铜处理对菠菜幼苗矿质营养吸收和细胞超微结构的影响

土壤重金属积累严重影响植物生长和生态系统平衡,探寻植物对重金属的耐性机理尤为重要.菠菜可能具有一定的耐铜性,但Cu对其矿质元素吸收、细胞超微结构等方面的耐性机理尚不明确.本研究以菠菜幼苗为研究对象,通过盆栽试验,探究不同浓度铜处理对菠菜幼苗生长、矿质元素吸收、叶片细胞超微结构等指标的影响.结果表明: 100 mg·L^-1 CuSO₄处理浓度时,菠菜幼苗根Cu²⁺积累量小于地上部,其根系生长量增加,地上部生长量稍有下降,继续增加铜处理浓度,植物体各器官生长参数均呈下降趋势.低浓度铜处理时(<400 mg·L^-1 CuSO₄),菠菜幼苗叶N、K、Ca、Mg、Fe含量增加,P含量减少;根N、P、K含量减少,Ca、Mg、Fe含量增加;叶片细胞内各细胞器清晰可见,基粒片层排列仍较为整齐,叶绿体内外膜完整.高浓度铜处理时(>600 mg·L^-1 CuSO₄),菠菜幼苗叶N含量增加,P、K、Ca、Mg、Fe含量减少;根N、P、K、Ca、Mg、Fe含量均减少;叶片细胞内叶绿体变圆,叶绿体膜变薄,基质、基粒片层变少,层堆积高度下降,细胞核解体,液泡、细胞壁中有黑色小点分布,可能是大量Cu²⁺聚集导致细胞内膨压增大所致.低浓度铜处理并未对菠菜幼苗的生长生理特性产生明显的负面影响,而高浓度铜处理并未终止菠菜幼苗的生长.说明菠菜幼苗具有一定的耐铜性.     

过表达水稻OsAQP增强转基因拟南芥耐盐性

水稻OsAQP是实验室前期从cDNA文库中筛选的功能未知的水通道蛋白质编码基因。本文采用DNA重组技术构建其植物过表达载体,并对拟南芥进行了遗传转化,筛选获得转基因拟南芥。采用50、100、125和150 mmol/L梯度盐胁迫处理,结果显示,转基因拟南芥的发芽率、根长以及鲜重分别比对照至少高17%、40.8%和14.29%,且差异达到显著水平（P<0.05）。在正常条件下,转基因植株叶片中抗坏血酸过氧化物酶(APX)活性显著高于WT;经300 mmol/L NaCl处理,转基因拟南芥叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)、APX酶活性均升高,与处理前相比分别提高7.37倍、30.87倍和1.77倍,且与WT的酶活性差异达到显著水平（P<0.05）;丙二醛(MDA)含量也在处理后上升,但在转基因植株中的含量低于WT,分别是WT的0.74倍、0.68倍和0.62倍,差异同样达到显著水平（P<0.05）。本研究提示,OsAQP过表达不仅能够促进拟南芥种子萌发和根系生长,而且在盐胁迫下通过提高拟南芥内源抗氧化酶活性、降低膜脂过氧化程度,增强了转基因植株对一定程度盐胁迫的耐受性。     

The distribution of the orange‐striped green anemone,Diadumene lineata,in relation to environmental factors along coastal British Columbia,Canada

The cosmopolitan nonindigenous sea anemone, Diadumene lineata, has been recorded from the Pacific coast of Canada since 1859. Despite its long historical presence in the region, the factors influencing the distribution of this species in British Columbia, Canada, are poorly understood, as are the factors that may restrict its local abundance. We conducted large‐scale surveys of D. lineata during the winter and summer of 2016, coupled with higher frequency surveys at one focal site. Furthermore, we used laboratory and field experiments to determine the potential importance of a large‐scale driver, salinity, and a small‐scale driver, microhabitat within boulders, in setting distributional limits at various spatial scales. Our results confirm that D. lineata is widely distributed within the Salish Sea. This broad distribution may be facilitated by post‐introduction dispersal; we observed anemones attached to floating substrata, and a few mature specimens contained eggs, suggesting that reproduction is perhaps not limited to asexual fission. We found that D. lineata was abundant throughout the year, although absent from the lowest salinity sites. This corresponded with our laboratory experiments, in which survival of individuals of D. lineata declined at salinities below 10 psu, and no survivors were observed at or below 2 psu. Manipulative experiments in the field demonstrated that survival was high under rocks where D. lineata is commonly found, but was reduced on the tops of rocks, highlighting the importance of microhabitat refugia in buffering temperature and reducing desiccation. A better understanding of the factors that limit the broad‐scale and local distribution of this anemone are an important step in determining potential ecological impacts of this organism and how distributions may shift into the future.     

Facilitation and herbivory during restoration of California coastal sage scrub

Using nurse plants to facilitate native plant recruitment in degraded habitats is a common restoration practice across various arid and semiarid environments. Living trees or shrubs are typically considered nurse plants, whereas dead shrubs left in the landscape from prolonged drought are understudied prospective facilitators for native plant recruitment. The interaction between nurse plants and biotic pressures, such as herbivory, on native recruitment is also not well understood in semiarid plant communities. We investigated the effects of facilitation and herbivory on native seedling germination, growth, and survival in the restoration of degraded coastal sage scrub (CSS) habitat. Native shrub seedlings (Artemisia californica and Salvia mellifera) were planted, and native annual species (Amsinckia intermedia, Deinandra fasciculata, Phacelia distans, and Pseudognaphalium californicum) were sown in three Shrub Type treatments (live shrub, dead shrub, and exposed areas), with a nested Cage treatment (no cage and cage) in each Shrub Type treatment. Annual species grew equally well in all Shrub Type treatments; shrub seedlings grew largest in exposed areas. While there was little evidence of facilitation for all species tested, there were strong positive effects of caging on growth and establishment of all species. Caging palatable native species or planting species with anti‐herbivory traits around target plants may be more strategic approaches compared to using nurse plants in restoring degraded CSS after extended drought.     

Evolutionary constraint on low elevation range expansion: Defense‐abiotic stress‐tolerance trade‐off in crosses of the ecological model Boechera stricta

Most transplant experiments across species geographic range boundaries indicate that adaptation to stressful environments outside the range is often constrained. However, the mechanisms of these constraints remain poorly understood. We used extended generation crosses from diverged high and low elevation populations. In experiments across low elevation range boundaries, there was selection on the parental lines for abiotic stress‐tolerance and resistance to herbivores. However, in support of a defense‐tolerance trade‐off, extended generation crosses showed nonindependent segregation of these traits in the laboratory across a drought‐stress gradient and in the field across the low elevation range boundary. Genotypic variation in a marker from a region of the genome containing a candidate gene (MYC2) was associated with change in the genetic trade‐off. Thus, using crosses and forward genetics, we found experimental genetic and molecular evidence for a pleiotropic trade‐off that could constrain the evolution of range expansion.     

Nemo-like Kinase Drives Foxp3 Stability and Is Critical for Maintenance of Immune Tolerance by Regulatory T Cells

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The Rad5 Helicase and RING Domains Contribute to Genome Stability through their Independent Catalytic Activities

Genomic stability is compromised by DNA damage that obstructs replication. Rad5 plays a prominent role in DNA damage bypass processes that evolved to ensure the continuation of stalled replication. Like its human orthologs, the HLTF and SHPRH tumor suppressors, yeast Rad5 has a RING domain that supports ubiquitin ligase activity promoting PCNA polyubiquitylation and a helicase domain that in the case of HLTF and Rad5 was shown to exhibit an ATPase-linked replication fork reversal activity. The RING domain is embedded in the helicase domain, confusing their separate investigation and the understanding of the exact role of Rad5 in DNA damage bypass. Particularly, it is still debated whether the helicase domain plays a catalytic or a non-enzymatic role during error-free damage bypass and whether it facilitates a function separately from the RING domain. In this study, through in vivo and in vitro characterization of domain-specific mutants, we delineate the contributions of the two domains to Rad5 function. Yeast genetic experiments and whole-genome sequencing complemented with biochemical assays demonstrate that the ubiquitin ligase and the ATPase-linked activities of Rad5 exhibit independent catalytic activities in facilitating separate pathways during error-free lesion bypass. Our results also provide important insights into the mutagenic role of Rad5 and indicate its tripartite contribution to DNA damage tolerance.     

昼夜温度波动对麦长管蚜生理生态表型影响及其相关性研究

昼夜温度波动变化是气候变暖的主要特征之一,昼夜变温幅度对生物的影响越来越受到科学家的关注。与恒温研究相比,变温幅度对昆虫生活史特征影响的研究还十分有限。因此,本研究模拟自然界24 h温度变化,并首次全面研究了相同平均温度（22℃）下不同变温幅度（±0℃、±6℃、±12℃）对麦长管蚜Sitobion avenae生理指标（温度耐受性、呼吸）与生态指标（发育、存活、寿命、繁殖、种群参数）的影响。结果表明,与变温幅度±0℃和±12℃相比,变温幅度±6℃显著提高了麦长管蚜整体存活、寿命、繁殖以及净增值率与世代周期。与其它处理相比,较大变温幅度±12℃显著阻碍了麦长管蚜若虫发育,抑制了整体存活,缩短了寿命,降低了繁殖量,且显著降低了种群内禀增长率、净增值率与世代周期。但是,较大变温幅度±12℃,显著提高了成蚜的耐热、耐寒性与CO2呼吸速率。研究还发现,在不同变温幅度中,麦长管蚜成蚜耐寒性的提高是以寿命为代价的。由此可见,以往以恒温为基础的昆虫种群表型及数量动态预测模型均存在局限,昼夜变温幅度作为必要因素,应考虑纳入种群表型及数量动态预测模型中,从而提高昆虫田间发生情况预测预报的准确性与气候变化对生物的风险评估的精确性。