Meeting Abstract
Initiation of the symbiosis between the squid Euprymna scolopes and its luminous bacterial partner Vibrio fischeri triggers profound cell-death mediated morphogenesis of the colonized organ. A rhythmic association follows in which the host controls the symbiont population over the day-night cycle. In this study, we examined whether symbiont luminescence affects host transcription of crumbs, a cell polarity gene involved in protecting against light-induced apoptosis of photoreceptive tissues. In the juvenile squid, we examined crumbs transcript expression and regulation in response to early V. fischeri colonization. At this stage of rapid morphogenesis the transcript was significantly down regulated in response to wild-type luminous V. fischeri relative to a mutant strain defective in light production and a control with no symbiont. In the mature squid, we examined transcript regulation over the 24-h day-night cycle. The transcript was significantly up regulated during the period of highest relative to lowest luminescence and did not correspond with environmental light. The results of our study indicate that the crumbs gene is regulated by bacterial luminescence, but this regulation differs depending on the stage of host development. In the juvenile squid down regulation of the transcript might be necessary for apoptosis induction, whereas in the mature squid up regulation of the transcript might be crucial for tissue protection during peak luminescence.
