The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation.
The smallest known eukaryotes, at approximately 1-mum diameter, are Ostreococcus tauri and related species of marine phytoplankton. The genome of Ostreococcus lucimarinus has been completed and compared with that of O. tauri. This comparison reveals surprising differences across orthologous chromosomes in the two species from highly syntenic chromosomes in most cases to chromosomes with almost no similarity. Species divergence in these phytoplankton is occurring through multiple mechanisms acting differently on different chromosomes and likely including acquisition of new genes through horizontal gene transfer. We speculate that this latter process may be involved in altering the cell-surface characteristics of each species. In addition, the genome of O. lucimarinus provides insights into the unique metal metabolism of these organisms, which are predicted to have a large number of selenocysteine-containing proteins. Selenoenzymes are more catalytically active than similar enzymes lacking selenium, and thus the cell may require less of that protein. As reported here, selenoenzymes, novel fusion proteins, and loss of some major protein families including ones associated with chromatin are likely important adaptations for achieving a small cell size.
Palenik
Brian
B
Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202, USA. bpalenik@ucsd.edu
Grimwood
Jane
J
Aerts
Andrea
A
Rouzé
Pierre
P
Salamov
Asaf
A
Putnam
Nicholas
N
Dupont
Chris
C
Jorgensen
Richard
R
Derelle
Evelyne
E
Rombauts
Stephane
S
Zhou
Kemin
K
Otillar
Robert
R
Merchant
Sabeeha S
SS
Podell
Sheila
S
Gaasterland
Terry
T
Napoli
Carolyn
C
Gendler
Karla
K
Manuell
Andrea
A
Tai
Vera
V
Vallon
Olivier
O
Piganeau
Gwenael
G
Jancek
Séverine
S
Heijde
Marc
M
Jabbari
Kamel
K
Bowler
Chris
C
Lohr
Martin
M
Robbens
Steven
S
Werner
Gregory
G
Dubchak
Inna
I
Pazour
Gregory J
GJ
Ren
Qinghu
Q
Paulsen
Ian
I
Delwiche
Chuck
C
Schmutz
Jeremy
J
Rokhsar
Daniel
D
Van de Peer
Yves
Y
Moreau
Hervé
H
Grigoriev
Igor V
IV
D000222:Adaptation, Physiological; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D000460:Chlorophyta / Q000235:genetics* / Q000378:metabolism; D002875:Chromosomes / Q000235:genetics; D004777:Environment; D005057:Eukaryotic Cells / Q000145:classification* / Q000378:metabolism*; D022761:Gene Transfer, Horizontal; D016678:Genome / Q000235:genetics*; D008670:Metals / Q000378:metabolism; D008969:Molecular Sequence Data; D010933:Plankton / Q000145:classification* / Q000235:genetics* / Q000378:metabolism; D051140:Selenoproteins / Q000378:metabolism; D014815:Vitamins / Q000378:metabolism
D008670:Metals; D051140:Selenoproteins; D014815:Vitamins