phylogeny of the
green algal genus dunaliella

The unicellular algae of the genus Dunaliella belong to the Chlorophyta (green algae). They fall into the class Chlorophyceae. Recently they were put into their own order of Dunaliellales and family of Dunaliellaceae. The genus Dunaliella consists of the two subgenera Pascheria (including five freshwater species) and Dunaliella (including 23 described saltwater species).

The subgenus Dunaliella:

• In the past 23 different species had been described. In addition, several subspecies had been distinguished.
• Many species are extreme halo-tolerant and propagate even in saturated salt (NaCl) solution.
• All species are unicellular and have two flagella in their motile vegetative phase. In addition, all species possess a cup-shaped chloroplast.
• For some species sexual reproduction has been reported with either homothallic or heterothallic behavior.
• Some species accumulate ß-carotene as a secondary carotenoid in the chloroplast under environmental stress conditions (high irradiance, high salt, low nutrients).
• It is known that the cell morphology changes throughout the life cycle. Moreover, cell morphology depends on environmental conditions.

Until a few years ago, morphological and physiological characteristics have been the major criteria for species distinction. However, cell morphology depends largely on environmental factors such as salinity and age of the cell culture. In addition, because of great morphological variation even within one species, there has been confusion as to the correct classification of various described species and subspecies. Moreover, some species deposited in culture collections do not resemble their original description any more. Only recently has additional molecular analysis with various techniques been used to further study the phylogeny of the genus Dunaliella. We isolated a large number of new Dunaliella strains from various locations that are currently being analyzed by microscopy, physiologically and at the molecular level. For molecular characterization sequence analysis of the nuclear internal transcribed spacer 1 and 2 regions (ITS1+ITS2) is being used for classification. In addition, sequence analysis of the nuclear 18s rDNA gene is being performed to further delineate Dunaliella species and subspecies from each other.

Secondary Structure of the nuclear ITS2 region.
Click to enlarge.

presentations

2003

New York Area Plant Molecular Biology, New York, NY, USA
"Use of molecular biology tools to investigate biodiversity of the algal genus Dunaliella."
Presenter: J.E.W. Polle



The 67th meeting of the Northeast Section of the American Society of Plant Biologists at Bucknell University in Lewisburg, PA, USA
"Analysis of the nuclear Internal Transcribed Spacer Region 2 (ITS2) for species characterization within the green algal genus Dunaliella."
Presenter: J.E.W. Polle, C. Louis, and D. Avery



The Annual Meeting of the American Society of Plant Biologists in Honolulu, Hawaii, USA
"Characterization of species within the green algal genus Dunaliella."
Presenter: Polle, Juergen E.W.
Authors: Polle, Juergen E.W. (A) Louis, Claudeline (A) Avery, Dionne (A) Jin, EonSeon (B)
Affiliations: (A): BROOKLYN COLLEGE of the CITY UNIVERSITY of NEW YORK, Department of Biology, 2900 Bedford Ave, Brooklyn, NY 11210, USA (B): KORDI, Research Building 1st #1222, Sa-Dong 1270, Ansan Kyung-Gi Do, Korea 425-744

2004

New York Area Plant Molecular Biology at Rutgers University, NJ, USA
"Comparative molecular and morphological study on the halotolerant unicellular green alga Dunaliella."
Presenter: Juergen E.W. Polle (1) and ES. Jin (2)
Affiliations: (1) Department of Biology, Brooklyn College, The City University of New York, Brooklyn, NY; (2) KORDI, Research Building 1st 222, SA-dong 1270, ANSAN Kyung Ki Do, Korea