Expression of HIF-1-α and HIF-1-β in Manduca sexta under normoxic and hypoxic conditions

 

Expression of HIF-1-α and HIF-1-β in Manduca sexta under normoxic and hypoxic conditions.

North Dakota State University

Taylor Lundquist, Kendra Greenlee, and Jeff Kittilson 

      Larval holometabolous insects grow exponentially from hatching to the penultimate instar, punctuated by periodic molts during which the exoskeleton and respiratory system are enlarged and replaced. Because major tracheae only increase in size after a molt, gas exchange capacity may be fixed within an instar. As a consequence, we hypothesize that growing larvae may become hypoxic at the end of each larval instar.  A key regulator of cellular responses to hypoxia in insects is the oxygen-sensing protein complex hypoxia-inducible factor 1 (HIF-1). In the absence of oxygen, HIF-1- α and HIF-1-β dimerize to form the HIF-1 complex, a transcription factor that controls expression of genes that contain the hypoxia response element.  If insects become hypoxic during growth within each instar, then we predict that gene expression of HIF -1-α and HIF-1-β will increase with body mass and decrease at the beginning of each larval molt. To test this hypothesis, we measured the gene expression of HIF-1-α and HIF-1-β across various stages of larval development in Manduca sexta. Preliminary results suggest that levels of HIF-1-α and HIF-1-β decrease at the beginning of each molt and increase towards the end of the instar. We look to insects for pollination, but they are also crop pests, requiring research on pesticides, and environmental impacts. To better predict physiological responses to pesticides and variation in environment, we must understand how the respiratory system develops in normal conditions because with age organisms grow in size and O2 demand.