1a. Objectives (from AD-416):
The objective of this cooperative agreement is to conduct collaborative research between the Harry K. Dupree-Stuttgart National Aquaculture Research Center of the Agricultural Research Service (ARS) and Auburn University to characterize changes in gene expression in superior and inferior performing hybrid striped bass with a principal focus on growth and resistance to pathogens.
1b. Approach (from AD-416):
Our approaches are two-fold: 1) Families of hybrid striped bass will be reared in communal ponds for a set duration to determine the performance of different families. After which, various tissues from the fastest and slowest growing fish will be collected and samples will be sent to Cooperator for gene expression analysis. 2) Families of hybrid striped bass will be challenged with Flavobacterium columnare. Tissues from naïve fish, moribund fish, and surviving fish will be isolated and sent to Cooperator for gene expression analysis.
3. Progress Report:
Scientists in this project are collaborating in research planning, data collection, and data analysis to better understand the molecular events contributing to columnaris disease resistance. Investigators conducted a study comparing the global changes in gene expression in tissues of channel catfish after challenge with Flavobacterium columnare, the causative organism of columnaris disease. In challenged fish, a rhamnose-binding lectin (RBL) was among the most highly upregulated genes in the differentially expressed set. It was determined that this upregulation was selective for fish that were susceptible to the disease, but was virtually absent in resistant fish after challenge. Next, by addition of L-rhamnose or D-galactose (RBL agonists) to water prior to challenge, fish could be protected from columnaris disease. Rhamnose-binding lectin expression was also determined to be tightly regulated by nutritional status, with fasted fish having >100-fold higher levels of RBL expression than fed fish. These data suggest that columnaris disease susceptibility may be in some part modulated by rhamnose-binding lectin expression. These findings are encouraging and are driving current studies to determine if RBL are useful markers to predict fish performance in the context of disease. Future studies are also focused on further characterizing the link between RBL expression and nutrition.