Differential gene expression of heat shock proteins in crowded and isolated Schistocerca americana

Schistocerca americana is one of many grasshopper species that exhibits density-dependent phenotypic plasticity in which insects in high population density environments display different morphological and behavioral characters than insects in low population densities. Insects in the crowded condition are exposed to many types of stress, which include increased temperature, higher risk of disease, and decreased nutrient availability. Heat shock proteins (HSPs) are a class of proteins that help respond to and cope with a wide range of stressors. Generally, HSPs act as molecular chaperones and it has been suggested that they play a major role in responding to environmental stress and can be used across many species as a biological marker to indicate exposure to stressful conditions. This project seeks to begin to elucidate the means by which these stresses are coped with at a molecular level by quantifying differences in gene expression of three small HSPs (Hsp20.5, Hsp20.6, Hsp20.7) and three large HSPs (Hsp40, Hsp70, Hsp90) in S. americana insects in the sixth instar developmental stage. Genes were identified by blasting the sequences from other Orthoptera against the S. americana transcriptome, and primers were designed from these sequences. Complementary DNA libraries were created from RNA extractions from the head and thoracic ganglia of isolated and crowded individuals and then run on qRT-PCR with β-actin as the reference gene.