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The Chloroplast Genome of the Toxic Stramenopile Heterosigma Akashiwo (Raphidophyceae)
Author(s) -
Veluppillai J. M.,
Jacobs M. A.,
Duplessis M. R.,
Choi L.,
Cattolico R. A.
Publication year - 2003
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.2003.03906001_165.x
Subject(s) - heterosigma akashiwo , biology , chloroplast , genome , gene , chloroplast dna , genetics , complementary dna , botany , algal bloom , ecology , phytoplankton , nutrient
Algae live in an informationally dense environment. To ensure survival, many phytoplankton species respond to specific environmental signals by alternating between motile vegetative and non‐motile resting life history phases. Heterosigma akashiwo (Raphidophyceae) can be induced to enter stasis by altering light, temperature and/or nutrient levels. In the resting phase, this obligate photoautotroph can survive for months in cold, dark coastal sediments. To understand how H. akashiwo modifies chloroplast function as it moves between life history phases, we want to (a) identify the signal transduction mechanisms and (b) transcriptional processes in this organelle. Sequencing the chloroplast genome represents the first step in this endeavor. Electron microscopy, reassociation kinetic analysis and restriction analysis show the Heterosigma chloroplast DNA to be 154 kb. Chloroplast DNA recovered by Hoescht dye/CsCl centrifugation has been sheared to 700 bp fragments, cloned in pUC19 and sequenced according to standard protocols. All Heterosigma chloroplast genes lack introns, some genes overlap, others contain large repeats. At least one gene encodes large (90–100 amino acid) domains that are inexplicably inserted within highly conserved proteins and finally, some chloroplast genes encode proteins that have an extended 5′ domain compared to homologues in other plastids. The Heterosigma genome has little co‐linearity with the stramenopile ( Odontella ), rhodophyte ( Cyanidium, Porphyra ), glaucophyte ( Cyanophora ), or cryptophyte ( Guillardia ) chloroplast DNAs that have been sequenced to date. Novel genes encoding signal transduction proteins have been identified.