香茅精油对番茄早疫病菌的抑菌作用及抑菌机制

为探明香茅精油的抑菌作用及其在植物病害生物防治中的应用价值,采用平板抑菌法和熏蒸法测定了香茅精油对番茄早疫病菌的抑菌活性,及其对菌丝体内电解质渗漏、可溶性蛋白质含量、丙二醛(MDA)含量、营养物质的吸收和超氧化物歧化酶(SOD)活性的影响.结果表明: 香茅精油对番茄早疫病菌有较强的抑菌作用,且该作用具有时间-剂量依赖性,但无杀菌作用.采用熏蒸法处理的抑制效果较平板抑菌法更好,处理48 h后,半抑制浓度(IC₅₀)分别为13.40 μL·L^-1和103.23 mg·L^-1;处理144 h后,IC₅₀分别为33.81 μL·L^-1和145.16 mg·L^-1.125 mg·L^-1香茅精油处理12 h后,菌丝体的电导率和MDA含量分别为对照的2.7和2.2倍,SOD活性和可溶性蛋白质含量分别提高88.5%和21.9%,还原糖的吸收减少11.3%.香茅精油可通过破坏病原菌细胞膜完整性和抑制菌体对营养物质的吸收来抑制病原菌菌丝的生长.香茅精油在植物病害生物防治中有一定的开发潜力.     

古尔班通古特沙漠水热梯度变化对短命植物生态化学计量特征影响

以古尔班通古特沙漠2种优势短命植物尖喙牻牛儿苗(Erodium oxyrhinchum M. Bieb.)和东方旱麦草(Eremopyrum orientale(L.) Jaubert&Spach)为研究对象,通过盆栽控制实验,设定2个温度梯度以及3个水分梯度,对它们在不同温、湿度处理下的C、N、P含量及其化学计量比的变化特点进行分析。结果显示：(1)温度显著影响尖喙牻牛儿苗的N、P、C∶P、N∶P以及东方旱麦草的C、N、P、C∶N、N∶P;水分显著影响2种短命植物的N、P、C∶N、C∶P以及东方旱麦草的N∶P,其中N含量随温度的变化符合温度-生物地球化学假说,而P含量随温度的变化符合温度-植物生理假说。(2)温度和水分的交互作用对2种植物的影响表现为：在高温处理时,随着水分梯度的增加,2种植物的N、P含量先升高再下降,C∶N、C∶P、N∶P先下降再升高;在低温处理时,尖喙牻牛儿苗的N、P含量变化与水分梯度呈反比,C∶P变化与水分梯度呈正比,而东方旱麦草化学计量变化差异不显著。(3)相关性分析结果表明,温度和水分显著影响2种短命植物各元素之间的相关关系,植物的生长速率和养分限制...     

古尔班通古特沙漠四种草本植物不同生长期C、N、P化学计量比的动态变化分析

以古尔班通古特沙漠地区广泛分布的4种荒漠草本植物沙蓬（Agriophyllum squarrosum（L.） Moq.）、雾冰藜（Bassia dasyphylla（Fisch.et Mey.） O.Kuntze）、角果藜（Ceratocarpus arenarius L.）和碱蓬（Suaeda glauca（Bge.） Bge.）为对象,对他们在不同生长期的C、N、P含量及计量比的动态变化进行研究。结果显示：4种植物的C、N、P含量以及C：N、C：P、N：P在整个生长期的变化趋势不同,不同生长期各个指标的变异系数在物种间存在明显差异;4种植物的C、N、P含量及计量比的季节性变异分析结果表明,N、P含量及C：N、N：P的季节性变异幅度较大,相反,C含量和C：P的变异幅度较小;4种植物C含量和C：P由季节变化所引起的变异系数范围分别为2.43%~15.80%和6.77%~18.67%,而N、P含量和C：N、N：P的变异系数范围分别为21.26%~34.38%、11.18%~30.26%、18.52%~27.11%、14.90%~25.91%;整个生长季内,4种植物C、N、P含量及计量比的变异系数依次为：N（30.00%） > C：N（22.87%） > N：P （20.12%） > P（17.76%） > C：P（11.72%） > C（9.02%）。研究结果表明4种植物在不同生长周期的C、N、P含量及计量比的变化规律与他们的生长周期和植物种类存在显著相关性。     

古尔班通古特沙漠南缘3种生活型草本植物生物量分配及相关生长关系

为了解古尔班通古特沙漠不同生活型草本植物的生物量分配特征,通过取样调查当地34种草本植物的生物量研究表明：（1）采集到的每个物种样本的总生物量大多小于4 g,其中多数个体（大于80%）的地上与地下生物量分别在2和0.5 g以内,根冠比主要集中在0.25以内;（2）类短命植物向地下部分分配较多生物量,根冠比较大,集中分布在1.67左右;短命和一年生长营养期草本向地下部分配的生物量远小于类短命植物,两者的根冠比较小,主要集中在0.15左右;（3）短命植物地下与地上部生物量间为等速生长关系,而类短命植物和一年生长营养期草本植物地下与地上生物量间为异速生长关系,其中类短命植物随个体增大向地下部分配生物量的比例增多,而一年生长营养期草本则相反。综上所述,短命、类短命和一年生长营养期草本植物地下与地上生物量间具有不同的分配特征,与各自独特的生活史特征相一致。     

Chemical Composition and Spectrum of Insecticidal Activity of the Essential Oils of Ocimum gratissimum L. and Cymbopogon citratus Stapf on the Main Insects of the Cotton Entomofauna in Côte d'Ivoire

Among the alternatives to environmentally toxic and socio-economically unacceptable chemical pesticides, essential oils from Ocimum gratissimum and Cymbopogon citratus were tested on the main pests and beneficial insects of the cotton plant in Côte d′Ivoire. After extraction and chemical analysis of the essential oils, field trials were carried out using a Fisher block system with three treatment repetitions where their effects compared with those of a registered synthetic insecticide (IBIS A 52 EC). Foliar applications of the products were carried out in accordance with the cotton plant protection extension programme in Côte d′Ivoire from the 45th to the 115th day after plant emergence, with one application every fortnight. Twenty-three and forty compounds representing about 96 and 99 % of the oil composition of O. gratissimum and C. citratus respectively were elucidated. The most abundant compounds were p-cymene and thymol (O. gratissimum) and myrcene, neral and geranial (C. citratus). The essential oil of O. gratissimum at concentrations of 2 and 5 % showed insecticidal activity on all pests (biting-sucking and carpophagous), except the phyllophagous Syllepte derogata. C. citratus, at a low concentration (1 %), was particularly toxic to whiteflies (Bemisia tabaci), however, it favoured the action of beneficial insects, specifically black ants and ladybirds in the cotton plots, unlike the chemical product. EO of O. gratissimum (1.60 and 4.62 mg GALAE/g, respectively) and C. citratus (2.26 and 2.78 mg GALAE, respectively) exhibited also significant acetyl and butyryl cholinesterase inhibitors. Insecticide formulations based on the essential oils of O. gratissimum and C. citratus offer favourable prospects for their use in cotton cultivation as an alternative to chemical pesticides.     

近30年古尔班通古特沙漠短命植物的时空格局

基于1985—1999年的GIMMS-NDVI数据和2000—2014年的MODIS-NDVI数据提取短命植物的时空格局,结合野外调查数据和1985—2014年气象站点气温和降水数据,从不同时空尺度上分析了古尔班通古特沙漠短命植物的时空变化及其对气候变化的响应。结果表明:(1)古尔班通古特沙漠中短命植物层片整体表现出物种组成简单,优势度高、多样性和覆盖度低等特征,且层片特征主要是由优势物种所主导,在早春至盛夏期间,由于短暂的生活史造成层片整体在物候上有一个明显的起伏差异。(2)沙漠中短命植物覆盖度最高的区域为南部和中东部,北部次之,西部最少。就时间变化趋势而言,受近30年早春温度和冬春降水增加的影响,短命植物覆盖的区域面积呈现出明显的增加趋势。(3)1985—2014年间3、4月温度和冬春两季降水量呈上升趋势,而反映短命植物长势的NDVI值与冬春两季降水量也呈正相关性,但就相关性程度而言,冬季降水量与NDVI呈显著性相关(P0.05,r=0.405),而春季降水由于时滞效应并未表现出显著相关性。     

Farm-scale trials to compare the entomopathogenic fungus Beauveria bassiana with pirimiphos methyl + deltamethrin and essential oil of lemon grass for protection of stored cowpea against Callosobruchus maculatus (Coleoptera: Bruchidae)

In trials conducted in Benin, conidia of Beauveria bassiana were evaluated as a control method against the cowpea weevil, Callosobruchus maculatus , in stored cowpea. In the first trial using a high artificial infestation of C.   maculatus in 8-kg batches of cowpea in jerry cans under typical conditions, concentrations of 1 × 10⁹ and 1 × 10¹¹ conidia kg⁻¹ were compared with lemon grass oil at 2 mL kg⁻¹ and the synthetic pesticide mixture of 1.5% pirimiphos methyl + 0.05% deltamethrin at 0.5 g kg⁻¹. After 2 months of storage, seed losses (SD) were 20.63 (5.3)% in the untreated control, 8.04 (3.2)% in the low-dose B.   bassiana group, 3.12 (1.3)% in the high-dose B.   bassiana group, 2.52 (0.4)% in the lemon grass oil group and 0% in the pirimiphos methyl + deltamethrin group. In a second trial with natural infestations in 50-kg batches of cowpea in 200-L drums, treatment with B.   bassiana 1 × 10¹¹ conidia kg⁻¹ was compared with pirimiphos methyl + deltamethrin at 0.5 g kg⁻¹. After 6 months of storage on six farms, losses reached 30.76 (1.5)% in the control, 1.28 (0.2)% in the pirimiphos methyl + deltamethrin group and 3.69 (0.6)% in the B.   bassiana group.     

Sucrose mobilization in relation to essential oil biogenesis during palmarosa (<Emphasis Type="Italic">Cymbopogon martinii</Emphasis> Roxb. Wats. var.<Emphasis Type="Italic">motia</Emphasis>) inflorescence development

Palmarosa inflorescence with partially opened spikelets is biogenetically active to incorporate [U-¹⁴C]sucrose into essential oil. The percent distribution of¹⁴C-radioactivity incorporated into geranyl acetate was relatively higher as compared to that in geraniol, the major essential oil constituent of palmarosa. At the partially opened spikelet stage, more of the geraniol synthesized was acetylated to form geranyl acetate, suggesting that majority of the newly synthesized geraniol undergoes acetylation, thus producing more geranyl acetate.In vitro development of palmarosa inflorescence, fed with [U-¹⁴C]sucrose, resulted in a substantial reduction in percent label from geranyl acetate with a corresponding increase in free geraniol, thereby suggesting the role of an esterase in the production of geraniol from geranyl acetate. At time course measurement of¹⁴CO₂ incorporation into geraniol and geranyl acetate substantiated this observation. Soluble acid invertase was the major enzyme involved in the sucrose breakdown throughout the inflorescence development. The activities of cell wall bound acid invertase, alkaline invertase and sucrose synthase were relatively lower as compared to the soluble acid invertase. Sucrose to reducing sugars ratio decreased till fully opened spikelets stage, concomitant with increased acid invertase activity and higher metabolic activity. The phenomenon of essential oil biosynthesis has been discussed in relation to changes in these physiological parameters.     

Dew as a key factor for the distribution pattern of the lichen species Teloschistes lacunosus in the Tabernas Desert (Spain)

The role of different sources of water (rain, dew and water vapor) has been investigated under natural conditions in order to explain the activity and the distribution patterns of Teloschistes lacunosus (Rupr.) Sav. in the Tabernas Desert (Almeria, Spain). This field work was carried out at two neighboring sites: a pediment where T. lacunosus is well developed and an east-facing slope where only few small thalli are developed. Diurnal courses of photosynthetic activity were assessed by the use of chlorophyll a fluorescence measurements, at each site for a total of 12 days distributed among different seasons over the year. Microclimatic data (thallus temperature, relative humidity (RH) and light intensity) were recorded continuously for a period of 1 year including all the days on which fluorescence measurements were made. Dried T. lacunosus in its natural habitat only became photosynthetically active after re-hydration with liquid water (dew or rain). In contact with an atmosphere of high RH (higher than 90%) but without dew condensation, thalli were not able to obtain sufficient water to become physiologically active. The microclimatic study showed notably differences between the two studied expositions. After dawn, thalli from the east-facing slope were exposed to higher temperatures and light intensity (PPFD) levels than thalli from the pediment. This was reflected in the length of time that the air remained saturated and the lichen remained wet and active. The high incident PPFD and the resultant increased temperatures at the east-facing slope led to short dew duration and, therefore to shorter periods of morning photosynthetic activity than on the pediment as fluorescence measurements showed. Additionally, the microclimatic differences between the two sites indicated a high frequency of dew fall events on the thalli from the pediment. The time periods of thallus dew imbibition vary strongly with the exposure of the lichens.     

Convergence in the distribution patterns of Europe’s plants and mammals is due to environmental forcing

Aim Our aims were to test: (1) the extent to which vascular plant associations are related in space to mammalian associations, and (2) whether the plant associations are more closely related than the mammalian associations to climate and to a published environmental stratification of Europe. Location Europe, as defined by the following boundaries: 11° W, 32° E, 71° N and 35° N. Methods The analysis is based on presence/absence records of mammal species and plant species with a resolution of 50 km × 50 km. The similarity of the overall spatial structure was tested using a partial Mantel test while controlling for the effect of geographical proximity. To further identify the main spatial components in the datasets, we used k‐means clustering and principal components analysis. The resulting geographical patterns were compared with one another, with climate variables and with the environmental stratification of Europe. Results The clustering of the plant data forms coherent areas that can be interpreted as reflections of floristic regions that are controlled to a large extent by climate and topography. In terms of the correlation between distance matrices, the relationship between plants and mammals is relatively strong. The relationships between mammals and climate, and between plants and climate, are more complex but always statistically significant. There is no evidence that the plant clusters are more closely related than the mammalian clusters to climate, although plant clusters are closer to environmental data than to climate. Main conclusions The clustering patterns of mammals and plants form groups that agree with one another in their spatial extent. The forcing of floristic patterns into coherent entities appears mainly to be caused by climatic variables (temperature, temperature range and rainfall), mediated by elevation differences. The formation of individual plant clusters is also related to species numbers and to local and regional floristic differences. The close correlation between the floristic and faunal patterns suggests that the mammal and plant distributions are controlled by the same environmental variables, although the extent to which the mammals are controlled directly by climate or through the influence of vegetation requires more detailed study.     

早春首次降雨时间及降雨量对古尔班通古特沙漠两种短命植物形态特征与叶绿素荧光的影响

早春降雨事件是影响荒漠短命植物生长的重要因子, 为了解古尔班通古特沙漠积雪完全融化后早春首次降雨时间及降雨量对短命植物光合生长的影响。该研究选取两种优势短命植物尖喙牻牛儿苗(Erodium oxyrhinchum)和琉苞菊(Centaurea pulchella)为研究对象, 设置3个首次降雨时间(积雪完全融化后第10、20和30天)和3个降雨水平(5、10和15 mm), 探究两物种的形态、生物量及光化学效率的响应差异。结果显示: 积雪完全融化后第10天进行首次降雨处理时, 随着首次降雨量的增加, 尖喙牻牛儿苗的叶面积和总生物量呈显著增加趋势, 最大光化学效率呈下降趋势。在第20和30天进行首次降雨处理时, 尖喙牻牛儿苗和琉苞菊的叶面积均呈显著增加趋势。在积雪完全融化后5 mm降雨处理时, 随着首次降雨时间的延迟, 尖喙牻牛儿苗和琉苞菊的最大光化学效率呈先下降后上升趋势; 10 mm降雨处理时, 尖喙牻牛儿苗的冠根比降低, 根长和总生物量呈先增加后下降趋势, 琉苞菊的根长呈显著增加趋势; 15 mm降雨处理时, 尖喙牻牛儿苗的叶面积、冠根比和最大光化学效率呈显著增加趋势; 琉苞菊的冠根比和最大光化学效率呈下降趋势, 总生物量呈显著增加趋势。尖喙牻牛儿苗和琉苞菊的根长分别与0-5 cm和5-10 cm土壤含水量呈显著正相关关系。这说明早春首次降雨量比首次降雨时间更能影响植株生长, 但不同物种对降雨格局变化的响应不一致, 这可能通过影响早春短命植物的形态特征, 进而影响早春荒漠生态系统的稳定性。     

The alternative sigma factor SigF is a key player in the control of secretion mechanisms in Synechocystis sp. PCC 6803

Cyanobacterial alternative sigma factors are crucial players in environmental adaptation processes, which may involve bacterial responses related to maintenance of cell envelope and control of secretion pathways. Here, we show that the Group 3 alternative sigma factor F (SigF) plays a pleiotropic role in Synechocystis sp. PCC 6803 physiology, with a major impact on growth and secretion mechanisms, such as the production of extracellular polysaccharides, vesiculation and protein secretion. Although ΔsigF growth was significantly impaired, the production of released polysaccharides (RPS) increased threefold to fourfold compared with the wild-type. ΔsigF exhibits also impairment in formation of outer-membrane vesicles (OMVs) and pili, as well as several other cell envelope alterations. Similarly, the exoproteome composition of ΔsigF differs from the wild-type both in amount and type of proteins identified. Quantitative proteomics (iTRAQ) and an in silico analysis of SigF binding motifs revealed possible targets/pathways under SigF control. Besides changes in protein levels involved in secretion mechanisms, our results indicated that photosynthesis, central carbon metabolism and protein folding/degradation mechanisms are altered in ΔsigF. Overall, this work provided new evidences about the role of SigF on Synechocystis physiology and associates this regulatory element with classical and non-classical secretion pathways.     

Antarctic macrolichen modifies microclimate and facilitates vascular plants in the maritime Antarctica – a reply to Casanova‐Katny et al. (2014)

In a current article in the Journal of Vegetation Science, Casanova‐Katny et al. addressed a comment about an article by Molina‐Montenegro et al., which demonstrated the climate modification induced by the macrolichen Usnea antarctica and its role as facilitator. They provided useful corrections concerning species identification and pointed out several issues that, in their view, weakened our study. They indicated that the role of U. antarctica as a facilitative species in the maritime Antarctica is merely philosophical and has no ecological relevance. In this commentary, we argue why these critiques are unsubstantial, and provide evidence that the macrolichen can modify the microclimate, ameliorating the harsh conditions prevailing in Antarctica, establishing positive interactions and eventually facilitating vascular species. Thus, the macrolichen U. antarctica would act as a ‘nurse species’, playing a key role in structuring the maritime Antarctic plant community.     

Studies of the response of peach and nectarine plants to gibberellin biosynthesis inhibitors in a hydroponic system

In small rooted peach and nectarine plants grown in a hydroponic system, low paclobutrazol (PBZ) levels applied to the roots suppressed shoot and root development, but to a different degree. A much stronger retarding effect was observed on the shoot, with a very limited effect on roots, resulting in a reduced shoot:root ratio. The effect of the inhibitor on the roots was a rapid increase in root diameter, with increased root branching upon recovery from the inhibiting effect. Root thickening, a typical response to PBZ, was detected also in nectarines when only the top was treated with the inhibitor, indicating a basal movement of PBZ, thus contradicting the accepted notion that its translocation is only acropetal. Root thickening was the earliest detected morphological response to PBZ, being observed already 3 days after exposure to the retardant. The return to a normal diameter was abrupt. Uniconazol (UNI) had a much stronger retarding effect on peach plants than did similar concentrations of PBZ. Reduced top growth resulted in a reduction in water consumption.Abbreviations PBZ paclobutrazol - UNI uniconazol - GA Gibberellin - GBI gibberellin biosynthesis inhibitor - ABA abscisic acid This research was supported by Grant no. 1-779-84 from the US-Israel Binational Agricultural Research and Development Fund (BARD).Contribution from the Agricultural research organization, The Volcani Center, Bet Dagan, Israel. No. 1506-E, 1994 series.     

The intrinsic flexibility of the aptamer targeting the ribosomal protein S8 is a key factor for the molecular recognition

Background

Aptamers are RNA/DNA biomolecules representing an emerging class of protein interactors and regulators. Despite the growing interest in these molecules, current understanding of chemical-physical basis of their target recognition is limited. Recently, the characterization of the aptamer targeting the protein-S8 has suggested that flexibility plays important functional roles. We investigated the structural versatility of the S8-aptamer by molecular dynamics simulations.

Increased anaerobic metabolism is a distinctive signature in a colorectal cancer cellular model of resistance to antiepidermal growth factor receptor antibody

Cetuximab is a chimeric antibody approved for the treatment of metastatic colorectal cancer that selectively targets epidermal growth factor receptor (EGFR) signaling. Treatment efficacy with this drug is often impaired by acquired resistance and poor information has been accumulated on the mechanisms underlying such a phenomenon. By taking advantage of a syngenic cellular system of sensitivity and acquired resistance to anti‐EGFR therapy in the colorectal carcinoma GEO cell line, we profiled protein expression differences between Cetuximab‐sensitive and ‐resistant cells. Combined 2D DIGE and MS analyses revealed a main proteomic signature resulting from selective deregulation of various metabolic enzymes, including glucose‐6‐phosphate dehydrogenase, transketolase, lactate dehydrogenase B, and pyruvate dehydrogenase E1, which was also confirmed by Western blotting experiments. Lactate dehydrogenase B downregulation has been already related to an increased anaerobic utilization of glucose by tumor cells; accordingly, we verified that Cetuximab‐resistant cells have a significantly higher production of lactate. Resistant cells also showed decreased nicotinamide adenine dinucleotide phosphate (NADPH) levels. Observed protein deregulations were not related to functional alterations of the hypoxia‐inducible factor 1‐associated pathways. Our data demonstrate that increased anaerobic metabolism is a prominent feature observed in the GEO syngenic model of acquired resistance to anti‐EGFR therapy in colorectal cancer.     

Binding of the Ets factor GA-binding protein to an upstream site in the factor IX promoter is a critical event in transactivation.

Factor IX is an essential vitamin K-dependent serine protease that participates in the intrinsic pathway of coagulation. The protein is expressed exclusively in the liver. The rare Leyden form of hemophilia B (inherited factor IX deficiency) results from point mutations in three proximal promoter elements that decrease factor IX expression. Recovery of expression occurs following puberty, with factor IX protein levels rising into the normal range. We have previously implicated the PAR domain D-site-binding protein (DBP) as well as an upstream element, site 5, as playing important roles in the phenotypic recovery of hemophilia B Leyden. Here we demonstrate that site 5 binds both the CCAAT/enhancer-binding protein (C/EBPalpha) and the ubiquitous Ets factor GA-binding protein (GABPalpha/beta). Transactivation of the factor IX promoter by the PAR proteins DBP and hepatic leukemia factor (HLF) is dependent on the binding of GABPalpha/beta to site 5, and coexpression of these two factors is required for optimal activation of this promoter. The binding of C/EBPalpha to site 5 also augments the activity of GABPalpha/beta. Analysis of the developmental regulation of site 5-binding proteins in rat liver has shown that C/EBPalpha and the GABPbeta subunit increase markedly in the 2 weeks after birth. These observations establish a functional association between the Ets factor GABPalpha/beta and C/EBPalpha and indicate that the two PAR proteins, DBP and HLF, may play complementary roles in factor IX activation. Given the developmental changes exhibited by these proteins, it is likely that they play a role in regulation of the normal factor IX promoter as well as promoters carrying hemophilia B Leyden mutations.     

Autophagy is a key factor in maintaining the regenerative capacity of muscle stem cells by promoting quiescence and preventing senescence

Autophagy, a highly regulated cellular degradation and recycling process, can occur constitutively at a basal level, and plays an essential role in many aspects of cell physiology. A recently published study (see the related punctum in Autophagy, Vol. 12, No. 4) suggests that basal autophagy is also important for maintaining the regenerative capacity of muscle stem cells, and that the decline of autophagy with aging is the cause of entry into senescence from quiescence in satellite cells.