Quantification of dissolved and particulate polyunsaturated aldehydes in the Adriatic sea

Polyunsaturated aldehydes (PUA) are supposed to play critical roles in chemically-mediated plankton interactions. Laboratory studies suggest that they act as mediators of chemical defense and chemical communication. PUA are oxylipins containing an α,β,γ,δ-unsaturated aldehyde structure element and are mainly found in diatoms. We present here a detailed surface mapping of PUA during a spring bloom of the diatom Skeletonema marinoi in the Adriatic Sea. We monitored dissolved PUA, as well as particulate PUA, which are produced by phytoplankton after cell disintegration. Our survey revealed a patchy distribution of PUA and shows that at most stations S. marinoi is the major contributor to the overall PUA. Our data also suggest that lysis of a diatom bloom can contribute significantly to the dissolved PUA concentrations and that other producers, which are smaller in cell size compared to diatoms, have to be taken into account as well if the total PUA content of marine samples is considered. The analyses of samples collected in deeper water suggests that diatom contribution to PUA decreases with depth, while smaller-sized unidentified organisms take place as dominant contributors to the PUA concentrations.     

Diatom derived polyunsaturated aldehydes do not structure the planktonic microbial community in a mesocosm study

Several marine and freshwater diatoms produce polyunsaturated aldehydes (PUA) in wound-activated processes. These metabolites are also released by intact diatom cells during algal blooms. Due to their activity in laboratory experiments, PUA are considered as potential mediators of diatom-bacteria interactions. Here, we tested the hypothesis that PUA mediate such processes in a close-to-field mesocosm experiment. Natural plankton communities enriched with Skeletonema marinoi strains that differ in their PUA production, a plankton control, and a plankton control supplemented with PUA at natural and elevated concentrations were observed. We monitored bacterial and viral abundance as well as bacterial community composition and did not observe any influence of PUA on these parameters even at elevated concentrations. We rather detected an alternation of the bacterial diversity over time and differences between the two S. marinoi strains, indicating unique dynamic bacterial communities in these algal blooms. These results suggest that factors other than PUA are of significance for interactions between diatoms and bacteria.     

Molecular Response to Toxic Diatom-Derived Aldehydes in the Sea Urchin Paracentrotus lividus

Diatoms are dominant photosynthetic organisms in the world’s oceans and represent a major food source for zooplankton and benthic filter-feeders. However, their beneficial role in sustaining marine food webs has been challenged after the discovery that they produce secondary metabolites, such as polyunsaturated aldehydes (PUAs), which negatively affect the reproductive success of many invertebrates. Here, we report the effects of two common diatom PUAs, heptadienal and octadienal, which have never been tested before at the molecular level, using the sea urchin, Paracentrotus lividus, as a model organism. We show that both PUAs are able to induce teratogenesis (i.e., malformations), as already reported for decadienal, the better-studied PUA of this group. Moreover, post-recovery experiments show that embryos can recover after treatment with all three PUAs, indicating that negative effects depend both on PUA concentrations and the exposure time of the embryos to these metabolites. We also identify the time range during which PUAs exert the greatest effect on sea urchin embryogenesis. Finally, we report the expression levels of thirty one genes (having a key role in a broad range of functional responses, such as stress, development, differentiation, skeletogenesis and detoxification processes) in order to identify the common targets affected by PUAs and their correlation with morphological abnormalities. This study opens new perspectives for understanding how marine organisms afford protection from environmental toxicants through an integrated network of genes.     

Polyunsaturated Aldehydes from Large Phytoplankton of the Atlantic Ocean Surface (42°N to 33°S)

Polyunsaturated aldehydes (PUAs) are organic compounds mainly produced by diatoms, after cell wounding. These compounds are increasingly reported as teratogenic for species of grazers and deleterious for phytoplanktonic species, but there is still scarce information regarding concentration ranges and the composition of PUAs in the open ocean. In this study, we analyzed the spatial distribution and the type of aldehydes produced by the large-sized (>10 μm) phytoplankton in the Atlantic Ocean surface. Analyses were conducted on PUAs released after mechanical disruption of the phytoplankton cells, referred to here as potential PUAs (pPUAs). Results show the ubiquitous presence of pPUA in the open ocean, including upwelling areas, as well as oligotrophic gyres. Total pPUA concentrations ranged from zero to 4.18 pmol from cells in 1 L. Identified PUAs were heptadienal, octadienal and decadienal, with heptadienal being the most common (79% of total stations). PUA amount and composition across the Atlantic Ocean was mainly related to the nitrogen:phosphorus ratio, suggesting nutrient-driven mechanisms of PUA production. Extending the range of trophic conditions considered by adding data reported for productive coastal waters, we found a pattern of PUA variation in relation to trophic status.     

The Effect of Dissolved Polyunsaturated Aldehydes on Microzooplankton Growth Rates in the Chesapeake Bay and Atlantic Coastal Waters

Allelopathy is wide spread among marine phytoplankton, including diatoms, which can produce cytotoxic secondary metabolites such as polyunsaturated aldehydes (PUA). Most studies on diatom-produced PUA have been dedicated to their inhibitory effects on reproduction and development of marine invertebrates. However, little information exists on their impact on key herbivores in the ocean, microzooplankton. This study examined the effects of dissolved 2E,4E-octadienal and 2E,4E-heptadienal on the growth rates of natural ciliate and dinoflagellate populations in the Chesapeake Bay and the coastal Atlantic waters. The overall effect of PUA on microzooplankton growth was negative, especially at the higher concentrations, but there were pronounced differences in response among common planktonic species. For example, the growth of Codonella sp., Leegaardiella sol, Prorodon sp., and Gyrodinium spirale was impaired at 2 nM, whereas Strombidium conicum, Cyclotrichium gigas, and Gymnodinium sp. were not affected even at 20 nM. These results indicate that PUA can induce changes in microzooplankton dynamics and species composition.     

Influence of IAA,NAA and 2,4-D on ethylene production by potato discs (Solanum tuberosum L. cv. Red Pontiac)

Various auxins induced an increase of ethylene production by potato discs (Solarium tuberosum L. cv. Red Pontiac). 2,4-Dichlorophenoxyacetic acid (2,4-D) at 10 μM was the most effective in stimulating ethylene (C₂H₄) production. Napthaleneacetic acid (NAA) and indole-3-acetic acid (IAA) also stimulated ethylene production with optimal concentrations of 50 μM and 100 μM, respectively. The periderm of the tuber was found to produce the highest levels of C₂H₄ with sections taken toward the center of the tuber producing much lower levels. In this system, it was shown that pH 4.0 was the optimum pH tested and methionine was required.     

Cysteinolic Acid Is a Widely Distributed Compatible Solute of Marine Microalgae

Phytoplankton rely on bioactive zwitterionic and highly polar small metabolites with osmoregulatory properties to compensate changes in the salinity of the surrounding seawater. Dimethylsulfoniopropionate (DMSP) is a main representative of this class of metabolites. Salinity-dependent DMSP biosynthesis and turnover contribute significantly to the global sulfur cycle. Using advanced chromatographic and mass spectrometric techniques that enable the detection of highly polar metabolites, we identified cysteinolic acid as an additional widely distributed polar metabolite in phytoplankton. Cysteinolic acid belongs to the class of marine sulfonates, metabolites that are commonly produced by algae and consumed by bacteria. It was detected in all dinoflagellates, haptophytes, diatoms and prymnesiophytes that were surveyed. We quantified the metabolite in different phytoplankton taxa and revealed that the cellular content can reach even higher concentrations than the ubiquitous DMSP. The cysteinolic acid concentration in the cells of the diatom Thalassiosira weissflogii increases significantly when grown in a medium with elevated salinity. In contrast to the compatible solute ectoine, cysteinolic acid is also found in high concentrations in axenic algae, indicating biosynthesis by the algae and not the associated bacteria. Therefore, we add this metabolite to the family of highly polar metabolites with osmoregulatory characteristics produced by phytoplankton.     

Recreational exposure to low concentrations of microcystins during an algal bloom in a small lake

We measured microcystins in blood from people at risk for swallowing water or inhaling spray while swimming, water skiing, jet skiing, or boating during an algal bloom. We monitored water samples from a small lake as a Microcystis aeruginosa bloom developed. We recruited 97 people planning recreational activities in that lake and seven others who volunteered to recreate in a nearby bloom-free lake. We conducted our field study within a week of finding a 10-μg/L microcystin concentration. We analyzed water, air, and human blood samples for water quality, potential human pathogens, algal taxonomy, and microcystin concentrations. We interviewed study participants for demographic and current health symptom information. Water samples were assayed for potential respiratory viruses (adenoviruses and enteroviruses), but none were detected. We did find low concentrations of Escherichia coli, indicating fecal contamination. We found low levels of microcystins (2 μg/L to 5 μg/L) in the water and (<0.1 ng/m³) in the aerosol samples. Blood levels of microcystins for all participants were below the limit of detection (0.147μg/L). Given this low exposure level, study participants reported no symptom increases following recreational exposure to microcystins. This is the first study to report that water-based recreational activities can expose people to very low concentrations of aerosol-borne microcystins; we recently conducted another field study to assess exposures to higher concentrations of these algal toxins.     

Volatile monitoring as a technique for differentiating betweenE. carotovora andC. sepedonicum infections in stored potatoes

The volatile production characteristics of ring rot (Corynebacterium sepedonicum) and soft rot (Erwinia carotovora) infected potatoes were investigated under controlled conditions in order to assess the monitoring of volatiles as a technique for differentiating between the infections in stored potatoes. Total volatile production/unit time was much greater from soft rot due to more rapid development after infection. Total volatile production during the period required for the development of the soft rot infection was similar to the output detected during the longer period required for the development of the ring rot infection. The volatile profiles of the two pathogens featured a number of commonly shared metabolites, but one compound was unique to the ring rot infections and two compounds were unique to the soft rot infections. There were also consistent disease-specific changes in the relative concentration of many of the metabolites detected in the volatile profiles.     

Oxylipin Diversity in the Diatom Family Leptocylindraceae Reveals DHA Derivatives in Marine Diatoms

Marine planktonic organisms, such as diatoms, are prospective sources of novel bioactive metabolites. Oxygenated derivatives of fatty acids, generally referred to as oxylipins, in diatoms comprise a highly diverse and complex family of secondary metabolites. These molecules have recently been implicated in several biological processes including intra- and inter-cellular signaling as well as in defense against biotic stressors and grazers. Here, we analyze the production and diversity of C₂₀ and C₂₂ non-volatile oxylipins in five species of the family Leptocylindraceae, which constitute a basal clade in the diatom phylogeny. We report the presence of species-specific lipoxygenase activity and oxylipin patterns, providing the first demonstration of enzymatic production of docosahexaenoic acid derivatives in marine diatoms. The differences observed in lipoxygenase pathways among the species investigated broadly reflected the relationships observed with phylogenetic markers, thus providing functional support to the taxonomic diversity of the individual species.     

Potential Polyunsaturated Aldehydes in the Strait of Gibraltar under Two Tidal Regimes

Diatoms, a major component of the large-sized phytoplankton, are able to produce and release polyunsaturated aldehydes after cell disruption (potential PUAs or pPUA). These organisms are dominant in the large phytoplankton fraction (>10 µm) in the Strait of Gibraltar, the only connection between the Mediterranean Sea and the Atlantic Ocean. In this area, the hydrodynamics exerts a strong control on the composition and physiological state of the phytoplankton. This environment offers a great opportunity to analyze and compare the little known distribution of larger sized PUA producers in nature and, moreover, to study how environmental variables could affect the ranges and potential distribution of these compounds. Our results showed that, at both tidal regimes studied (Spring and Neap tides), diatoms in the Strait of Gibraltar are able to produce three aldehydes: Heptadienal, Octadienal and Decadienal, with a significant dominance of Decadienal production. The PUA released by mechanical cell disruption of large-sized collected cells (pPUA) ranged from 0.01 to 12.3 pmol from cells in 1 L, and from 0.1 to 9.8 fmol cell⁻¹. Tidal regime affected the abundance, distribution and the level of physiological stress of diatoms in the Strait. During Spring tides, diatoms were more abundant, usually grouped nearer the coastal basin and showed less physiological stress than during Neap tides. Our results suggest a significant general increase in the pPUA productivity with increasing physiological stress for the cell also significantly associated to low nitrate availability.     

短光低温不育水稻宜D S成熟胚培养的研究

对短光低温不育水稻宜D S成熟胚在组织培养中的愈伤组织诱导和分化进行了研究,结果表明:愈伤组织诱导率与绿苗分化率之间无对应关系;诱导培养基的成分对转分化后的愈伤组织有后效作用,2,4-D与6-BA和NAA搭配使用比单独使用2,4-D诱导的愈伤组织更易于分化;同时还发现,不同诱导培养基诱导的愈伤组织在转分化后对分化培养基的要求不同.     

油菜素内酯在不同生育期对两品系甘蓝型油菜的生长调控

为了解油菜素内酯对甘蓝型油菜品质及弱光反应的影响，以湘油15号的2个辐照突变品系（含油量和产油量明显不同的XY881和XY883）为材料，研究表油菜素内酯（epibrassinolide, 2,4-BL）在不同生育阶段对甘蓝型油菜生长发育的影响。通过盆栽试验和2014-2016年两年度田间试验，分析2,4-BL对种子萌发、营养生长、产油量及相关构成因子的影响。结果表明，2,4-BL对2品系的影响具有相似规律，包括：对种子萌发具有剂量效应，低浓度下促进种子萌发，高浓度下抑制种子萌发；在全生育期低剂量的2,4-BL促进主茎伸长、提高光合效率、促进结实，但不影响成熟种子大小和含油量；在盛花后使用，延缓种子成熟而造成授粉后40 d种子含油量下降；长期短间隔使用2, 4-BL降低调控作用。在分子水平上，2,4-BL诱导油菜素类固醇信号通路和光信号通路关键转录因子BnaPIF4、 BnaBZR1 和BnaBES 的基因表达。推测2,4-BL通过诱导甘蓝型油菜中油菜素内酯和光信号途径相关转录因子基因表达，激活下游调控的基因网络，通过促进光合作用延长营养生长时间、促进主茎生长和结实，进而影响产油量。因此认为表油菜素内酯可以作为生长调节剂在油菜生产中使用，建议低浓度或长间隔施用，且尽量在油菜盛花期之前使用。     

A Stable-Isotope Mass Spectrometry-Based Metabolic Footprinting Approach to Analyze Exudates from Phytoplankton

Phytoplankton exudates play an important role in pelagic ecology and biogeochemical cycles of elements. Exuded compounds fuel the microbial food web and often encompass bioactive secondary metabolites like sex pheromones, allelochemicals, antibiotics, or feeding attractants that mediate biological interactions. Despite this importance, little is known about the bioactive compounds present in phytoplankton exudates. We report a stable-isotope metabolic footprinting method to characterise exudates from aquatic autotrophs. Exudates from ¹³C-enriched alga were concentrated by solid phase extraction and analysed by high-resolution Fourier transform ion cyclotron resonance mass spectrometry. We used the harmful algal bloom forming dinoflagellate Alexandrium tamarense to prove the method. An algorithm was developed to automatically pinpoint just those metabolites with highly ¹³C-enriched isotope signatures, allowing us to discover algal exudates from the complex seawater background. The stable-isotope pattern (SIP) of the detected metabolites then allowed for more accurate assignment to an empirical formula, a critical first step in their identification. This automated workflow provides an effective way to explore the chemical nature of the solutes exuded from phytoplankton cells and will facilitate the discovery of novel dissolved bioactive compounds.     

叶面喷施含钾有机水溶肥对油菜生长发育和产量的影响

为油菜生产的提质增效,探究含钾有机水溶肥对油菜生长发育及产量构成的影响,以甘蓝型油菜旺城油8号为材料,采用双因素随机区组设计,设置3个喷施时期（苗期、花期、苗期+花期）和5个含钾有机水溶肥施用量（0、375、750、1125、1500 g/hm²）处理,调查油菜产量性状。结果发现,在苗期或初花期喷施750 g/hm²的含钾有机水溶肥,油菜的株高、根颈粗、生物量等指标较对照组显著增加,两个时期均喷施的处理其促进效果更优。在苗期和初花期均喷施750 g/hm²水溶肥,增加了单株有效角果数和每角粒数,显著提高油菜产量,较对照增加39.07%,产油量增加44.22%。认为可通过在油菜苗期和初花期每公顷各喷施750 g的含钾有机水溶肥,促进油菜的生长发育,提高菜籽产量,增加产油量,提升经济效益。     

象山港底栖硅藻群落结构特征

于2005年5月(春季)和11月(秋季)对浙江省象山港海域底栖硅藻进行采样调查,分析底栖硅藻的种类组成、丰度、优势种、多样性及群落结构的季节变化和平面分布特征,并讨论底栖硅藻与水温、盐度等环境因子之间的关系。共鉴定硅藻46属179种,硅藻种类数在春季共有46属164种,秋季减少到22属52种。种类组成以广温种为主,其次是暖水种和温水种。主要优势种有柱状小环藻(Cyclotella stylorum)、琼氏圆筛藻(Coscinodiscus jonesianus)等。细胞丰度范围在(0.007~6.851)×103个/g之间,平均值为1.522×103个/g。春季硅藻丰度较高,平均值为2.974×103个/g,秋季为0.071×103个/g。不同站位间硅藻的分布也表现出显著的差异,硅藻细胞丰度最高值位于港顶部鱼排密集区9号站位,春季细胞丰度值为6.851×103个/g,秋季细胞丰度值为0.143×103个/g。硅藻丰度较高的有位于鱼排区的3号、4号、5号、7号站位,其余较低。硅藻群落多样性指数和均匀度春季较高,秋季降低。底栖硅藻数量分布随季节变化明显,与盐度关系不大。     

模拟酸雨伤害龙眼的酸度阈值研究

以盆栽2龄实生龙眼乌龙岭(DimorcarppuslonganaLour.cv.wulongling)幼苗为材料,按闽南天然酸雨中硫酸根与硝酸根离子的量比为5:1,pHSH-4型酸度计将蒸馏水配成pH为4.5,3.5,3.0,2.5,1.5等5种不同酸度的模式酸雨,以pH5.6的蒸馏水为对照,研究模拟酸雨伤害龙眼的酸度阈值。结果表明:pH1.5的模拟酸雨胁迫1次就使龙眼发生急性伤害;pH3.5的胁迫8d才可见叶片退绿现象;而pH4.5的胁迫8d不会出现可见症状。在相同pH的酸雨胁迫下,红色叶片、转绿叶片、成熟叶片,花蕾、初开的花、全开的花的细胞内含物渗漏量存在差异。渗漏量以成熟叶片<转绿叶片<红色嫩叶;花蕾<初开的花<全开的花。伤害程度以红色嫩叶>转绿叶片>成熟叶片;全开的花>初开的花>花蕾。红色嫩叶和全开的花对酸雨的反应最敏感。酸雨对龙眼各器官伤害的阈值:红色嫩叶、转绿叶、功能叶、全开的花、初开的花、花蕾的pH分别为4.5,3.5,3.0,4.5,3.5和3.0。当酸雨pH<3.5时,细胞内含物渗漏量急剧增加且各指标变化趋势一致;当酸雨的pH>3.5时,各指标值对酸雨的敏感性不一样,K+最敏感,pH4.5的酸雨胁迫6h就可检测到K+的大量渗漏,其渗漏量与对照的+差异达显著水平。因此,K+的渗漏量可作为酸雨危害龙眼的一个重要指标。     

油菜素内酯诱导小白菜初生根不对称生长

油菜素内酯（Brassinolide,BL）能诱导单子叶植物初生根发生不对称生长,而在双子叶植物中还未见报道。本试验通过外源施加不同浓度2,4-表油菜素内酯（2,4-Epibrassinolide,2,4-eBL）观察小白菜（Brassica chinensis L.）初生根生长状况。结果表明：2,4-eBL能诱导小白菜初生根发生不对称生长形成卷曲。随着2,4-eBL浓度的升高,根卷曲比例和曲率逐渐增大,同时向地性逐渐降低。试验发现外源施加2,4-eBL可诱导双子叶植物根不对称生长的现象,为研究油菜素甾醇（Brassinosteroids,BRs）在根生长发育中的作用提供新途径。     

In Situ Detection of Antibiotic Amphotericin B Produced in Streptomyces nodosus Using Raman Microspectroscopy

The study of spatial distribution of secondary metabolites within microbial cells facilitates the screening of candidate strains from marine environments for functional metabolites and allows for the subsequent assessment of the production of metabolites, such as antibiotics. This paper demonstrates the first application of Raman microspectroscopy for in situ detection of the antifungal antibiotic amphotericin B (AmB) produced by actinomycetes—Streptomyces nodosus. Raman spectra measured from hyphae of S. nodosus show the specific Raman bands, caused by resonance enhancement, corresponding to the polyene chain of AmB. In addition, Raman microspectroscopy enabled us to monitor the time-dependent change of AmB production corresponding to the growth of mycelia. The Raman images of S. nodosus reveal the heterogeneous distribution of AmB within the mycelia and individual hyphae. Moreover, the molecular association state of AmB in the mycelia was directly identified by observed Raman spectral shifts. These findings suggest that Raman microspectroscopy could be used for in situ monitoring of antibiotic production directly in marine microorganisms with a method that is non-destructive and does not require labeling.     

模拟干热浪导致大豆症青的实证研究

近年来我国黄淮海夏大豆产区频繁出现症青，严重威胁本地的大豆生产。本研究通过人工气候室模拟干热浪胁迫，在大豆花荚期（R2-R4）进行持续3 d和7 d的干热胁迫处理，探究干热浪与大豆症青之间的关联性。研究结果表明：大豆盛花期遭遇持续3 d的模拟干热浪处理后，大豆植株生长正常，而持续7 d的处理则导致部分大豆植株出现症青。进一步的研究证实，从盛花期（R2期）到盛荚期（R4期）任何一个阶段遭遇连续7 d的模拟干热浪胁迫，都会导致大豆植株有效荚数和正常粒数严重下降，其中有效荚数降幅顺序为R3（85.14%）>R2（62.12%）>R4（50.97%），正常粒数降幅顺序为R3（81.02%）>R2（60.00%）>R4（56.32%）。因此，结荚初期（R3）持续7 d的模拟干热浪胁迫可导致大豆症青发生。同时提出，将大豆症青划分为荚而不实型、无荚型、局部型和全株滞育型四种类型。建议用底部节位新叶再生和花芽再分化现象进行大豆症青的早期诊断。