色疣节梗孢属一中国新记录种

【目的】调查我国植物病原真菌资源与多样性。【方法】采用经典真菌形态分类方法并结合序列分析结果对研究样品进行鉴定。【结果】从浙江省绍兴市平水镇的林下枯叶上分离到尖色疣节梗孢,对尖色疣节梗孢的形态特征进行了详细的观察和描述,并对其ITS rDNA序列进行分析。【结论】金缕梅叶斑病的尖色疣节梗孢病原菌在我国是首次发现,为我国真菌新记录种。     

Comparison of Vibrio harveyi strains isolated from shrimp farms and from culture collection in terms of toxicity and antibiotic resistance

Vibrio harveyi strains isolated from shrimp farms (wild strains) were compared with those from culture collections in terms of minimum inhibitory concentration (MIC) and toxicity. Wild strains had higher MIC values for four antibiotics (kanamycin, carbenicillin, oxytetracycline and ampicillin) and also showed higher toxicity compared with culture collection strains. Vibrio harveyi with the lowest antibacterial resistance was chosen to test if a gradual increase in antibiotic concentration and frequent subculture would enhance its antibiotic resistance. Results showed that V. harveyi was able to develop resistance to oxytetracycline. The MIC value was 250 times higher compared with the MIC before subculturing. Moreover, the V. harveyi strain developed slightly higher toxicity. Therefore, it is possible that there is a relationship between antibiotic resistance and toxicity in V. harveyi.     

FREEZE-FRACTURE STUDY OF THE SINGLE MEMBRANE BETWEEN HOST CELL AND ENDOCYTOBIONT IN THE DINOFLAGELLATES GLENODINIUM FOLIACEUM AND PERIDINIUM BALTICUM1

The dinoflagellates Glenodinium foliaceum Stein and Peridinium balticum (Levander) Lemmermann harbor a chrysophytic endocytobiont which is bounded by only a single membrane. This unique membrane is of particular interest because it could correspond to an intermediate stage in the evolution of “complex” plastids found in many Plastids of this type are surrounded by three or membranes instead of the usual two. With freeze-fracture techniques, we show that the single membrane in P. balticum has a pronounced polarity with respect to the distribution of intramembrane particles (IMPs) on the two corresponding fracture faces. The inner face exhibited more IMPs than the outer. We suggest that this stdedness identifies the separating membrane as the plasma membrane of the endocytobiont. A symbiontophoric vacuole with a separate membrane apparently is lacking. In the endocytobiosis of G. foliaccum, the single membrane separating host and endocylobiont exhibits a symmetrical particle partition. Nevertheless, from the size distribution of the IMPs it appears likely that this membrane, too, corresponds to the plasma membrane of the symbiont.     

Huia caspica gen. & comb. nov., a dinoflagellate species that recently crossed the marine‐freshwater boundary

The dinoflagellate subfamily Diplopsalidoideae encompasses 11 genera whose plate patterns show a large diversity. In a recently published molecular phylogeny (Liu et al. 2015) some of these genera (e.g. Diplopsalis, Diplopelta) are polyphyletic, suggesting that further subdivision of these genera is needed. Here we established the cyst‐theca relationship of Diplopsalis caspica by incubating cysts collected from the East China Sea. Cells of D. caspica display a plate formula of Po, X, 3′, 1a, 6″, 3c+t, ?4s, 5″′, 1″″, characterized by a small, parallelogrammic anterior intercalary plate (1a) located in the middle of the dorsal part of the epitheca. The cysts are spherical and smooth‐walled with a theropylic archeopyle. In addition, we obtained four large subunit ribosomal DNA (LSU rDNA) sequences from the germinated motile cells by single‐cell polymerase chain reaction. Strains of D. caspica from the marine environment of the East China Sea differ at 0–2 positions of LSU rDNA sequences from that of lacustrine strains from NE China. In the molecular phylogeny, D. caspica was close to Lebouraia pusilla but distant from D. lenticula, the type species of Diplopsalis. Our results support the systematic importance of plate 1a, and therefore D. caspica was transferred to a new genus, Huia. The conservative LSU rDNA sequences in H. caspica suggest that the marine‐freshwater transition occurred recently.     

Leaf green‐up in a semi‐arid African savanna ‐separating tree and grass responses to environmental cues

Question: Can satellite time series be used to identify tree and grass green‐up dates in a semi‐arid savanna system, and are there predictable environmental cues for green‐up for each life form? Location: Acacia nigrescens /Combretum apiculatum savanna, Kruger National Park, South Africa (25° S, 31° E). Methods: Remotely‐sensed data from the MODIS sensor were used to provide a five year record of greenness (NDVI) between 2000 and 2005. The seasonal and inter‐annual patterns of leaf display of trees and grasses were described, using additional ecological information to separate the greening signal of each life form from the satellite time series. Linking this data to daily meteorological and soil moisture data allowed the cues responsible for leaf flush in trees and grasses to be identified and a predictive model of savanna leaf‐out was developed. This was tested on a 22‐year NDVI dataset from the Advanced Very High Resolution Radiometer. A day length cue for tree green‐up predicted 86% of the green‐ups with an accuracy better than one month. A soil moisture and day length cue for grass green‐up predicted 73% of the green‐ups with an accuracy better than a month, and 82% within 45 days. This accuracy could be improved if the temporal resolution of the satellite data was shortened from the current two weeks. Conclusions: The data show that at a landscape scale savanna trees have a less variable phenological cycle (within and between years) than grasses. Realistic biophysical models of savanna systems need to take this into account. Using climatic data to predict these dynamics is a feasible approach.     

Growth responses of a woody species to clipping and goat saliva

Studies on the role of mammalian herbivore saliva in plant–animal interactions have mostly focused on graminoid species and bovine saliva. A trial was performed in Botswana with clipping treatments to simulate browsing of shoots and the application of goat saliva on the woody species Combretum apiculatum Sonder (Combretaceae). Treatments were performed during early growing season while shoot growth was rapid, and responses of trees were recorded later in the same season. Clipped shoots with saliva had significantly enhanced shoot growth (tripled in length) and leaf production (2.7 times more leaves) compared to clipped shoots without saliva. However, unclipped shoots still grew more than clipped shoots, with or without saliva treatment.     

STRUCTURAL ORGANIZATION OF PLASTID DNA IN TWO ANOMALOUSLY PIGMENTED DINOFLAGELLATES1

The structural organization of DNA in the plastids of two anomalously pigmented dinoflagellates, Glenodinium foliaceum Stein and Gyrodinium aureolum Hulburt, was determined using the DNA-specific fluorochrome DAPI and correlated with TEM observations. The plastids of G. foliaceum were found to possess both a peripheral DNA ring and isolated point nucleoids. This arrangement was shown to be similar to that of the diatom Asterionella formosa Hass. and may be characteristic of the Bacillariophyceae. G. aureolum exhibited a novel distribution of plastid. DNA as one or two beaded bands, whereas the plastids of the similarly pigmented haptophyte, Emiliania huxleyi (Lohm.) Hay & Mohler, possessed scattered point nucleoids. These findings support the idea that G. foliaceum harbours an endosymbiotic diatom, but suggest that the plastids of G. aureolum and E. huxleyi are unrelated. The use of plastid DNA configuration as a phylogenetic marker is considered.     

EFFECTS OF ULTRAVIOLET‐A RADIATION AND NUTRIENT AVAILABILITY ON THE CELLULAR COMPOSITION OF PHOTOPROTECTIVE COMPOUNDS IN GLENODINIUM FOLIACEUM (DINOPHYCEAE)1

The photoprotective response in the dinoflagellate Glenodinium foliaceum F. Stein exposed to ultraviolet‐A (UVA) radiation (320–400 nm; 1.7 W · m²) and the effect of nitrate and phosphate availability on that response have been studied. Parameters measured over a 14 d growth period in control (PAR) and experimental (PAR + UVA) cultures included cellular mycosporine‐like amino acids (MAAs), chls, carotenoids, and culture growth rates. Although there were no significant effects of UVA on growth rate, there was significant induction of MAA compounds (28 ± 2 pg · cell^?1) and a reduction in chl a (9.6 ± 0.1 pg · cell^?1) and fucoxanthin (4.4 ± 0.1 pg · cell^?1) compared to the control cultures (3 ± 1 pg · cell^?1, 13.3 ± 3.2 pg · cell^?1, and 7.4 ± 0.3 pg · cell^?1, respectively). In a second investigation, MAA concentrations in UVA‐exposed cultures were lower when nitrate was limited (P < 0.05) but were higher when phosphate was limiting. Nitrate limitation led to significant decreases (P < 0.05) in cellular concentration of chls (chl c₁, chl c₂, and chl a), but other pigments were not affected. Phosphate availability had no effect on final pigment concentrations. Results suggest that nutrient availability significantly affects cellular accumulation of photoprotective compounds in G. foliaceum exposed to UVA.     

Development of the pellicle and thecal plates following ecdysis in the dinoflagellateGlenodinium foliaceum

Summary The ultrastructure and development of the amphiesma of the dinoflagellateGlenodinium foliaceum was studied using conventional electron microscopy and immunocytochemistry. Ecdysis (shedding of the flagella, the outer two membranes of the cell, and the thecal plates) was induced by centrifugation. The cells were resuspended and the thickening of the pellicle and the development of the new thecal vesicles and plates was studied over a 9 h period. After ecdysis, the thin pellicle which underlay the thecal plates in the motile cells thickens to form a complex structure of four distinct layers: an outer layer of randomly oriented fibrils, a 50 nm layer of fibrils oriented perpendicular to the dense layer, the dense layer which has a trilaminate structure, and a wide inner homogeneous layer. The new thecal vesicles form in these pelliculate cells by the migration of electron translucent amphisomal vesicles over the layer of peripheral microtubules to a position directly under the plasmalemma. The thecal vesicles then flatten and elongate. A discontinuous pellicular layer appears within them. Subsequently, the thecal vesicles widen and are filled with a fibrillogranular substance overlying the pelliculate layer. The thecal plates form on top of this fibrillogranular material. By this time, most cells have escaped from the pellicle and are motile. At first, the outer thecal vesicle membrane is continuous with the inner thecal vesicle membrane at the sutures, but when this connection is broken, the dense pelliculate layers become continuous across the suture as does the inner thecal vesicle membrane. At ecdysis, this membrane becomes the new plasmalemma of the cell. Cells at each stage of pellicle thickening and thecal development were labelled with a polydonal antiserum raised against the 70 kDa epiplasmic protein ofEuglena acus. This antiserum labelled both the thecal plates of the motile cells and the inner homogeneous layer of the pellicle of ecdysed non-motile cells. No other amphiesmal structure was labelled, nor was any intracellular compartment.Abbreviations PBS phosphate-buffered saline - PIPES piperazine-N,N-bis[2-ethane sulfonic acid]