26.3 Monday, Jan. 5 Molecular evolution of light detection in a bioluminescent squid PANKEY, M.S.*; MCFALL-NGAI, M.N.; OAKLEY, T.H.; University of California, Santa Barbara; University of Wisconsin; University of California, Santa Barbara firstname.lastname@example.org
Identifying the molecular bases of adaptive changes leading to novelty and increased complexity is one of the central goals of modern evolutionary biology. We approach this challenge by studying how existing molecular components underlying a certain trait may be modied following gene duplication or redeployed via co-option to give rise to novel phenotypes. Light-emitting organs are commonly found in pelagic sh and cephalopods for means of crypsis via counter-illumination. Recent physiological, immunocytochemical and transcriptome evidence suggests that the central core of the light organ in the squid Euprymna is equipped with photoreceptors responsive to light. While both eye and light organ share expression of some phototransduction genes, the physiological response to light differs greatly between these organs. Light organ tissues also express a duplicated G-protein and several vision genes previously undocumented in mollusk photoreceptors. To better understand how key phototransduction genes have played a role in the evolution of this morphological and behavioral trait we used Real Time PCR to quantify the relative expression of genes constituting this visual network from ocular and luminous tissues. We found that while the visual pigment opsin is shared between tissues, the downstream components of the signaling pathway differ between light organ and the eye photoreceptors. Our results provide molecular support for earlier physiological evidence of light-induced hyperpolarization in the light organ. Our findings also suggest a possible mechanism for novel phototransduction in the light organ in which an alternative signaling pathway may have been co-opted.