Hypericin‐Like Photoreceptors

Song, Pill‐Soon

doi:10.1002/352760510x.ch20

Cited by 3 publications

(9 citation statements)

References 28 publications

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“…The photophobic response of S. coeruleus is described as follows (35,36,38,39,87). When cells experience a sudden increase in irradiance flux they first stop.…”

Section: Photoresponses In Heterotrichsmentioning

confidence: 99%

“…There is also photodispersal of S. coeruleus into shade or darkness (see below). The chain of events proposed for the photophobic reaction (39) is that some initial photoprocess (perhaps proton release, see next section) starts a signaling cascade leading to a reversal of the ciliary stroke.…”

Section: Photoresponses In Heterotrichsmentioning

confidence: 99%

“…Toxicity of blepharismin and stentorin chromophores in the light comes about primarily because they generate singlet molecular oxygen ( 1 O 2 ) and/or other reactive oxygen species, both in situ and in the medium (see section , above) (39,40,49,51). Surprisingly, some blepharismins and oxyblepharismins are also exogenously toxic in the dark to the predatory haptorid ciliate Dileptus margaritifer (42); this must be due to some other mechanism.…”

Section: Toxicity Uv‐protection and Other Possible Roles For Hypericmentioning

confidence: 99%

“…3) and Blepharisma japonicum these pigments are the photoreceptors for abrupt light‐avoidance responses. This role is well established, but there are few details of the signaling cascades leading to ciliary stroke reversal (35–40). These species are, however, susceptible to light in the presence of oxygen and must stay in dim light or darkness to survive endogenous toxicity of their own pigment (37,41,42).…”

Section: Introductionmentioning

confidence: 99%

“…Stentorin The first class of naturally occurring hypericin‐like chromophores studied in complex with their proteins was that of the stentorins (39). As indicated above, the stentorins are membrane‐bound chromoproteins found in pigment granules of the blue‐green ciliate, S. coeruleus.…”

mentioning

confidence: 99%

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Photophysics and Multifunctionality of Hypericin‐Like Pigments in Heterotrich Ciliates: A Phylogenetic Perspective

Lobban

Hallam

Mukherjee

et al. 2007

Photochem & Photobiology

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In this paper, we review the literature and present some new data to examine the occurrence and photophysics of the diverse hypericin-like chromophores in heterotrichs, the photoresponses of the cells, the various roles of the pigments and the taxa that might be studied to advance our understanding of these pigments. Hypericin-like chromophores are known chemically and spectrally so far only from the stentorids and Fabrea, the latter now seen to be sister to stentorids in the phylogenetic tree. For three hypericin-like pigments, the structures are known but these probably do not account for all the colors seen in stentorids. At least eight physiological groups of Stentor exist depending on pigment color and presence ⁄ absence of zoochlorellae, and some species can be bleached, leading to many opportunities for comparison of pigment chemistry and cell behavior. Several different responses to light are exhibited among heterotrichs, sometimes by the same cell; in particular, cells with algal symbionts are photophilic in contrast to the well-studied sciaphilous (shadeloving) species. Hypericin-like pigments are involved in some well-known photophobic reactions but other pigments (rhodopsin and flavins) are also involved in photoresponses in heterotrichs and other protists. The best characterized role of hypericin-like pigments in heterotrichs is in photoresponses and they have at least twice evolved a role as photoreceptors. However, hypericin and hypericin-like pigments in diverse organisms more commonly serve as predator defense and the pigments are multifunctional in heterotrichs. A direct role for the pigments in UV protection is possible but evidence is equivocal. New observations are presented on a folliculinid from deep water, including physical characterization of its hypericin-like pigment and its phylogenetic position based on SSU rRNA sequences. The photophysics of hypericin and hypericin-like pigments is reviewed. Particular attention is given to how their excited-state properties are modified by the environment. Dramatic changes in excited-state behavior are observed as hypericin is moved from the homogeneous environment of organic solvents to the much more structured surroundings provided by the complexes it forms with proteins. Among these complexes, it is useful to consider the differences between environments where hypericin is not found naturally and those where it is, notably, for example, in heterotrichs. It is clear that interaction with a protein modifies the photophysics of hypericin and understanding the molecular basis of this interaction is one of the outstanding problems in elucidating the function of hypericin and hypericin-like chromophores.

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“…The photophobic response of S. coeruleus is described as follows (35,36,38,39,87). When cells experience a sudden increase in irradiance flux they first stop.…”

Section: Photoresponses In Heterotrichsmentioning

confidence: 99%

Section: Photoresponses In Heterotrichsmentioning

confidence: 99%

Section: Toxicity Uv‐protection and Other Possible Roles For Hypericmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Photophysics and Multifunctionality of Hypericin‐Like Pigments in Heterotrich Ciliates: A Phylogenetic Perspective

Lobban

Hallam

Mukherjee

et al. 2007

Photochem & Photobiology

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Cluster dynamics in Maristentor dinoferus, a gregarious benthic ciliate with zooxanthellae and a hypericin-like pigment, in relation to biofilm grazing by the fish Ctenochaetus striatus

Lobban

Schefter²,

Donaldson

2014

Symbiosis

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Maristentorin, a Novel Pigment from the Positively Phototactic Marine CiliateMaristentordinoferus, Is Structurally Related to Hypericin and Stentorin

et al. 2006

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The photoreceptor pigment of the heterotrich ciliate, Maristentor dinoferus, has been characterized. It is structurally similar to those of Stentor coeruleus and Blepharisma japonicum but differs significantly in that it bears no aromatic hydrogens. The structure of the pigment, maristentorin, is based upon the hypericin skeleton, and its spectra are nearly identical to those of hypericin but shifted toward the red. Within experimental error, its fluorescence lifetime is identical to that of hypericin, approximately 5.5 ns in dimethylsulfoxide. It is remarkable that while the pigments are structurally similar in S. coeruleus and M. dinoferus, in the former there is an abrupt photophobic response, whereas in the latter there is a slow response toward light. The roles of the hypericin-like pigments in the heterotrich ciliates are discussed as potentially analogous in Maristentor.

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Hypericin‐Like Photoreceptors

Cited by 3 publications

References 28 publications

Photophysics and Multifunctionality of Hypericin‐Like Pigments in Heterotrich Ciliates: A Phylogenetic Perspective

Photophysics and Multifunctionality of Hypericin‐Like Pigments in Heterotrich Ciliates: A Phylogenetic Perspective

Cluster dynamics in Maristentor dinoferus, a gregarious benthic ciliate with zooxanthellae and a hypericin-like pigment, in relation to biofilm grazing by the fish Ctenochaetus striatus

Maristentorin, a Novel Pigment from the Positively Phototactic Marine CiliateMaristentordinoferus, Is Structurally Related to Hypericin and Stentorin

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