Phototaxis of the Unicellular Red Alga Cyanidioschyzon merolae Is Mediated by Novel Actin-Driven Tentacles

Phototaxis, which is the ability to move towards or away from a light source autonomously, is a common mechanism of unicellular algae. It evolved multiple times independently in different plant lineages. As of yet, algal phototaxis has been linked mainly to the presence of cilia, the only known locomotive organelle in unicellular algae. Red algae (Rhodophyta), however, lack cilia in all stages of their life cycle. Remarkably, multiple unicellular red algae like the extremophile Cyanidioschyzon merolae (C. merolae) can move towards light. Remarkably, it has remained unclear how C. merolae achieves movement, and the presence of a completely new mechanism has been suggested. Here we show that the basis of this movement are novel retractable projections, termed tentacles due to their distinct morphology. These tentacles could be reproducibly induced within 20 min by increasing the salt concentration of the culture medium. Electron microscopy revealed filamentous structures inside the tentacles that we identified to be actin filaments. This is surprising as C. merolae’s single actin gene was previously published to not be expressed. Based on our findings, we propose a model for C. merolae’s actin-driven but myosin-independent motility. To our knowledge, the described tentacles represent a novel motility mechanism.

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Phototaxis of the unicellular red alga Cyanidioschyzon merolae is mediated by novel actin-driven tentacles

10.1101/2020.05.09.085928 ◽

2020 ◽

Author(s):

Sascha Maschmann ◽

Karin Ruban ◽

Johanna Wientapper ◽

Wilhelm J. Walter

Keyword(s):

Electron Microscopy ◽

Life Cycle ◽

Actin Filaments ◽

Culture Medium ◽

Red Alga ◽

Common Mechanism ◽

Cyanidioschyzon Merolae ◽

Actin Gene ◽

Unicellular Algae ◽

Distinct Morphology

Phototaxis – which is the ability to move towards or away from a light source autonomously – is a common mechanism of unicellular algae. It evolved multiple times independently in different plant lineages1. As of yet, algal phototaxis has been mainly linked to the presence of cilia, the only known locomotive organelle in unicellular algae. Consequently, phototaxis was believed to be largely absent in red algae (Rhodophyta) that lack cilia in all stages of their life cycle1. Remarkably, the unicellular red alga Cyanidioschyzon merolae (C. merolae) is able to move towards the light. However, it has remained unclear how C. merolae can achieve movement, and the presence of a completely new mechanism was suggested2.Here we show that the basis of this movement are novel retractable projections that were termed tentacles due to their distinct morphology. The tentacles could be reproducibly induced within 20 minutes by increasing the salt concentration of the culture medium. Electron microscopy revealed filamentous structures inside the tentacles that we identified to be actin filaments. This is surprising as C. merolae’s single actin gene was previously published to not be expressed3,4. Based on our findings, we propose a model for C. merolae’s actin-driven but myosin-independent motility. To our knowledge, the described tentacles represent a novel motility mechanism.

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Isolation, characterization and chromosomal mapping of an actin gene from the primitive red alga Cyanidioschyzon merolae

Current Genetics ◽

10.1007/bf00310820 ◽

1995 ◽

Vol 28 (5) ◽

pp. 484-490 ◽

Cited By ~ 24

Author(s):

Hidenori Takahashi ◽

Hiroyoshi Takano ◽

Akiko Yokoyama ◽

Yoshiaki Hara ◽

Shigeyuki Kawano ◽

...

Keyword(s):

Red Alga ◽

Chromosomal Mapping ◽

Cyanidioschyzon Merolae ◽

Actin Gene

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Hexagonal Phytolithes from Red Alga Tichocarpus crinitus

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.386.256 ◽

2018 ◽

Vol 386 ◽

pp. 256-261

Author(s):

Kirill S. Golohvast ◽

Vladimir V. Chaika ◽

Alexander M. Zakharenko ◽

Alexander A. Sergievich ◽

Ivan A. Zemchenko ◽

...

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Red Algae ◽

Silicon Oxide ◽

Red Alga ◽

The Sea Of Japan ◽

Plant Life ◽

Scanning Electron ◽

Tichocarpus Crinitus

In current work unique hexagonal microparticles of silicon oxide (phytolite), isolated from the red algae Tichocarpus crinitus, which grows in the Sea of Japan described. The structures of poytolites are characterized by the methods of optical microscopy and scanning electron microscopy. The role of these formations in plant life and the mechanism of their synthesis remains unclear.

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Electron Microscopy of Cytoplasmic Contractile Proteins

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070333 ◽

1978 ◽

Vol 36 (3) ◽

pp. 606-614 ◽

Cited By ~ 1

Author(s):

T.D. Pollard ◽

P. Maupin

Keyword(s):

Electron Microscopy ◽

Actin Filaments ◽

Three Dimensional ◽

Uranyl Acetate ◽

Contractile Proteins ◽

Dimensional Structure ◽

X Ray Diffraction ◽

Cytoplasmic Matrix ◽

Computer Image Processing ◽

Nonmuscle Cells

In this paper we review some of the contributions that electron microscopy has made to the analysis of actin and myosin from nonmuscle cells. We place particular emphasis upon the limitations of the ultrastructural techniques used to study these cytoplasmic contractile proteins, because it is not widely recognized how difficult it is to preserve these elements of the cytoplasmic matrix for electron microscopy. The structure of actin filaments is well preserved for electron microscope observation by negative staining with uranyl acetate (Figure 1). In fact, to a resolution of about 3nm the three-dimensional structure of actin filaments determined by computer image processing of electron micrographs of negatively stained specimens (Moore et al., 1970) is indistinguishable from the structure revealed by X-ray diffraction of living muscle.

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Structure of Myosin Subfragment-1 from Electron Microscopy and Crystallography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102869 ◽

1988 ◽

Vol 46 ◽

pp. 156-157

Author(s):

Donald A. Winkelmann

Keyword(s):

Electron Microscopy ◽

Molecular Weight ◽

Actin Filaments ◽

Light Chains ◽

Myosin Filament ◽

Primary Role ◽

Heavy Chains ◽

Myosin Subfragment ◽

Myosin Subfragment 1 ◽

Globular Head

The primary role of the interaction of actin and myosin is the generation of force and motion as a direct consequence of the cyclic interaction of myosin crossbridges with actin filaments. Myosin is composed of six polypeptides: two heavy chains of molecular weight 220,000 daltons and two pairs of light chains of molecular weight 17,000-23,000. The C-terminal portions of the myosin heavy chains associate to form an α-helical coiled-coil rod which is responsible for myosin filament formation. The N-terminal portion of each heavy chain associates with two different light chains to form a globular head that binds actin and hydrolyses ATP. Myosin can be fragmented by limited proteolysis into several structural and functional domains. It has recently been demonstrated using an in vitro movement assay that the globular head domain, subfragment-1, is sufficient to cause sliding movement of actin filaments.The discovery of conditions for crystallization of the myosin subfragment-1 (S1) has led to a systematic analysis of S1 structure by x-ray crystallography and electron microscopy. Image analysis of electron micrographs of thin sections of small S1 crystals has been used to determine the structure of S1 in the crystal lattice.

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Ultrastructural studies of the relationship between actin filaments and secretory granules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159837 ◽

1990 ◽

Vol 48 (3) ◽

pp. 458-459

Author(s):

Ellen Holm Nielsen

Keyword(s):

Electron Microscopy ◽

Colloidal Gold ◽

Actin Filaments ◽

Secretory Granules ◽

Secretory Cells ◽

Ultrastructural Studies ◽

Transmission Electron ◽

Granule Membrane ◽

Ultrathin Sections ◽

Lowicryl K4m

In secretory cells a dense and complex network of actin filaments is seen in the subplasmalemmal space attached to the cell membrane. During exocytosis this network is undergoing a rearrangement facilitating access of granules to plasma membrane in order that fusion of the membranes can take place. A filamentous network related to secretory granules has been reported, but its structural organization and composition have not been examined, although this network may be important for exocytosis.Samples of peritoneal mast cells were frozen at -70°C and thawed at 4°C in order to rupture the cells in such a gentle way that the granule membrane is still intact. Unruptured and ruptured cells were fixed in 2% paraformaldehyde and 0.075% glutaraldehyde, dehydrated in ethanol. For TEM (transmission electron microscopy) cells were embedded in Lowicryl K4M at -35°C and for SEM (scanning electron microscopy) they were placed on copper blocks, critical point dried and coated. For immunoelectron microscopy ultrathin sections were incubated with monoclonal anti-actin and colloidal gold labelled IgM. Ruptured cells were also placed on cover glasses, prefixed, and incubated with anti-actin and colloidal gold labelled IgM.

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Actin filaments in two spermatozoa of crustacea decapoda

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100157899 ◽

1990 ◽

Vol 48 (3) ◽

pp. 70-71

Author(s):

E. Dupré ◽

G. Schatten

Keyword(s):

Electron Microscopy ◽

Actin Filaments ◽

Low Voltage ◽

Active Role ◽

Main Body ◽

Robinson Crusoe ◽

Decapod Crustaceans ◽

Actual Participation ◽

Voltage Scanning ◽

Scanning Electron

Sperm of decapod crustaceans are formed by a round or cup-shaped body, a complex acrosome and one a few appendages emerging from the main body. Although this sperm does not have motility, it has some components of the cytoskeleton like microtubules, which are found inside the appendages. Actin filaments have been found in the spike of penaeidae sperms. The actual participation of the crustacean decapod sperm cytoskeleton during fertilization is not well understood. Actin is supposed to play an active role in drawing the penaeidae shrimp sperm closer to the egg after bending of the spike. The present study was aimed at the localization of actin filaments in sperm of the Robinson Crusoe island lobster, Jasus frontalis and in the crayfish Orconectes propincus, by fluorescent probes and low voltage scanning electron microscopy.

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Faculty Opinions recommendation of Genome sequence of the ultrasmall unicellular red alga Cyanidioschyzon merolae 10D.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1017635.208540 ◽

2004 ◽

Author(s):

William Martin

Keyword(s):

Genome Sequence ◽

Red Alga ◽

Cyanidioschyzon Merolae

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Studies on the Regulation of Algal Growth by Gibberellin

Australian Journal of Biological Sciences ◽

10.1071/bi9711115 ◽

1971 ◽

Vol 24 (4) ◽

pp. 1115 ◽

Cited By ~ 5

Author(s):

RC Jennings

Keyword(s):

Red Algae ◽

Algal Growth ◽

Red Alga ◽

General Phenomenon ◽

Hypnea Musciformis ◽

Fast Growing ◽

High Concentrations ◽

Amo 1618 ◽

Slow Growing

CCC and Amo.1618, at relatively high concentrations only, inhibited the growth of excised branch apices of the red alga Hypnea musciformis. Neither GA3 nor GA7 stimulated growth of the alga in the presence or absence of these compounds, and gibberellin-like material extracted from H. musciformis also failed to stimulate growth. However, both gibberellins stimulated the growth of slow-growing, but not fast-growing, branch apices of the related red alga Gracilaria verucosa. It is concluded that endogenous gibberellins may not regulate the growth of H. musciformis, but this is likely to be a peculiarity of this species and not a general phenomenon in red algae.

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