Meeting Abstract

26.4  Wednesday, Jan. 4  Eye-Associated Genes in the Eye and Light Organ of the Squid Euprymna scolopes PEYER, Suzanne M*; MCFALL-NGAI, Margaret J.; University of Wisconsin, Madison; University of Wisconsin, Madison

Research on visual systems has revealed conservation of eye-associated genes across animal phyla, including those involved in eye specification [pax6 (paired box gene 6), eya (eyes absent), six (sine oculis), dac (dachshund)]. The squid, Euprymna scolopes, has evolved at least two independent sets of tissues that interact with light, a complex eye and a ‘light organ’ that houses the luminous bacterial symbiont Vibrio fischeri. Recent studies indicated biochemical similarities between the two organs, such as the presence of visual transduction proteins. Such findings prompted the question: are the two organs under the same developmental specification? We obtained light-organ sequences of each eye-specification gene (RACE-PCR) and determined whether each is expressed in the eye, the light organ, or both (RT-PCR). We localized eye-specification and visual transduction gene transcripts with in situ hybridization, throughout development, comparing the patterns of expression in the two organs. At least one isoform of each eye-specification gene was expressed in both organs of embryonic and early postembryonic squid. The eye-specification and visual transduction gene transcripts localized to tissues associated with the visual system ~1/4 into embryogenesis (Naef stage 20). These transcripts localized to the light organ later in development, ~3/4 into embryogenesis (Naef stage 29). We are now examining the effect of symbiosis and endogenous light on gene expression in the light organ, comparing wild-type luminous strains of V. fischeri to those defective in light production. Such results promise to provide evidence that eye-specification genes are critical for development of light-interacting tissues, independent of their embryonic origin.