title: Evolution of discrete Notch-like receptors from a distant gene duplication in Caenorhabditis.
abstract: SUMMARY Caenorhabditis elegans possesses two Notch-like receptors, LIN-12 and GLP-1, which have both overlapping and individual biological functions. We examined the lin-12 and glp-1 genes in closely related nematodes to learn about their evolution. Here we report molecular and functional analyses of lin-12 orthologs from two related nematodes, C. briggsae (Cb) and C. remanei (Cr). In addition, we compare these lin-12 findings with similar studies of Cb-glp-1 and Cr-glp-1 orthologs. Cb-LIN-12 and Cr-LIN-12 retain the same number and order of motifs as Ce-LIN-12. Intriguingly, we find that LIN-12 conservation differs from that of GLP-1 in two respects. First, individual motifs are conserved to a different degree for the two receptors. For example, the transmembrane domain is 16-32% identical among LIN-12 orthologs but 65-70% identical among GLP-1 orthologs. Second, certain amino acids are conserved in a receptor-specific manner, a phenomenon most prevalent in the CC-linker. We suggest that LIN-12 and GLP-1 have been molded by selective constraints that are receptor specific and that the two proteins may not be entirely interchangeable. To analyze the functions of the lin-12 orthologs, we used RNA-mediated interference (RNAi). Cb-lin-12(RNAi) or Cr-lin-12(RNAi) progeny are nearly 100% Lag, a larval lethality typical of C. elegans lin-12 glp-1 double mutants, but not the primary defect observed in Ce-lin-12 null mutants or Ce-lin-12(RNAi). Therefore, LIN-12 functions are similar, but not identical, among the Caenorhabditis species. We suggest that ancestral functions may have been divided between LIN-12 and GLP-1 receptors in a process contributing to the retention of both genes after gene duplication (i.e., subfunctionalization).
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D015139:Blotting, Southern; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D003001:Cloning, Molecular; D017931:DNA Primers; D020440:Gene Duplication; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D051880:Receptors, Notch; D017386:Sequence Homology, Amino Acid
chemical_list: D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; D015801:Helminth Proteins; C082460:Lin-12 protein, C elegans; D008565:Membrane Proteins; D012333:RNA, Messenger; D051880:Receptors, Notch