9601155 Mcfall-Ngai The goal of this research program is to define specific aspects of the complex morphological, biochemical and molecular conversation that underlies the development of the cooperative association between the sepiolid squid Euprymna scolopes and its luminous bacterial partner, Vibrio fischeri. The present proposal draws directly from the foundation created by recent developmental studies of this model system, and focuses on four specific questions: 1. What are the characteristics of the bacteria-induced cell death that occurs in the light organ during the colonization process, and how do the bacteria signal this process? 2. How is development of the accessory structures of the light organ induced, and to what extent are the bacteria symbionts involved in this process? 3. What are the identities of symbiosis-induced bacterial genes? 4. Is bacterial catalase induction essential for symbiotic competency, and/or for the triggering of host development? These questions will be addressed both by examining diagnostic characteristics of embryonic and postembryonic development, and by experimentally manipulating symbiotic and aposymbiotic juvenile animals. In addition, development of the bacterial symbionts will be probed using promoter-reporter constructs that will lead to the identification of bacterial genes that are induced specifically during symbiosis, and reveal the role(s) of these genes in host development. Light and electron microscopy will be used in concert with in situ hybridization dn immunocytochemistry to visualize regions of host and symbiont gene expression, and the presence of resultant protein products.
