Meeting Abstract

80.1  Friday, Jan. 6  Thermal and hypoxic gene expression in the mayfly (Centroptilum triangulifer). KIM, K.S.; FUNK, D.H.; BUCHWALTER, D.B.*; NC State University; Stroud Water Research Center; NC State University david_buchwalter@ncsu.edu

Despite the widespread use of aquatic insects in biomonitoring programs, there are currently no established model organisms for ecophysiological studies of stream insects. The mayfly Centroptilum triangulifer has many attributes that make it promising as a laboratory model. Its thermal reaction norms are well established and relatively short life cycles (at laboratory temperatures) and high fecundity (typically >1,000 clonal and non-diapausing eggs/individual) allow for complete life cycle experiments with large sample sizes. Recent work in our lab has generated ~24,000 partial gene sequences which we are beginning to exploit to better understand how mayflies respond to thermal and hypoxic stress. To date, we have partially cloned 13 genes of interest related to heat shock, cellular oxygen status, and antioxidant enzymes. Larvae were subjected to 4 different sets of conditions for 6 hours each– controls (22 °C, 8 mg O2/L), hypoxia (22 °C, 2 mg O2/l), thermal stress (32 °C, 8 mg O2/l), and thermal stress combined with hypoxia (32 °C, 2 mg O2/l). Real-time PCR revealed both expected and unexpected results. Expected results included the elevated expression of HSPs 40, 70 and 90 by high temperature and the suppression of superoxide dismutases by hypoxia. Hypoxia inducible factor (HIF) mRNA levels were stimulated by hypoxia at 22 °C, but were surprisingly not different from controls at 32 °C. Interestingly, EGL9 mRNA levels were elevated by a combination of heat and hypoxia, but not hypoxia alone. EGL9 is an oxygen sensing gene that is reported to suppress HIF. Thus, EGL9 (and the influence of temperature on its activity) may play an important role in appropriate physiological response to thermally induced hypoxia.