Acetabularia
Encyclopedia
Acetabularia is a genus of green algae
, specifically of the Polyphysaceae
family, Typically found in subtropical waters, Acetabularia is a single-celled organism, but gigantic in size and complex in form, making it an excellent model organism for studying cell biology
. In form, the mature Acetabularia resembles the round leaves of a nasturtium
, being 0.5 to 10 cm tall and having three anatomical parts: a bottom rhizoid that resembles a set of short roots; a long stalk in the middle; and a top umbrella of branches that may fuse into a cap. The single nucleus of Acetabularia is located in the rhizoid, and allows the cell to regenerate completely if its cap is removed. The caps of two Acetabularia may also be exchanged, even from two different species.
Acetabularia is most famous from the experiments of Joachim Hämmerling
in the 1930s-1950s, which demonstrated that its genetic
information is contained in the nucleus. This was the first demonstration that gene
s are encoded by DNA
in eukaryote
s; earlier studies by Oswald Avery
and others had shown that this was true for prokaryote
s. Hämmerling exchanged the caps from two species, A. mediterranea and A. crenulata. The caps of these species are different in form; however, after exchange, the caps gradually changed from their original form to that typical of its base, where the nucleus is located. In another experiment, the addition of a nucleus from another species into a single intact Acetabularia produced a hybrid cap, showing that both nuclei are influencing the form of the cap.
Acetabularia are among the largest single-celled organisms, having also a remarkably large nucleus. During sexual reproduction, the nucleus undergoes multiple rounds of mitosis
, forming many daughter nuclei all within one nuclear membrane. These nuclei undergo meiosis
and are transported to the tips of the branches, the sporangia, where they are released as gamete
s.
The name, Acetabularia, derives from the Latin word acetabulum, a broad, shallow cup used for dipping bread; the upturned cap of Acetabularia resembles such a cup. For this reason, it is also sometimes called mermaid's wineglass.
s.
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
, specifically of the Polyphysaceae
Polyphysaceae
The Polyphysaceae is a taxonomic family of green algae, one of two families in the order Dasycladales.-Scientific databases:...
family, Typically found in subtropical waters, Acetabularia is a single-celled organism, but gigantic in size and complex in form, making it an excellent model organism for studying cell biology
Cell biology
Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...
. In form, the mature Acetabularia resembles the round leaves of a nasturtium
Nasturtium
Tropaeolum , commonly known as Nasturtium literally "nose-twister" or "nose-tweaker"), is a genus of roughly 80 species of annual and perennial herbaceous flowering plants and the only genus in the family Tropaeolaceae...
, being 0.5 to 10 cm tall and having three anatomical parts: a bottom rhizoid that resembles a set of short roots; a long stalk in the middle; and a top umbrella of branches that may fuse into a cap. The single nucleus of Acetabularia is located in the rhizoid, and allows the cell to regenerate completely if its cap is removed. The caps of two Acetabularia may also be exchanged, even from two different species.
Acetabularia is most famous from the experiments of Joachim Hämmerling
Joachim Hämmerling
Dr. Joachim Hämmerling was a pioneering Danish-German biologist funded by Nazi Germany who determined the nucleus of a cell controls the development of organisms by containing the hereditary information, or DNA...
in the 1930s-1950s, which demonstrated that its genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
information is contained in the nucleus. This was the first demonstration that gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s are encoded by DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
in eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
s; earlier studies by Oswald Avery
Oswald Avery
Oswald Theodore Avery ForMemRS was a Canadian-born American physician and medical researcher. The major part of his career was spent at the Rockefeller University Hospital in New York City...
and others had shown that this was true for prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...
s. Hämmerling exchanged the caps from two species, A. mediterranea and A. crenulata. The caps of these species are different in form; however, after exchange, the caps gradually changed from their original form to that typical of its base, where the nucleus is located. In another experiment, the addition of a nucleus from another species into a single intact Acetabularia produced a hybrid cap, showing that both nuclei are influencing the form of the cap.
Acetabularia are among the largest single-celled organisms, having also a remarkably large nucleus. During sexual reproduction, the nucleus undergoes multiple rounds of mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
, forming many daughter nuclei all within one nuclear membrane. These nuclei undergo meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
and are transported to the tips of the branches, the sporangia, where they are released as gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s.
The name, Acetabularia, derives from the Latin word acetabulum, a broad, shallow cup used for dipping bread; the upturned cap of Acetabularia resembles such a cup. For this reason, it is also sometimes called mermaid's wineglass.
Anatomy and life cycle
Acetabularia has three basic parts: its rhizoid, a short set of root-like appendages that contain the nucleus and anchor the cell to fissures in a substrate; its median stalk, which accounts for most of its length; and its apex, where its cap forms. There are usually several whorls of hair-like appendages close to the apex.Morphogenesis
Although a single cell, Acetabularia exhibits a remarkably complex shape and has therefore long been a model organism for studying gene expression and morphogenesis. It seems to transport messenger RNA molecules (in an inactive riboprotein form) from the nucleus to its apical tips, where they are translated into proteins. These molecules may be activated by proteolysis of their protein carrier molecules, but this has not been verified as yet.Internal chemical gradients
In addition to its gradient in specific mRNA molecules, Acetabularia exhibits concentration gradients in several types of molecules, such as ascorbic acid.Circadian rhythms
Acetabularia is often used to study circadian rhythmCircadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
s.
Further reading
- Serio, D., Alongi, G., Catra, M., Cormaci, M. & Furnari, G. (2006). Changes in the benthic algal flora of Linosa Island (Straits of Sicily, Mediterranean Sea). Botanica Marina 49: 135-144.
- Berger, S. & Liddle. L.B. (2003). The life cycle of Acetabularia (Dasycladales, Chlorophyta): textbook accounts are wrong (Commentary). Phycologia 42(2): 204-207, 3 figs.
- Berger, S., Fettweiss, U., Gleissberg, S., Liddle, L.B., Richter, U., Sawitsky, H. & Zuccarello, G.C. (2003). 18S rDNA phylogeny and evaluation of cap development in Polyphysaceae (formerly Acetabulariaceae; Dasyladales, Chlorophyta). Phycologia 42: 506-561.
Sundry references
- Cinelli, F. (1979). Acetabularia acetabulum (L.) Silva, Acetabularia parvula Solms-Laubach and Dasycladus vermicularis (Scopoli) Krasser (Chlorophyta, Dasycladales): ecology and distribution in the Mediterranean Sea.. In: Developmental Biology of Acetabularia. (Bonotto, S., Kefeli, V. & Puiseux-Dao, S. Eds), pp. 3–14. Amsterdam: Elsevier North Holland Biomedical Press.
- Cooper, J.J. & Mandoli, D.F. (1999). Physiological factors that aid differentiation of zygotes and early juveniles of Acetabularia acetabulum (Chlorophyta). Journal of Phycology 35: 143-151, 9 figs.
- Dazy, A. C., Borghi, H., Durand, M. & Puiseux-Dao, S. (1984). The effects of blue and red light on the transcellular electric potential, cytoplasmic streaming and rRNA transport in Acetabularia acetabulum. Proceedings of the International Seaweed Symposium 11: 193-197.
- Hunt, B.E. & Mandoli, D.F. (1996). A new, artificial seawater that facilitates growth of large numbers of cells of Acetabularia acetabulum (Chlorophyta) and reduces the labor inherent in cell culture. Journal of Phycology 32: 483-495, 6 figs, 3 tables.
- Kingsley, R.J., Van Gilder, R., LeGeros, R.Z. & Watabe, N. (2003). Multimineral calcareous deposits in the marine alga Acetabularia acetabulum (Chlorophyta; Dasycladaceae). Journal of Phycology 39: 937-947.
- Kratz, R.F., Young, P.A. & Mandoli, D.F. (1998). Timing and light regulation of apical morphogenesis during reproductive development in wild-type populations of Acetabularia acetabulum (Chlorophyceae). Journal of Phycology 34: 138-146, 6 figs, 2 tables.
- Lüttke, A. (1988). The lack of chloroplast DNA in Acetabularia mediterranea (acetabulum) (Chlorophyceae): A reinvestigation. Journal of Phycology 24: 173-180, 12 figs.
- Mandoli, D.F., Wexler, A., Teschmacher, J. & Zukowski, A. (1995). Note: Brief incubation of gametangia-bearing caps in antibiotics eliminates branching in progeny of Acetabularia acetabulum (Chlorophyta). Journal of Phycology 31: 844-848, 4 figs, 3 tables.
- Menzel, D. (1981). Development and fine structure of plugs in the cap rays of Acetabularia acetabulum (mediterranea) (L.) Silva (Dasycladales). Phycologia 20: 56-64, 21 figs.
- Nishimura, N.J. & Mandoli, D.F. (1992). Population analysis of reproductive cell structures of Acetabularia acetabulum (Chlorophyta). Phycologia 31: 351-358, 9 figs, 2 tables.
- Nishimura, N.J. & Mandoli, D.F. (1992). Vegetative growth of Acetabularia acetabulum (Chlorophyta): structural evidence for juvenile and adult phases in development. Journal of Phycology 28: 669-677, 7 figs.
- Zeller, A. & Mandoli, D.F. (1993). Growth of Acetabularia acetabulum (Dasycladales, Chlorophyta) on solid substrata at specific cell densities. Phycologia 32: 136-142
External links
- www.accessexcellence.org
- Berger, Sigrid (2006).- Photo-Atlas of living Dasycladales.- ISBN 2-916733-01-9, Carnets de GéologieCarnets de GéologieCarnets de Géologie is an electronic journal that publishes in the field of geosciences, and particularly paleontology, stratigraphy, and sedimentology. The open-access journal is one of the founding members of the OA portal Geoscience e-Journals...
, Brest, Book / Livre 2006/02 (CG2006_BOOK_02), 348 p., 1 fig., 332 micrographs. - UTEX culture collection of algae, at the University of Texas at AustinUniversity of Texas at AustinThe University of Texas at Austin is a state research university located in Austin, Texas, USA, and is the flagship institution of the The University of Texas System. Founded in 1883, its campus is located approximately from the Texas State Capitol in Austin...
- CCAP: Culture Collections of Algae and Protozoa