Population genetic structure of Titanotrichum oldhamii (Gesneriaceae), a subtropical bulbiliferous plant with mixed sexual and asexual reproduction

• Background and Aims Titanotrichum oldhamii is a monotypicgenus distributed in Taiwan, adjacent regions of China and theRyukyu Isands of Japan. Its conservation status is vulnerableas most populations are small and widely scattered. Titanotrichumhas a mixed system of reproduction with vegetative bulbils andseeds. The aim of this study was to understand the populationgenetic structure of Titanotrichum in relation to its specificreproductive behaviour and to determine possible implicationsfor conservation strategies. • Methods After an extensive inventory of most wild populationsof Titanotrichum in East Asia, samples from 25 populations withinits major distribution were carried out utilizing RAPD and inter-SSRmolecular fingerprinting analysis. • Key Results The findings support the conclusion thatmany populations reproduce predominantly asexually but thatsome genetic variation still exists within populations. However,significant amounts of variation exist between populations,perhaps reflecting population differentiation by drift. Thispartitioning of genetic diversity indicates that the level ofinter-population gene exchange is extremely low. These findingsare consistent with field observations of very limited seedproduction. The Chinese populations are similar to those ofNorthern Taiwan, while the Ryukyu populations fall within therange of variation of the north-central Taiwan populations.The Taiwanese populations are relatively variable and differentiationbetween north, east and south Taiwan is evident. • Conclusions The distribution of Titanotrichum seems tobe consistent with a former land connection between China, Taiwanand the Ryukyu Islands at a glacial maximum during the Quaternary,followed by progressive fragmentation of the populations. North-centralTaiwan is the centre of genetic diversity, possibly due to theproximity of the former land bridge between the regions, togetherwith the variety of suitable habitats in north Taiwan. The significanceof these findings for conservation is discussed.     

Infection of Gymnodinium sanguineum by the dinoflagellate Amoebophrya sp.: effect of nutrient environment on parasite generation time, reproduction, and infectivity

Preliminary attempts to culture Amoebophrya sp., a parasite of Gymnodinium sanguineum from Chesapeake Bay, indicated that success may be influenced by water quality. To explore that possibility, we determined development time, reproductive output, and infectivity of progeny (i.e. dinospores) for Amoebophyra sp. maintained on G. sanguineum grown in four different culture media. The duration of the parasite's intracellular growth phase showed no significant difference among treatments; however, the time required for completion of multiple parasite generations did, with elapsed time to the middle of the third generation being shorter in nutrient-replete media. Parasites of hosts grown in nutrient-replete medium also produced three to four times more dinospores than those infecting hosts under low-nutrient conditions, with mean values of 380 and 130 dinospores/host, respectively. Dinospore production relative to host biovolume also differed, with peak values of 7.4 per 1,000 microm3 host for nutrient-replete medium and 4.8 per 1,000 microm3 host for nutrient-limited medium. Furthermore, dinospores produced by "high-nutrient" parasites had a higher success rate than those formed by "low-nutrient" parasites. Results suggest that Amoebophrya sp. is well adapted to exploit G. sanguineum populations in nutrient-enriched environments.     

五种典型藻类对C，N，P吸收动力学分析及种间竞争模拟

目的:获得五种典型藻类(甲藻属微小亚历山大藻(Alexandrium minutum)和锥状斯氏藻(Scrippsiella trochoidea),赤潮硅藻中肋骨条藻(Skeletonema costatum)以及绿藻属杜氏藻(Dunaliella salina)和青岛大扁藻(Platymonas helgolandica tsingtaoensis))对C,N,P营养的吸收动力学参数,并利用经典藻类种间竞争模型,构建一个藻类混合共存的生态平衡体系,揭示藻类种间竞争规律,为赤潮爆发机制和预测的研究提供一个新思路。方法:监测批次培养过程中藻体的生长规律以及培养基中C,N,P营养的消耗,计算出藻类营养吸收动力学参数,将参数代入Huisman-Weissing竞争模型,模拟藻类种间竞争。结果:(1)在单独培养条件下,杜氏藻具有最高的比生长率(0.834 d~(-1))和最大细胞浓度(3.4×10~6 cells/mL),锥状斯氏藻和微小亚历山大藻的比生长率μ和最大细胞浓度与其它三种藻相比均明显偏低,p0.01;(2)随着环境总碳浓度从5 mM提高到20 mM,五种藻的比生长率和最大细胞浓度均显著上升,其中杜氏藻和青岛大扁藻对C浓度改变的响应更加敏感;(3)杜氏藻和中肋骨条藻理论最大比生长率(μmax)明显高于其它三种藻类,锥状斯氏藻和微小亚历山大藻对C,N,P营养盐的需求量相比于其它三种藻明显偏高,p0.01;(4)藻类共生平衡系统中,N营养添加有利于杜氏藻和中肋骨条藻发挥更好的种间竞争优势,P营养添加有利于微小亚历山大藻和锥状斯氏藻发挥种间竞争优势;结论:不同环境条件下,五种藻类最大比生长速率μmax和营养吸收半饱和常数Ks直接影响它们的种间竞争能力,基于藻类动力学参数的种间竞争模型为赤潮爆发机制和预测的研究提供一个新思路。     

Leveraging algal omics to reveal potential targets for augmenting TAG accumulation

Ongoing global efforts to commercialize microalgal biofuels have expedited the use of multi-omics techniques to gain insights into lipid biosynthetic pathways. Functional genomics analyses have recently been employed to complement existing sequence-level omics studies, shedding light on the dynamics of lipid synthesis and its interplay with other cellular metabolic pathways, thus revealing possible targets for metabolic engineering. Here, we review the current status of algal omics studies to reveal potential targets to augment TAG accumulation in various microalgae. This review specifically aims to examine and catalog systems level data related to stress-induced TAG accumulation in oleaginous microalgae and inform future metabolic engineering strategies to develop strains with enhanced bioproductivity, which could pave a path for sustainable green energy.     

Photosymbiotic ascidians in Singapore: turbid?waters?may reduce living space

The photosymbiotic ascidian fauna at Changi Beach, Pulau Semakau, Sentosa and St. John’s Island, Singapore were surveyed. A total of five species, Diplosoma simile, Lissoclinum bistratum, Lissoclinum punctatum, Lissoclinum timorense and Trididemnum cyclops, were recorded, with Lissoclinum timorense and Trididemnum cyclops being newly recorded in Singapore. However, no photosymbiotic species were found at Changi Beach probably due to the polluted waters in the region. Coastal development has caused Singapore waters to become turbid, leading to decrease in suitable habitats for photosymbiotic ascidians. Clean waters in Pulau Semakau probably provide a better environment for the growth of photosymbiotic ascidians and this area has a greater variety of these ascidians than the other areas in Singapore. Each of the five species has also been recorded in the Ryukyu Archipelago (Japan) and three species (Diplosoma simile, Lissoclinum bistratum and Trididemnum cyclops) have also been recorded in Taiwan.     

Effect of ageing on survival of benthic diatom propagules

A comparison of viable benthic diatom propagules based on the observations recorded immediately and after 5 years of ageing at 5 °C is presented. The number of viable benthic diatom propagules decreased with ageing. However, they exhibited an apparently longer lag phase. Although diatoms belonging to the genera Amphora, Navicula and Thalassiosira were dominant during immediate observation, only Amphora and Navicula survived the ageing process. The non-viability of Thalassiosira indicates that ageing for five years was beyond its critical period of survival. The other diatom genera that survived the ageing process were Odontella and Grammatophora.     

Electrospray ionization mass spectrometry of oligosaccharides derived from fucoidan of Ascophyllum nodosum

Algal fucoidan is a complex sulfated polysaccharide whose structural characterization requires powerful spectroscopic methodologies. While most of the structural investigations reported so far have been performed using NMR as the main spectroscopic method, we report herein data obtained by negative electrospray ionization mass spectrometry. MS analysis has been carried out on oligosaccharides obtained by partial hydrolysis of fucoidan from the brown algae Ascophyllum nodosum. Oligosaccharide mixtures were fractionated by size exclusion chromatography, which allowed the analysis of oligomers ranging from monosaccharide to pentasaccharide. Monosaccharides were detected as monosulfated as well as disulfated forms. Besides, part of the oligosaccharides exhibited a high content of sulfate, evidencing that fucoidan contains disulfated fucosyl units. Fragmentation experiments yielded characteristic fragment ions indicating that the fucose units are mainly 2-O-sulfated. This study demonstrates that highly sulfated oligosaccharides from fucoidan can be analyzed by ESIMS which gives additional information about the structure of this highly complex polysaccharide.     

Sulfated xylomannans isolated from red seaweeds Chondrophycus papillosus and C. flagelliferus (Ceramiales) from Brazil

Sulfated xylomannans were isolated from two species of genus Chondrophycus by aqueous extraction followed by KCl fractionation. Structural determination of the native, desulfated and Smith-degraded KCl-precipitated polysaccharides carried out by composition and methylation analysis and NMR spectroscopy (1D and 2D experiments) showed the following general structure: [see text] These xylomannans present different degrees of branching (15-25%) by beta-D-Xylp (70-80%) and beta-D-Manp-2-S (20-30%) and molecular weights (33-222kDa). This is the first report of the presence of a sulfated xylomannan in species of order Ceramiales.     

Asexual reproduction and protonemal development in vitro in Fontinalis antipyretica Hedw.

As sporophytes are very rare and asexual propagules unknown it is generally assumed that the moss Fontinalis antipyretica spreads almost exclusively via detached shoots carried in water currents. This study of regeneration in vitro reveals that F. antipyretica produces a variety of filament systems originating from virtually every part of the gametophyte, including: cortical cells in the bases of detached shoots, the margins and abaxial surfaces of leaves, stems following leaf removal and the laminae of detached leaves. The filaments vary from protonemata comprising short rectangular cells with transverse cross-walls to unbranched rhizoids. Filamentous gemmae, liberated by schizolysis, and spherical brood cells are produced in ageing and desiccating cultures. In nature these asexual propagules are probably produced in response to falling water levels and may have an important and hitherto unsuspected role in the spread and spatial genetic structure of F. antipyretica. In F. antipyretica the high level of phenotypic plasticity, that characterizes the mature gametophytes of aquatic bryophytes, also extends to the filamentous phase in the life cycle. Major differences between axenic and contaminated cultures are likely due to positive associations between the moss and bacterial and/or fungal contaminants.