Differential gene expression of H. Bacteriophora TTO1 in response to heat stress

Marc Christian, The College of Wooster


Heterorhabditis bacteriophora is an entomopathogenic nematode whose use as a biocontrol agent against insects within agriculture is currently deficient due to significant nematode mortality during high stress storage. While heat stress has been studied with respect to individual genes, no full transcriptome analysis has been performed. In this study, we investigated the differential regulation by H. bacteriophora during heat stress using the Illumina Genome Analyzer, a next generation sequencing technology. Our hypothesis is that we will observe differential mRNA levels, and this will aid us in establishing a tolerance model within H. bacteriophora. We were able to determine that there are many differentially expressed genes. These genes were grouped by common function using RNAi phenotype, gene ontology, and protein domain information. Generally, we saw the up-regulation of reproduction, growth, transcriptional regulation, and survival genes. These include ribosomes, histones, heat shock proteins, fat alteration, and nuclear remodeling genes. Down-regulated genes include programmed cell death, energy production, and cyto-skeletal elements, which included ATPases, myosin (and other structural proteins), and an aquaporin. With respect to the mathematical investigation posed here, we used the Estimation Maximization (EM) algorithm to model our data on a Poisson mixture model. This type of analysis has been shown to predict transcriptomic data significantly better than simpler models. We were able to program a simple EM algorithm using Maple 13(R), indicating the widespread availability of this algorithm for use in modeling data similar to this.


© Copyright 2010 Marc Christian