Dissecting the Interaction Between the Genome and the Environment During Embryological Development in the Annual Killifish Austrofundulus limnaeus

Portland State University, Portland OR

Investigators

Abstract

The environment in which an embryo develops can alter the activity of genes and cause developmental changes that last throughout the organism's life span. For example, in many cold-blooded animals (e.g., many species of reptiles and fish) the sex of an individual is determined by temperature-sensitive genes during embryonic and larval development. In the annual killifish Austrofundulus limnaeus, environmental factors including temperature, oxygen availability, and photoperiod have profound effects on embryonic development. These fish live in small seasonal mud puddles in tropical desert regions and must survive for long periods of time without water. When water is present in the puddles, the adult fish thrive. However, when the ponds dry each year, the adult fish die because they can not survive without water. The species survives the duration of the dry season in the form of drought-tolerant embryos that enter a state of "suspended animation" termed diapause. The amount of time that an embryo spends in diapause is dependent on environmental conditions during development. When environmental conditions are poor (e.g., low temperatures, short day lengths, or lack of water) embryos of annual killifish remain in diapause for long periods of time in order to "wait out" the harsh conditions associated with the dry season. However, when environmental conditions are favorable for survival of adult fish (e.g., warm temperatures, and abundant water) the embryos may stay in diapause for only a short period of time, or may skip diapause all together. The research outlined in this proposal is aimed at understanding how environmental cues can alter the developmental pattern of annual killifish to either include or exclude a period of dormancy in diapause. Entry or exit from diapause in annual killifish is likely caused by the action of specific genes. This research will use microarray or "gene chip" technology to identify these genes. The annual killifish "gene chip" will contain a large percentage of the annual killifish genes and will be used as a screening tool to identify which genes are associated with entry into and exit from diapause in annual killifish. The identification of these genes is the first step towards understanding how environmental cues can alter the developmental program of annual killifish.