The rod opsin pigments from two marsupial species, the South American bare-tailed woolly opossum and the Australian fat-tailed dunnart.
Rod visual pigment genes have been studied in a wide range of vertebrates including a number of mammalian species. However, no marsupials have yet been examined. To correct this omission, we have studied the rod pigments in two marsupial species, the nocturnal and frugivorous bare-tailed woolly opossum, Caluromys philander, from Central and South America, and the arhythmic and insectivorous fat-tailed dunnart, Sminthopsis crassicaudata, from Australia. Phylogenetic analysis establishes that the cloned opsin sequences are orthologues of rod opsin genes from other vertebrate species. The deduced amino acid sequences show that both possess glutamate at residue 122, a feature of rod opsins, and the corresponding gene follows the typical vertebrate rod opsin pattern of five exons separated by four introns. Compared to other vertebrates, a stretch of five residues near the C-terminus is deleted in the rod opsin of both marsupials and all eutherian mammals. From microspectrophotometric measurements, the pigments in the two species show an 8 nm difference in peak absorbance; the molecular basis for this spectral shift is discussed and two candidate substitutions are identified.
Hunt
David M
DM
Division of Molecular Genetics, Institute of Ophthalmology, University College London, Bath Street, EC1V 9EL, London, UK. d.hunt@ucl.ac.uk
Arrese
Catherine A
CA
von Dornum
Miranda
M
Rodger
Jenny
J
Oddy
Alison
A
Cowing
Jill A
JA
Ager
Eleanor I
EI
Bowmaker
James K
JK
Beazley
Lyn D
LD
Shand
Julia
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D005091:Exons; D005796:Genes / Q000235:genetics; D007438:Introns; D008394:Marsupialia / Q000235:genetics*; D008969:Molecular Sequence Data; D009893:Opossums / Q000235:genetics*; D010802:Phylogeny; D017299:Rod Opsins / Q000032:analysis / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry / Q000379:methods
D018076:DNA, Complementary; D017299:Rod Opsins