增温对青藏高原高寒草甸呼吸作用的影响

生态系统呼吸(ER)和土壤呼吸(SR)是草地生态系统碳排放的关键环节,其对气候变化极为敏感。高寒草甸是青藏高原典型的草地生态系统,其呼吸作用对气候变化的响应对区域碳排放具有重要的影响。以高寒草甸生态系统为对象,于2012—2016年采用模拟增温的方法研究呼吸作用对增温的响应。结果表明:增温对高寒草甸ER的影响存在年际差异,2013年和2014年增温对ER无显著影响,其他年份显著增加ER(P0.05),综合5年结果,平均增幅达22.3%。增温显著促进了高寒草甸SR(P0.05),较对照处理5年平均增幅高达67.1%;增温总体上提高了SR在ER中的比例(P0.05),最高增幅达到59.9%。ER和SR与土壤温度有显著的正相关关系(P0.05),与土壤水分没有显著的相关关系(P0.05)。对照样地中,土壤温度分别能解释33.0%和18.5%的ER和SR变化。在增温条件下,土壤温度可以解释20.5%和13.0%的ER和SR变化。在增温条件下,SR的温度敏感性显著增加,而ER的温度敏感性变化较小,导致SR的比重进一步增加。因此,在未来气候变暖条件下,青藏高原高寒草甸生态系统碳排放,尤其是土壤碳排放有可能进一步增加,土壤碳流失风险增加。     

A novel case of autogamy and cleistogamy in Dendrobium wangliangii: A rare orchid distributed in the dry‐hot valley

Dendrobium wangliangii is an epiphytic orchid distributed in the Jinshajiang dry‐hot valley in Luquan County, Yunnan Province, China. Most Dendrobium spp. typically have a low fruit set, but this orchid shows a higher fruit set under natural conditions despite the lack of effective pollinators. The pollination biology of the critically endangered D. wangliangii was investigated in this study. A fruit set rate of 33.33 ± 4.71% was observed after bagging treatment in 2017 and a high fruit set rate (65.72 ± 4.44% in 2011; 50.79 ± 5.44% in 2017) was observed under natural conditions, indicating that D. wangliangii is characterized by spontaneous self‐pollination. The anther cap blocked the growing pollinium; thus, the pollinium slid down and reached the stigmatic cavity, leading to autogamous self‐pollination. Specifically, 51.50% of 162 unopened flowers (total 257 flowers) of this Dendrobium species under extreme water‐deficit conditions developed into fruits, suggesting the presence of cleistogamy in D. wangliangii. Here, cleistogamy may represent the primary mode of pollination for this orchid. Spontaneous self‐pollination and specific cleistogamous autogamy could represent major adaptions to the drought and pollinator‐scarce habitat in the Jinshajiang dry‐hot valley.     

松嫩平原盐碱化草地治理方法的比较研究

采用生物、化学和物理方法对盐碱化草地治理进行了比较研究．生物方法采用枯草处理;化学方法采用石膏处理;物理方法采用铺沙处理,种植羊草、野大麦和碱茅３种牧草．结果表明,３种方法均能降低土壤ｐＨ值、电导率和增加土壤含水率．在生物治理中,羊草和野大麦在枯草量达１５００ｇ·ｍ－２,碱茅在枯草量达１０００ｇ·ｍ－２时,便可良好生长．在化学治理中,石膏施用量达１．２５ｋｇ·ｍ－２,即可达到改良效果．在物理方法治理中,羊草和野大麦在沙层厚度为１３ｃｍ,碱茅在１１ｃｍ时即可正常生长发育．     

The shedding of CD62L (L-selectin) regulates the acquisition of lytic activity in human tumor reactive T lymphocytes

CD62L/L-selectin is a marker found on naïve T cells and further distinguishes central memory (Tcm, CD62L+) from effector memory (Tem, CD62L−) T cells. The regulation of CD62L plays a pivotal role in controlling the traffic of T lymphocytes to and from peripheral lymph nodes. CD62L is shed from the cell membrane following T cell activation, however, the physiological significance of this event remains to be elucidated. In this study, we utilized in vitro generated anti-tumor antigen T cells and melanoma lines as a model to evaluate the dynamics of CD62L shedding and expression of CD107a as a marker of lytic activity. Upon encounter, with matched tumor lines, antigen reactive T cells rapidly lose CD62L expression and this was associated with the acquisition of CD107a. By CD62L ELISA, we confirmed that this transition was mediated by the shedding of CD62L when T cells encountered specific tumor antigen. The introduction of a shedding resistant mutant of CD62L into the tumor antigen-reactive T cell line JKF6 impaired CD107a acquisition following antigen recognition and this was correlated with decreased lytic activity as measured by ⁵¹Cr release assays. The linkage of the shedding of CD62L from the surface of anti-tumor T cells and acquisition of lytic activity, suggests a new function for CD62L in T cell effector functions and anti-tumor activity.     

Nanopods: a new bacterial structure and mechanism for deployment of outer membrane vesicles

Background

Bacterial outer membrane vesicles (OMV) are packets of periplasmic material that, via the proteins and other molecules they contain, project metabolic function into the environment. While OMV production is widespread in proteobacteria, they have been extensively studied only in pathogens, which inhabit fully hydrated environments. However, many (arguably most) bacterial habitats, such as soil, are only partially hydrated. In the latter, water is characteristically distributed as films on soil particles that are, on average thinner, than are typical OMV (ca. ≤10 nm water film vs. 20 to >200 nm OMV;).

Methodology/Principal Findings

We have identified a new bacterial surface structure, termed a “nanopod”, that is a conduit for projecting OMV significant distances (e.g., ≥6 µm) from the cell. Electron cryotomography was used to determine nanopod three-dimensional structure, which revealed chains of vesicles within an undulating, tubular element. By using immunoelectron microscopy, proteomics, heterologous expression and mutagenesis, the tubes were determined to be an assembly of a surface layer protein (NpdA), and the interior structures identified as OMV. Specific metabolic function(s) for nanopods produced by Delftia sp. Cs1-4 are not yet known. However, a connection with phenanthrene degradation is a possibility since nanopod formation was induced by growth on phenanthrene. Orthologs of NpdA were identified in three other genera of the Comamonadaceae family, and all were experimentally verified to form nanopods.

Conclusions/Significance

Nanopods are new bacterial organelles, and establish a new paradigm in the mechanisms by which bacteria effect long-distance interactions with their environment. Specifically, they create a pathway through which cells can effectively deploy OMV, and the biological activity these transmit, in a diffusion-independent manner. Nanopods would thus allow environmental bacteria to expand their metabolic sphere of influence in a manner previously unknown for these organisms.     

云南元江印楝植物内生真菌的种类组成

为了探悉内生真菌在植物体内的多样性,从中寻找新的具有生物活性的微生物资源,我们研究了云南元江4个不同地理种源印楝(Azadirachta indiea)生真菌的种类组成、数量及分布规律.从印楝植物茎和果实中共分离到372株内生真菌,分属于50属,分布最广的类群是刺盘孢菌属(Colletotrichum),占总菌株的25.54%;其次是交链孢属(Alternaria)(11.56%)和炭角菌属(Xylaria)(7.80%).各组织获得菌株数量比例最大的分别为ka种源茎部(19.89%)、ck种源茎部(19.62%)和ma种源茎部(18.82%);最小的为ka种源果实部(5.11%)和ku种源果实部(6.18%).丰富度最大的为ma种源(包含29属),最小的为ku种源(23属).印楝植物茎部分离到的菌株类群和数量明显多于果实.不同地理种源印楝植物内生真菌的种类组成没有明显差异,但是有的内生真菌表现出一定的宿主或组织专一性.印楝植物丰富的内生真菌资源可能成为产生具有生物活性次生代谢产物的重要来源,尤其是与宿主植物相关的印楝素类四降三萜化合物.