Evolutionary shifts in courtship pheromone composition revealed by EST analysis of plethodontid salamander mental glands

Mechanisms of action and co-optive evolution for hypervariable courtship pheromones in plethodontid salamanders.

“…As expected, the majority of transcripts coded for pheromone, including PRF and PMF, but also (in lower abundance) many putative pheromones that were identified in other plethodontid species (natriuretic peptide, vasoactive intestinal peptide, sodefrin precursor-like factor, cysteine rich secretory protein) [89]. Included in these sequences was a predicted protein related to the tissue inhibitor of metalloproteinase (TIMP) family that included an extraordinarily long 3' UTR (~3700 nt); through mass spectrometry, this sequence was matched to a protein previously termed C3 based on its chromatographic elution conditions.…”

“…Combined DNA sequencing and mass spectral proteomics efforts revealed that many of these proteins are products of gene co-option: gene duplication followed by mutation to drive neofunctionalization. In particular, many hormones (insulin, glucagon, insulin-like growth factor, leptin) were targets of gene co-option in D. ocoee and may adjust female physiology during courtship [88,89]. One protein, sodefrin precursor-like factor (SPF),…”

“…Similarly, cDNA sequence analysis revealed that ~70% of the total mRNA coded for pheromones [89]. Following the end of the courtship season, the gland seemingly resorbs and a new one forms each subsequent year.…”

“…Sequencing of ~300 clones from a P. shermani pheromone gland cDNA library revealed that >70% coded for PRF and PMF isoforms, and included 32 unique PMF derived protein sequences [89]. Initial analyses of the PMF expressed sequence tags (ESTs) indicated the CDSs were highly dissimilar while both the 5' and 3' UTRs were highly conserved.…”

Co-option and adaptation of novel gene duplications for pheromone activity in a dusky salamander.

“…For example, approximately 5% of the cDNA sequences from the mental gland of D. ocoee were identified as PMF sequences (32). However, unlike P. shermani, which has more than 50 isofonns, only one single unique translation was identified.…”