Role of Pax genes in eye evolution: a cnidarian PaxB gene uniting Pax2 and Pax6 functions.
PaxB from Tripedalia cystophora, a cubomedusan jellyfish possessing complex eyes (ocelli), was characterized. PaxB, the only Pax gene found in this cnidarian, is expressed in the larva, retina, lens, and statocyst. PaxB contains a Pax2/5/8-type paired domain and octapeptide, but a Pax6 prd-type homeodomain. Pax2/5/8-like properties of PaxB include a DNA binding specificity of the paired domain, activation and inhibitory domains, and the ability to rescue spa(pol), a Drosophila Pax2 eye mutant. Like Pax6, PaxB activates jellyfish crystallin and Drosophila rhodopsin rh6 promoters and induces small ectopic eyes in Drosophila. Pax6 has been considered a "master" control gene for eye development. Our data suggest that the ancestor of jellyfish PaxB, a PaxB-like protein, was the primordial Pax protein in eye evolution and that Pax6-like genes evolved in triploblasts after separation from Cnidaria, raising the possibility that cnidarian and sophisticated triploblastic eyes arose independently.
Kozmik
Zbynek
Z
Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Daube
Michael
M
Frei
Erich
E
Norman
Barbara
B
Kos
Lidia
L
Dishaw
Larry J
LJ
Noll
Markus
M
Piatigorsky
Joram
J
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001665:Binding Sites; D005075:Biological Evolution; D003063:Cnidaria / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology; D003459:Crystallins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology; D005123:Eye / Q000254:growth & development*; D005136:Eye Proteins; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009799:Ocular Physiological Phenomena; D051762:PAX2 Transcription Factor; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D010641:Phenotype; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D003459:Crystallins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D051762:PAX2 Transcription Factor; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C414094:Pax-B protein, Podocoryne carnea; D011506:Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C105578:Rh6 protein, Drosophila; D014157:Transcription Factors; D012243:Rhodopsin