季温度,其重要性从西到东呈现递增趋势。滑动窗口相关分析表明,在中西喜马拉雅地区,影响树木生长的冬季温度信号在减弱,然而在藏东南地区该信号随着1980年以来的快速升温而增强。本研究结果表明,若该地区升温持续,在西喜马拉雅地区可能会因变暖引起的水分亏缺而造成森林衰退,而在藏东南地区因树木生长得益于变暖而使得森林扩张。     

Eco-evolutionary consequences of habitat warming and fragmentation in communities

Eco-evolutionary dynamics can mediate species and community responses to habitat warming and fragmentation, two of the largest threats to biodiversity and ecosystems. The eco-evolutionary consequences of warming and fragmentation are typically studied independently, hindering our understanding of their simultaneous impacts. Here, we provide a new perspective rooted in trade-offs among traits for understanding their eco-evolutionary consequences. On the one hand, temperature influences traits related to metabolism, such as resource acquisition and activity levels. Such traits are also likely to have trade-offs with other energetically costly traits, like antipredator defences or dispersal. On the other hand, fragmentation can influence a variety of traits (e.g. dispersal) through its effects on the spatial environment experienced by individuals, as well as properties of populations, such as genetic structure. The combined effects of warming and fragmentation on communities should thus reflect their collective impact on traits of individuals and populations, as well as trade-offs at multiple trophic levels, leading to unexpected dynamics when effects are not additive and when evolutionary responses modulate them. Here, we provide a road map to navigate this complexity. First, we review single-species responses to warming and fragmentation. Second, we focus on consumer–resource interactions, considering how eco-evolutionary dynamics can arise in response to warming, fragmentation, and their interaction. Third, we illustrate our perspective with several example scenarios in which trait trade-offs could result in significant eco-evolutionary dynamics. Specifically, we consider the possible eco-evolutionary consequences of (i) evolution in thermal performance of a species involved in a consumer–resource interaction, (ii) ecological or evolutionary changes to encounter and attack rates of consumers, and (iii) changes to top consumer body size in tri-trophic food chains. In these scenarios, we present a number of novel, sometimes counter-intuitive, potential outcomes. Some of these expectations contrast with those solely based on ecological dynamics, for example, evolutionary responses in unexpected directions for resource species or unanticipated population declines in top consumers. Finally, we identify several unanswered questions about the conditions most likely to yield strong eco-evolutionary dynamics, how better to incorporate the role of trade-offs among traits, and the role of eco-evolutionary dynamics in governing responses to warming in fragmented communities.     

Gastrointestinal stress as innate defence against microbial attack

The human gastrointestinal (GI) tract has been bestowed with the most difficult task of protecting the underlying biological compartments from the resident commensal flora and the potential pathogens in transit through the GI tract. It has a unique environment in which several defence tactics are at play while maintaining homeostasis and health. The GI tract shows myriad number of environmental extremes, which includes pH variations, anaerobic conditions, nutrient limitations, elevated osmolarity etc., which puts a check to colonization and growth of nonfriendly microbial strains. The GI tract acts as a highly selective barrier/platform for ingested food and is the primary playground for balance between the resident and uninvited organisms. This review focuses on antimicrobial defense mechanisms of different sections of human GI tract. In addition, the protective mechanisms used by microbes to combat the human GI defence systems are also discussed. The ability to survive this innate defence mechanism determines the capability of probiotic or pathogen strains to confer health benefits or induce clinical events respectively.     

Linking Ocean's Benefits to People (OBP) with Integrated Ecosystem Assessments (IEAs)

The fundamental challenge of the inclusion of the human dimension of the oceans in the Integrated Ecosystem Assessments (IEAs) provides an opportunity for a transdisciplinary approach to create synergies between the current research by the International Council for the Exploration of the Sea (ICES) and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). We have highlighted the importance of ocean inequality as a critical aspect to consider to unlock current barriers to integrate social sciences in marine integrated assessments. To create bridges between them, we develop an Ocean's Benefits to People (OBP) framework that embraces the blue economy, equity, the UN SDGs goals and support an Ecosystem-Based Management (EBM) for the oceans.     

Epithelial cell adhesion molecule promotes breast cancer resistance protein-mediated multidrug resistance in breast cancer by inducing partial epithelial–mesenchymal transition

Overexpression of breast cancer resistance protein (BCRP) plays a crucial role in the acquired multidrug resistance (MDR) in breast cancer. The elucidation of molecular events that confer BCRP-mediated MDR is of major therapeutic importance in breast cancer. Epithelial cell adhesion molecule (EpCAM) has been implicated in tumor progression and drug resistance in various types of cancers, including breast cancer. However, the role of EpCAM in BCRP-mediated MDR in breast cancer remains unknown. In the present study, we revealed that EpCAM expression was upregulated in BCRP-overexpressing breast cancer MCF-7/MX cells, and EpCAM knockdown using siRNA reduced BCRP expression and increased the sensitivity of MCF-7/MX cells to mitoxantrone (MX). The epithelial–mesenchymal transition (EMT) promoted BCRP-mediated MDR in breast cancer cells, and EpCAM knockdown partially suppressed EMT progression in MCF-7/MX cells. In addition, Wnt/β-catenin signaling was activated in MCF-7/MX cells, and the inhibition of this signaling attenuated EpCAM and BCRP expression and partially reversed EMT. Together, this study illustrates that EpCAM upregulation by Wnt/β-catenin signaling induces partial EMT to promote BCRP-mediated MDR resistance in breast cancer cells. EpCAM may be a potential therapeutic target for overcoming BCRP-mediated resistance in human breast cancer.     

LEC–BiFC: a new method for rapid assay of protein interaction

Abstract

Protein–protein interactions play fundamental roles in most biological processes. Bimolecular fluorescence complementation (BiFC) is a promising method for its simplicity and direct visualization of protein–protein interactions in cells. This method, however, is limited by background fluorescence that appears without specific interaction between the proteins. We report here a point mutation (V150L) in one Venus BiFC fragment that efficiently decreases background fluorescence of BiFC assay. Furthermore, by combining this modified BiFC and linear expression cassette (LEC), we develop a simple and rapid method (LEC–BiFC) for protein interaction analysis that is demonstrated by a case study of the interaction between Bcl–X_L and Bak BH3 peptide. The total analysis procedure can be completed in two days for screening tens of mutants. LEC–BiFC can be applied easily in any lab equipped with a fluorescence microscope.     

Conformational insights on the molecular recognition processes of carbohydrate molecules by proteins and enzymes: A 3D view by using NMR

This review focuses, in a non-exhaustive manner, on the essential structural and conformational features of protein–carbohydrate interactions and on some applications of NMR spectroscopy to deal with this topic from different levels of complexity.     

Three Dimensional Modeling of the Cerebrospinal Fluid Dynamics and Brain Interactions in the Aqueduct of Sylvius

A computational fluid dynamics (CFD) method is presented to investigate the flow of cerebro-spinal fluid (CSF) in the cerebral aqueduct. In addition to former approaches exhibiting a rigid geometry, we propose a model which includes a deformable membrane as the wall of this flow channel. An anatomical shape of the aqueduct was computed from magnetic resonance images (MRI) and the resulting meshing was immersed in a marker-and-cell (MAC) staggered grid for to take into account fluid–structure interactions. The time derivatives were digitized using the Crank–Nicolson scheme. The equation of continuity was modified by introducing an artificial compressibility and digitized by a finite difference scheme.

Calculations were validated with the simulation of laminar flow in a rigid tube. Then, comparisons were made between simulations of a rigid aqueduct and a deformable one. We found that the deformability of the walls has a strong influence on the pressure drop for a given flow.