Collaborative Research: Applying cell biology and biochemistry to understand honest signaling via red feathers

Bright coloration plays a central role in mate choice and social communication, yet a fundamental question about such ornamental traits remains unresolved: How does such coloration serve as an honest signal of individual health and vitality? This project addresses this long-standing puzzle by investigating how the biochemical mechanisms that produce red coloration in birds are inherently linked to core processes required for cellular health. By integrating organismal biology with modern cell biology and biochemistry, this research seeks to uncover why some traits provide reliable information about health, performance, and reproductive potential. Understanding how biological signals reliably convey information has broad implications for evolutionary biology, medicine, agriculture, and conservation, because similar principles govern how cells maintain function under stress and how organisms respond to environmental change. The project also contributes to education and workforce development in biotechnology-relevant fields by training undergraduate students, graduate students, and postdoctoral researchers in interdisciplinary research that bridges molecular biology and organismal biology. Outreach activities will engage K–12 students and families in hands-on demonstrations illustrating how scientists test hypotheses. By advancing fundamental understanding of how complex biological traits are produced and maintained, and by using cell lines engineered via biotechnological approaches to test key hypotheses, this project promotes the progress of science and strengthens education in STEM fields, thereby supporting the national interest. This project tests the hypothesis that red carotenoid-based coloration functions as an honest signal of individual condition because pigment production is linked directly to fundamental cellular processes including redox balance, mitochondrial function, and lipid homeostasis in the endoplasmic reticulum. Recent discoveries show that the enzymes CYP2J19 and BDH1L, along with the modifying factor TTC39B, catalyze the conversion of dietary yellow carotenoids to red ketocarotenoids used in ornamental coloration. Preliminary studies by this team of collaborators demonstrate that these enzymes localize to the endoplasmic reticulum and that carotenoid metabolism is sensitive to variation in mitochondrial membrane potential and cellular redox state. The project integrates biotechnological, biochemical, cellular, and organismal approaches across three aims. Aim 1 uses heterologous protein expression and artificial microsomal membranes to characterize the enzymatic kinetics and cofactor requirements of CYP2J19 and BDH1L under controlled redox and lipid conditions. Aim 2 employs recombinant avian cell lines expressing CYP2J19, BDH1L, and TTC39B to experimentally manipulate mitochondrial function, oxidative state, and endoplasmic reticulum stress using pharmacological agents, followed by quantification of carotenoid metabolites and cellular performance metrics. Aim 3 tests predictions derived from biochemical and cellular experiments by experimentally manipulating cellular condition in a focal avian species, the northern cardinal (Cardinalis cardinalis), and measuring resulting variation in carotenoid metabolism, plumage pigmentation, metabolic performance, and immune function. Together, these approaches will provide an unprecedented mechanistic framework linking cellular physiology to the expression of condition-dependent traits and will advance understanding of the biological foundations of honest signaling, not only in birds, but also in other animals that use red coloration in inter-individual signaling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2445892 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Yufeng Zhang | Institution: University of Memphis, MEMPHIS, TN | Award Amount: $467,837 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2445892 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2445892.html