Über den Feinbau derEuglena-Zelle

Frey‐Wyssling, A.; Mühlethaler, K.

doi:10.1007/bf02503263

Cited by 7 publications

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References 10 publications

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“…A system of contractile vacuoles (one main vacuole with several accessory vacuoles) is associated with the reservoir, believed to be involved in osmoregulation (Rosati et al 1996;Komsic-Buchmann and Becker 2012). At the base of the reservoir two flagella originate in basal bodies, but only one of them extends as a trailing flagellum from the reservoir while the other one reaches up to the paraxonemal body (PAB, also called paraflagellar body) (Tollin 1973;Piccinni and Mammi 1978), located on the long flagellum half way between the bottom and the opening of the invagination, called pharynx (Frey-Wyssling and Mühlethaler 1960;Kisielewska et al 2015). The PAB is a small organelle (1 μm × 0.7 μm × 0.7 μm) (Wolken 1977;Omodeo 1980;Rosati et al 1991) (Fig.…”

Section: The Organismsmentioning

confidence: 99%

Photomovement in Euglena

Häder

Iseki

2017

Advances in Experimental Medicine and Biology

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Motile microorganisms such as the green Euglena gracilis use a number of external stimuli to orient in their environment. They respond to light with photophobic responses, photokinesis and phototaxis, all of which can result in accumulations of the organisms in suitable habitats. The light responses operate synergistically with gravitaxis, aerotaxis and other responses. Originally the microscopically obvious stigma was thought to be the photoreceptor, but later the paraxonemal body (PAB, paraflagellar body) has been identified as the light responsive organelle, located in the trailing flagellum inside the reservoir. The stigma can aid in light direction perception by shading the PAB periodically when the cell rotates helically in lateral light, but stigmaless mutants can also orient with respect to the light direction, and negative phototaxis does not need the presence of the stigma. The PAB is composed of dichroically oriented chromoproteins which is reflected in a pronounced polarotaxis in polarized light. There was a long debate about the potential photoreceptor molecule in Euglena, including carotenoids, flavins and rhodopsins. This discussion was terminated by the unambiguous proof that the photoreceptor is a 400 kDa photoactivated adenylyl cyclase (PAC) which consists of two α- and two β-subunits each. Each subunit possesses two BLUF (Blue Light receptor Using FAD) domains binding FAD, which harvest the light energy, and two adenylyl cyclases, which produce cAMP from ATP. The cAMP has been found to activate one of the five protein kinase s found in Euglena (PK.4). This enzyme in turn is thought to phosphorylate proteins inside the flagellum which result in a change in the flagellar beating pattern and thus a course correction of the cell. The involvements of PAC and protein kinase have been confirmed by RNA interference (RNAi). PAC is responsible for step-up photophobic responses as well as positive and negative phototaxis, but not for the step-down photophobic response, even though the action spectrum of this resembles those for the other two responses. Analysis of several colorless Euglena mutants and the closely related Euglena longa (formerly Astasia longa) confirms the results. Photokinesis shows a completely different action spectrum. Some other Euglena species, such as E. sanguinea and the gliding E. mutabilis, have been investigated, again showing totally different action spectra for phototaxis and photokinesis as well as step-up and step-down photophobic responses.

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