Relocation to avoid costs: A hypothesis on red carotenoid-based signals based on recent CYP2J19 gene expression data

Area of Science:

• Biochemistry
• Evolutionary Biology
• Animal Coloration

Background:

• Dietary yellow carotenoids are enzymatically converted into red keto-carotenoids, which color vertebrate ornaments.
• The enzyme cytochrome P450 2J19 (CYP2J19) is a key factor in this oxidation process.
• The intracellular location of CYP2J19 suggests a link between ornament coloration and essential cell functions, potentially ensuring signal reliability.

Approach:

• Investigated the hypothesis that ornament type and production costs influenced tissue-specific gene relocation of CYP2J19.
• Reviewed avian tissue-specific CYP2J19 expression data.
• Conducted a phylogenetically controlled analysis of 25 red-colored species.

Key Points:

• Most red-billed species with CYP2J19 bill expression showed limited hepatic expression.
• Species with red bare parts were less likely to exhibit strong hepatic CYP2J19 expression compared to those with red plumage.
• This suggests that tissue-specific gene expression may have evolved to mitigate costs associated with CYP2J19 activity.

Conclusions:

• Both the potential costs of CYP2J19 activity on vital functions and the existence of shared biochemical pathways likely influenced the evolution of red coloration signals.
• Tissue-specific expression of CYP2J19 may represent an adaptive strategy to maintain honest signaling of individual quality while minimizing physiological trade-offs.