title: Tetracoding increases with body temperature in Lepidosauria.
abstract: Codons expanded by a silent position (quadruplet or tetracodons) may solve the conundrum that at life's origins, the weak tricodon-anticodon interactions could not promote translation in the absence of complex ribosomes. Modern genomes have isolated tetracodons resulting from insertion mutations. Some bioinformatic analyses suggest that tetracoding stretches overlap with regular mitochondrial protein coding genes. These tetragenes are probably decoded by (antisense) tRNAs with expanded anticodons. They are GC-rich, which produce stronger basepairs than A:T interactions, suggesting expression at high temperatures. The hypothesis that tetracoding is an adaptation to high temperatures is tested here by comparing predicted mitochondrial tetracoding in Lepidosauria (lizards, amphisbaenia, and Sphenodon), in relation to body temperature, expecting more tetracoding in species with high body temperature. The association between tRNAs with expanded anticodons and tetracoding previously described for mammals and Drosophila is confirmed for Lepidosauria. Independent evidence indicates that tetracoding increases with body temperature, supporting the hypothesis that tetracoding is an adaptation for efficient translation when conditions (temperature) make triplet codon-anticodons too unstable to allow efficient protein elongation.
authors.affiliation: National Natural History Museum Collections, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel; Center for Ecological and Evolutionary Synthesis, Department of Bioscience, University of Oslo, Blindern, N-0316 Oslo, Norway; Department of Life Sciences, Ben Gurion University, 84105 Beer Sheva, Israel. Electronic address: varanuseremius@gmail.com.
authors.forename: Hervé
authors.initials: H
authors.lastname: Seligmann
authors.forename: Antonieta
authors.initials: A
authors.lastname: Labra
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D020029:Base Pairing; D001831:Body Temperature / Q000502:physiology*; D003062:Codon / Q000235:genetics* / Q000502:physiology; D019295:Computational Biology; D008116:Lizards / Q000235:genetics* / Q000502:physiology; D008957:Models, Genetic; D016254:Mutagenesis, Insertional / Q000235:genetics; D010802:Phylogeny; D012343:RNA, Transfer / Q000235:genetics; D018709:Statistics, Nonparametric
chemical_list: D003062:Codon; D012343:RNA, Transfer
keywords: Developmental stability; Genetic code expansion; Suppressor tRNAs; Synonymous codon usage; tRNA cloverleaf structure