Hypoxic Stress Induced Gene Modulation in Medaka (Oryzias latipes) and Xiphophorus maculatus

Abstract

Hypoxic zones in aquatic systems are becoming an increasing worldwide problem due to the stress these hypoxic zones place on economically important fishery resources. Evaluating gene modulation responses in fishes exposed to hypoxic conditions may provide the tools to better understand the physiological adaptations made by fish to survive environmental stress. In addition, shifts in gene regulation upon exposure to hypoxia may lead to the establishment of transcriptional profiles or identification of genetic biomarkers associated with the extent and duration of hypoxic conditions. Such profiles or biomarkers would be useful in regulation of anthropogenic factors that are known to produce hypoxia. The studies detailed herein are an attempt to identify genes that show robust changes in transcriptional expression when two different fish are exposed to hypoxia. Genes showing a robust and consistent response to hypoxia in these two divergent fish may be utilized as biomarkers to profile hypoxia. In this study, we employed quantitative Real-Time PCR (qRT-PCR) to assess modulated gene expression in four tissues (brain, liver, gill, and fin) of Oryzias latipes and Xiphophorus maculatus. We analyzed six potential gene targets that had previously been shown in microarray studies to exhibit robust (> 5.0 fold) changes in mRNA abundance when medaka were exposed hypoxic conditions. Herein we present results of the qRT-PCR studies to assess their potential utility as hypoxia biomarkers.