Vomeronasal reptilian transcriptome

The vomeronasal organ (VNO) is an olfactory sensory structure that detects pheromones and environmental cues. It consists of sensory neurons that express several evolutionarily unrelated groups of transmembrane chemoreceptors. The vomeronasal receptor V1R and V2R repertoires are the predominant receptors and are believed to detect airborne and water-soluble molecules, respectively. It has been suggested that the shift in habitat of early tetrapods from water to land is reflected by an increase in the ratio of V1R/V2R genes. Snakes, a large group of terrestrial vertebrates, are missing from this analysis. Snakes heavily depend on the VNO for prey trailing, courtship, and shelter selection and the organ is highly developed and associated with a sophisticated tongue delivery system. However, the vomeronasal receptor repertoire of snakes had not been characterized so far.

We used RNA-seq and RNA in-situ hybridizations to study the diversity, evolution, and expression pattern of the corn snake vomeronasal receptor repertoires. Our analyses indicate that snakes retain an extremely limited number of V1R genes. In contrast, we find a very large number of V2R genes, including multiple lineages of reptile-specific and snake-specific expansions.

Our results do not support the hypothesis that the shift to a vomeronasal receptor repertoire dominated by V1Rs in mammals reflects the evolutionary transition of early tetrapods from water to land. This study sheds light on the evolutionary dynamics of the vomeronasal receptor families in vertebrates and reveals how mammals and Sauropsida reptiles differentially adapted the same ancestral vomeronasal repertoire to succeed in a terrestrial environment.

Associated Publication
Brykczynska U., Tzika A.C., Rodriguez I. & M. C. Milinkovitch
Contrasted evolution of the vomeronasal receptor repertoires in Mammals and Squamate reptiles
Genome Biology & Evolution 5: 389-401 (2013)
Supplementary Materials

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Supplementary File 1
‣ Sequences of corn snake putative functional V2R transcript fragments (FASTA file)

Supplementary File 2
‣ Sequences of corn snake expressed putative V2R pseudogene fragments (FASTA file)

Supplementary File 3
‣ List of putative Python and Garter snake V2Rs along with the best TBLASTX hit obtained against the NCBI nr database (May 2012) (Microsoft Excel file)

Supplementary File 4
‣ ORF sequences of Python putative V2Rs (FASTA file)

Supplementary File 5
‣ Corn snake putative olfactory genes (FASTA file)

Supplementary File 6a
‣ Assembled Illumina contigs (FASTA file)

Supplementary File 6b
‣ Assembled (contigs) and Roche/454 singleton sequences (>200bp) (FASTA file)

Supplementary File 7
‣ Sequences of putative reptilian V1Rs (FASTA file)