Bioinformatics of the Hessian fly
Abstract
The Hessian fly, Mayetiola destructor (Say), is a major pest affecting wheat-growing regions worldwide, and is annually responsible for significant financial loss. All deleterious effects of the insect on wheat are due to a biological reprogramming of the infested plant that allows the insect's survival. Artificially disrupting this interaction would protect wheat from pest damage and provide a new form of resistance to combat the diminishing effectiveness of currently deployed resistance (R) genes. RNA interference (RNAi) is a useful reverse genetics tool for studying such insect virulence pathways, but requires a systemic phenotype, which is not found in all species. In an effort to correlate the systemic RNAi phenotype with a genetic basis, we have aggregated and compared RNAi related genes across five species. While most of the micro RNA (miRNA) and transcriptional silencing pathway genes were highly conserved across species, the small interfering RNA (siRNA) pathway genes showed increased relative variability. In particular, the Piwi/Argonaute/Zwille (PAZ) domain of Dcr2 had the least amount of sequence similarity of any domain between species surveyed, with a trend of increased conservation by those species with amenable systemic RNAi. Furthermore, the Dicer dsRNA-binding fold domain of Dcr2 was absent from M. destructor, possibly indicating functional incompetence. M. destructor also had the highest degree of RNAi gene expansion of all insect species surveyed, as measured by number of gene duplications observed, suggesting that such pathway expansions do not correlate with efficacy of systemic RNAi. Pathways peripheral to dsRNA uptake and RNAi, including endocytosis, phagocytosis, tunneling nanotubes (TNTs), microvesicles (MVs), and secretory exosomes, were uniformly intact across all insects considered, implying their conservation. Finally, over 100 novel miRNA precursors were identified in the M. destructor genome through highly stringent computational means, which may serve as a reference for future M. destructor small RNAseq research. Taken together, the annotations and associated trends reported here may help describe the disparity of systemic RNAi phenotypes between insect species.
Degree
M.S.
Advisors
Williams, Purdue University.
Subject Area
Entomology|Bioinformatics
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