The Stramenopile Chloroplast Genomics Project

About Heterosigma akashiwo
Heterosigma akashiwo (formerly Olisthodiscus luteus) is a naturally wall-less, toxic alga that blooms in coastal regions world-wide. In the field, Heterosigma forms massive brown tides that impact the survival of eco-cohorts at every trophic level. This alga has been shown to kill finfish, compromise fish and sea urchin egg development and impact copepod as well as oyster survival. Heterosigma blooms have caused economic losses amounting to many millions of dollars in fish species, including salmonids, sea bream, yellowtail, sea bass and flounder and commercially important invertebrates such as oysters and clams. It has been suggested that Heterosigma produces a species-specific allelopathic substance that can affect the survival of algae and possibly other phytoplankton. Heterosigma's ability to flourish in these diverse habitats is probably due in part to: (a) its tolerance of a wide range of environmental conditions (e.g., a salinity range of 2 to >50; temperature range of <5°C to >30°C) and adaptability to anthropogenic growth conditions; and (b) the ability of Heterosigma resting cells to survive long-range transport by natural currents and ship ballast water.

About the Chloroplast Genome
The 154 Kb chloroplast genome of Heterosigma akashiwo strain 452 contains an inverted repeat sequence of 22kb separating two single-copy regions of 37 and 73 kb, respectively. Genes not normally found in terrestrial plants or green algal chloroplast genomes are present in Heterosigma plastid DNA (e.g. the small subunit of Rubisco; a prokaryotic-like two-component signal transduction array). Genes are tightly packed (often overlapping) lack introns and do not have the multiple promoter domains frequently associated with the chloroplasts genes of green algae and terrestrial plants.

References:

A conserved His-Asp signal response regulator-like gene in Heterosigma akashiwo chloroplasts
Jacobs,M.A., Connell,L. and Cattolico,R.A.
PLANT MOLECULAR BIOLOGY
41 (5), 645-655 (1999)

Chloroplast DNA: Structure and organization of chromophyte and rhodophyte plastid genomes: Implications for the ancestry of plastids
Shivji, M. S., N. Li and R. A. Cattolico
MOLECULAR AND GENERAL GENETICS
232: 65-73 1992

Synchronous growth and plastid replication in the naturally wall-less alga Olisthodiscus luteus
Cattolico, R. A., J. C. Boothroyd and S. P. Gibbs
PLANT PHYSIOLOGY
57: 497-503. 1976