Cultivated walnut trees showed earlier but not final advantage over its wild relatives in competing for seed dispersers

Little is known about seeding regeneration of cultivated trees compared to wild relatives in areas where seed dispersers are shared. Here, we investigated the differences in seed fates of cultivated walnut (Juglans regia) and wild Manchurian walnut (Juglans mandshurica) trees under rodent predation and dispersal. J. regia seeds have higher nutritional value (large size, mass and kernel mass) and lower mechanical defensiveness (thin endocarp) than J. mandshurica seeds. We tracked seeds of J. regia and J. mandshurica under both enclosure and field conditions to assess differences in competing for seed dispersers of the two co‐occurring tree species of the same genus. We found that rodents preferred to harvest, eat and scatter‐hoard seeds of J. regia as compared to those of J. mandshurica. Seeds of J. regia were removed and scatter‐hoarded faster than those of J. mandshurica. Caches of J. regia were more likely to be rediscovered by rodents than those of J. mandshurica. These results suggest that J. regia showed earlier dispersal fitness but not the ultimate dispersal fitness over J. mandshurica in seeding regeneration under rodent mediation, implying that J. regia has little effect on seeding regeneration of J. mandshurica in the field. The effects of seed traits on seed dispersal fitness may vary at different dispersal stages under animal mediation.     

特用竹种——酒竹的引种繁育初报

酒竹,以其可以伤流形式分泌出含酒精的天然营养液而闻名于世,但目前,世界上对酒竹研究、开发和利用尚处于初始阶段。本文对酒竹这一重要经济竹种的引种和初期的扦插、培育、密度限制等工作做了详细的报告,为收集种质和培育特种竹种提供了基础资料。     

转录后基因沉默

 转录后基因沉默(PTGS)普遍存在于生物界,如植物的共抑制、源于病原的RNA介导的病毒抗性、真菌的基因沉默和动物的RNA干扰等。这类现象有许多共同特点,如都是以向细胞内引入核酸(转基因、双链RNA或病毒RNA)为诱因,依赖RNA的RNA聚合酶(RdRP)活性与基因沉默密切相关,在发生基因沉默的细胞中大多存在特定长度的小分子RNA (21~25 nt),PTGS导致细胞质内mRNA的特异性降解,不同生物的PTGS相关基因及产物具有很高的相似性,基因沉默能够在细胞间传播并能以表型遗传的方式传递给下一代等。这说明各种生物的转录后基因沉默可能有相似的遗传起源,是一种抵抗外来核酸(如病毒和转座子)入侵的共同的防御机制     

Density effects on the conifer mortality in declining spruce-fir forest in northern Japan: Implication of bark beetle attack to, cause spruce decline

We examined mortality patterns of two conifer species in relation to tree abundance and species composition in a declining spruce-fir forest in Akan National park, Hokkaido, northern Japan. The data taken from eleven 58 m × 58 m square study plots showed that percentage basal area (BA) of dead trees of canopy trees during the last decade was 49% forPicea jezoensis (Sieb. et Zucc.) Carr and 30% forAbies sachalinensis (Fr. Schm.) Masters. InP. jezoensis, percentage basal area (BA) of dead trees was positively related to both BA of its own species and proportion of it to BA of all species, whereas it was not significantly related to both of these variables inA. sachalinensis. Multiple logistic regression with dbh as a confounding factor also indicated that, inP. jezoensis, the proportion of dead stems was positively affected by the stem density of conspecific trees, whereas it was negatively affected by the stem density of the other species in each study plot. However, inA. sachalinensis, the proportion of dead stems was significantly related to neither of these factors. The different mortality pattern between two conifer species suggests that the spruce bark beetle,Ips typographus (L.), which is a serious pest of spruce, may have caused theP. jezoensis decline. Instead of wind-throw or thinning that usually initiate this bark beetle attack, some unknown factors seemed to predispose the trees to insect attack. These unknown factors may also explain the high mortality ofA. sachalinensis in this forest. This research was supported by FFPRI Project, Ministry of Agriculture, Forestry and Fishery.     

Habitat use of cownose rays (Rhinoptera bonasus) in a highly productive,hypoxic continental shelf ecosystem

Highly productive surface waters and hypoxic (dissolved oxygen, DO ≤ 2.0 mg L^?1) bottom waters develop seasonally on the northwestern Gulf of Mexico continental shelf due to nutrient and freshwater inputs from the Mississippi‐Atchafalaya River system. We investigated the spatial distribution of the cownose ray (Rhinoptera bonasus), a highly mobile, bentho‐pelagic species that is a seasonal resident of the shelf, in relation to surface chlorophyll, bottom‐water hypoxia, and other environmental variables (salinity, temperature, depth). We used synoptic trawl and aerial surveys to investigate ray distributions at both shelfwide (100–1000s km) and local (5–50 km) spatial scales. Shelfwide sampling indicated that rays were associated with regions of high surface chlorophyll and low bottom salinity and DO, conditions characterizing the Mississippi‐Atchafalaya plume region. Local sampling in and around the hypoxic zone indicated that rays preferred habitats where bottom waters were hypoxic but they primarily occupied normoxic (DO > 2.0 mg L^?1) waters above the bottom hypoxic layer. Stomach fullness and diet composition were similar between rays sampled in habitats with hypoxic versus normoxic bottom waters. These results indicate that cownose rays are strongly associated with riverine‐influenced regions of the shelf and preferentially use habitats with hypoxic bottom waters, perhaps for benthic foraging. Collectively, our results highlight the importance of considering the responses of mobile species to enhanced productivity and to hypoxia‐induced habitat degradation, which are both the products of coastal eutrophication.     

Angler apps as a source of recreational fisheries data: opportunities,challenges and proposed standards

Recreational fisheries surveys are limited in time and place in many countries. This lack of data limits scientific understanding and sustainable management. Smartphone applications (apps) allow anglers to record the details of their fishing trips and catches. In this study, we describe the opportunities and challenges associated with angler apps as a source of recreational fisheries data, and propose minimum standards for data collection via angler apps. Angler apps are a potentially valuable source of conventional and novel data that are both frequent and extensive, and an opportunity to engage anglers through data sharing and citizen science. Realizing this potential requires that we address significant challenges related to angler recruitment and retention, data quality and bias, and integration with existing fisheries programmes. We propose solutions to each of these challenges. Given that the angler app market is diverse, competitive and unpredictable, we emphasize minimum standards for data collection as a way to ensure large and reliable data sets that can be compared and integrated across apps. These standards relate to trips and catches, and angler demographics and behaviour, and should be supported through consultation and research. Angler apps have the potential to fundamentally change how anglers interact with the resource and with management.     

松嫩平原野大麦种群可塑性生长及密度调节

松嫩平原野大麦种群数量特征的野外调查和统计分析结果表明:在籽实乳熟～成熟期,野大麦种群尚未达到环境最大容纳量,其生物量随种群密度增加呈极显著增长;营养蘖可塑性大于生殖蘖,生殖蘖生产力约是营养蘖的1.3倍;种群抽穗率有较大的变异度;分蘖株的生长已经受到种群密度的调节,分蘖株单蘖重与种群密度和营养蘖密度,以及营养蘖、生殖蘖单蘖重与种群密度间均为幂函数关系.     

GIP/GIPR经Akt-TCF4-GIPR正反馈增强GIP效应

旨在从GIP/GIPR下游的Akt和PKA信号通路中筛选出调控GIPR表达的调控因子,并解析GIPR的表达调控机制。本研究以小鼠胰岛瘤细胞系Min6为试验材料,在Akt、PKA信号通路阻断的条件下,通过Western blot筛选出与GIPR表达相关的转录因子T细胞因子4（TCF4）;利用双荧光素酶报告系统确定TCF4对GIPR表达调控的影响,再通过敲除或过表达TCF4进一步验证两者之间的调控关系;采用CCK8法检测TCF4介导的促增殖作用,ELISA检测胰岛素分泌能力。结果显示,GIP可激活Akt磷酸化,并促进GIPR表达;在GIP激活及Akt、PKA信号通路阻断时,GIPR蛋白表达趋势与TCF4始终一致;TCF4可与GIPR核心启动子区结合,进而调控其表达;TCF4过表达时,GIPR的mRNA和蛋白表达上调,并促进β细胞增殖及胰岛素分泌;干扰TCF4显著降低GIP作用下GIPR的mRNA和蛋白表达,抑制β细胞增殖。综上,GIP结合GIPR后,经Akt信号通路上调TCF4进而增强GIPR表达,形成正反馈加强GIP信号,提高β细胞增殖和胰岛素分泌的功能,维持血糖稳态。因此,在胰岛素抵抗阻断Akt及上游信号通路时,经转录因子TCF4增强GIPR表达可作为改善胰岛β细胞功能障碍的靶点。     

猪繁殖与呼吸综合征致病机理的研究进展

PRRS(猪繁殖与呼吸综合征)复杂的发病机制包括抗体依赖性增强、引起机体免疫抑制和在机体内持续性感染等现象,以及病毒遗传多样性;这些是该病难以防控的主要原因,本文就近年有关进展进行综述。