木霉对草酸耐受和消除作用的初步分析

【目的】草酸(Oxalic acid,OA)是灰霉菌(Botrytis cinerea)等植物致病菌的致病因子,一些木霉(Trichoderma spp.)生防菌可消除草酸并降低植物发病率,但其消除草酸防治病害的途径和机制尚未研究透彻。【方法】首先从42株木霉菌株中筛选出一株在30 mmol/L草酸胁迫下耐受性最强的哈茨木霉T.harzianum LTR-2,通过形态学方法观察和原位分析了不同浓度草酸胁迫下LTR-2的发育特征变化,并测定了草酸消除水平、滤液p H和菌丝干重,分析了LTR-2在草酸为唯一碳源的生长情况。通过Real-time PCR分析了OXDC基因LTR_4445在草酸处理下的表达水平。【结果】在PDA固体培养基中,25°C半光照条件下培养5 d,在草酸浓度为50-80 mmol/L时,LTR-2可存活,但无正常菌落形态;在30-50 mmol/L浓度下,LTR-2先萌发厚垣孢子,而后再次萌发菌丝形成菌落;在30 mmol/L浓度下,LTR-2发育正常,仅生长速度减缓。25°C、160 r/min振荡培养5 d,LTR-2可消除草酸。在20 mmol/L浓度时,草酸消除率最高,为66.50%;10 mmol/L浓度中的消除率次之,为55.06%。草酸浓度50 mmol/L时,消除能力下降为6.75%-38.94%。相应地,培养液p H被不同程度地提高,在10、20 mmol/L草酸浓度下提高的幅度更大。当草酸浓度20 mmol/L时,木霉的菌丝干重有不同程度的提高。将草酸作为唯一碳源进行液体培养5 d时,在10、20 mmol/L浓度下,LTR-2可形成肉眼可见的绿色菌丝球,但高于50 mmol/L条件下无法生长。草酸处理下,LTR_4445表达水平上调。【结论】通过分析LTR-2在草酸胁迫条件下的形态特征变化及消除草酸的特性,暗示在木霉消除草酸作用中除了已知的草酸降解代谢途径,还存在响应草酸胁迫模式的转变、将草酸作为前体转化为营养物质的途径等其他消除途径。     

由任务驱动的团队自主合作学习教学模式在微生物学课程中的探索和实践

为了提高学生的自主学习及合作学习能力,在微生物学教学中,采取由任务驱动的团队自主合作学习教学模式。该模式以任务为主线,把教学内容和能力培养目标隐含在任务之中;以教师为主导,引导学生主体利用学习资源,通过个人自主学习及团队合作学习来建构知识和提升能力。三轮教学实践表明,由任务驱动的团队自主合作学习教学模式,激发了学生的学习积极性,培养了学生的综合能力和创新意识,也促进了教师教学水平的提高。     

Characterisation of antioxidants in photosynthetic and non‐photosynthetic leaf tissues of variegated Pelargonium zonale plants

Hydrogen peroxide is an important signalling molecule, involved in regulation of numerous metabolic processes in plants. The most important sources of H₂O₂ in photosynthetically active cells are chloroplasts and peroxisomes. Here we employed variegated Pelargonium zonale to characterise and compare enzymatic and non‐enzymatic components of the antioxidative system in autotrophic and heterotrophic leaf tissues at (sub)cellular level under optimal growth conditions. The results revealed that both leaf tissues had specific strategies to regulate H₂O₂ levels. In photosynthetic cells, the redox regulatory system was based on ascorbate, and on the activities of thylakoid‐bound ascorbate peroxidase (tAPX) and catalase. In this leaf tissue, ascorbate was predominantly localised in the nucleus, peroxisomes, plastids and mitochondria. On the other hand, non‐photosynthetic cells contained higher glutathione content, mostly located in mitochondria. The enzymatic antioxidative system in non‐photosynthetic cells relied on the ascorbate–glutathione cycle and both Mn and Cu/Zn superoxide dismutase. Interestingly, higher content of ascorbate and glutathione, and higher activities of APX in the cytosol of non‐photosynthetic leaf cells compared to the photosynthetic ones, suggest the importance of this compartment in H₂O₂ regulation. Together, these results imply different regulation of processes linked with H₂O₂ signalling at subcellular level. Thus, we propose green‐white variegated leaves as an excellent system for examination of redox signal transduction and redox communication between two cell types, autotrophic and heterotrophic, within the same organ.     

Western myall groves (Acacia papyrocarpa) determine the fine‐scale distribution of soil Collembola in semi‐arid South Australia

Vegetation can exert a strong influence on the distribution and activity of biotic communities across a broad range of spatial scales, especially in arid and semi‐arid ecosystems. At fine spatial scales, patches created by individual plants can support different faunal and floral communities even at locations distant from the plant. These differences can have profound effects on a range of ecosystem processes, including seed dispersal, nutrient cycling and resource distribution. In semi‐arid Australia, areas surrounding groves of western myall (Acacia papyrocarpa) trees are largely devoid of vegetation, being referred to as ‘halos’. Here, we investigate the soil‐dwelling Collembola in groves of western myall trees, the surrounding halos and nearby chenopod shrubland. We also investigated whether the abundance of Collembola was influenced by soil depth (0–5 cm layer vs. 6–10 cm layer) in groves. We found that collembolan density was approximately nine times lower and taxonomic richness half that in a halo compared with the grove and chenopod vegetation. Furthermore, analyses at finer taxonomic levels indicate that vegetation patches differed in species composition, with some species restricted to or preferring particular patches. In the grove, we found a higher abundance of Collembola in the 0–5 cm soil layer compared with the 6–10 layer. Our results indicate vegetation patches strongly influence collembolan abundance and species composition in bare patches around western myall. As patches created by vegetation are a common feature of semi‐arid and arid regions, we suspect that these effects are widespread although seldom reported. Furthermore, as Collembola are involved in the decomposition process, Acacia papyrocarpa patches will be influencing nutrient cycling through their effects on the soil biota. Our results also emphasize that comprehensive fauna survey and management of woodland ecosystems need to consider fine‐scale processes.     

Translating niche features: Modelling differential exposure of Argentine reptiles to global climate change

Global climate change affects the distributions of ectotherms and may be the cause of several conservation problems, such as great displacement of climatic suitable spaces for species and, consequently, important reductions of the extent of liveable places, threatening the existence of many of them. Species exposure (and hence vulnerability) to global climate change is linked to features of their climatic niches (such as the relative position of the inhabited localities of each species in the climatic space), and therefore to characteristics of their geographic ranges (such as the extent of the distributions or altitudinal range inhabited by the species). In order to analyze the pattern of response of Argentine reptiles to global climate change, we ran phylogenetic generalized least squares models using species exposure to global climate change as a response variable, and (i) niche properties (breadth and position of the species in the climate space) and (ii) general features of the distribution of species (maximum latitude, altitudinal range, maximum elevation, distributional range and proximity to the most important dispersal barrier) as predictors. Our results suggest that the best way to explain climate change exposure is by combining breadth and position of climatic niche of the species or combining geographic features that are indicators of both niche characteristics. Our best model shows that in our study area, species with the narrowest distributional ranges that also inhabit the highest elevations are the most exposed to the effects of global climate change. In this sense, reptile species from Yungas, Puna and Andes ecoregions could be especially vulnerable to the effects of climate change. We believe that these types of models may represent an interesting tool for determining species and places particularly threatened by the effects of global climate change, which should be strongly considered in conservation planning.     

Long-term monitoring data meet freshwater species distribution models: Lessons from an LTER-site

Long-term monitoring datasets provide a solid framework for ecological research. Such a dataset from the German long-term ecological research (LTER) site Rhine-Main-Observatory was used to set up a species distribution model (SDM) for the Kinzig catchment. The extensive knowledge on the monitoring data provided by the LTER-site framework allowed to calibrate a robust model for 175 taxa of stream macroinvertebrates and to project their distributions on the Kinzig River stream network using bioclimatic, topographical, hydrological, land use and geological predictors. On average, model performance was good, with a TSS of 0.83 (±0.09 SD) and a ROC of 0.95 (±0.03 SD). The model delivered valuable insights on three sources of bias that plague SDMs in general: (a) level of taxonomic identification of the modeled organisms, (b) the spatial arrangement of sampling sites, and (c) the sampling intensity at each sampling site. Taxonomic resolution did not affect SDM performance. The distribution of high predicted probabilities of occurrence in the stream network coincided with those segments in the stream network most densely and frequently sampled, indicating both a spatial and temporal sampling bias. Species richness curves confirmed the temporal sampling bias. Next to spatial bias, sampling frequency also plays an important role in data collection, affecting further analysis and modeling procedures. Results indicate an underrepresentation of low order streams, an important aspect that should be addressed by both monitoring schemes and modeling approaches.     

Insect distribution in response to climate change based on a model: Review of function and use of CLIMEX

The significant dependence of agricultural productivity on pest control requires pest distribution predictions at an early stage of pest invasion. Because pest cycles are critically affected by climate, climate is one of the most important factors for predicting an invasive pest. CLIMEX is a highly effective tool that can predict potential geographical species distributions, and test the regional suitability for a target species' habitat based on data including climate change scenarios. CLIMEX has been recently used in Europe, North America, China and Australia, among others. However, for modeling species distributions in Korea, the use of the model has been limited to date. This study aimed to first introduce the function and application of CLIMEX by reviewing important studies using this model. Second, we investigated previous studies using the model simulation to demonstrate the practical applicability of CLIMEX for the agricultural sector, and its use in forecasting.     

肉桂双瓣卷蛾发生期预测与幼虫空间分布型研究

肉桂双瓣卷蛾Polylopha cassiicola是危害肉桂Cinnamomum cassia和樟树Cinnamomum canphora嫩梢的一种重要钻蛀性害虫,对华南地区肉桂和樟树的发展造成了严重威胁。为了有效地控制该害虫,准确掌握其最适防治时期是非常必要的。2013-2015年采用物候法、期距法和空间分布型分析方法,对肉桂双瓣卷蛾的发生期进行预测和幼虫空间分布型进行了研究。结果表明,肉桂双瓣卷蛾在林间属聚集分布,是害虫本身的生物学特性和樟树林不同样地不同生境共同作用的结果。采用物候法预测樟树林肉桂双瓣卷蛾成虫盛发日,采用期距法预测幼虫发生时间基本吻合,可按照预测的时间进行防治或适当提前进行防治。