Individual Variation in Pheromone Isoform Ratios of the Red-Legged Salamander, Plethodon shermani
For more than 15 years, pheromone signalling in plethodontid salamanders has served as an important amphibian system for studying how molecules can influence reproductive behaviour. In the red-legged salamander (Plethodon shermani), males utilise proteinaceous pheromones from a submandibular (mental) gland to affect female behaviour and reduce the duration of courtship. The two major proteins, Plethodontid Receptivity Factor (PRF) and Plethodontid Modulating Factor (PMF), exist as multiple isoforms within the gland of an individual male. While previous research has focused on biochemical characterisation of these proteins, this study explores the degree of intraspecific variability of pheromone isoform ratios among males of a single population. Biochemical analyses were performed on the mental gland extracts of individual male salamanders (n = 108) via high-performance liquid chromatography to quantify components of the pheromone mixture and establish the extent of individual variability. The results of these individual analyses revealed that the two main proteins (PMF and PRF) comprise over 80% of the total mixture, with a 5:3 ratio (PMF:PRF). Numerous minor peaks also appeared in the elution range of PRF, which could account for an excess of mRNA transcripts that have not been proteomically characterised. Lastly, these data demonstrate a remarkable diversity of isoform ratios among males. Taken together, these aspects of pheromone complexity and diversity could have profound functional effects on reproductive behaviour in this family of salamanders.
KeywordsMajor Isoforms Accessory Olfactory Bulb Ternary Plot Multicomponent Signal Pheromone Composition
We thank Kathleen Bowen, Pamela Feldhoff, Kari Leichty, Sarah Eddy and Josef Uyeda for help in the lab or field and/or for comments on the manuscript. We also thank James Costa and the staff of the Highlands Biological Station (Highlands, NC). Funding was supported by National Science Foundation grants to LDH (IOS-0818554) and RCF (IOS-0818649).
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