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Title: Transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis bacteriophora

item ADHIKARI, BISHWO - Brigham Young University
item LIN, CHIN-YO - The Ohio State University
item BAI, XIAODONG - The Ohio State University
item CICHE, TODD - Michigan State University
item GREWAL, PARWINDER - The Ohio State University
item DILLMAN, ADLER - California Institute Of Technology
item CHASTON, JOHN - University Of Wisconsin
item Shapiro Ilan, David
item BILGRAMI, ANWAR - Rutgers University
item GAUGLER, RANDY - Rutgers University

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2009
Publication Date: 12/15/2009
Citation: Adhikari, B.N., Lin, C., Bai, X., Ciche, T.A., Grewal, P.S., Dillman, A.R., Chaston, J.M., Shapiro Ilan, D.I., Bilgrami, A.L., Gaugler, R. 2009. Transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis bacteriophora. Biomed Central (BMC) Genomics. 10:609.

Interpretive Summary: Biological control agents such as entomopathogenic (insect-killing) nematodes are useful as environmentally friendly pest control agents. When biological control agents are cultured repeatedly in the laboratory, or in an industrial setting, important beneficial traits can deteriorate such as loss of virulence, reproductive capacity, environmental stress, etc. Our objective is to understand why and how beneficial traits deteriorate in the nematode biological control agent called Heterorhabditis bacteriophora. In this study, we compared gene expression in a deteriorated population and non-deteriorated population of the nematode. We discovered that a variety of genes change their expression drastically as the nematodes are cultured repeatedly. The gene expression differences corresponded to important traits such as virulence (killing power). This study serves as a model for understanding changes in entomopathogenic nematodes and other biological control agents. Building off of this study, we may learn how to stabilize beneficial traits and facilitate better efficacy in biological pest suppression.

Technical Abstract: Trait deterioration under laboratory conditions has been widely documented in the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora (Hb) but the specific mechanisms behind these genetic processes remain unclear. This research investigates the molecular mechanisms of trait deterioration of two experimental lines of Hb, an inbred line (L5M) and its original parental line (OHB). We generated transcriptional profiles, indentified the differentially expressed genes (DEGs) and validated their differential expression in the deteriorated line. Microarray analysis showed 1,185 DEGs comprising of 469 down- and 716 up-regulated genes in trait deteriorated nematodes. Functional analysis of the DEGs showed that trait deterioration involves massive changes of the transcripts encoding metabolic and signal transduction enzymes. We observed a pattern of reduced expression of enzymes related to primary metabolic processes and induced secondary metabolism. As the most closely related major entomopathogen to C. elegans, Hb provides an attractive near-term application for using a model organism to better understand interspecies interactions and to enhance our understanding of the mechanisms underlying trait deterioration in biological control agents. This information could also be used to improve the beneficial traits of biological control agents and better understand fundamental aspects of nematode parasitism and mutualism.