Novel Findings Regarding Photoinduced Commitments of G1-, S- and G2-phase Cells to Cell-cycle Transitions in Darkness and Dark-induced G1-, S- and G2-phase Arrests in Euglena¶
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Abstract:
Effects of light and darkness on cell-cycle progression were studied in the log-linear photoautotrophic growth mode of Euglena gracilis. We found that there are light-dependent restriction points in the post-G1 phases, quite in contrast to Chlamydomonas, where a light-dependent restriction is known to exist only in the G1 phase. Thus, in E. gracilis, there are photoinduced commitments of G1-, S- and G2-phase cells that allow them to progress to the G1, S and G2 phases in darkness, and there are dark-induced G1-, S- and G2-phase arrests. In darkness, only committed cells were able to progress to the committed phases (G1, S or G2), whereas uncommitted cells were unable to undergo a cell-cycle transition. Whether or not cells were induced to commit by irradiation, they were eventually arrested somewhere in the G1, S or G2 (but not M) phase within 14 h of being transferred to darkness. We also describe the dependence of photoinduced commitment on light intensity and discuss the results as they relate to cell-cycle progression in continuous light.Keywords:
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Euglena gracilis
Euglena
Euglena gracilis
Euglena
Live food
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Abstract Euglena gracilis lacks catalase and contains ascorbate peroxidase (APX) which is localized exclusively in the cytosol. Other enzymes that scavenge reactive oxygen species (ROS) in Euglena have not yet been identified; therefore, ROS metabolism, especially in organelles, remains unclear in Euglena. The full-length cDNAs of four Euglena peroxiredoxins (EgPrxs) were isolated in this study. EgPrx1 and -4 were predicted to be localized in the cytosol, and EgPrx2 and -3 in plastids and mitochondria, respectively. The catalytic efficiencies of recombinant EgPrxs were similar to those of plant thiol-peroxidases, but were markedly lower than those of APX from Euglena. However, transcript levels of EgPrx1, -2, and -3 were markedly higher than those of APX. The growth rate of Euglena cells, in which the expression of EgPrx1 and -4 was suppressed by gene silencing, was markedly reduced under normal conditions, indicating physiological significance of Prx proteins.
Euglena gracilis
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Euglena
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Euglena gracilis
Euglena
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Euglena gracilis をSCPとして利用することを目的とし, 安価な廃糖蜜を用いた培養条件の検討と, 廃糖蜜培地培養で得られたEuglenaタンパク質の栄養価を測定した。細胞収量およびタンパク質含量の多いEnglenaを得る培養条件の検討を行なった結果, 廃糖蜜量40g/l, リン酸アンモニウム5.5g/lを含む初発pH3.5～5.5の培地での培養が最も適したものであった。 上記培養条件で培養したEuglenaのアミノ酸組成は, 栄養豊富なグルコース-グルタミン酸培地で培養したE. gracilisのアミノ酸組成に類似し, そのアミノ酸価は89～91と高く, 藻類, 酵母のタンパク質と比較して優れた栄養価を有することを明らかにした。また廃糖蜜培地培養E. gracilisの人工消化実験およびラット飼育試験を行なった結果, Euglenaは, トリプシンとペプシンによりそれぞれ84.6%, 82.8%消化され, 高い消化率を示した。 ラット飼育試験で, Euglenaの栄養価を求めたところ, PER=3.28, NPR=4.50, 真の消化率=93.2%, 生物価=80.2, NPU=74.7であった。これらの値は, PER, NPRにおいて同時に行なったカゼインの値と一致し, 真の消化率, 生物価, NPUにおいて, 細谷・北岡のグルコース-グルタミン酸培地培養のE. gracilisおよびカゼインの値に近似していた。これらの結果より, 廃糖蜜培地培養Euglenaタンパク質はグルコース-グルタミン酸培地培養Euglenaタンパク質と同様のカゼインに匹敵する優れた栄養価をのしており, Euglenaタンパク質生産に廃糖蜜が炭素源としての効に利用できることがわかった。
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Euglena
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In Experiment 1, two hundred eighty 32wks old ISA brown layers were assigned to seven dietary treatments for 4weeks. Each treatment was consisted of 4 replications with 10 birds per replication. Control diet was formulated 17%CP 2,750㎉ME/㎏. Euglena gracilis was added to control diet at the level of 0.25, 0.5, 1.0% and Euglena bleached(DHA enriched) at the level of 0.5, 1.0, 2.0% in the diet. In Experiment 2, three hundred 84wks old ISA brown layers were assigned to seven dietary treatments: Tl; Control, T2; Tl + Euglena bleached(DHA enriched)0.5%, T3; Tl + Euglena gracilis(DHA enriched)0.5%, T4; Tl + Euglena gracilis(DHA enriched)1.0%, T5; Tl +Euglena gracilis(DHA enriched)2.0%. In Experiment 1, 2.0% Euglena bleached treatment showed highest DHA level in Egg yolk(P＜0.05). In Experiment 2, 0.5% Euglena bleached treatment showed highest DHA level in Egg yolk(P＜0.05).
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Euglena
Yolk
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Summary. Using Ross's modification of Hutner's method for quantitative determination of vitamin B 12 with Euglena gravities var. bacillaris , experiments were carried out which showed that the supernatant from a centrifuged vigorously growing Euglena culture contains a thermolabile factor, which has a growth‐inhibiting effect on Euglena cells when they are transferred to a freshly prepared medium containing vitamin B 12 . Density and uniformity of growth in the tubes inoculated are increased by washing and diluting the Euglena culture used for inoculation. The sensitivity and the accuracy of the method are thereby increased.
Euglena gracilis
Euglena
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Cell-free homogenates of Euglena gracilis contain very low levels of catalase activity as compared to higher plants and some other algae. Purified Euglena cytochrome c acts catalytically as a peroxidase. The observed catalytic activity of cytochrome c in extracts from heterotrophically grown cells was more than enough to account for the observed rates of hydrogen peroxide destruction. The peroxidative activity of Euglena cytochrome c was completely inhibited by 20 mm 3-amino-1,2,4-triazole.
Euglena gracilis
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SYNOPSIS Euglena gracilis strain Z, at a concentration of 10 6 cells/ml and in containers of ∽ 0.1‐mm thickness, spontaneously forms dynamic ring patterns in the dark. These patterns are modified differentially by illumination with red and with blue light. The red light effect is abolished by treatment with an inhibitor of photosynthesis. Pattern formation is apparently the result of chemophobic responses to oxygen dissolved in the medium. Euglena can respond to both negative and positive concentration gradients, depending upon the absolute magnitude of oxygen concentration. The photo‐ and chemosensory transduction systems of Euglena interact at a stage which precedes the overt expression of motor responses.
Euglena gracilis
Euglena
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Euglenaの細胞 (Euglena gracilis z) をタンパク源にして調製した飼料を脳卒中易発症性高血圧自然発症ラット (SHRSP) に5週齢から投与して血圧, 脳卒中病変および血管病変の発生, 寿命への影響を調べた。SHRSPは系統により血圧の上昇の緩急や生存日数が異なるので血圧上昇が緩やかで寿命の長い系統 (グループI) と血圧上昇が急激で寿命の短い系統 (グループII) で検討した。得られた結果の概要は次のとおりである。1. 5週齢からEuglena飼料を投与しても血圧上昇期の血圧を抑制する効果は認められなかった。しかし, グループIIでは10週齢以後の血圧は対照群よりやや緩やかであった。2. 生存日数は対照群に比べてEuglena群では著しい延長が認められた。そして自然死したラットの脳卒中病変の発生率は, 対照群に比べやや低かった。また, 腎臓, 副腎における血管病変の発生も幾分か抑えられた。3. 血管病変の進行程度を同一年齢で比較するためにグループIのSHRSPを35週齢時に屠殺して調べた。脳卒中病変および睾丸副腎における血管病変の発生割合は対照群に比しEuglena群では低かった。4. Euglena飼料を投与した群の35週齢時の血漿レニン活性 (PRA) 値は対照群よりやや低値であった。5. 大動脈の比体重は対照群に比べてEuglena群では有意に小さく, 血管壁の肥厚が抑制された。また, 大動脈エラスチンの加齢にともなう含有量の減少も抑制された。6. 腸間膜動脈末梢部の電顕観察でもEuglena群は, 対照群に比し変化が少なく, 血管壁の基本構造がよく保持されていた。7. 血清過酸化脂質は対照群では15週齢頃から増加したが, Euglena群では増加は抑制された。以上の結果から, Euglena飼料では血圧の上昇抑制作用を示さないが, 血管壁を強化し脳卒中病変や血管病変の進行を遅延させた結果, 生存日数の延長をもたらしたものと考えられる。
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Euglena gracilis
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Treatment of Euglena gracilis with furadantin results in colorless cells which produce only white descendants. The treatment also prevents the greening of dark-grown euglena which are exposed to light. This finding suggests that furadantin acts upon some stage of chloroplast synthesis subsequent to that blocked by darkness.
Euglena gracilis
Euglena
Darkness
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