Explosive lineage-specific expansion of the orphan nuclear receptor HNF4 in nematodes.
The nuclear receptor superfamily expanded in at least two episodes: one early in metazoan evolution, the second within the vertebrate lineage. An exception to this pattern is the genome of the nematode Caenorhabditis elegans, which encodes more than 270 nuclear receptors, most of them highly divergent. We generated 128 cDNA sequences for 76 C. elegans nuclear receptors, confirming that these are active genes. Among these numerous receptors are 13 orthologues of nuclear receptors found in arthropods and/or vertebrates. We show that the supplementary nuclear receptors (supnrs) originated from an explosive burst of duplications of a unique orphan receptor, HNF4. This origin has specific implications for the role of ligand binding in the function and evolution of the nematode supplementary nuclear receptors. Moreover, the supplementary nuclear receptors include a group of very rapidly evolving genes found primarily on chromosome V. We propose a model of lineage-specific duplications from a chromosome on which duplication and substitution rates are highly increased. Our results provide a framework to study nuclear receptors in nematodes, as well as to consider the functional and evolutionary consequences of lineage-specific duplications.
Laboratoire de Biologie Moléculaire de la Cellule, UMR CNRS 5161, Ecole Normale Supérieure de Lyon, France.
Marc
M
Robinson-Rechavi
Claude V
CV
Maina
Chris R
CR
Gissendanner
Vincent
V
Laudet
Ann
A
Sluder
D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics*; D019295:Computational Biology; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D030561:Databases, Nucleic Acid; D019143:Evolution, Molecular; D020440:Gene Duplication; D051557:Hepatocyte Nuclear Factor 4; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D010750:Phosphoproteins / Q000235:genetics*; D010802:Phylogeny; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics*
D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051557:Hepatocyte Nuclear Factor 4; D010750:Phosphoproteins; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors