Annotation | Euglena gracilis growth with antibacterial agents leads to bleaching, permanent plastid gene loss. Colorless Euglena (Astasia) longa resembles a bleached E. gracilis. To evaluate the role of bleaching in E. longa evolution, the effect of streptomycin, a plastid protein synthesis inhibitor, and ofloxacin, a plastid DNA gyrase inhibitor, on E. gracilis and E. longa growth and plastid DNA content were compared. E. gracilis growth was unaffected by streptomycin and ofloxacin. Quantitative PCR analyses revealed a time dependent loss of plastid genes in E. gracilis demonstrating that bleaching agents produce plastid gene deletions without affecting cell growth. Streptomycin and ofloxacin inhibited E. longa growth indicating that it requires plastid genes to survive. This suggests that evolutionary divergence of E. longa from E. gracilis was triggered by the loss of a cytoplasmic metabolic activity also occurring in the plastid. Plastid metabolism has become obligatory for E. longa cell growth. A process termed "intermittent bleaching", short term exposure to subsaturating concentrations of reversible bleaching agents followed by growth in the absence of a bleaching agent, is proposed as the molecular mechanism for E. longa plastid genome reduction. Various non-photosynthetic lineages could have independently arisen from their photosynthetic ancestors via a similar process.
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Repercussion category | LEANDER, Brian S. - LAX, Gordon - KARNKOWSKA, Anna - SIMPSON, Alastair G.B. Euglenida. In Handbook of the protists : second edition, 2017. ISBN 978-331928149-0, pp. 1047-1088. ZECCA, Giovanni - GRASSI, Fabrizio - TABIDZE, Vazha - PIPIA, Ia - KOTORASHVILI, Adam - KOTARIA, Nato - BERIDZE, Tengiz. Dates and rates in grape's plastomes : evolution in slow motion. In Current genetics. ISSN 0172-8083, 2020, vol. 66, no. 1, pp. 123-140. QIN HUAN - GUO QINGQING - LIU CHENCHEN - LI FENGLAN - ZHANG HUA - CHU ZIHAN - WANG JIANGXIN - LEI ANPING. Occurrence and light response of residual plastid genes in a Euglena gracilis bleached mutant strain OflB2. In Journal of oceanology and limnology. ISSN 2096-5508, 2020, vol. 38, no. 6, pp. 1858-1866. O’NEILL, Ellis. Using new techniques to study old favorites: a case study of Euglena. In Handbook of algal science, technology and medicine. [Amsterdam] : Elsevier, 2020. ISBN 978-0-12-818305-2, pp. 161-170. LI, Chao - CHEN, Zhenfan - CHEN, Zixi - LEI, Anping - LIU, Qiong - WANG, Jiangxin. Euglena-based synthetic biology and cell factory. In Algal Biotechnology. Wallingford : CABI International, 2023. ISBN 978-180062194-7, pp. 61-76.
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