Norrisiella sphaerica gen. et sp. nov., a new coccoid chlorarachniophyte from Baja California, Mexico

金沢大学大学院自然科学研究科生物多様性動態学A new chlorarachniophyte, Norrisiella sphaerica S. Ota et K. Ishida gen. et sp. nov., from the coast of Baja California, Mexico is described. We examined its morphology, ultrastructure, and life cycle in detail, using light microscopy, transmission electron microscopy, and time-lapse videomicroscopy. We found that this chlorarachniophyte possessed the following characteristics: (1) vegetative cells were coccoid and possessed a cell wall, (2) a pyrenoid was slightly invaded by plate-like periplastidial compartment from the tip of the pyrenoid, (3) a nucleomorph was located near the pyrenoid base in the periplastidial compartment, (4) cells reproduced vegetatively via autospores, and (5) a flagellate stage was present in the life cycle. This combination of characteristics differs from any of the described chlorarachniophyte genera, and therefore a new genus is established. Fluorescent microscopic observations suggested that the alga formed multinucleate cells prior to forming autospores. Time-lapse observations during autospore formation showed that cytokinesis occurred simultaneously in the multinucleate cells. Zoospores were also produced, and video sequences captured the release of zoospores from coccoid cells. © 2007 The Botanical Society of Japan and Springer

シンビオジェネシスにおける共生者ゲノムの縮小進化に関する研究

金沢大学理工研究域本研究では、二次共生由来の生物であり、葉緑体の祖先真核藻の痕跡核であるヌクレオモルフ(Nm)を有するクロララクニオン藻について、Nmゲノムサイズの多様性を明らかにし、その進化傾向を推察することを目的とした。これまでNmゲノムサイズの調査がされていない主要系統群を代表する3株:BC52、CCMP2058(Lotharella amoebiformis)、CCMP2057(Gymnochlora stellata)を含む合計5株について、パルスフィールド電気泳動法を用いNm染色体を分離し、各Nm染色体に必ず存在する18SrDNAをプローブにサザンハイブリダイゼーションを行ない、各Nm染色体の数とサイズを推定した。その結果、5株のうち4株は、以前の報告と同様3本の直鎖状Nm染色体をもつことがわかった。残る1株(L.amoebiformis)は4本の染色体を持つ可能性が示唆された。Nm染色体の数は必ず3本であるとされており、もし4本の染色体が本当だとしたら、今後のNmゲノム進化の研究の発展において重要な知見となる。いずれにせよ本藻群全体のNmゲノムサイズは、約350〜405(あるいは455)kbの範囲となり、クロララクニオン藻内でゲノムサイズに多様性があることが再確認された。また核コード18SrDNAの分子系統樹をもとにNmゲノムサイズの進化を考えると、1)Nmゲノムは、本藻群の分岐以前に現存のサイズと同程度まで縮小し、その後非コード領域等でサイズの増減がおこった、2)Nmゲノムは、常に減少傾向にあり、全ての系統群で独立にサイズの減少がおこった、のどちらかである可能性が示唆された。なお、本研究成果は、第15回国際進化原生生物学会大会(2005年1月、メルボルン・オーストラリア)および第29回日本藻類学会大会(2005年3月、京都)で口頭発表を行なった。研究課題/領域番号:16013214, 研究期間(年度):2004出典：「シンビオジェネシスにおける共生者ゲノムの縮小進化に関する研究」研究成果報告書　課題番号16013214（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-16013214/)を加工して作

Human group II phospholipase A2 in normal and diseased intervertebral discs

AbstractWe measured calcium-dependent phospholipase A2 (PLA2) activity and immunoreactive group II PLA2 levels of 54 normal discs obtained from cadavers and 73 disc samples surgically obtained from patients with spinal disorders, including intervertebral disc herniations, spondylosis, and spondylolisthesis. Both cadaveric and surgical disc specimens contained about two-fold greater PLA2 activity than the ileal mucosa, one of the richest sources of group II PLA2. Discs of middle-aged cases had significantly higher activity than those of younger and elder cases. In cadaveric normal discs, calcium-dependent PLA2 activity was significantly higher in females than in males. Annulus fibrosus and nucleus pulposus contained the same PLA2 levels. In diseases discs, herniated fragments that had extruded or protruded out of the discs possessed lower activity than other parts of discs in the intervertebral space. Immunoreactive group II PLA2 levels of intervertebral discs closely correlated with PLA2 enzymatic activity. We purified a PLA2 from human intervertebral disc to homogeneity to further identify the isozymic nature of discal PLA2. Its NH2-terminal amino acid sequence and molecular weight were identical to those of human group II PLA2. Immunohistochemical analysis using a monoclonal anti-group II PLA2 antibody showed that in both annulus fibrosus and nucleus pulposus chondrocyte contained intense grou II PLA2 immunoreactivity in their cytoplasm, and that the matrix contained no substantial immunoreactivity. These results suggest that group II PLA2 in chondrocytes has important physiological roles in discal ordinary metabolism, maintaining discal homeostasis

Norrisiella sphaerica gen. et sp. nov., a new coccoid chlorarachniophyte from Baja California, Mexico

A new chlorarachniophyte, Norrisiella sphaerica S. Ota et K. Ishida gen. et sp. nov., from the coast of Baja California, Mexico is described. We examined its morphology, ultrastructure, and life cycle in detail, using light microscopy, transmission electron microscopy, and time-lapse videomicroscopy. We found that this chlorarachniophyte possessed the following characteristics: (1) vegetative cells were coccoid and possessed a cell wall, (2) a pyrenoid was slightly invaded by plate-like periplastidial compartment from the tip of the pyrenoid, (3) a nucleomorph was located near the pyrenoid base in the periplastidial compartment, (4) cells reproduced vegetatively via autospores, and (5) a flagellate stage was present in the life cycle. This combination of characteristics differs from any of the described chlorarachniophyte genera, and therefore a new genus is established. Fluorescent microscopic observations suggested that the alga formed multinucleate cells prior to forming autospores. Time-lapse observations during autospore formation showed that cytokinesis occurred simultaneously in the multinucleate cells. Zoospores were also produced, and video sequences captured the release of zoospores from coccoid cells

A single origin of the photosynthetic organelle in different Paulinella lineages

<p>Abstract</p> <p>Background</p> <p>Gaining the ability to photosynthesize was a key event in eukaryotic evolution because algae and plants form the base of the food chain on our planet. The eukaryotic machines of photosynthesis are plastids (e.g., chloroplast in plants) that evolved from cyanobacteria through primary endosymbiosis. Our knowledge of plastid evolution, however, remains limited because the primary endosymbiosis occurred more than a billion years ago. In this context, the thecate "green amoeba" <it>Paulinella chromatophora </it>is remarkable because it very recently (i.e., minimum age of ≈ 60 million years ago) acquired a photosynthetic organelle (termed a "chromatophore"; i.e., plastid) <it>via </it>an independent primary endosymbiosis involving a <it>Prochlorococcus </it>or <it>Synechococcus</it>-like cyanobacterium. All data regarding <it>P. chromatophora </it>stem from a single isolate from Germany (strain M0880/a). Here we brought into culture a novel photosynthetic <it>Paulinella </it>strain (FK01) and generated molecular sequence data from these cells and from four different cell samples, all isolated from freshwater habitats in Japan. Our study had two aims. The first was to compare and contrast cell ultrastructure of the M0880/a and FK01 strains using scanning electron microscopy. The second was to assess the phylogenetic diversity of photosynthetic <it>Paulinella </it>to test the hypothesis they share a vertically inherited plastid that originated in their common ancestor.</p> <p>Results</p> <p>Comparative morphological analyses show that <it>Paulinella </it>FK01 cells are smaller than M0880/a and differ with respect to the number of scales per column. There are more distinctive, multiple fine pores on the external surface of FK01 than in M0880/a. Molecular phylogenetic analyses using multiple gene markers demonstrate these strains are genetically distinct and likely comprise separate species. The well-supported monophyly of the <it>Paulinella chromatophora </it>strains analyzed here using plastid-encoded 16S rRNA suggests strongly that they all share a common photosynthetic ancestor. The strain M0880/a is most closely related to Japanese isolates (Kanazawa-1, -2, and Kaga), whereas FK01 groups closely with a Kawaguchi isolate.</p> <p>Conclusion</p> <p>Our results indicate that <it>Paulinella chromatophora </it>comprises at least two distinct evolutionary lineages and likely encompasses a broader taxonomic diversity than previously thought. The finding of a single plastid origin for both lineages shows these taxa to be valuable models for studying post-endosymbiotic cell and genome evolution.</p

Novel alkenone-producing strains of genus Isochrysis (Haptophyta) isolated from Canadian saline lakes show temperature sensitivity of alkenones and alkenoates

Alkenone-producing species have been recently found in diverse lacustrine environments, albeit with taxonomic information derived indirectly from environmental genomic techniques. In this study, we isolated alkenone-producing algal species from Canadian saline lakes and established unialgal cultures of individual strains to identify their taxonomical and molecular biological characteristics. Water and sediments collected from the lakes were first enriched in artificial seawater medium over a range of salinities (5–40 g/L) to cultivate taxa in vitro. Unialgal cultures of seven haptophyte strains were isolated and categorized in the Isochrysis clade using SSU and LSU rRNA gene analysis. The alkenone distributions within isolated strains were determined to be novel compared with other previously reported alkenone-producing haptophytes. While all strains produced the typical C37 and C38 range of isomers, one strain isolated from Canadian salt lakes also produced novel C41 and C42 alkenones that are temperature sensitive. In addition, we showed that all alkenone unsaturation indices (e.g., UK37 and UK'37) are temperature-dependent in culture experiments, and that alkenoate indices (e.g., UA37, UA38, RIA38 and A37/A38) provide alternative options for temperature calibration based on these new lacustrine algal strains. Importantly, these indices show temperature dependence in culture experiments at temperatures below 10 °C, where traditional alkenone proxies were not as sensitive. We hypothesize that this suite of calibrations may be used for reconstructions of past water temperature in a broad range of lakes in the Canadian prairies

Characterization of spliced leader trans-splicing in a photosynthetic rhizarian amoeba, Paulinella micropora, and its possible role in functional gene transfer

Paulinella micropora is a rhizarian thecate amoeba, belonging to a photosynthetic Paulinella species group that has a unique organelle termed chromatophore, whose cyanobacterial origin is distinct from that of plant and algal chloroplasts. Because acquisition of the chromatophore was quite a recent event compared with that of the chloroplast ancestor, the Paulinella species are thought to be model organisms for studying the early process of primary endosymbiosis. To obtain insight into how endosymbiotically transferred genes acquire expression competence in the host nucleus, here we analyzed the 5′ end sequences of the mRNAs of P. micropora MYN1 strain with the aid of a cap-trapper cDNA library. As a result, we found that mRNAs of 27 genes, including endosymbiotically transferred genes, possessed the common 5′ end sequence of 28–33 bases that were posttranscriptionally added by spliced leader (SL) trans-splicing. We also found two subtypes of SL RNA genes encoded by the P. micropora MYN1 genome. Differing from the other SL trans-splicing organisms that usually possess poly(A)-less SL RNAs, this amoeba has polyadenylated SL RNAs. In this study, we characterize the SL trans-splicing of this unique organism and discuss the putative merits of SL trans-splicing in functional gene transfer and genome evolution

Horizontally-acquired genetic elements in the mitochondrial genome of a centrohelid Marophrys sp. SRT127

Mitochondrial genomes exhibit diverse features among eukaryotes in the aspect of gene content, genome structure, and the mobile genetic elements such as introns and plasmids. Although the number of published mitochondrial genomes is increasing at tremendous speed, those of several lineages remain unexplored. Here, we sequenced the complete mitochondrial genome of a unicellular heterotrophic eukaryote, Marophrys sp. SRT127 belonging to the Centroheliozoa, as the first report on this lineage. The circular-mapped mitochondrial genome, which is 113,062 bp in length, encodes 69 genes typically found in mitochondrial genomes. In addition, the Marophrys mitochondrial genome contains 19 group I introns. Of these, 11 introns have genes for homing endonuclease (HE) and phylogenetic analyses of HEs have shown that at least five Marophrys HEs are related to those in green algal plastid genomes, suggesting intron transfer between the Marophrys mitochondrion and green algal plastids. We also discovered a putative mitochondrial plasmid in linear form. Two genes encoded in the circular-mapped mitochondrial genome were found to share significant similarities to those in the linear plasmid, suggesting that the plasmid was integrated into the mitochondrial genome. These findings expand our knowledge on the diversity and evolution of the mobile genetic elements in mitochondrial genomes

Ectopic fat deposition and global cardiometabolic risk : New paradigm in cardiovascular medicine

The obesity epidemic is a global public health concern that increases the likelihood of morbidity and mortality of metabolic and cardiovascular disease (CVD) and threatens to reduce life expectancy around the world. The concept of the metabolic syndrome (MetS) takes into account that visceral fat plays an essential role in the development of metabolic and cardiovascular diseases. However, MetS cannot be used to assess global CVD risk but is at best one more modifiable CVD risk factor. Thus, global cardiometabolic risk (the global risk of cardiovascular disease resulting from traditional risk factors combined with the additional contribution of the metabolic syndrome and/or insulin resistance) should be considered individually. There is solid evidence supporting the notion that excess abdominal fat is predictive of insulin resistance and the presence of related metabolic abnormalities currently referred to as MetS. Despite the fact that abdominal obesity is a highly prevalent feature of MetS, the mechanisms by which abdominal obesity is causally related to MetS are not fully elucidated. Besides visceral fat accumulation, ectopic lipid deposition, especially in liver and skeletal muscle, has been implicated in the pathophysiology of diabetes, insulin resistance and obesity-related disorders. Also, ectopic fat deposition could be deteriorated in the heart components such as (1) circulatory and locally recruited fat, (2) intra- and extra-myocellular fat, (3) perivascular fat, and (4) pericardial fat. In this review, the contribution of ectopic lipid deposition to global cardiometabolic risk is reviewed and also discussed are potential underlying mechanisms including adipocytokine, insulin resistance and lipotoxicity