Search

The emergence of novel traits is often preceded by a potentiation phase, when all the genetic components necessary for producing the trait are assembled. However, elucidating these potentiating factors is challenging. We have previously shown that an anthocyanin-activating R2R3-MYB, STRIPY, triggers the emergence of a distinct foliar pigmentation pattern in the monkeyflower Mimulus verbenaceus. Here, using forward and reverse genetics approaches, we identify three potentiating factors that pattern STRIPYexpression: MvHY5, a master regulator of light signaling that activates STRIPYand is expressed throughout the leaf, and two leaf developmental regulators, MvALOG1and MvTCP5, that are expressed in opposing gradients along the leaf proximodistal axis and negatively regulate STRIPY. These results provide strong empirical evidence that phenotypic novelties can be potentiated through incorporation into preexisting genetic regulatory networks and highlight the importance of positional information in patterning the novel foliar stripe.

Steady-state absorption, transient absorption, and transient grating spectroscopies were employed to elucidate the role of a conjugated carbonyl group in the photophysics of carotenoids. Spheroidenone and spheroidene have similar molecular structures and differ only in an additional carbonyl group in spheroidenone. Comparison of the optical responses of these two molecules under similar experimental conditions was used to understand the role of this carbonyl group in the structure. It was found that the carbonyl group has two main effects: first, it dramatically increases the depopulation rate of the excited states of the molecule. The lifetimes of all the excited states of spheroidenone were found to be almost half of the ones for spheroidene. Second, the presence of the carbonyl group in the chain alters the decay mechanism to the symmetry-forbidden S1state of the molecule, so that the higher vibrational levels of the S1state are populated much more effectively. It was also revealed that for both molecules, the S2/Sx→ S1(hot) → S1decay process is not purely sequential and follows a branched model.

Light absorption by carotenoids is known to vary substantially with the shape or conformation of the pigment molecule induced by the molecular environment, but the role of interactions between carotenoid pigments and the proteins to which they are bound, and the resulting impact on organismal coloration, remain unclear. Here, we present a spectroscopic investigation of feathers from the brilliant red scarlet ibis (Eudocimus ruber,Threskiornithidae), the orange-red summer tanager (Piranga rubra,Cardinalidae) and the violet-purple feathers of the white-browed purpletuft (Iodopleura isabellae,Tityridae). Despite their striking differences in colour, all three of these feathers contain canthaxanthin (β,β-carotene-4,4′-dione) as their primary pigment. Reflectance and resonance Raman (rR) spectroscopy were used to investigate the induced molecular structural changes and carotenoid–protein interactions responsible for the different coloration in these plumage samples. The results demonstrate a significant variation between species in the peak frequency of the strong ethylenic vibration (ν1) peak in the rR spectra, the most significant of which is found in I. isabellaefeathers and is correlated with a red-shift in canthaxanthin absorption that results in violet reflectance. Neither polarizability of the protein environment nor planarization of the molecule upon binding can entirely account for the full extent of the colour shift. Therefore, we suggest that head-to-tail molecular alignment (i.e. J-aggregation) of the protein-bound carotenoid molecules is an additional factor.