ALDH3A2 Enzyme Controls Red-Yellow Pigment Balance in Parrots

A single enzyme fine-tunes red and yellow pigments in parrots' polychromatic plumage, according to a new study. The findings reveal new insights into the molecular mechanisms underlying the evolution and display of color variation in one of nature's most colorful birds. Colors play a central role in ecological adaptation and communication in the natural world.

This is particularly true for birds, which are especially notable among animals for their wide range of vibrant plumage colors and patterns. Among birds, parrots are regarded as one of the most brilliantly colored species, capable of producing a stunning spectrum of plumage through characteristic pigments called psittacofulvins. Although a key enzyme, polyketide synthase (PKS), is known to play a role in this process, the molecular mechanism underlying parrots' ability to generate such diversity of hues remains poorly understood.

Using a comprehensive combination of chemical and enzymatic analyses, genetic mapping, and single-cell genomic techniques, Roberto Arbore and colleagues explored how psittacofulvins are biochemically modified to produce yellow-to-red and green hues in parrot plumage.

Arbore et al. found that much of the color variation in parrots is controlled by fine-tuning the expression of a single key enzyme, ALDH3A2, which modulates aldehyde metabolism and regulates shifts between red and yellow plumage. According to the findings, ALDH3A2 influences psittacofulvin pigment composition by oxidizing red aldehyde molecules into yellow carboxyl-containing molecules, which are selectively deposited into developing feathers, controlling the balance of red and yellow psittacofulvin pigments in a parrot's plumage. Arbore et al. argue that this simple mechanism, driven by a single gene with a large effect, offers insight into the rapid and widespread evolution of diverse colors in parrots.